Uranium - gsn.gov.na · Uranium occurrences in and associated with plutonic rocks comprise both potentially economic deposits and source rocks for uranium deposits in pedogenic and

7.1-1

1. Introduction

The upswing in the uranium market in the1970s led to extensive uranium exploration inNamibia. Several airborne radiometric surveyswere conducted by the Geological Survey duringthis period and several uranium deposits werelocated. These are grouped into three basictypes: a) occurrences in and associated withplutonic rocks, b) pedogenic occurrences andc)sedimentary occurrences. An overlap existsbetween the pedogenic and the other maindeposit types.

Uranium occurrences in and associated withplutonic rocks comprise both potentiallyeconomic deposits and source rocks for uraniumdeposits in pedogenic and sedimentarysequences. These deposits are confined mainlyto the western portion of the Damara Orogen(Fig. 1), which contains the only currently

Uranium

by H Roesener and CP Schreuder

7.1-1 1. Introduction7.1-3 2. Occurrences in and associated with

plutonic rocks7.1-4 2.1 Alaskites7.1-4 2.1.1 The Rössing Deposit7.1-10 2.1.2 The “SH”-uranium deposit7.1-11 2.1.3 The G.P. Louw Deposits7.1-15 2.1.4 The Valencia Deposit7.1-21 2.1.6. The Ida Dome Area7.1-23 2.1.7 The Rössing Mountain deposits7.1-25 2.1.8 Minor Occurrences7.1-25 2.1.8.1. The Wolfkoppe deposits7.1-25 2.2 Granites and Gneisses7.1-25 2.2.1 Pre-Damaran Rocks7.1-25 2.2.1.1 Huab Metamorphic Complex7.1-25 2.2.1.2 Abbabis Complex7.1-25 2.2.2 Damaran Granites7.1-25 2.2.2.1 Red Granite-gneiss Suite7.1-26 2.2.2.2 Salem Granitoid Suite7.1-26 2.2.3.3 Very late- to post-tectonic

granites7.1-26 2.2.3 Post Damaran Rocks7.1-26 2.2.3.1 The Erongo7.1-27 2.3 Mineralisation associated with

pegmatites and quartz veins7.1-27 2.3.1 Pre-Damaran Rocks7.1-27 2.3.2 Damara Sequence7.1-27 2.3.2.1 Auris7.1-27 2.3.2.2 Minor Occurrences7.1-29 3. Pedogenic Occurrences7.1-29 3.1 The Mile 72 deposit7.1-31 4. Sedimentary Occurrences7.1-31 4.1 Syngenetic Occurrences7.1-31 4.1.1 Karoo Sequence7.1-31 4.1.1.1 The Engo River Occurrence7.1-34 4.1.1.2 The Huab deposit7.1-37 4.2 Epigenetic Occurrences7.1-37 4.2.1 Karoo Sequence7.1-37 4.2.2 Tertiary occurrences in the

Namib Desert7.1-38 4.2.2.1 The Namib Park Region7.1-39 4.2.2.1.1 The Langer Heinrich Deposit7.1-42 4.2.2.1.2 The Tubas Uranium deposit7.1-43 4.2.2.1.3 Oryx7.1-45 4.2.2.1.4 Tumas Deposit7.1-46 4.2.2.1.5 The Aussinanis Deposit

7.1-47 4.2.2.1.6 Minor Occurrences7.1-47 4.2.2.2 Spitskop Area7.1-47 4.2.2.2.1 The Klein Trekkopje Deposit7.1-50 4.2.2.2.2 Arandis Deposits7.1-51 4.2.2.2.3 Hakskeen7.1-51 4.2.2.2.4 Swakopmund Grant7.1-52 4.2.2.2.5 The Klein Spitzkoppe

Deposit7.1-54 4.2.2.2.7 Welwitschia Flats7.1-55 4.2.2.2.8 Minor Occurrences7.1-56 4.2.2.3 Brandberg Area7.1-56 4.2.2.3.1 Henties Bay Grant7.1-56 4.2.2.3.2 Cape Cross7.1-56 4.2.2.3.2 Namib Rock Grant7.1-57 4.2.2.3.4 Brandberg South Area7.1-58 4.2.2.3.5 Area NW of Henties Bay7.1-58 5. Secondary occurrences of uncertain

origin7.1-58 5.1 Meob Bay7.1-58 5.2 Uis Mine7.1-59 5.3 Area south of the Kuiseb River7.1-59 5.4 Tsumeb Mine7.1-59 6. References

7.1-2

Figure 1: The Damara Orogenic Belt: Generalised geology of the western portion (after Jacob et al,1986)

operating uranium mine at Rössing.

In the southern part of Namibia, a number ofuranium- and thorium-bearing granite bodies of

relatively low tenor are developed in theNamaqua Mobile Belt (Jacob, et al., 1986)

7.1-3

Mineral Resources of Namibia Nuclear and Fossil Fuels - Uranium

2. Occurrences in and associated with plutonicrocks

The uraniferous granite occurrencesdiscovered so far are situated in the CentralZone of the Damara Orogen between theOmaruru and Okahandja Lineaments (see Table1 for generalized stratigraphy of the CentralZone). The Central Zone exhibits dome-and-basin patterns where extensive graniteemplacement is associated with the domes.Several phases of deformation can berecognised in the Central Zone and are indicatedby fold interference patterns. The mainstructural grain is northeast trending and is dueto an intense F3 deformation period. This waspreceded by one or possibly two periods offolding. The early phases of folding producedoverturned and recumbent structures and wereaccompanied by thrusting and shearing. Theearly fold axial planes were roughlynorthwesterly trending. A number of lessintense phases of folding occurred after F3 andproduced folds oriented in northeast andnorthwest directions. Uraniferous granites wereemplaced post-F3 and are oriented north-northeast, which direction manifests itself in theprominent north-northeasterly trendingmagnetic Welwitschia lineament. Corner (1982)considered this north-northeasterly structuraldirection to have an important bearing on theemplacement of the uraniferous alaskiticgranites since firstly, the currently knownoccurrences are located either in the vicinity ofor to the west of the Welwitschia Lineamentand, secondly, the major fold axes of the domesand structures with which these occurrences areassociated, are parallel to this lineament ratherthan to the general northeasterly trend of theCentral Zone.

The-dome-and basin structures are a featureof the Central Zone, but their origin remainscontroversial. Smith (1965) and Bunting (1977)ascribed them to interference folding, whereasJacob believes that they have formed as a resultof diapiric uprising at about the time of andfollowing the F3 deformation. The domes resultfrom an interplay of both these components.The correlation of the direction of the majoraxes of the domes with which the uraniferous

granites are associated with the north-northeasterly F4 structural direction, supportsthe inference of a strong measure of structuralcontrol in the formation of these domes.

Between 660 and 460 million years ago, theCentral Zone was subjected to polyphasedeformation accompanied by the intrusion ofpre-tectonic, syn-tectonic and post-tectonicgranites. The granites where classified byMarlow (1983) into four main types; syn-topost-tectonic Salem-type granites, red granites,late-to post-tectonic leucogranites and alaskites.

In the Central Zone the peak temperature ofmetamorphism was estimated to increase from555o C at Karibib to 645 o C southwest ofSwakopmund. The pressure of metamorphismwas estimated to be 2.6 kbar northeast of theconfluence of the Khan and Swakop Rivers and3.4 kbar near Swakopmund.

The Salem granites constitute a suite ofdifferent generations of granodiorites, granitesand adamellites with an age of 601±79 millionyears and are the most abundant granitic type.These granites, which are typically batholitic inform, occur well below the level of the KaribibFormation.

The red granites, with an age of 516±23million years, also occur below the level of theKaribib Formation and were considered bySmith (1965) to be confined to anticlinal anddome structures in the area around the Khan andSwakop Rivers. They occur as domes, which canrange up to 15 km across, as dykes throughoutthe Central Zone and as lit-par-lit intrusionssouthwest of Usakos.

The leucogranites, typified by the Donkerhukand Bloedkoppie granites, have an age of484±25 million years and occur mainly as largebatholiths, but diapirs and small plugs are notuncommon.

Alaskites range in age between 458±8 millionyears at Rössing to 542±33 million years in theSwakop River. They are confined to the areas ofhighest metamorphic grade. They are fine- tocoarse-grained or pegmatitic granites,

7.1-4


characterised by their high alkali content andextremely leucocratic nature, as well as theiranastomosing and vein-like style of intrusion.They commonly display sharp contacts with therocks which they intrude. They occurpreferentially in and around anticlinal domestructures and intrude into the basement, theNosib and lower Swakop Groups.

2.1 Alaskites

2.1.1 The Rössing Deposit

The Rössing Mine is located approximately70 km northeast of Swakopmund in the NamibDesert. Although the presence of radioactiveminerals in the area has been known since 1910,it was only in 1956 that serious but limitedprospecting was done on a radioactive anomalyknown as SJ. In 1966 Rio Tinto South Africacommenced an intensive programme ofunderground bulk sampling and pilot plant testwork, which was completed in March 1973.This investigation indicated the existence of avery large, low-grade deposit of uranium thatcould be mined by open-pit methods and alsoshowed that the uranium could be recovered bymeans of conventional metallurgical processes.

The Rössing uranium deposit occurs in amigmatite zone in which uraniferous alaskiticgranite/pegmatite and metamorphosed countryrock show concordant, discordant andgradational relationships. The country rockcomprises deformed metasedimentary rocks ofthe Khan and Rössing Formations (Table 1),whereas the alaskitic rocks range from smallquartzo-feldspathic lenses of secretion origin, tolarge intrusive and replacement bodies varyingwidely in texture, size and emplacement habit.

A prominent band of feldspathicmetaquartzite of the Etusis Formation encirclesthe intensely granitized core (AbbabisComplex) which forms a domal structure lyingto the north of the uranium deposit (Fig. 2).Despite the high degree of recrystallisation andmetamorphism, small-scale cross-beddingstructures are well preserved throughout thisunit. A thick unit of biotite gneiss constitutes an

outer rock shell surrounding the dome. Thegneiss is migmatised along the planes ofgneissosity and also intruded by large amountsof late to post-kinematic uraniferous alaskite.

In the Khan Formation, clinopyroxene andhornblende are the main dark minerals present,whereas biotite is predominant in the gneisses ofthe Etusis Formation. The Khan Formation canbe divided into four units of which the lowerpyroxene-hornblende gneiss is favoured as a sitefor the emplacement of numerous veins anddykes of alaskite, usually parallel to the foliationthough also transgressing it at various angles.

An interbedding of pyroxene-garnet gneissbetween the upper and lower pyroxene-hornblende gneiss units shows metamorphicbanding in the area east of the deposit, but has amassive and mottled appearance to the west.This unit carries discontinuous massive bodiesand lenses of amphibolite that are exposed in thenorthwestern prong of the uranium deposit.

In the upper pyroxene-hornblende gneiss theamount of amphibole increases at the expense ofclinopyroxene. The gneiss has a bandedappearance caused by the orientation of themigmatization products parallel to the foliation.The contact with the underlying gneiss isgradational and pebble bands of limited lateralextent are present locally.

Six units have been recognised in the RössingFormation, comprising a basal, impureserpentinitic and graphitic marble overlain inturn by biotite-cordierite gneiss, conglomerate,marble, biotite-cordierite gneiss and feldspathicquartzite. The conglomerate serves as a usefulmarker horizon, although it grades into a grittyarkose to the east.

Metasedimentary strata of the overlyingChuos, Karibib and Kuiseb Formations occurwell to the south of the Rössing deposit. TheChuos mixtite has a grey, massive to schistosematrix containing unsorted, elongated, angularerratics measuring up to one metre in diameter.It is overlain by the Karibib Formation,comprising a succession of white to bluish grey,well-bedded marble units containing thin

7.1-5


Table 1: Stratigraphic column of the Damara Orogen (after Jacob et al., 1986).

Group Subgroup Formation Max thickness Lithology

Swakop Khomas Kuiseb >3000 Pelitic and semi-pelitic schist and gneiss,migmatite, calc-silicate rock, quartzite.Tinkas member: Pelitic and semi-pelitic schist,calc-silicate rock, marble, para-amphibolite.

Karibib 1000 Marble, calc-silicate rock, pelitic and semi-pelitic schist and gneiss, biotite amphiboliteschist, quartz schist, migmatite.

Chuos 700 Diamictite, clac-silicate rock, pebbly schist,quartzite, ferruginous quartzite, migmatite.

Discordance

Ugab Rossing 200 Marble, pelitic schist and gneiss, biotite-horneblende schist, migmatite, calc-silicaterock, quartzite, metaconglomerate.

Discordance

Nosib Khan 1100 Migmatite, banded and mottled quartzofelds-pathic clinopyroxene-amphibolite gneiss,horneblende-biotite schist, biotite schist andgneiss, migmatite, pyroxene-garnet gneiss,amphibolite, quartzite, metaconglomerate.

Etusis 3000 Quartzite, metaconglomerate, pelitic and semi-pelitic schist and gneiss, migmatite, quartzo-feldspathic clinopyroxene-amphibolite gneiss,calc-silicate rock, metaphyolite.

Major unconformity

Abbabis Complex Gneissic granite, augen gneiss, quartzofelds-pathic gneiss, pelitic schist and gneiss,migmatite, quartzite, marble, calc-silicate rock,amphibolite.

interbeds of quartzose calc-silicate. The KaribibFormation is overlain by the biotite-cordierite-sillimanite schists of the Kuiseb Formationcontaining numerous pegmatitic dykes andveins.

Contact metamorphic effects are evident inmetasedimentary rocks adjoining the alaskitic

intrusives. These are insignificant in the gneissesof the Khan Formation, but in the biotite-cordierite schists and gneissses of the RössingFormation feldspar blastesis is present alongcontacts that are predominantly gradational. Themost marked effects are evident where thepegmatitic alaskites have invaded the marbles ofthe Rössing Formation. Nash (1971) reported

7.1-6


Figure 2: Geological map showing the setting of the Rossing uranium deposit (after Berning, 1986).

7.1-7


that: “skarn bodies, ranging in size from a fewcentimetres to several metres are widespread,the majority being composed of coarseaggregates of pale green clinopyroxene, browncalcic garnet and varying amounts of scapolite.Although generally hornfelsic, the rocks maycontain individual growths of pyroxene andgarnet up to several centimetres in size”.

The Rössing uraniferous body is situatedalong the northern limb of a complexsynclinorium developed between the domalstructure (Fig. 2) and the Khan Formationmetasedimentary rocks present about 2.5 kmfurther south. Three different structural trendsare recognisable on a regional scale, but tightvertical or slightly overturned F2 folds strikingnortheast - southwest are the most prominentfeature of the regional structure. Verticaloblique-slip faults, with horizontaldisplacements ranging from a few centimetresto more than 50 m, occur in the region of thedomal structure and are most prolific in the coreof the “mine”synclinorium. They are youngerthan both the F2 folds and the alaskites, butolder than dolerite dykes of Karoo age.

The uranium-bearing syntectite of theRössing deposit has been termed “pegmatite”

by Smith (1965), “potash granite” by Nash(1971) and “alaskite” by the staff of the RioTinto Exploration Company.

The biotite gneiss of the Etusis Formationand the rocks of the Khan and RössingFormations are the favoured host rock of thealaskite, regardless of whether it is mineralisedor barren, whereas the feldspathic metaquartzitesat the base of the Etusis Formation areessentially free of alaskite.

The alaskite occurs as narrow dykesconcordant or discordant to large irregularbodies that transgress the foliation or banding ofthe country rock. In the northern sector of theore body the alaskite is present in the lower andupper pyroxene-hornblende gneiss and formsregular dykes that have been emplaced parallelto the regional bedding and metamorphicfoliation of the metasediments (Fig. 3). Thealaskite present in the less-banded pyroxene-garnet gneiss and amphibolite occurring furthersouth assumes a more massive habit. Thestructure of the country rock also influences thehabit of the alaskite which in many localities isemplaced along the axial planes of F3 folds asdykes that transgress concentric shells ofdifferent lithologies. In the central part of the ore

Figure 3: Generalised geological map of the Rossing alaskite body (after Berning, 1986).

7.1-8


body, massive alaskite has completely engulfedlarge undisturbed country rock xenoliths morethan 100 m in size.

Textural variations ranging from aplitic,granitic to pegmatitic are displayed by thealaskite, with the latter predominating. Graphictexture is also evident in certain localities.

The bulk of the economic mineralisation inthe Rössing deposit (Figs. 3 and 4) is containedin alaskite on the northern limb of the “mine”synclinorium. The alaskite is preferentiallyemplaced into the pyroxene-hornblende gneissand biotite-amphibole schist units of the KhanFormation in the northern ore zone, and intobiotite-amphibole schist/lower marble/lowerbiotite-cordierite gneiss of the RössingFormation in the central ore zone. On thewestern edge of the deposit the two ore zonesare separated by a considerable width of largelybarren upper pyroxene-hornblende gneiss,whereas further east, thinning of the stratacoupled with steeping of dip, narrows thesurface exposures of ore zones and also the gapbetween them to a point where they merge.Towards the western end of the deposit, rich orein both zones is exposed on surface, but drillinghas established that it is of limited vertical

extent. Further east the better grade ore extendsto progressively deeper levels, and towards thefar eastern limit of the pit blind bodies ofuraniferous alaskite are encountered at depth.

The alaskite is widely distributed beyond thelimits of the open pit but is not uniformlyuraniferous. Portions are entirely barren or onlyslightly mineralized while only a few restrictedsections are sufficiently rich to supportexploitation. The reason for the localisation ofthe rich ore is still unclear.

Alaskite hosts all the primary and most of thesecondary uranium minerals. In certain localitiessecondary mineralization spreads into thecountry rock and /or into a sporadicallydeveloped layer of surficial limestone. Withinthe uraniferous zone, enrichment is presentalong biotite-rich selvages in the alaskite, atplaces where robust alaskite bodies displaysharp upward-narrowing to form dykes or veins,in alaskite emplacement along the axial planesof folds and in localities where amphibolite hasbeen replaced by alaskite in the ore zones.

Uraninite [UO2], the dominant primary

mineral, occurs as grains ranging in size from afew microns to 0.3 mm, with the majority in the0.05 to 0.1 mm fraction. It is included in quartz,

Figure 4: Cross-section of the Rossing alaskite body showing geology and boreholes (drill sectionzero) (after Berning, 1986).

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feldspar and biotite, and also appearsinterstitially to these minerals or along crackswithin them. The uraninite displays apreferential association with biotite and zircon,the latter appearing as inclusions withinuraninite grains or as clusters of grains attachedto them. Alteration haloes around the uraninitegrains are common.

Monazite is widespread in some samples ofore and commonly closely associated withuraninite. Single monazite crystals seldommeasure more than 0.04 mm in diameter.

Betafite [(U,Ca,Ce)(Ti,Fe) 2O

6] is

subordinate to uraninite and contains a minorproportion of the uranium in the ore. It shows astriking range of colours, from the usual darkbrown variety with typical conchoidal fracture,to a bright yellow variety resembling carnotiteand uranophane, but is distinguished from themby its greasy lustre. Betafite, commonly presentas inclusions in quartz and feldspar, has beenfound to contain high concentrations of niobiumand titanium, a fair amount of uranium andsmall amounts of tantalum and tungsten.

Brannerite [(U,Ca,Ce)(Ti,Fe) 2O

6OH] is rare,

but may contain a significant proportion ofuranium.

Zircon, apatite and sphene are commonlyassociated with the radioactive minerals. Pyrite,chalcopyrite, bornite, molybdenite, arsenopyriteand the oxides magnetite, hematite and ilmeniteare encountered in places, whereas fluorite isfrequently present.

The alteration of uraninite and betafite givesrise to secondary uranium minerals that areusually bright yellow in colour. These occur insitu, replacing the original minerals from whichthey were formed, or they commonly form incracks as thin coatings or occasionally asdiscrete crystals.

Of the secondary uranium minerals, beta-uranophane [Ca(UO

2)Si

2O

7.6H

2O] is by far the

most abundant. It is not always confined toalaskite but may spread into the envelopingcountry rocks. Uraninite; contains about 55% of

the uranium present, betafite less than 5%, andsecondary minerals about 40%.

Ore reserves of the Rössing deposit werecalculated from the data obtained from thesurface diamond-drilling programme undertakenby the Rio Tinto Exploration Company between1967 and 1971. Using computer techniques, aseries of long-term mining plans was developedfrom the ore reserve data until an optimum 20-year plan was obtained. This called for anopencast mining operation with 15 m-highbenches resulting in a pit, which at the end ofthe 20 year period will be 3 km long, 1 km wideand 0.3 km deep.

Data obtained from detailed drilling are usedto develop medium- and short-term plans ofmining sequences designed to optimise miningof the ore body. The controlling factor informulating the mining plans is that sufficientore of the required grade should be available formining at any time, in order to meet the plant’srequirements.

The mineability of the Rössing ore body iscomplicated by the following factors:

i) it consists of a mixture of uranium-bearingalaskite and barren metamorphic rock;

ii) the uranium content of the alaskite isextremely variable;

iii) in some areas the alaskite is present aslarge masses, whereas in others it consists ofnarrow bodies intercalated with barrenmetasedimentary rock;

iv) the acid consumption of the rocks (in themetallurgical process sulphuric acid is used toleach the uranium from the ore) varies greatlyfrom low consumption for alaskite to very highconsumption for marble.

Control of the uranium grade coupled withthe acid consumption characteristics of the rocksis therefore of major importance. Special careneeds to be taken with the blasting techniquesused. Maximum fragmentation of the rocks isdesired, but this often results in excessive

7.1-10


movement of the rock resulting in a mixing ofhigh-grade, low-grade and waste material, aswell as of low- and high-acid-consuming ore.

In a further attempt to control grade,radiometric truck scanners are used todetermine the level of radioactivity of eachtruck load of ore removed from the pit.Depending on the level of radioactivityrecorded, a truck is dispatched either to the orecrushers, or to the low-grade stockpile, or to thewaste dumps (Berning, 1986).

The plant was commisioned in June 1976and commercial production started in January1978. Table 2 gives annual production for theyears 1976 to 1994.

Table 2. Uranium Production of Rössing Mine

The betafite grains, up to 3 mm in diameter, arecharacteristically surrounded by a narrowbrownish grey alteration rim. The grains arecommonly associated with inclusions or veinletsof sphene, rutile, leucoxene, anatase, branneriteand davidite.

Uraninite is present in minor amounts, theapproximate ratio of betafite to uraninite being8:1. The mineral forms small euhedral tosubhedral equidimensional crystals some 0.3mm across. Minor amounts of galena,presumably originating from radiogenic lead, aregenerally present as small round inclusionswithin the uraninite, or as narrow, irregularlyshaped veinlets.

A small proportion of grains are a darkerbrown than the betafite and are thought to bedavidite [(Fe,U,Ca,Zr,Th)(Ti,Fe,V,Cr)

15

(O,OH)36

], a mineral that has a similarcomposition to betafite, but contains more rare-earths and titanium. Beta-uranophane and othersecondary minerals are abundant (Berning,

Year Metric tons U1976 6701977 23401978 27661979 37661980 40981981 39811982 38031983 37371984 36951985 3324

Year Metric tons U1986 34711987 35991988 34911989 30801990 31271991 24351992 16601993 16791994 1895

Figure 5: Geological map showing the settingand crosscutting nature of the SH alaskitebody (after Rio Tinto Exploration Company).

2.1.2 The “SH”-uranium deposit

The “SH”-uranium deposit is situated 1.5 kmsouthwest of the Rössing ore body andmeasures some 500 by 250 m. The long axis ofthis body trends in a northwestly direction andtransgresses the strike of the surroundingmetasedimentary formations. The body isemplaced in marble, quartzite and schist of theRössing Formation, and consists of coarsely-crystalline to pegmatitic alaskite with numerousamphibolite- and biotite-schist inclusions (Fig.5).

The main uranium-bearing mineral isbetafite, which is not soluble in the acidsolutions normally used in uranium leaching.

7.1-11


pers.comm. Schreuder).

The deposit was investigated by detailedmapping, ground radiometric surveys andpercussion and diamond drilling.

2.1.3 The G.P. Louw Deposits

The G.P. Louw prospecting grant areasurrounds the Rössing mining grant and wasfirst examined after an airborne geophysicalsurvey in 1968 indicated a number ofradiometric anomalies (Fig. 6). Reconnaissanceground radiometric surveying, geologicalmapping and limited test diamond drilling (3boreholes) of the SK-area (Fig. 7) werecompleted in 1970.

The G.P. Louw area is underlain by the samerock types as the Rössing uranium deposit andthe stratigraphy, structure and metamorphismare broadly similar.

Uranium mineralisation is closely associatedwith alaskitic granites and pegmatites emplacedin highly metamorphosed and migmatizedcountry rocks. The alaskite bodies range fromsmall quartzo-feldspathic lenses of secretionaryorigin to large bodies of intrusive andreplacement habit. Alaskite hosts all the primaryand most of the secondary uranium minerals.

Mineralised alaskites tend to be more deeplycoloured (reddish) on weathered surfaces thanunmineralised bodies. However, there areexceptions, as almost white mineralizedalaskites have been found. Smoky quartz isusually associated with uranium mineralisation.

Uraninite is the dominant hypogeneradioactive mineral. It occurs as grains rangingin size from a few microns to 0.3 mm with themajority falling in the 0.05 to 0.1 mm fraction.It is included in quartz, feldspar and biotite, butalso occurs interstitially to these minerals oralong cracks and fractures within them.Uraninite displays a preferential associationwith biotite and zircon, with the latter mineraloccurring as inclusions within uraninite grainsor as clusters of grains attached to them.

Alteration haloes around the uraninite grains arecommon.

Minor amounts of monazite and betafite areusually present. Zircon, apatite and sphene arecommonly associated with the radioactiveminerals. Trace amounts of pyrite, chalcopyrite,bornite, molybdenite, arsenopyrite and theoxides magnetite, hematite and ilmenite areencountered occasionally, whilst flourite isabundant.

Of the secondary uranium minerals, beta-uranophane is by far the most abundant. Othersecondary minerals include gummite (genericterm for amorphous hydrous oxides of uraniumformed as alteration products of uraninite andpitchblende), uranophane [Ca(UO

2)

2Si

2O

7.6H

2O],

torbernite [Cu(UO2)

2 (PO4)

2.8-12H

2O], carnotite

[K2,(UO

2)

2 (VO

4)

2.3H

2O], metahaiweeite

[Ca(UO2)

2Si

6O

15.5H

2O] and thorogummite.

These occur in situ, replacing the originaluraninite grains from which they were formed,along cracks as thin films, or occasionally asdiscrete crystals.

The individual occurrences of the G.P.Louwarea are described briefly below and theirlocalities are indicated in Figure 6.

RA. Low-grade uranium mineralization isassociated with numerous closely-spacedalaskite dykes in the nose region of a complexanticlinal fold structure. The metasedimentaryhost rock consists predominantly of bandedamphibole- and pyroxene-rich gneiss of theKhan Formation.

Uranium mineralisation is accompanied byconcentrations of smoky quartz and biotite. Aprogramme of shallow percussion drilling hasrevealed the presence of low-grade uraniumvalues over an area measuring approximately200 by 200 m.

SK4. This deposit is located some 2 km eastof the Rössing open pit, on the southern contactof a large, irregular body of alaskite (Fig. 7). Thealaskite body is associated with a zone offaulting and fracturing along a synclinalstructure. The metasedimentary rocks include

7.1-12


Figure 6: Locality map showing the radiometric anomalies in the viscinity of Rossing Mine (afterRio Tinto Exploration Company).

7.1-13


cordierite gneiss, marble, quartzite, biotiteschist of the Rössing Formation and amphiboleschist, pyroxene- and amphibole gneiss of theKhan Formation.

The mineralisation was investigated by 62diamond drill holes, totaling 6 038 m. Thisdelineated an ore body with a strike length of150 m and width averaging 12 m. The bodydips steeply north and persists to 90 m belowsurface (Fig. 8).

SK3. The uranium mineralisation of thisdeposit is associated with an elongate, irregularalaskite emplaced along a zone of faulting.Country rocks consist of intensely foldedcordierite gneiss, quartzite, marble, biotite- andamphibole schist.

A total of 3 908 m ( 36 boreholes) wasdrilled on sections 50 m apart. On surface themineralised alaskite extends for 600 m alongstrike, dips 70 o northwest and the width varies

between less than one metre to 25 m.

Z10. This mineralised zone is associated withan irregular, elongate body of alaskite emplacedalong a zone of faulting and shearing. Countryrocks are diamictite, marble, quartzite,amphibole schist and gneiss.

The deposit was investigated by 2 640 m (31boreholes) of diamond drilling on sections 50 mapart. The main mineralized zone has a strikelength of 350 m, with an average width of 7 m.The ore dips 60o to 80 o north and extends to adepth of approximately 90 m.

Z21c. Situated within the Rössing Formationare irregular and elongated bodies of alaskite,which outcrop along a zone with a strike lengthof 1 700 m. The rocks dip 50 o to 80o north, withthe alaskite showing both intrusive andreplacement relationships with the host rock.

A drilling programme consisting of 2 575 m

Figure 7: Geological map showing the setting of the SK4 alaskite body (after Rio Tinto ExplorationCompany)

7.1-14


(27 boreholes) located two mineralised alaskitezones; an eastern zone which has a strike lengthof 250 m and average width of 25 m, and awestern zone which has a strike length of 140 mand an average width of 30 m.

Z19. Anomalous radioactivity is present in azone 4 000 m long and varying in width from30 to 300 m. Alaskite occurs as broadlyconcordant, irregular masses, bands and lenseswithin mixtite and marble units. Highradioactivity is commonly associated with zonesof hematite staining and with concentrations ofbiotite.

Z17. Radioactive alaskites are present inmarble, calc- silicate rocks, cordierite gneissand biotite schist. The area lies on the southernflank of the regional Khan Syncline. Traces ofsecondary uranium minerals are present asisolated specks within biotite and occasionallyas narrow fracture fillings in alaskite.

Z21d. Mineralised alaskite has beenemplaced along the contact between the Chuos

and Karibib Formations. The country rockconsists of biotite-garnet schist, marble andpyritic quartzite. Two small zones ofmineralisation, measuring 180 by 12 m and 75by 18 m respectively, are present at the surface.

Z28. Mineralised alaskite is found in marbledipping 65o to 85o north, calc-silicate skarn andbiotite schist of the Karibib Formation and in redgranite gneiss. The area is largely scree covered.

Z32. Alaskite has intruded marble, biotiteschist and garnet-biotite schist of the KaribibFormation. Structurally the anomalous zone lieswithin a synform. Dips are generally steep to thesouth with the marble being strongly deformed.Traces of beta-uranophane are present in outcropand under leached exfoliated cappings. Smokyquartz is associated with the anomalous zones.Large areas are covered by sand and scree.

Z34. Alaskites occur in mixtite, pyriticquartzite and marble of the Chuos Formation.The alaskites are broadly conformable with theregional structural trend.

Figure 8: Drill section of the SK4 deposit (after Rio Tinto Exploration Company).

7.1-15


Two low grade zones of mineralisation,measuring 350 by 10 m and 275 by 10 mrespectively, were outlined by surfaceradiometric surveys (Cooke,1981).

2.1.4 The Valencia Deposit

The deposit is situated on the farm Valencia122, about 75 km southwest of Usakos. TheValencia radiometric anomaly (Anomaly 26) ismanifest on the 1968 Geological Surveyairborne radiometric map, but the significanceof the anomaly was only realised in 1973 after adetailed helicopter radiometric survey wasconducted across the area. Between 1973 and1983 exploration in the form of mapping anddiamond drilling was conducted by theTrekkopje Exploration and Mining Company.

The rocks occurring in this area are basementrocks of the Abbabis Complex and the Etusis,Khan, Rössing (referred to as Dome GorgeFormation by Labuschagne, 1979), Chuos,Karibib and Kuiseb Formations of the DamaraSequence (Fig. 9).

Grey porphyritic Salem Granite is emplacedin the Khan Formation and locally into the otherformations around the major anticlinal structure.

Vast areas in the basement inlier and thesurrounding Damaran rocks have been invadedby granitic pegmatites, generally referred to asalaskites. The alaskites are present as massivestock-like bodies, dykes of varying thicknessesand veins and veinlets which can be eitherconformable with or transgressive to the hostrock (Fig. 9).

The basement inlier represents the core of aneroded anticlinorium, which plunges to thenortheast. The surrounding limbs vary in dipfrom almost flat to steeply overfolded. Isoclinalfolding is evident on the southeastern limb ofthe anticlinorium as well as over the centralportion of the adjoining synclinorium. The latteris recumbent with both limbs dipping to thesoutheast. The uraniferous alaskite has beenemplaced on the northwestern limb of thisrecumbent synclinorium. The emplacement of

the alaskite seems to have been controlled by ayounger north-northwesterly to south-southwesterly trending anticlinal fold which cutsthrough the older folding at more or less a rightangle.

The alaskites vary in grain size from trulyaplitic, through fine- and medium-grainedphases to pegmatitic. The phases arehaphazardly intermixed. Misiewicz (1984)correlated different alaskite pulses from fourboreholes sunk at the corners of a proposedprospect shaft. He identified eight alaskitesbased on textural and other descriptive qualitiesand quantities which included uranium content.Only two of these alaskites could categoricallybe identified as separate pulses. Within each ofthese alaskites textural changes occur,suggesting additional pulses, but in only eightinstances could these be correlated over thespace of four boreholes.

The different grain size phases are usually allleucocratic, but the biotite content oftenincreases in the fine- and medium- grainedphases and also in the pegmatitic phases. Thegeneral composition of these phase types isquartz and alkali- feldspar with or withoutbiotite. Accessory minerals are tourmaline,apatite, garnet and iron- and copper sulphides.The accessories tourmaline, apatite and garnetlocally may become so abundant that they forma major constituent of the alaskites.

The conformable nature of relatively thinveins in tightly isoclinally folded schistsequences suggests a pre- or early- syntectonicgenesis. The strongly transgressive nature ofcertain dyke-like bodies may indicate a later syn-to post-tectonic history, which means that thealaskites may possibly represent two distinctperiods of intrusion (Labuschagne, 1979).Körner (1978) ascribed ages of 470 and 510million years respectively to the transgressingand conformable intrusion types.

The alaskites contain xenoliths of the hostrocks in which they were emplaced, and thesexenoliths may vary in size from tiny fragmentsto bodies several tens of metres long. They havean almost perfectly conformable relationship

7.1-16


Figure 9: Geological map of the Valencia deposit (after Gold Fields of South Africa).

with the local structure, with their strikes anddips not varying significantly from those of thecountry rock. It appears as if little tilting anddisorientation took place during emplacement

of the alaskite. However, vertical movementcannot be ruled out.

A number of basic dyke-like bodies of

7.1-17


doleritic composition occur on and around theprospect. They have dips varying from fairly flatto almost vertical, and two main azimuths, viz.north - south and southwest - northeast. Thesedykes only rarely excede a few metres inthickness.

Pneumatolitic pegmatites and quartz veinsoccur throughout the area. They are usuallyrelatively thin and short and do not formconspicuous outcrops.

The secondary uranium minerals uranophane[Ca(UO

2)

2Si

2O

7.H

2O] and uranothallite

[Ca2U(CO

3)

4.10H

2O] are present in the upper

few metres of the alaskite bodies as yellowcoatings on exfoliation planes and joints, wherethey form specks and tiny flakes on feldspar,quartz, biotite and apatite. The uraninite presentis usually fresh, with only sporadic very minoralteration rims.

Uranium mineralisation usually occurs in thefiner-grained alaskite and only occasionally inthe coarse pegmatitic phases. It has beenestablished that the degree of darkness of thequartz is usually directly indicative of therelative uranium content. A close directrelationship also exists between the uraniumand biotite content as well as between thedegree of uranium mineralisation and apatitecontent. These minerals account for the increasein total Fe, CaO and PO

4 at the expense of SiO

2,

Al2O

3 and K

2O in the alaskite (see Table 3).

Reddish-brown feldspar colouring oftenindicates a higher uranium content.

The uranium is variably distributed throughthe alaskite and in many places high-grade oreis in contact with barren or very poorly-mineralised material. However, enrichedalaskite zones are commonly found on or nearthe contacts between marble or schist xenoliths.

A feasibility study of the Valencia depositwas completed in 1989 (Kruger, 1990).

Table 3: Major element whole rock analyses ofalaskites from Valencia

Sample No. 1 2SiO

2 74.50 66.30

TiO2

0.08 0.42Al

2O

3 13.10 10.18

Fe2O

3* 1.46 5.15

FeO* 0.86 3.23MnO* 0.01 0.23MgO* 0.10 1.40CaO 0.44 5.40Na

2O 2.80 2.20

K2O 6.42 3.23

P2O

5# 0.13 4.01

CO2

0.30 0.40H2O+ 0.60 1.10L.O.I. 0.29 0.78

101.09 104.03U

3O

8(kg/T) 0.06 3.09

* biotite # apatite

Table 4: Ore reserve calculation of the Valenciaoccurrence. (after Labuschagne 1979)

Wall Block Ton Grade Total cut-off cut-off x 106 kg/t U

3O

8

kg/t kg/t kgx103

U3O

8U

3O

8

0.30 0.78 1.05 1.00 1 048 0.30 0.46 5.01 0.68 3 274 0.30 0.34 10.08 0.53 5 304 0.30 0.30 12.86 0.48 6 176 0.20 0.25 17.06 0.43 7 301 0.20 0.20 25.21 0.36 9 116 0.10 0.15 36.16 0.30 10 936 0.10 0.12 47.15 0.26 12 371 0.10 0.10 50.27 0.25 12 760

Table 5: Summary of ore and waste calculations(after Labuschagne, 1979).

Ore Grade External Internal Total Ratio t x 106 kg/t waste waste waste waste: U

3O

8 t x 106 t x 106 t x 106 ore

1) 53.1 0.22 127.7 35.0 162,7 3.1:1 2) 42.5 0.23 82.1 23.5 105.6 2.5:1 3) 30.9 0.23 54.0 15.7 69.6 2.3:1

1) pit depth = 300 m 2) pit depth = 210 m 3) pit depth = 150 m

7.1-18


2.1.5 The Goanikontes Deposit

During 1974, an airborne radiometric surveylocated a prominent radiometric anomaly alongthe western flank of the Goanikontes Dome,

which is situated immediately south of theSwakop River, some 4 km east of Goanikontes(Fig. 10). Subsequent investigation of theradiometric anomaly led to the discovery of theGoanikontes uranium deposit.

Figure 10: Geological map of the Goanikontes area.

7.1-19


The Goanikontes dome is a marginal lobe ofa larger and deeply eroded basement structurecontaining pre-Damaran rocks (AbbabisComplex) and red granitic gneiss. Thesedimentary rocks immediately surrounding thedome comprise arkosic quartzites of the EtusisFormation. The contact with the underlyingunits is transitional and of a migmatitic nature.The Etusis Formation rocks are overlain by theKhan Formation which consists of a lower dark-grey biotite-amphibolite-pyroxene schist andgneiss with intercalations of amphibolite andcalc-silicate beds. The upper unit ischaracterised by scattered quartz pebbles andgenerally has a lighter colour than the lowerunit. The Rössing Formation is not prominent inthe Goanikontes area. Various beds of restrictedlateral extent make up an alternating sequenceof diopside marble, quartzite and biotite-garnetschist (Mouillac et al., 1986).

In places the strata are intricately folded andtwo major thrusts involving large-scaledisplacement are present. The thrust faultsdivide the Goanikontes area into three domains,viz. an eastern domain occupied by the domalstructure, a central domain occupied by rocks ofthe Khan Formation and a northwestern domainunderlain by strata of the Nosib and SwakopGroups (Barbour, 1980).

The stratigraphy and structural history of thearea is complicated and was interpreteddifferently by Smith (1965) Mouillac (1976),Barbour (1980), Mouillac et al., (1986) andBrandt (pers.comm. C.P. Schreuder).

The first tectonic episode F1 of the DamaraOrogen is not well defined in this area but theinitial quartz - feldspar mobilisation is related tothis early episode. The second tectonic episodeF2 was not identified in this area. The thirdepisode F3 resulted in the major structuralframework consisting of northeast striking foldaxes with axial planes dipping to the southeast.The fourth episode F4 resulted in updoming andwas accompanied by open folding. These folds,tens of metres in amplitude, affect the rocks ofthe dome and adjacent metasediments butdecrease in amplitude with distance from thedome.

The major alaskite bodies appear to be relatedto the F4 structural episode. The alaskiteintrusions largely follow S3 foliation planeswhich were folded around the dome structureduring the upward movement. Three majorradial fractures with minor horizontaldisplacement transect the dome. One of theseconcentric fractures appears to have played animportant role in the distribution of the uraniummineralisation.

The thickness of the alaskites can vary from afew millimetres to nearly 100 m. On surface themajor alaskite dykes can be followed alongstrike for several hundred metres althoughcontinuity with depth is quite unpredictable (Fig.11). The alaskite dykes are generally concordantwith, but sometimes transgress the main S3foliation. Field evidence suggests that therecrystallisation of the alaskite occurred duringand after F4 deformation.

The uranium mineralisation in theGoanikontes area is restricted to alaskite granitesand in particular, to those of post-F3 generation.Locally, uranium may be found in calc- silicaterocks in contact with mineralised alaskite, butthis type of occurrence represents a negligibleproportion of the mineralisation.

The alaskite bodies are not uniformlymineralized. The mineralized bodies arecharacterized on surface by reddish colouringand the presence of frequent alteration rings.These comprise irregular reddish-brown rings, afew centimetres to a metre in diameter,surrounding fresh, grey alaskite, and areinterpreted as oxidation fronts affecting thealaskite and the distribution of uranium within it.Uranium occurs as erratic disseminations in rockfractures, at crystal interfaces, on cleavageplanes and cracks and as inclusions in differentminerals. There is no evident correlationbetween uranium content and texture ormineralogical composition of the alaskite.However biotite-rich zones are often morehighly mineralised than the normal alaskite.

The major mineralised bodies are restricted tothe lower part of the Khan Formation and occurwithin 400 m of the contact between the Etusis

7.1-20


Figure 11: Generalised geology of the Goanikontes deposit showing the distribution of the alaskite(after Mouillac et al., 1986).

7.1-21


and Khan Formations (Fig. 12). The amount ofalaskite decreases rapidly outward from thecentre of the dome and only a few thin dykesoccur in the upper Khan and RössingFormations.

The Th/U ratio of a typically mineralisedalaskite, with a grade in excess of 50 g/t U

3O

8,

varies between 0.05 and 2.00. The correlationbetween uranium and thorium is not linear andthe Th/U ratio decreases as uranium gradesincrease. In the 400 g/t U

3O

8 range this ratio is

between 0.05 and 0.3.

The most abundant primary uranium mineralis uraninite, but betafite is also present. Theuraninite is commonly associated withchloritized biotite in the alaskite of the lowerKhan Formation and with titanium-bearingoxides in foliated alaskite.

Secondary uranium minerals such asautunite, occur as replacements of the primary

minerals or as films and coatings alongmicrofractures. These secondary minerals arenot restricted only to near-surface zones buthave also been encountered in drill cores atdepths of more than 200 m.

The potential ore reserves have beenestimated to be several tens of millions of toneswith a low average ore grade (Mouillac et al.,1986).

2.1.6. The Ida Dome Area

Mineralisation in the Ida Dome area isconfined to the southern, southeastern andeastern side of the Ida Dome. Mineralisedalaskite occurs along the contact between theKhan Formation and marbles of the HusabFormation. Radioactivity detected is patchy overa distance of 9 km along strike, on either side ofthe Swakop River (Fig. 13).

Figure 12: Cross-section of the Goanikontes deposit based on borehole information (after Mouillacet al., 1986).

7.1-22


The alaskite is well exposed over much of itslength and at the defunct Ida Mine the width ofthe mineralised zone is about 60 m. A shaft andseveral gullies and trenches have beenexcavated in cupriferous biotite-hornblendeschists and banded gneisses of the KhanFormation, which are preserved as xenoliths inthe alaskites. The xenoliths vary considerablyfrom less than 1 m to more than 1 km in length.The alaskite has incorporated some coppermineralisation from the schists and containssmoky quartz, red feldspar and a variety ofuraniferous minerals including uraninite and

uranophane. The schist xenoliths are highlymineralized and yield scintillometer readings of3 000 cps. Readings of up to 1 700 cps havebeen recorded over the alaskite. To the north ofthe shaft the mineralisation becomes patchy.Further northwards, irregular xenoliths of redgranite gneiss have greater radioactivity than thealaskites. Younger, less radioactive red granite/aplite veins transect the alaskite. The verypatchy mineralisation persists up until a pointwhere a north-northeasterly trending doleritedyke cuts across the alaskite, 3 km north of theIda Mine.

Figure 13: Regional geology of the Ida Mine area (after Anglo American Corporation of SouthAfrica).

7.1-23


To the south of the shaft, in the direction ofthe Swakop River, the mineralisation rapidlybecomes more patchy, although the width of themineralised zone increases. South of theSwakop River mineraliation is patchy for nearly2 km, but beyond this the alaskite is moreuniformly mineralised and smoky quartz andyellow secondary minerals are widespread. Themineralised zone varies between 80 and 90 m inwidth. On the eastern side, scarn zones aredeveloped against the marbles and to the westthe mineralisation within the alaskite rapidlydiminishes.

To the west of this occurrence, towards theZebraberge, banded gneisses of the KhanFormation have been extensively invaded byalaskite dykes, several of which are patchilymineralized. The alaskite is reddish to pinkishin colour and contains irregular to more-or-lesscircular pods and patches of coarse-grainedsegregations of smoky quartz, minor feldspar,magnetite, some biotite and visible secondarygummite. The edges of these patches aremarked by iron staining. The pods vary indiameter from several centimetres to more than2 m but they are scattered and large areas ofbarren alaskite are exposed.

Biotite-schist xenoliths in the mineralisedalaskitic pegmatitic granites are normallyenriched in uranium relative to the alaskites andhave acted as precipitants or traps forradioactive minerals. Similar effectscharacterise the immediate country rocks ofmineralised alaskite. In many places the schistssurrounding the alaskite bodies are moreheavily mineralised than the intrusives fordistances of up to one or two metres from thecontacts. The presence of isolatedporphyroblasts of K-feldspar derived from thealaskite melts and abundant quartz veining inthe schists attests to metasomatic activity.

Skarn bodies are developed along the contactbetween intrusive granitic rocks with mostlyalaskite and calcareous metasediments. Theyare generally small and sporadically developed,but southeast of the Ida Dome some of themreach several hundred metres in length andmore than ten metres in width. Where the skarn

bodies have formed adjacent to mineralisedalaskite they are mineralised as well and smallamounts of gummite are visible (Jacob, 1974).

2.1.7 The Rössing Mountain deposits

A large number of radiometric anomalieshave been located immediately to the south andwest of the Rössing Mountain (Fig. 14). Theanomalies were investigated in detail todetermine their economic potential and toestablish whether a possible genetic relationshipexists between them and known base metaldeposits in this area.

Radiometric anomalies were located over avariety of lithologies of the Nosib and SwakopGroups and over red gneissic granite. Evaluationafter field investigations reduced the initial 15anomalies to only 3 namely Anomalies 3, 5 and11. These were tested by detailed geologicalmapping, surface radiometric surveys anddiamond drilling.

Anomaly 3: The northern portion of the areais essentially covered by gypsum scree, whereasthe southern area contains numerous smallexposures of isolated granitic rock and quartz-biotite schist. No uranium mineralisation wasobserved, but high scintillometer readings werefound to be associated with granitic rockscontaining smoky quartz.

Boreholes intersected mainly granite andbiotite schist with uranium grading between 10and 30 g/t.

Anomaly 5: This anomaly is located on thenorthern limb of a southwesterly- plungingsynform, consisting of marble and biotite schistof the Swakop Group. The formations strikenortheast and dip between 54o and 75 o southeast.Several zones of alaskite, varying in width froma few centimetres to about 30 m, occur parallelto the strike of the country rock.

High radiometric readings were found to beassociated with alaskite outcrops. No uraniummineralisation was observed and only isolatedoccurrences of smoky quartz are present.

7.1-24


Figure 14: Location and geological setting of the Rossing Mountain radiometric anomalies (afterRio Tinto Exploration Company).

Subsequent drilling intersected alaskite,marble and calc-silicate rocks. Average uraniumgrades recorded were 30 g/t, with high values ofup to 360 kg/t recorded over short intersections.

Anomaly 11. The uranium mineralisation isassociated with alaskite emplaced into marblesof the Rössing Formation and mixtite of theChuos Formation. No uranium mineralisationwas recognised on surface, but abundant smoky

quartz was observed in areas of highradioactivity.

A borehole drilled to a depth of 70 mintersected alaskite, marble, calc-silicate rockand mixtite. The average uranium grade wasabout 200 g/t, although short intersectionsassayed as high as 660 g/t.

The surface extent of the anomalous area

7.1-25


measures 100 by 185 m, with the southernportion being covered by desert scree and soil.

The individual deposits are associated withsmall, low-grade alaskite bodies (Cooke, 1978).

2.1.8 Minor Occurrences

2.1.8.1. The Wolfkoppe deposits

Airborne radiometric surveys indicated anumber of radiometric anomalies on the farmsWolfkoppe 105, Bergrus 94 and Tsawisis 16, inthe Karibib District.

The area is underlain mainly by quartzite ofthe Nosib Group and mixtite and marble of theSwakop Group. Alaskitic granite andtourmaline-rich pegmatites have subsequentlyintruded the bedded formations of this area.

Although some sedimentary units (especiallythe quartzite of the Etusis Formation) areradioactive, it is mainly the alaskitic granite andalaskite which show anomalous radioactivity. Inaddition, the pegmatites on Wolfkoppe 105 aredecidedly more radioactive than those furthereast on Bergrus 94 and Tsawisis 16 and averagescintillometer readings 2 to 3 times higher thanover the enclosing sedimentary strata arecommon. A number of highly radioactivelocalities have been encountered. These,however, are extremely limited in extent (1 to 2m2 or less) and at best occur within moderatelyradioactive zones which themselves are only afew tens of metres in extent.

Inspection of the promising areas has shownthat the radioactivity is caused mainly bythorium with subordinate uranium (Cooke,1977).

2.2 Granites and Gneisses

Even though the uranium occurrences in thistype of setting can be regarded as sub-economic, they contribute an important uraniumsource for the sedimentary deposits.

2.2.1 Pre-Damaran Rocks

2.2.1.1 Huab Metamorphic Complex

A radioactive anomaly was located overgneisses of the Huab Metamorphic Complex onthe farm Hochland 56, northeast of Franzfontein.The anomaly was percussion drilled and thefollowing results were obtained (Hartleb, 1980):

Table 6: Summary of drillhole results

Borehole No HL2 HL3 HL4Depth drilled (m) 40.5 44.5 28.0Metres mineralized 18.0 28.5 1.5Average grade (g/t) 150 250 133

2.2.1.2 Abbabis Complex

The basement gneissic granites and augengneisses of the Abbabis Complex are the oldestgranitic rocks of the Central Zone (Fig. 1).Outcrops of these rocks occur in the samegeneral area as the uraniferous deposits and theydisplay a higher radioactivity than averagegranites, probably due to the presence ofthorium. Values of 3 to 5 ppm U

3O

8 and 38 to 50

ppm ThO2 have been reported (Jacob et al.,

1986).

2.2.2 Damaran Granites

2.2.2.1 Red Granite-gneiss Suite

Very closely associated with the Abbabisrocks is a group of red granitic rocks (Fig. 1),which also exhibits a higher than normalradioactivity. Uranium and thorium values aregenerally of the order of 2 to 20 ppm and 10 to50 ppm, respectively, although much higherlocalised values have been recorded. The suiteconsists of gneisses, gneissic granites,leucogranites and pegmatitic granites of theRössing Mine-type, varying in age from syn- topost-tectonic. Most members of the suite arefound either below or at the level of the EtusisFormation but some intrude to higher levels. Inareas of lower metamorphic grades the red

7.1-26


granite gneiss fills ductile shear zones but isvolumetrically small, whereas in the high-gradecore of the belt around the Khan-Swakop riverconfluence this suite makes up the bulk of therocks and basement augen gneisses occur asxenoliths and skialiths.

Preliminary dating of the suite yields agesbetween 950 and 550 million years, the oldestof which may represent partial resetting ofbasement ages as a result of Damaranmetamorphism (Jacob et al., 1986).

2.2.2.2 Salem Granitoid Suite

Rocks of this suite crop out over a wide areain the Transition and Central Zones of theDamara Orogen and comprise a number ofgranitic rocks that have intruded over anextended period (Fig. 1). The suite, in mostplaces, is concordantly emplaced into synclinalstructures and normally occupies volumepreviously taken up by the Kuiseb Formation.The majority of the suite comprises porphyriticbiotite- granodiorite/adamallite. Early membersare strongly foliated and are pre-tectonic andsyn-tectonic, whereas later members appearundeformed and are post-tectonic. The youngestmembers are less porphyritic, contain more K-feldspar and are leucocratic in appearance. Inplaces the suite is anomalously radioactive andsuch areas are normally underlain by lateleucogranite. No economic concentrations ofuranium have been found in the granites but atcertain localities, superficial calcareoussediments overlying the Salem granite aremineralised, their uranium content having beenderived from the granites (Jacob et al., 1986).

2.2.3.3 Very late- to post-tectonic granites

Most of the other granitic rocks are regardedas being very late- to post-tectonic in age.Amongst this group are a number of stocks andbosses of mesocratic granodiorite. These bodiesyield a very low level of radioactivity, cut acrossfold structures and also deform the countryrocks.

Numerous other bodies of post-tectonicgranite occur, including the red homogenousgranite, the Bloedkoppie Granite, which is thesource rock for the Langer Heinrich superficial-uranium deposit, the Sorris Sorris granite andseveral others not yet named. The largest bodyof post tectonic granite in the Damara Belt is theDonkerhuk Granite which is emplaced along andimmediately south of the Okahandja Lineament.

Vast amounts of pegmatite are associatedwith this muscovite-bearing Donkerhuk Granitewhich has a relatively low uranium content.Values of less than 5 ppm U

3O

8 and between 20

and 90 ppm ThO2 have been recorded. The

granite has tentatively been dated at 528 ±7million years (Jacob et al., 1986).

2.2.3 Post Damaran Rocks

2.2.3.1 The Erongo

As a result of an airborne radiometric survey,anomalous radioactivity was detected at thewestern corner of the farm Omandumba West137 and at the common boundary of the farmsOmandumba West 137 and Anibib 136, in theOmaruru District (Fig. 15).

Figure 15: Simplified geology of the ErongoProspect (after Trekkopje Exploration).

7.1-27


The anomalous areas are underlain by whiteto pinkish granite of the Erongo Complex. Thegranite is medium to coarse grained, commonlycontains biotite and nests of black tourmaline,and in places displays a pegmatitic phase.

Ground radiometric surveys on thesouthwestern anomaly revealed erratic uraniummineralisation and localised highly radioactivezones (up to 380 g/t U

3O

8) associated with

jointing. The set of joints is vertical tosubvertical and commonly strikes northeast -southwest. Percussion drilling confirmed theclose correlation between joint zones andmineralisation, however, there is a decrease inmineralisation below 30 m (Bertram, 1981).

2.3 Mineralisation associated with pegmatitesand quartz veins

2.3.1 Pre-Damaran Rocks

Small specks of a yellow uranium mineralhave been were detected in a zoned pegmatite inthe lower Fish River area, southern Namibia(Anon., 1967).

2.3.2 Damara Sequence

2.3.2.1 Auris

The Auris grant area is situated ±60 km westof Khorixas. A regional radiometric surveydelineated anomalies on the southern part of thefarm Austerlitz 515. The geology of the areaconsists of folded metasedimentary rocks of theDamara Sequence which are overlain bysediments of the Karoo Sequence. Thedominant structural feature in this region is theeast - west trending Austerlitz anticline (Fig.16).

The radiometric anomalies are situated onthe northern and southern limb of the anticline.On the northern limb, the mineralisation ishosted by iron oxide-stained quartz- and calciteveins which occur within dolomitic limestonesof the Karibib Formation. Chip samples takenfrom this area assayed between 500 and 1 000

ppm U3O

8 and 30 ppm thorium. The limestone

anomaly is 10 by 60 m in outcrop and thereserves calculated for this area are 16 000 t at agrade of 300 g/t U

3O

8.

The anomaly on the southern limb is situatedin feldspathic quartzites of the KuisebFormation. It is 13 by 30 m in size and thecalculated reserves are 10 000 t at 200 g/t U

3O

8

and 5 000 g/t thorium (Quoix, 1980).

2.3.2.2 Minor Occurrences

Quartz-flourite veins at the Husab Mine areradioactive and occur as an en echelon set oflenses and dykes over a distance of 4 km,northeast and southwest of the Husab Mine.Field relationships suggest that both fissure-filling and replacement processes have occurred.The veins are associated with certain zonedpegmatites but the relative ages are difficult todetermine. Patchy uranium mineralization wasdeposited with flourite (Jacob, 1974).

Chip samples collected from a pegmatite inthe Otjimbingwe area assayed up to 324 g/t U

3O

8

(Bothe,1981).

In the Horebis area, 100 km east ofSwakopmund, a pegmatite assayed averagevalues of 445 g/t U3O8 and high values up to675 g/t U

3O

8 (Pienaar, 1975).

North of Usakos, on the farm Davib Ost 61,values of up to 7 370 g/t U

3O

8 were recorded

from a pegmatitic rock (Hiemstra, 1968).

A zoned pegmatite, containing radioactiveminerals, forms a conspicuous hill 3 kmnorthwest of the Husab Mine. The radioactivemineralisation occurs in the wall zone, whereyellow secondary minerals, smoky quartz andred feldspar are found in areas which yieldscintillometer readings of more than 1 000 cps.The wall zone is not uniformly mineralised.Secondary uranium minerals occur alongfracture planes and as thin films on crystals inother parts of the pegmatite (Jacob, 1974).

Three kilometres east-southeast of the

7.1-28


western corner of the farm Modderfontein 131in the Usakos District, a large zoned pegmatitewith a northwesterly trend is developed. Thispegmatite is several hundred metres in lengthand about 20 m in width. A wall zone, twointermediate zones and a quartz core arerecognizsable. Small patches of smoky quartzcontaining radioactive minerals occur in theintermediate zone near the core wherescintillometer readings have recorded 1 000 cps.Small amounts of beryl and minor amounts ofcalcite are present in this pegmatite.

The Bloedkoppie Granite, southeast ofLanger Heinrich, contains many narrow zonedpegmatites. Close to the cores of the narrowpegmatites, concentrations of magnetite occur,together with reddened feldspar and smallamounts of secondary uranium minerals. Thegeneral trend of the pegmatites is east to east-southeast and many of them are more highlyradioactive than the Bloedkoppie Granite itself,which produces count rates almost three timehigher than the surrounding Tinkas Formationand pegmatites of Donkerhuk type (Jacob,1974).

Figure 16: Simplified geology of the farm Austerlitz 515 (after Geological map of Damara Orogen1:500 000).

7.1-29


Several layered pegmatites occur in thevicinity of the Gawib valley between the LangerHeinrich Mountain and the BloedkoppieGranite. Local low-order anomalies wererecorded over some of the pegmatites, generallybetween 90 and 120 cps, but in one place, up to250 cps were recorded (Jacob, 1974).

3. Pedogenic Occurrences

An overlap between these and primarydeposit types exists as the decomposition ofprimary alaskite by weathering producespedogenic deposits. Most of the primarydeposits have associated with them a zone ofsupergene enrichment which in places containsmore uranium than the primary source. Thetransport mode and distance travelled of theliberated uranium therefore determine if adeposit can be classed as a sedimentary orpedogenic.

3.1 The Mile 72 deposit

The Mile 72 uranium occurrences aresituated immediately east of the coastal roadapproximately 100 km north of Swakopmund(Fig. 17). The topography in this area is slightlyundulating with dolerite sills, dykes and quartzveins forming positive erosional features.

The basement metasedimentary rocks belongmainly to the Khomas Subgroup and consist ofmarbles, metaquartzites, calc-silicates andschists, into which various granites such as thesyntectonic Salem Granite and post-tectonicpegmatites and alaskites were intruded. Primaryuraniferous minerals such as uraninite andbetafite, as well as monazite and apatite, occurmainly in the alaskite. The thin veneer ofTertiary to recent surficial material overlyingthe basement rocks consists of aeolian sand,isolated remnants of fluvial gravel and desertsoil, all of which have been cemented bygypsum and to a lesser extent by halite andcalcite. The secondary cementing mineralsextend down into the basement rocks, fillingjoints, fissures and cleavage planes.

A ground radiometric survey indicated thatanomalous radiation was confined to a granitearea and its contact zone towards the northernboundary of the original grant area. It was foundthat the radiation was caused by carnotite andsubordinate uraninite, possibly leached out ofthe underlying granite. The upper 50 to 100 cmof the bedrock formations are intensely crackedand gypsum after calcite is present in abundancein these openings, including the foliation andcleavage planes. Carnotite has been precipitatedin the gypsum veins by evaporitic processes.Selective samples of uraniferous gypsumanalysed as high as 50 kg/t U

3O

8, although large

tonnages would probably average less than 50 g/t.

Regional and detailed radiometric surveysindicated about 8 anomalies in the area. Theuranium mineralisation was found to be patchyand occurs in several pockets associated withmetasediments, granite and dolerite. Secondaryminerals, such as carnotite (the dominant phase)and minor amounts of phosphuranylite[Ca(UO

2)

3(PO

4)

2.6H

2O], occur principally above

the water table. Phosphuranylite is closelyassociated with apatite.

Potential ore bodies of irregular shape anderratic mineralisation were delineated (Fig. 18).One specific occurrence in metasediments variesfrom 1 to 30 m in width and extends to 18 m indepth. Trenching operations indicated that theuranium mineralisation occurs near the contactbetween calc-silicates and schists in associationwith quartz veins and alaskites. Themetasediments are deeply weathered in placesand replaced by crystalline and powdery gypsumand carnotite. Alaskites within this zone tend tobe more radioactive than those occurring in less-weathered material. However, this could becaused by either primary or secondaryenrichment (Hambleton-Jones, 1984).

Estimated ore reserves of the best-mineralised zones are 386 000 t U

3O

8 averaging

230 g/t (Labuschagne, 1976).

7.1-30


Figure 17: General geology of the Mile 72 area (after General Mining and Finance Corporation).

7.1-31


4. Sedimentary Occurrences

4.1 Syngenetic Occurrences

4.1.1 Karoo Sequence

4.1.1.1 The Engo River Occurrence

The Engo Valley is situated along thenorthern Kaokoland coast in the extremenorthwest of Namibia. The prospect area liesapproximately 200 km north of Möwe Bay tothe north of the defunct Angra Fria RadioStation.

A radiometric survey detected uranium onthe eastern flank of the Engo river valley.

The succession of rock types found in theEngo Valley consists of rocks of the DamaraSequence which are unconformably overlain byKaroo Sequence rocks.

The Damara Sequence in this area comprisesschists, gneisses and calc-silicate rocks whichare considered to be the equivalent of theKuiseb Formation in central Namibia. Therocks are highly metamorphosed and

structurally complex. The Kuiseb Formation isintruded by numerous small irregular bodies ofsyn- and post-tectonic granites, with a highradioactive response. Large post-tectonic graniteintrusions occur on the western flank of theEngo Valley. These granites are thought to be thesource of the uranium mineralisation in the area(Fletcher 1981).

In places the Damaran basement isunconformably overlain by sedimentary strata ofthe Karoo Sequence. The basal DwykaFormation consists mainly of tillite, shale,pebbly shale and lenses of conglomerate, grit,marl, mudstone and sandstone (Fig. 19).

The coarse clastic material has a black, denseargillaceous matrix, but this becomes arkosic inplaces, whereas the medium-to -large pebbleconglomerates generally have an arenaceousgrey matrix. Pebble sorting varies from poor tofairly good. The pebble sizes range from 3 mmin diameter to large cobbles and boulders, wherethe polimictic pebbles and boulders are generallysubangular (Fletcher, 1976).

The individual rock units in this successionare generally lensoid and discontinuous.

Figure 18: Radiometric profile showing irregular mineralisation of the Mile 72 deposit (afterGeneral Mining and Finance Corporation).

7.1-32


Figure 19: Lithology and stratographic subdivision of sediment in the Engo Valley (after GeneralMining and Finance Corporation).

Detailed field studies have suggested a possiblefluvio-glacial to lacustrine depositionalenvironment.

The overlying Engo Formation of the EccaGroup is made up of a succession of pinksandstone, mudstone, shale and marl. The

presence of concretions throughout virtually theentire succession is diagnostic. A prominentsandstone containing concretions up to onemetre in diameter near the middle of thesuccession serves as a useful marker horizon.

A number of sporadic prominent radiometric

7.1-33


anomalies have been recorded in the valley overa distance of some 20 km (Fig. 20). Follow-upground radiometric surveys delineated fouranomalous areas, termed D1, D2, D3 and the“main uranium occurrence”.

No direct correlations between anomalies andlithologies could be established. However, theuranium mineralisation was found to beconfined to the Dwyka and Engo Formation ofthe Karoo Sequence.

Figure 20: Geological map of the Engo Valley area (after General Mining and Finance Corporation).

7.1-34


In the Dwyka Formation, discoformity-typeuranium mineralisation occurs in fluvio-glacialalluvial fan-type deposits. At the “mainoccurrence” (Fig. 20) visible uraniummineralization (carnotite) is disseminated in thecoarse clastic strata of the Dwyka Formation.The black shale of the Dwyka Formationcontains large amounts of sulphides, mainlypyrite. The general uranium background contenttends to be higher in this unit than in otherlithotypes. In the shale band of the middleEngo Formation the uranium occurs as veryfine-grained uraninite associated with pyrite andchalcopyrite.

The ore reserves calculated for twomineralised zones termed M.U.O. (MainUranium Occurrence) and D1 Extension Northare as follows:

M.U.O. 3.20 million t at 331 g/tD1 2.48 million t at 352 g/tTotal 5.68 million t at 34 g/t

The grade within the mineralised zones variesgreatly over small distances. Therefore thewhole mineralised section would have to bemined to take out patches of high grade ore(Fletcher, 1981).

4.1.1.2 The Huab deposit

In 1976 the General Mining and FinanceCorporation conducted an airborne radiometricsurvey over the area north of the Doros Crater.The area covered comprises of the farmsTwyfelfontein 534, Verbrande Berg 725 andProbeer 535. A number of radiometric anomalieswere detected and these were subsequentlyinvestigated (Fig. 21).

Horizontal beds, mainly of the KarooSequence, unconformably overlie folded schistand dolomitic marble of the Damara Sequence.The sedimentary formations of the KarooSequence have been intruded by numerousdolerite dykes and sills, and are capped covered

Figure 21: Simplified geology of the Huab area showing outcrops of the uranium-bearing strata(after Hartleb, 1979).

7.1-35


by several hundred metres of lava flows of theEtendeka Formation.

The Prince Albert Formation is the lowestunit of the Karoo Sequence in the area. Itconsists of an occasional basal breccia whichfills depressions on the eroded Damaransurface. The breccia is succeeded by shales witha total thickness of 70 m. The shales consist of35 m of black shale at the bottom, overlain by10 m of white shale and an upper 25 m ofvaricoloured shale.

The upper Prince Albert Formation consistsof the Draaihoek Sandstone Member, whichcontains intercalations of impure, sandy andconcretionary sandstone. The member is usually8 to 15-m-thick and serves as a useful markerhorizon. The upper 1 to 2 m of the DraaihoekSandstone are calcareous and uranium-bearing.

The Probeer Formation overlies theDraaihoek Sandstone Member and it consists ofan alternating sequence of limestone, shale andmarl. The basal portions are made up of about 8m of grey and blue impure shale and claystone,overlain by a hard, 2-m-thick limestone bed,containing calcareous concretions up to 25 cmin diameter. This unit is overlain by 8 m ofshale which are topped by alternating bands ofgrey, dark yellow, brown or purple limestone.The uppermost limestone bed varies inthickness from 1.0 to 3.6 m and is uranium-bearing. The uraniferous limestone is overlainby a “disc limestone” consisting of 30-cm-longlimestone discs and lenses, which are containedin a purple gritty matrix. The “disc limestone”also contains uranium and serves as a markerhorizon.

The succeeding Gai-As Formation consistsof a rapidly alternating succession of red-bedsequence, purple siltstone and shale beds. Inplaces, conglomerate intercalations aredeveloped in the siltstone. The red-bedsequence is capped by at least 5 m of softpurple, red or blue shale. Concretions ranging indiameter from 0.5 to 2.0 m are developed inshaley units near the base of the Gai-AsFormation.

The aeolian sandstone of the Etjo Formationoverlies the Gai-As Formation. The massivesandstone is pinkish to yellow in colour anddisplays bedding. In places, reworking of thesandstone by flowing water is evident (Hartleb,1979).

Geological mapping and ground radiometricsurveys have revealed a stratigraphic control onthe mineralisation. Two uraniferous lithologicalunits have been recognised. These are the“uranium sandstone” of the Draaihoek Memberand the “uranium limestone” at the top of theProbeer Formation (Fig 21). However, withinthese units the uranium content variessignificantly.

Ground radiometric responses over theuranium sandstone were encouraging. However,the results of the follow-up geochemicalsampling revealed lower equivalent values thanthose expected. Subsequent statistical analysison the data indicated that the uranium is indisequilibrium with its daughter products; i.e.the radioactivity was mostly caused by daughterproducts. Only four samples contained morethan 100 g/t U

3O

8 and the highest recorded value

was 138 g/t. The 1-50 g/t anomaly covers anarea of 0.3 km2 at an average grade of 92 g/t.The mineralisation in the uranium sandstone wasfound to be confined to numerous small isolatedpatches within the top layers. The combinedtonnage of these patches, of which only a fewexist, is less than 1 000 t at a grade well below100 g/t.

All anomalous uranium occurrences withinthis limestone are confined to an areaimmediately west of the farm Probeer 535 andabout 10 km north of the Doros Crater.Mineralisation is very erratic and the gradevaries. Averages are given below in Table 7.

Table 7: Average grade of limestone-hosteduranium mineralisation

U3O

8 Area Thickness Average Tonnage

ppm km2 cm Grade g/t mt + 50 2 580 106 122 6.833 +100 0.234 92 198 0.539

7.1-36


The mineralisation in both the above settingsis confined to palaeochannels within asedimentary basin. The expected source of theuranium is granite, from which it wastransported in the solid state. No uraniumminerals were observed even in a sampleassaying 600 g/t U

3O

8 (Hartleb, 1979).

4.1.2 Offshore Marine Deposits

A series of offshore marine basins, filledwith diatomaceous muds, is situated on theNamibian continental shelf (Fig. 22).Bathymetric and echographic techniques wereused to map the area from latitudes 19o00’S to25 o 30’S, extending some 100 km offshore.

The shelf was found to have a smoothgradual slope from a depth of 50 m at 10 kmoffshore to a depth of 150 m at 70 km offshore.No relationship was found to exists between themorphology of the shelf and the distribution ofthe diatomaceous muds (Meyer, 1973). Fourbasins with a total areal extent of 19 000 km2

and a maximum depth of 15 m were identified.The largest basin is centred off Swakopmundand lies between 21 o 00’S and 24 o 00’S. Apalaeo-submarine channel of the Swakop Riverforms a protrusion normal to the strike of thebasin. Two boreholes (SWA 30 and SWA 50)have been drilled in this area (Fig. 22).

The diatomaceous mud from the basins isolive green in colour with slight colourvariations causing laminations. The mud iscomposed of skeletal diatoms, organic matter(19% - 40%), terrigenous constituents (6% -34%) (Calvert and Price, 1970) and water (77%- 93%) (Meyer, 1973). Below the diatomaceousmud are silty to sandy layers and fossil shelllayer containing gastropods, lamellibranchs andshark teeth (Meyer, 1973). Palaeontologicalinvestigations date the muds to be of Holoceneage, but the lower fossil shell layer is latepleistocene (Hambleton-Jones, 1983). Forfurther information see also the diatomite andphosphate chapters.

The uranium values recorded from boreholesamples vary between 15 g/t to 45 g/t (Fig. 23).

The highest uranium concentrations in thesubmarine basins are situated opposite palaeo-and recent river mouths (Fig. 22). South ofWalvis Bay these are off old choked rivermouths of the Tsondab and Tsauchab Riversrespectively and north of Walvis Bay, the highesturanium concentrations lie opposite the Kuiseb,Swakop, Omaruru, Ugab, Unjab and HoanibRiver mouths (Hambelton-Jones, 1983).

Figure 22: Offshore uranium occurrences (afterHambleton-Jones, 1983).

7.1-37


4.2 Epigenetic Occurrences

4.2.1 Karoo Sequence

A coal sample from a drillcore from theOvambo Basin assayed 2530 g/t U

3O

8 (von

Backström, 1968).

4.2.2 Tertiary occurrences in the Namib Desert

Surficial uranium deposits in Namibia occuron the coastal plain of the Namib Desert, mainlybetween the Great Escarpment in the east andthe “western cutoff line” in the west (Fig. 24).The deposits are associated with fluviatileenvironments within palaeovalleys of ancientrivers that flowed westwards from the GreatEscarpment during Upper Cretaceous andLower Tertiary times (88 to 25 million years).

Climatically the Namib Desert is extremelydry, and all of the major surficial uraniumdeposits occur within the 100 mm isohyet. Thearid environment has preserved these uraniumdeposits.

Uranium in the Namib Desert occurs chieflyin the form of the mineral carnotite, but soddyite[(UO

2)

5Si

2O

9.6H

20] has also been reported from

the Welwitschia Flats occurrence. Carnotiteoccurs interstitially along grain boundaries,filling cavities and has maximum developmentin zones of high porosity.

The age of the uranium mineralisation isdifficult to establish, but determinations usingthe disequilibrium technique indicate that it isgreater than 0.5 million years. However,geological relationships suggest that an UpperTertiary age (2 to 5 million years) is more likely(Hambleton-Jones 1983).

Numerous secondary uranium deposits occurin this area and to facilitate the description of thedeposits they have been divided into 3geographic regions (Fig. 24): 1. the Namib ParkRegion which covers the area between the

Figure 23: Uranium content in boreholes (afterHambleton-Jones, 1983).

Figure 24: General map of the Namib indicatinggeographic regions and sedimentary uraniumdeposits.

7.1-38


Swakop River in the north and the Kuiseb Riverin the south; 2. the Spitskop Region whichcovers the area between the Omaruru River inthe north and the Swakop and River in the southand 3. the Brandberg Region which covers thearea north of the Omaruru River.

4.2.2.1 The Namib Park Region

An overview of the Namib Park Region isgiven in Fig. 25.

Figure 25: Uranium occurrences in the Namib Park region.

7.1-39


4.2.2.1.1 The Langer Heinrich Deposit

The Langer Heinrich grant area is situated inthe Gawib River valley on the southern side ofthe Langer Heinrich Mountain, 90 km east ofSwakopmund.

Carnotite was first discovered in the Gawibvalley, 90 km east of Swakopmund by A.H. vonStryk in the late 1950s and the radioactivity inthe area was confirmed by J. Klein. However,no active prospecting has been undertaken.

An airborne radiometric survey located alinear radiometric anomaly in the Gawib Rivernear the Langer Heinrich Mountain.

The lowermost rocks of the DamaraSequence outcropping in this area are pinkquartzites of the Etusis Formation, Nosib Group.The quartzites form the Langer Heinrichanticlinorium, which is a major structure in thisarea (Fig. 26). Unconformably overlying thesequartzites are rhythmically interbedded fine-grained metapelite, metagreywacke andcalcsilicate beds of the Tinkas Member (KhomasSubgroup).

Figure 26: Generalised geological map of the Langer Heinrich area (modified after Jacob, 1974).

7.1-40


The orogenic Salem Granite has intruded themetasediments and covers large areas north ofthe Langer Heinrich Mountains. Southeast ofthe mountains, the Bloedkoppie Granite, whichis a leucocratic late to post-tectonic member ofthe Salem Granite Suite, has intruded the meta-sediments and covers an area of about 25 km2.The Bloedkoppie Granite is medium grainedand consists of quartz, microcline andplagioclase with about 5% biotite. On average itcontains 10 to 15 g/t U

3O

8 and values up to 100

g/t U3O

8 have been measured radiometrically.

The Bloedkoppie Granite is of the same age asthe alaskites and may be genetically related tothem.

The Langer Heinrich valley is a portion of a13-km-long east-west trending palaeochannelwhich transects the Bloedkoppie Granite in theeast, and the Khomas Schist in the central andwestern parts. The northern bank of thepalaeochannel is formed by the NosibQuartzites.

Climatic changes, which probably occuredduring the Tertiary, led to a switch fromerosional to depositional conditions. During theonset of the depositional cycle the palaeo-morphology of the channel was very rugged andformed a constriction between the LangerHeinrich Mountain and the Schieferberge in thesouth. Calcrete terraces within the LangerHeinrich valley indicate an original sedimentthickness of 60 m and a channel width rangingfrom 200 to 1000 m. However, subsequentheadwater erosion in the central and easternportions of the paleochannel by the Tinkas andGawib rivers removed 30 to 40 m of theoriginal sediment. In the Langer Heinrich valleythe sediments are only exposed in a few places,being mostly covered by 1 to 3 m of scree.

Bedding of the fluvial sediments within thepalaeochannel is sharp and lenticular.Crossbedding is present, with vertical lithologychanges being rapid and irregular. Sorting ispoor to moderate and there is a general upwardsdecrease in grain size. The characteristicsediments are siltstones, conglomerates andbreccias with either a silty or calcareous matrix.Sedimentation normally began with a basal

conglomerate or breccia, followed by analternation of siltstone, conglomerate, brecciaand calcareous arkose. The beds vary from a fewdecimetres to a few metres thick. Towards thetop, calcareous arkose (calcrete) becomes amajor component (Hartleb, 1988).

The mineralisation is hosted by fluvialsediments of the palaeochannel (Figs 27 and 28).

Figure 27: Horizontal projection of mineralisedareas (after General Mining and FinanceCorporation).

7.1-41


It is confined to several thin tabular bodiesalong the length of the palaeochannel and isgenerally situated a few metres above thebottom of the channel fill. In vertical sectionthere is only one ore-bearing zone which hasirregular gradational hangingwall and footwallcontacts. The grade of mineralisation tends tobe higher in the centre of the zone.Mineralisation is not controlled by lithology andoccurs throughout the different sediment types.The mineralisation extends westwards, crossesthe northward-flowing Gawib River andcontinues under the recent sediment cover for2.5 km.

Yellow carnotite is irregularly distributedthroughout the uraniferous sediments. It occursas small patches and lenses, around pebbles andin cracks and may be finely disseminated in thehost rock.

The poorly calcium-cemented sandy gritstend to contain the highest grades ofmineralisation. Carnotite is concentrated inirregularly shaped calcium-carbonateconcretions in the silty sediments. Carnotitespecks, up to 2 mm in diameter are irregularlydistributed within the calcium-carbonate matrix(Hartleb, 1988).

Figure 28: Diagrammatic cross-sections showing the relationship of the mineralised calcrete tobedrock, terraces and fans at Langer Heinrich.

Table 8: Ore reserve calculation of the Langer Heinrich occurence (after Linning, 1976)

Area Tonnage Grade Overburden Ore Overburden Probable Grade kg/t width (m) width :ore depth ext. kg/t

(m) tonnageI 7 729 687 0.44 6.64 7.39 1:1.19 1 553 125 0.438II 10 050 000 0.46 5.28 5.94 1:1.13 853 125 0.527III 4 931 250 0.30 6.90 8.05 1:1.2 681 250 0.389IV 11 575 000 0.30 10.38 6.34 1:0.61 1 250 000 0.304V 11 000 000 0.33Total 35 285 937 0.36 4 337 500 0.409

7.1-42


Ore reserves were calculated for the differentareas and are presented in Table 8. The grade ofthe ore decreases and the overburden ratiosdecrease from west to east.

The geometry of the deposit and the ore tooverburden ratio are such that the most feasiblemining method envisaged would be by ashallow opencast operation. An alkaline leachprocess was proposed because of the highcarbonate content of the ore (Linning, 1976).

4.2.2.1.2 The Tubas Uranium deposit

The Tubas deposit is situated along theTumas River some 40 km east of Walvis Bay.The deposit was located during explorationconducted over the Tubas Grant (Fig. 25).

Anomalous zones were located in thesouthern part of the grant which is transected bythe westwards-flowing Tumas River. T-cupsurvey anomalies were percussion drilled andthis located secondary uranium mineralisationassociated with the palaeochannel of the Tumasvalley.

The Tumas valley is in excess of 40-m-deepand the rock types occupying the palaeovalleyconsist of red to brick-red sand or sandstone,grits, conglomerates, gypsum and calcrete. Redsands occur up to 10 m below surface. Calcretesof ranging shades are present below the redsands. Within the calcretes are looselyconsolidated grits and gravels (Fig. 29).

Uranium mineralisation in the Tumas Riverdrainage is present mainly in tabular bodies ofthe upper 20 m. The mineralisation is

Figure 29: Plan showing drillhole positions in the Tubas River area (after Anglo AmericanProspecting Services).

7.1-43


predominantly associated with red sands butvalues in excess of 100 g/t have also beenrecorded from calcretes and gravels.

Carnotite occurs as yellow specks andstreaks, or coats worm burrows or shrinkagespaces around larger clasts. Traces of uraniumhave also been identified in refractory heavyminerals.

Anomalous U3O

8 results have been

intersected in 41% of the boreholes drilled inthe Tumas River (Fig. 30). These values rangebetween 50 to 200 g/t. The highest individualassay result recorded was 951 g/t U

3O

8 over one

metre, some 11 m below surface. The sameborehole returned an average value of 639 g/tU

3O

8 over three metres.

A preliminary estimate of the results of thisprogramme indicated 130 million t at 90 g/tU

3O

8 over an average thickness of 7 m with an

average overburden of 3 m.

An additional percussion-drill programmewas conducted over selected small areas andconfirmed the gypsiferous red sandstone as themain host for mineralisation. Higher gradeswere also indicated with values in excess of 1000 g/t U

3O

8 being returned from boreholes on

three of the twelve lines drilled. The singlehighest assay was 8 177 g/t over 1 m (Wagener,1977b).

Pitting and trenching in selected areasindicated extreme variability of mineralisationover small areal separations of ±2 m. During thelater phases of exploration, metallurgical testswere undertaken on the ore but the unfavorableuranium market led to the termination ofexploration activities (Wagener, 1983).

4.2.2.1.3 Oryx

The Oryx Grant area is situated in the NamibDesert Park, 70 km east of Walvis Bay (Fig.25).

Rocks of the Damara Sequence overlie redgranite and metasedimentary rocks of the

Abbabis Formation, which form dome-likestructures in the western part of the grant area.The Damara Sequence is represented byquartzites, biotite gneisses and conglomerates ofthe Nosib Group in the west and the ChousFormation and Tinkas Member of the SwakopGroup in the east. The Swakop Group rocks areintruded by a north-south trending oval-shapedmass of post tectonic granite.

The grant area is characterised by northerly-tonortheasterly-trending structures. Folding hasproduced large-scale basin-and-dome structuresas well as smaller isoclinal folds. The majoraxes and plunge directions of the fold structuresparallel the regional fabric of the area.

Two anomalies termed OA and OB weredefined by the initial exploration programmeand subsequent follow-up surveys focused onthese areas (Fig. 25).

Anomaly OA is covered by superficialdeposits of alluvium, residium, calcrete andgypsum. The area is bounded in the east byoutcrops of the Tinkas Member and in the westby red granite gneisses of the AbbabisFormation. Projecting through the surficial coverare numerous small outcrops of pegmatite andmarble. A radiometric survey defined anorthwesterly-trending anomaly over surficialmaterial. The anomaly is defined by a 20 g/tU

3O

8 isoline and contains areas of higher values

which peak at 80 g/t U3O

8.

Soil samples were analysed for U3O

8 and

ThO2 and anomalies of these were found to

coincide with the total-count radiometricanomalies. In the eastern part of the detailed gridonly, U

3O

8 anomalies occur and are due to the

presence of secondary uranium in calcrete andgypcretes. Uranium anomalies were defined asbeing greater than 25 g/t U

3O

8, with the highest

value recorded being 137 g/t U3O

8. Thorium

anomalies are defined by the 30 g/t ThO2 isoline

and peak in the western part of the grid at 127g/t ThO

2.

Anomaly OB is covered by alluvium,calcrete, gypcrete and scree, through whichfrequent outcrops of Tinkas Member schist,

7.1-44


Figure 30: General stratigraphic column of the Tubas secondary uranium deposit (after AngloAmerican Prospecting Services).

7.1-45


Chuos Formation mixtite and Nosib Groupquartzite protrude. The eastern part of thisanomaly is underlain by late tectonic granite.Structurally the area is complex with fold areastrending both east-west and north-south.

Two anomalies were defined by aradiometric survey. The first measures 300 by130 m with a peak value of 180 g/t equivalentU, and is located over weathered outcrop ofTinkas Member schist. The second anomaly is400 by 60 m in extent and is located oversurficial sediments. It has a peak value of 90 g/tequivalent U.

An assessment of all results led to the shift ofexploration emphasis towards secondaryuranium mineralisation in the Tumas drainageand its tributaries.

A drilling programme located secondaryuranium mineralisation in the calcrete andgypcrete surficial sedimentary deposits. Themineralisation consists of sporadic anomalousU

3O

8 which occurs at variable depths and is

confined to the palaeochannel.

Metallurgical testwork on selectedpercussion-drill samples indicated that wetscrubbing could upgraded the secondarymineralization (Marsh, 1984).

The anomalies associated with the TumasRiver were found to extend southwards into amajor tributary channel and the Oryx ExtensionGrant was subsequently taken out to investigatethese.

Six small weakly-mineralised areas coveredby 6.2 m of overburden were delineated. Theyindicated approximately 8 000 000 t U

3O

8 at a

grade of about 140 g/t (Bothe, ca. 1975).

4.2.2.1.4 Tumas Deposit

The Tumas grant is situated 70 km due eastof Walvis Bay and covers a portion of theNamib Desert Park (Fig. 25).

The area is underlain mainly by biotite

schists, quartzites, meta-greywackes, marblesand silicates of the Tinkas Member of theKaribib Formation. The rocks have beenintensely folded and locally have a north-northeast - south-southwest strike and steepdips. Intrusive Salem type granites andpegmatites occur mainly in the west. Karoo agedolerite dykes have intruded parallel to theregional foliation trend of the Damaranmetasediments.

Aeromagnetic surveys located one major andthree other significant anomalies. A detailedblock, termed Block A, was designed to coverthese anomalies.

Block A is situated in the northeastern part ofthe grant area. A marked ridge of TinkasMember metasediments on the westernboundary of the grant has given rise to arestriction in the east-west drainage resulting inonly one outlet to the west. This has resulted in adamming effect to the east and sedimentation ofmainly calcareous lithologies took place withinthe palaeochannels (Fig. 31).

The calcareous grit is a mature sedimentcontaining grains of rounded to sub-angularquartz and feldspar cemented by calciumcarbonate. Clasts of Damaran metasediments

Figure 31: Simplified geology of the Tumasdeposit (after Falconbridge of SWA).

7.1-46


and Karoo dolerites are rarely present. The rockis very similar to the Langer HeinrichFormation found at the Langer Heinrich deposit.Carnotite mineralisation is generally sparselydistributed although rich patches associatedwith smoky quartz grains grade up to 510 g/tU

3O

8.

An immature brown calcareous siltstone,containing greater amounts of angularfragments and a higher percentage of maficminerals, is considered to be younger than thecalcareous grits described above. It is cementedby calcium carbonate and its brown colouring isdue to the weathering of mafic minerals.

It crops out over an area of some 700 by 150m, but radon cup surveys have indicated that itmay extend for a further 1 000 m within thesand-filled present Tumas drainage system.

The rock is consistantly mineralised acrossthe outcrop and carnotite occurs as cavity-fillsand also as a finely disseminated phase. Thegrades vary between 315 and 770 g/t U

3O

8.

Surficial sands cover most of the plains inBlock A. Calcretisation of these sediments hasoccurred and concretionary calcretes form acontinuous capping beneath the sand-coveredareas.

Gypcretes form the youngest of thesediments and occur as cements in river gravelsand sedimentary breccias. Gypsiferoussedimentary breccias were found to contain upto 60 kg/t U

3O

8 (Borton, 1977).

Five mineralised zones were detected withinthe northern channel. The zones correspondwell with the palaeochannel which has beendissected by metasedimentary barriers. Thethickness of the palaeochannel varies between 1and 15 m, averaging 10 m, whereas thethickness of the mineralisation itself variesbetween 1 and 5 m, averaging 3.2 m. Thegrades are constant and average 200 g/t U

3O

8.

The southern channel is far more consistentlymineralised and presumably formed the mainpalaeochannel. Thicknesses of calcretized gritty

fluvio-sediments vary between 1 m and >20 m,averaging 12 m. The thickness of mineralisationis also variable between 1 m and 11 m with anaverage of 3.5 m. The grade averages 260 g/tU

3O

8. However, a high-grade area containing

approximately 1 million t at 560 g/t is present inthe south of the southern channel.

The total reserves of the Tumas deposit havebeen estimated at 13 million t at an averagegrade of 244 g/t U

3O

8 (Ransom, 1981).

The southern channel extends eastwards intothe Namib Park II grant area (Fig. 25). The areahas been covered by a 1 by 1 km T-cup grid anda 0.5 by 1 km soil sample grid. Anomalous areaswere then covered by a detailed T-cup grid.

The reserves calculated are presented in Table9.

Table 9: Ore reserve calculation of the NIIWDEarea (after Kotze, 1978)

Cut-off Tonnage Grade Overburden grade g/t (tons) (g/t) 100 30 201 200 237 20 887 600 200 8 617 600 352 20 887 600 300 8 617 600 466 19 486 400

Two aero-radiometric anomalies situated overweathered schist were surveyed and drilled. Nosignificant U

3O

8 mineralisation was encountered

(Kotzé, 1978).

4.2.2.1.5 The Aussinanis Deposit

This deposit is situated north of the GobabebDesert Ecological Research station (Fig. 25) andwas located during an airborne radiometricsurvey.

The pediplain consists of a more recentveneer of calcrete and in places, gypcrete, whichattains a thickness of one metre. The pediplain isshallowly dissected by a recent drainage systemdraining towards the Kuiseb River.

7.1-47


A palaeochannel with a northeasterly trendwas located in this area. Schists of the KuisebFormation and Salem and Donkerhuk Granitesoccur as shallow outcrops along the northernand southern fringes of the palaeochannel.Pedogenic calcrete forms a superficial cover tothe palaeochannel which has a depth of notmore than 20 m.

The palaeochannel has been infilled andchoked with tertiary detritus, which consistslargely of angular to sub-angular cobbles andfragments of a variety of granitic rocks andquartz pebbles of local derivation.

A ground radiometric survey conducted inthis area delineated an anomalous areameasuring 1 800 by 14 000 m.

Uranium occurs as irregular dispersedcarnotite in blebs, reworked veinlets and as thincoatings surrounding pebbles. Themineralisation was found to occur with randomand irregular frequency in a tabular horizonlying near surface and extending up to depths ofbetween 7 and 10 m. The ore zone is some 15-km-long and varies between 2 km and 200 m inwidth. The thickness of the ore body is between1 and 2 m and occasionally up to 5 m(Debaveye, 1981).

The ore body extends to the northwest,where field investigation of airborneradiometric anomalies led to the discovery ofsmall showings of carnotite in schists, SalemGranite and drainage channels.

Selected secondary uranium anomaliesassociated with southwesterly-trending channelswere investigated in detail by a percussiondrilling programme. However, only 3 holesintersected grades of higher than 100 g/t U

3O

8

(Linning, 1976).

4.2.2.1.6 Minor Occurrences

Elspe GrantRadiometric surveys located anomalous

areas over river sediments, where carnotiteoccurs in joints. Values of up to 260 g/t U

3O

8

were recorded. Drilling focused on thepalaeovalleys of the Gawib River and uraniummineralisation of less than 100 g/t U

3O

8 was

found to occur in isolated mineralised zones(Linning, 1977).

Gobabeb Grant AreaAirborne spectrometer and magnetometer

surveys conducted over this area located threeanomalies which were termed A, B, and C (Fig.25).

Anomaly A is 10-km-long and 1 to 2-km-wide, with some zones having more than 100cps. Anomaly B has some values in excess of100 cps. Anomaly C consist of 3 different smallareas with values over 100 cps (Mouillac, 1978).

BloedkoppieThe Bloedkoppie Granite contains between

10 to 15 g/t with a maximum of 100 g/t U3O

8.

Percussion holes were drilled into calcretechannels in the northern, eastern and southernpart of the grant area. The average thickness ofthe calcrete was found to be 7 m and two holesassayed values grater than 100 g/t U3O8(Hartleb, 1981).

Kuiseb GrantA palaeochannel with a northeasterly trend

was investigated. However, only small traces ofcarnotite were observed (Galloway and Ransom,1982).

Ruimte 125In the central-northwestern part of this farm

an anomaly with an areal extent of 3.3 millionm2 was located. Surface chip samples from thisarea analysed between 340 and 540 g/t U

3O

8

(Kotzé, 1978).

4.2.2.2 Spitskop Area

4.2.2.2.1 The Klein Trekkopje Deposit

An airborne radiometric survey located theKlein Trekkopje uranium deposit, some 17 kmnorthwest of the Trekkopje Siding (Fig. 32). Themain uranium mineralisation is associated with apalaeochannel that extends from an area in

7.1-48


Figure 32: Uranium occurrences in the Spitzkoppe region.

7.1-49


Damaraland, immediately west of the farmTrekkopje 120, towards the farm Hakskeen 89in the east (Fig. 33).

The area consists essentially of a flatpediplain shallowly dissected by a westwarddraining, reticulate, recent drainage systemwhich trends southwest-northeast. In places

inconspicuous outcrops of marble and biotiteschist of the Khomas Subgroup delineate apalaeoriver system.

A crust of gypcrete, less than 3-m-thick,covers an extensive area underlain by calcrete(Fig. 34). The contact of gypcrete with theunderlying calcrete is transitional. Textures and

Figure 33: The Klein Trekkopje occurrence (after Omitara Mines).

Figure 34: Section of pit 8400/1600N (after Omitara Mines).

7.1-50


structures in the gypcrete suggest that it is not anormal evaporite deposit but rather acombination of detrital and chemical sediments.

The calcrete consists predominantly ofcoarse, unsorted, angular to subrounded graniticand quartzitic fragments that have beencemented by lime. The rock was described as amoderately well cemented, open textured,permeable pebbly grit and conglomerate.

An airborne radiometric survey delineated ananomaly associated with an east-west trendingpalaeochannel, which has a maximum length of15 km and a width of 1 to 2 km. Theradiometric anomalies had a moderate to strongresponse in the uranium channel, but little or noeffect was detected on the thorium andpotassium channels.

The mineralisation is present as a 16-km-long and 2-km-wide tabular sheet, which occursat depths ranging between 2 and 17 m below thepresent surface. The ore zone thickness rangesbetween 1 and 2 m and does not occur at aconstant level or horizon. Carnotite is present as

irregularly distributed blebs or veinlets and asthin coatings on mainly quartz cobbles andpebbles (du Plessis, 1983).

The ore reserves, using a cut off grade of 80ppm U

3O

8, and including the eastwards

extension into the adjacent Arandis Grantareshown in Table 10.

Table 10: Ore reserves of the Klein Trekkopjeoccurrence

Ore tonnage 360 000 000U

3O

8 tonnage 39 500

Average grade (g/t) 100Average stripping of overburden (m) 3Average thickness of ore (m) 8

4.2.2.2.2 Arandis Deposits

An airborne geophysical survey conductedduring 1971 as part of the evaluation of theArandis tin prospect located five anomalousradioactive zones (Figs 32 and 35), all

Figure 35: The Arandis occurrence (after Heath, 1973).

7.1-51


associated with the Klein Trekkopjepalaeochannel. Zones B, C, and D measuring156, 78 and 105 hectares respectively, appearedto be the most promising and were subsequentlyinvestigated.

Exploration results indicated the widespreadexistence of sporadic uranium mineralisation inthe nearsurface portion of a thick (about 150 m)blanket of Tertiary calcareous conglomerate.

The mineralisation is primarily concentratednear the surface in portions of the recently-deposited host rock. Values slightly in excess ofbackground were encountered in the vicinity ofthe water table (Heath, 1973).

4.2.2.2.3 Hakskeen

A radiometric survey located the easternextension of the mineralized Klein Trekkopjepalaeochannel on the farm Hakskeen 89 (Fig.32).

Carnotite mineralisation appears to besurface accumulation confined to the northern

side of a wide calcrete basin. A fair proportionof this mineralisation occurs in gypcrete whichaccounts for the prominent surface radiometricanomaly. The proven ore reserves are 361 250 tof U

3O

8 at 331 g/t (Johnston, 1978).

4.2.2.2.4 Swakopmund Grant

The grant area is situated in the Namibdessert between Swakopmund and Henties Bay(Fig. 32) and is mostly underlain by KuisebFormation schists and Karibib Formationmarbles. The metasediments have a northeast-southwest regional trend but show localvariations due to the doming effect of granites.Igneous rocks occurring in this area includeSalem Granite, various pegmatites and doleritedykes. Red granite gneisses area also common.The rocks of the Damara Sequence are oftenoverlain by extensive deposits of Tertiary sands,gravels, gypcrete and calcrete.

Airborne radiometric and magnetic surveysindicated two anomalies, one developed over apalaeochannel located in the eastern part ofdetailed grid 2 (Fig. 32 and 36), and the second

Figure 36: Locality map of the detailed grids on the Swakopmund Grant (after Rand Mines Corp.).

7.1-52


situated over granite in detailed grid 5.

Regional ground surveys were undertaken inthe southern half of the grant. Several anomalieswere located and investigated by detailedsurveys in grids 1 to 6.

Grid 1: Uranium mineralisation wasidentified in several types of settings:

a) Secondary surface mineralisation occursassociated with red granite gneiss and alaskites.The uranium appears to have been leached fromthe underling rocks and precipitated in theweathered zone in joints and fractures linedwith gypcrete and calcrete. A percussion drillsample from this area assayed 132 g/t U

3O

8 over

the upper 5 m.

b) Secondary mineralisation occurs in shearzones between two red granite gneiss domes.The mineralised zones, assaying 200 to 11 300g/t U

3O

8, are narrow and widely spaced.

Towards the south of the shear zone, oneparticular shear with a strike length of 3 000 mand a width ranging between 1 to 10 m assayedas follows:

530 g/t U3O

8 over 4.0 m over a strike

length of 175 m.370 g/t U

3O

8 over 1.25 m over a strike

length of 450 m.200 g/t U

3O

8 over 26.0 m over an

unknown strike length.

Percussion drilling also indicated a numberof 0.2-m-thick zones which occur over a widthof 2 to 10 m. These assayed between 500 and 5000 g/t U

3O

8, averaging 300 g/t U

3O

8.

No primary mineralisation was identified,but the close association between the secondarymineralisation and the red granite gneiss,alaskite and granite, favours these rocks asbeing the source of uranium.

Grid 2: Secondary uranium mineralisation isassociated with an east-west trendingpalaeochannel. The mineralisation occurs in azone between 25 and 50 m in width and 100and 300 m in length. Ore reserves calculated for

this area are 970 000 t U3O

8 at 71 g/t.

Along the westward extension of the palaeo-channel a weakly mineralised zone of 16 by 400m is present. The ore reserves calculated for thisarea are 1.87 million t at a grade of 70 g/t U

3O

8.

Secondary uranium also occurs within a shearzone developed along the northern margin of thered granites. Trench sample results from thisarea ranged between 150 and 500 g/t U

3O

8 over

widths of 1.5 to 1.7 m (Dodd, 1980a).

4.2.2.2.5 The Klein Spitzkoppe Deposit

During 1968 an airborne radiometric surveyindicated anomalous radioactivity on the farmKlein Spitzkoppe 70 (Fig.32).

The anomaly is situated over calcretes to thesoutheast of the Klein Spitzkoppe (Figs. 32 and37). The regional geology of this area consists of

Figure 37: Locality map of the Klein SpitzkoppeDeposit (after General Mining and FinanceCorporation).

7.1-53


Damaran granites, marbles and schist and theCretaceous Spitzkoppe Granite. The bedrockgeology occurs as inliers in the calcrete as wellas along erosion channels of the larger streamsand particularly in the Spitzkop river channel.

Detailed percussion drilling and onediamond drillhole indicated calcrete depths ofup to 30 m (Fig. 38). The calcretes are believedto be of fluviatile origin and occur in apalaeochannel, which extends southwards.Within the palaeochannel lenses of clay andsand/silt are interbedded with coarse grits andconglommerates, all of which weresubsequently calcretised.

The mineralisation within the main anomalyzone consists of carnotite-enriched calcrete. Thecarnotite occurs interstitially within thecarbonate matrix of the calcretes and also asgrain coatings in the coarser calcrete types. Themineralisation has an average depth of 10 m,with a maximum of 20 m. The degree ofmineralisation is isolated and variable. The totaltonnages calculated for this area are 4 466 000 tat a grade of 239 g/t U

3O

8 (Johnston, 1978).

4.2.2.2.6. Marinica

The Marinica Grant is situated about 70 kmwest of Usakos on the gravel road towardsHenties Bay (Fig. 32).

The regional geology of this area consits ofbasin-and-dome tectonic features, wheremassive marbles of the Karibib Formation formthree domal structures, while steeply-dippingbiotite schists (Kuiseb Formation) form thebasins. Four uranium anomalies are associatedwith the domal structures and this indicates thatthese structures have extended a considerableinfluence over deposition of secondary uraniumminerals.

Anomaly 1: Results obtained from this areawere poor, with only a few boreholesencountering values in excess of 200 g/t U

3O

8.

Only one hole exceeded 300 g/t. The best resultswere recorded from the south, and valuesdecreased to the north and west. Themineralisation was found to be restricted to theuppermost 5 to 6 m.

Figure 38: Section along line 2700E, detailed Grid 2 (after Rand Mines Corporation).

7.1-54


Ore reserves:Surface area (m2) 49 600Tonnes 432 000Average grade U

3O

8 (g/t) 132

Average thickness of ore body 3.5 m

Anomaly 2: The mineralisation in this area ispresent in two zones, 2A and 2B.

Anomaly 2A trends east-west and onedrillhole assayed 480 g/t U

3O

8 over 8.1 m.

Secondary uranium mineralisation occurs inboth granite and pegmatite.


3O

8 (g/t) 160

Average thickness of ore body 4 m

Anomaly 2B: This anomaly consists of athick diffused body that thins out laterally.


3O

8 (g/t) 102


Anomaly 3: The mineralisation isconcentrated in an elongated semi-horizontallense, trending northeast.


3O

8 (g/t) 194


Anomaly 4: This anomaly is calcrete-covered. The values in the calcrete are erraticand most of the mineralisation was intersectedin the upper 5 to 6 m. Locally high values of upto 500 g/t U

3O

8 over 2.5 m were recorded.

A second drilling phase on 120 m gridintervals and to depths of 15 m covered theareas of anomalies 1 to 3. The results of theprogrammes were combined and four mainareas of mineralisation were located (Fig. 39).Mineralised Area 1 is situated to the east of

Anomaly 1. Area 2 straddles the boundary ofAnomalies 1 and 2. Area 3 lies in an elongatedeast-west configuration and was detected by theinitial drilling programme. Area 4 lies in thenorthern portion of anomaly 3 and was alsodetected by the initial drilling programme.

Area 2 has the richest mineralisation. Valuesexceed 150 g/t U

3O

8 over a fairly large area and

mineralised zones are wider than 3 m(Labuschagne 1976).

Two distinctly different types of secondaryuranium mineralisation occur. In thenorthwestern portion of the mineralised area themineralisation is present in weathered schist,granite and pegmatites. It fills joints, cleavageplanes, fracture surfaces and schistosity planes.Calcite and gypsum have been observed inassociation with the uranium minerals (mostlycarnotite). This mineralisation occurs at shallowdepths and is rarely present below 12 m, withthe bulk of it above 8 m.

The second type of mineralisation occurs incalcrete filling a palaeodrainage channel. Thecalcrete is mainly covered by sand and is onlyexposed in a limited number of shallowexcavations. The best mineralisation observed inthese excavations is also associated with thewidespread development of gypsum. Thecarnotite tends to concentrate in nodular andtube-like structures in the host rock. Some finedisseminations of uranium minerals have alsobeen noticed in other excavations.

On a regional scale the mineralisation tendsto follow the outline of three marble domestructures. In the northern sector of themineralised area, a correlation between the trendof mineralisation (palaeochannel) and thepresent drainage system exists (Bertram, 1975).

4.2.2.2.7 Welwitschia Flats

Secondary uranium mineralisation wasdiscovered in the Welwitschia Flats (Fig. 32) incalcretes exposed by erosion channels. A T-cupsurvey indicated that the mineralisation extendsnorthwards.

7.1-55


Figure 39: Precussion drillhole profiles of the Main Anomaly Zone, Klein Spitzkoppe deposit (afterGeneral Mining and Finance Corporation).

Percussion drilling in this area was done on a250 m square grid and consisted of 127 holestotaling 1391 m. The ore reserves for this area,using boreholes containing at least one 1 mintersection of 100 g/t U

3O

8 with a lower cutoff

grade of 50 g/t, are 35 million t at an averagegrade of 120 g/t U

3O

8. This mineralised zone

has a thickness of 5.3 m and a stripping ratio ofless than 1. Two alternative separatemineralised blocks containing a total of 5.4million t at an average grade of 180 g/t, athickness of 4.4 m and a cover of 4 m, weredelineated using boreholes containing at leastone 1 m intersection of 200 g/t with a lower cut-off grade of 100 g/t.

A pitting programe in this area indicated that

the mineralisation is extremely variable (Bothe,1980)

4.2.2.2.8 Minor Occurrences

GelukThe Geluk Grant area covers 80 000 ha and is

situated to the west of the Marinica grant, in thesouthwestern part of Damaraland. The OmaruruRiver bisects the northwestern portion of thearea and the main road between Henties Bay andUsakos traverses the southeastern portion (Fig.32).

Work within the grant area consisted of anareo-radiometric/magnetic survey which was

7.1-56


followed up by ground exploration.

An area in the extreme southeastern portionof the grant, which covers the western extensionof the Marinica palaeochannel, was investigatedin detail. Results of the work performedindicated that carnotite is sporadicallydistributed within calcretised gritty sediments.Mineralisation occurs as blebs within thecarbonate-rich portion of the matrix. It issometimes finely disseminated or occurs ascoatings around quartz, schist or clay fragments.

The estimated tonnage for this area is 4.5million t at an average grade of less than 100 g/tU

3O

8 (Ransom, 1980).

OotmoedPercussion drilling on a few low-

scintillometre anomalies associated with apalaeochannel indicated the existence of a fewthousand tonnes with a grade of ±150 g/t U

3O

8

(Du Plessis, 1982).

4.2.2.3 Brandberg Area

4.2.2.3.1 Henties Bay Grant

The grant area is situated 20 km north ofHenties Bay at 21o50’S and 14 o 15’E (Fig. 40).Prospecting in this area was directed atsecondary uranium mineralisation associatedwith palaeochannels.

The regional geology of this area consists ofnortheast-southwest trending Kuiseb Formationschists and gneisses of the Damara Sequence.Intrusive in this area are granite, pegmatite anddolerite.

Radiometric and magnetic surveys wereconducted over the area. A radiometric anomalywith a U/Th ratio of more than 2:1 was locatedin the northeastern corner of the grant area. Theanomaly is situated over red granite gneiss.

A regional T-cup survey over tertiarydeposits located further uranium anomalies overpalaeochannels and thorium anomalies oversandy delta regions. Trenching of the

paleochannel anomalies exposed carnotite whichassayed 48 g/t U

3O

8 on average . Assays from

percussion drill holes returned 162 g/t U3O

8 over

0.3 m some 0.95 m below surface.

A further palaeochannel was investigated by49 percussion drillholes totalling 505 m. Amineralised zone with a length of 7 km and awith of between 0.2 and 0.5 km was located.The thickness of the mineralised zone variesfrom 0.3 to 3.8 m and grade between 60 and 140g/t U

3O

8 (Dodd, 1980b).

4.2.2.3.2 Cape Cross

An aero-radiometric survey located severalanomalous zones which coincided with a majorpalaeodrainage feature some 400 m in width andextending for ±30 km in a southwesterlydirection (Fig. 40).

Surface radiometric surveys detected fivetarget areas, four of which are associated withthe paleo channel. The most promising of these,Block A, was percussion drilled. The resultsobtained indicated that sporadic uraniummineralisation with a low grade is associatedwith an upper gypsiferous layer and withunderlying calcareous fluviatile sediments(Ransom, 1978).

The anomaly on the southern limb is situatedin feldspathic quartzites of the KuisebFormation. It is 13 m by 30 m in size and thecalculated reserves are 10 000 t at 200 g/t U

3O

8

and 5 000 g/t thorium (Quoix, 1980).

4.2.2.3.2 Namib Rock Grant

The grant area is situated 150 km northeast ofSwakopmund and is underlain by Damaraschists and granites. The bed rock is obscuredfor the most part by a thin veneer of gravels andsands which are sporadically calcretised (Fig.40).

Regional scintillometer surveys isolated 8anomalous areas of which the most promisingwere drilled. The results obtained show a

7.1-57


Figure 40: Uranium occurrences north of the Omaruru River.

uranium enrichment of the near-surface areas.The grades ranged between 200 g/t and 300 g/tU

3O

8. However, extensive tonnages could not

be located (Keenan, 1983).

4.2.2.3.4 Brandberg South Area

A ground-radiometric survey located fouranomalous areas which are associated withcalcareous and gypsiferous palaeochannels withan average depth of 33 m (Fig. 40).

All anomalies were percussion drilled, butonly one proved to be of economic significance.Ore reserves of 3 million t at an average grade of212 g/t U

3O

8 were calculated. The deposit has an

average thickness of 1.9 m and the highest resultrecorded during the drilling was 702 g/t U

3O

8.

The overburden to ore ratio in the northern partis 3:1 and increases towards the south where itbecomes 6.7 : 1.2 (Dippenaar, 1979).

7.1-58


4.2.2.3.5 Area NW of Henties Bay

This area (Grant M46/3/664) is situated 60km northwest of Henties Bay (Fig. 40) and threeradioactive anomalies, associated with calcrete-filled channels were located within it.

Anomaly 1 : Some 27 percussion holes,totaling 591 m, were drilled on this anomaly.The highest value recorded was 861 g/t U

3O

8

over 80 cm. The values were found to be erraticand average 90 g/t.

Anomaly 2 : This anomaly is underlain bycoarse-grained granite, granitic pegmatite,smoky-quartz veins and occasional peliticmetasediment. Up to 3 000 cps were recordedover smoky quartz blows.

Anomaly 3 : Readings above 100 cps wererecorded from an area 50 by 300 m in size(Veldsman, 1980).

5. Secondary occurrences of uncertain origin

5.1 Meob Bay

In 1973 an airborne geophysical survey of thecoastal portion of Diamond Area No. 2 outlineda number of high-grade radiometric anomaliesapproximately equidistant between Meob Bayand Conception Bay (Fig. 41). Groundexamination of the anomalies revealed thepresence of carnotite mineralisation in alteredbiotite schists and pegmatites beneath a thincapping of red and buff-coloured aeolian sands.The mineralisation is of high grade but covers asmall surface area. A diamond drillingprogramme failed to intersect the mineralisationat depth showing it to be of purely secondaryorigin and of surficial extent. It is estimated thatthe main anomaly, termed ACE, has a total of 2250 t of ore, at a grade of 1 424 g/t U

3O

8

adopting a 500 g/t cutoff.

The uranium is believed to have beendeposited on an old erosion surface of probableMiocene age at the interface of weatheredbedrock and the overlying red aeolian sandswhich acted as an aquifer for uraniumbearingmeteoric waters (Wilson, 1978).

5.2 Uis Mine

The Uis Mine is situated 170 km north-northeast of Swakopmund and lies along anortheasterly-trending Sn-Li-Be-Nb-Tapegmatite belt in Khomas schist. The pegmatitesoccupy tension fractures within a major north-south shear and are inclined at large angles tothe foliation in the schist.

Calcrete up to 10-m-thick has formed in thelower parts of some narrow valleys in the minearea overlying at least one pegmatite dyke.Weathering extends to perhaps 10 to 50 m indepth. Weathered pegmatite and immediatelyadjacent schist are more strongly fractured thanthe main body of schist. Films of carnotite occurwithin the weathered and fractured pegmatiteand schist up to 10 m from the contact and up to20 m below the present erosion surface.

Figure 41: Simplified geology of the Meob Bayarea (after Geological Map of Namibia

1:1 000 000

7.1-59


Carnotite also occurs along fracturesconfined to the weathered schist in associationwith “vein” calcrete and gypcrete (Carlisle,1978). For a detailed description of the UisMine see the tin chapter.

5.3 Area south of the Kuiseb River

Aeromagenetic and radiometric surveys wereconducted south of the Kuiseb River (Fig. 24).The surveys did not produce any reliable resultsdue to the deep sand cover of the dune fields.Exsisting Water Affairs boreholes were thenradiometrically logged and two target areas,Area 1 and Area 2, were delineated.

In Area 1 anomalous values (67 g/tequivalent U

3O

8) were recorded from weathered

granites and schists.

The best intersection recorded in Area 2 wasfrom the broad shallow Kuiseb palaeochannelwere 104 g/t equivalent U

3O

8 over 12.2 m were

detected (Fletcher, 1977).

5.4 Tsumeb Mine

Kasolite {Pb(UO2)(SiO

4).2H

20] and

metazeunerite [Cu(UO2)

2 (AsO

4)

2.8H

2O] occur

as minor constituents in the oxidation zone ofthe Tsumeb polymetallic orebody (Keller,1984;H.J. Laurenstein, pers.comm.).

6. References

Anon. Klein Trekkopje. Unpubl. rep., 5 pp.Barbour, E.A. 1980. Report on prospecting

activities for the period 9th April 1977 to 8thApril 1980 - Prospecting Grant M46/3/600.Unpubl. rep., Western Mining Group (Pty)Ltd.

Barbour, E.A. 1983. Swakop Project,Prospecting Grant M46/3/600. Unpubl. rep.,Western Mining Group (Pty), Ltd, 6pp.

Berning,J. 1986. The Rössing uranium deposit,South West Africa/Namibia. In: Anhaeusser,C.R. and Maske, E. (Eds), Mineral depositsof Southern Africa, II. Spec. publn geol. Soc.

S.Afr., 1819-1832.Bertram N.G.E. ca. 1975 Geological Report in

Support of Application for Renewal of GrantM46/3/399. Unpubl. rep., Gold Fields Miningand Development Company Ltd, 6 pp.

Bertram, N.G.E. 1981. Geological report inSupport of Application for Renewal of GrantM46/3/956. Unpubl. rep., Gold Fields Miningand Development Company Ltd, 10 pp

Bertram N.G.E. 1982. Report in Support ofApplication for Renewal of ProspectingGrant M46/3/449. Unpubl. rep., TrekkopjeExploration and Mining Company (Pty), Ltd,16 pp.

Borton D. 1977. Interim Report on the TumasProject. Prospecting Grant M46/3/738.Unpubl. rep., Falconbridge of S.W.A. (Pty)Ltd, 6 pp.

Bothe H.W. 1977. Kuiseb Joint UraniumVenture. Unpubl. rep., Anglo AmericanProspecting Company, 3 pp.

Bothe H.W. 1980. Prospecting Grant M46/3/487Welwitschia Uranium Joint Venture. RenewalReport August 1980. Unpubl. rep., AngloAmerican Prospecting Company, 4 pp.

Bothe H.W. 19??. Oryx Extension UraniumVenture Grant No M46/3/708. FinalGeological Report. Unpubl. rep., AngloAmerican Prospecting Company, 2 pp.

Bothe H.W. 1981. Otjimbingwe Uranium JointVenture. Prospecting Grant M46/3/890.Unpubl. rep., Anglo American ProspectingServices.

Bunting, F.J.L. 1977. Geology of part of theCentral Damara Belt around the Tumas River,South West Africa. Unpubl. M.Sc thesis,Rhodes Univ., 168 pp

Carlisle, D. 1978. The distribution of calcretesand gypcretes in southwestern United Statesand their uranium favorability based on astudy of deposits in western Australia andNamibia. United States dep. of Energy,. Univ.California, Los Angeles, 274 p.

Corner, B. 1982. An interpretation of theaeromagnetic data covering portion of theDamara Orogenic Belt with special referenceto the occurrence of uraniferous granite.NUCOR PER-95, 115 pp.

Cooke, R. 1977. Wolfkoppe Uranium Prospect -Prospecting grant M46/3/773, KaribibDistrict, South West Africa. Final and

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Progress Report. Unpubl. rep., Rio TintoExploration (Pty), Ltd, 4 pp.

Cooke, R. 1978. Progress report for periodJanuary 1977 - December 1977 - Prospectinggrant M46/3/517. Unpubl. rep., Rio TintoExploration (Pty), Ltd.

Cooke, R. 1981. Uranium Occurrences in theVicinity of the R™ssing Deposit (G.P.LouwArea). Unpubl. rep., Rio Tinto Exploration(Pty) Ltd, 7 pp.

Debaveye, M.P.A. 1981. Aussinanis Grant.Prospecting Grant M46/3/721. Namib DesertPark - South West Africa ProspectingReport. Unpubl. rep., Omitara mines, 6 pp.

Dippenaar S.Z.E. 1979. Brandberg Suid:Bronmaterial Ondersoek. Unpubl. rep.,Enok, 7 pp.

Dodd, M.J. 1980a. Swakopmund Grant M46/3/889 Progress Report. Unpubl. rep., RandMines Windhoek Exploration (Pty) Ltd, 12pp.

Dodd, M.J. 1980b. Henties Bay Grant M46/3/875 Final Report. Unpubl. rep., Rand MinesWindhoek Exploration (Pty) Ltd, 8 pp.

Du Plessis J. 1982. Prospecting Report to theDirectorate of Economic Affairs. ProspectingGrant M46/3/930 Ootmoed No. 86. Unpubl.rep., Cadrim Namibia (Pty) Ltd, 2 pp.

Du Plessis J. 1983. Geological, ExplorationProgress and Financial Report. ProspectingGrant M46/3/725. Unpubl. rep., CadrimNamibia (Pty) Ltd, 7 pp.

Esterhuizen, A.G. 1983. Progress report insupport of an application of renewal GrantM46/3/501. Unpubl. rep., TrekkopjeExploration and Mining Company (Pty) Ltd,2 pp.

Fletcher, B.A. 1976. Interim geological reporton the Engo Valley, Skeleton CoastProspecting Grant M46/3/51. Unpubl. rep.,General Mining and Finance Corp. Ltd.

Fletcher, B.A. 1977. Report on the ProspectingActvities in the Dunes South of the KuisebRiver Prospecting Grants M46/3/761 + 763.Unpubl. rep., General Mining and FinanceCorp.

Fletcher, B.A. 1981. Engo Valley - SkeletonCoast, Geological report grants M46/3/51,490 and 722. Unpubl. rep., GeneralMining and Finance Corp.

Galloway, S.S., Ransom, A.H. 1982. Interim

Report on work carried out during 1981 onGrant M46/3/730. Unpubl. rep., Falconbridgeof S.W.A. (Pty) Ltd, Bull. No 2269, 4 pp.

Hambleton-Jones, B.B. 1983. The Geology andGeochemistry of some Epigenetic UraniumDeposits near the Swakop River, South WestAfrica. NUCOR PER-78 Pretoria, 306 pp.

Hartleb, J.W.O. 1979. Geological interim reporton Prospecting concession M46/3/780 for theperiod September 1978 - August 1979.Unpubl. rep., General Mining and FinanceCorp. Ltd, 10 pp.

Hartleb, J.W.O. 1980. Final geological report oncertain farms in the Outjo District (GrantM46/3/911). Unpubl. rep., General MiningUnion Corporation Ltd, 4 pp.

Hartleb, J.W.O. 1981. Final Report on theBloedkoppie Concession M. 46/3/561.September 1978 - August 1981. Unpubl. rep.,General Mining Union Corporation Ltd, 1 pp.

Hartleb, J.W.O. 1988. The Langer HeinrichUranium deposit: Southwest Africa/Namibia.Ore Geology Reviews, 3, 277-287.

Heath D.C. 1973. Prospecting Grant M46/3/259Karibib District, South West Africa. FinalReport on the Exploration of the ArandisUranium. Unpubl. rep., Rio Tinto Exploration(Pty) Ltd, 9 pp.

Hiemstra, S.A. 1968. Identification and analysisof radioactive minerals in a sample fromDavib Ost. Unpubl. rep., National Institutefor Metallurgy, 1 p.

Jacob, R.E. 1974. The radioactive mineralisationin part of the central Damara Belt, Namibia,and its possible origin. Atomic Energy Board.Pin 234, 17pp.

Jacob, R.E., Corner, B., and Brynard, H.J. 1986.The Regional Geological and StructuralSetting of the Uraniferous Granitic Provincesof Southern Africa. In: Anhaeusser, C.R. andMaske, E. (Eds) Mineral Deposits ofSouthern Africa, II, Spec. publn geol. Soc. S.Afr., 1807-1818.

Johnston C.H. 1978. Report on SpitzkoppeConcession - Damaraland. Unpubl. rep.,General Mining and Finance Corp. Ltd, 11pp.

Keenan, J.H.G. 1983. Final report Namib RockGrant M46/3/655. Unpubl. rep., AngloAmerican Prospecting Services.

Keller, P. 1984. Tsumeb. Lapis 7/8, 82 pp.

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Kotzé, W.H. 1978. Summary of Exploration inthe Namib Park Concession Areas. Unpubl.rep., General Mining and Finance Corp. Ltd,10 pp.

Kruger, T.L. 1990. Renewal Aplication:Prospecting Grant M46/3/1496 (Valencia).Unpubl. rep., Gold Fields Namibia Ltd, 2pp.

Labuschagne, A.N. 1976. Report on the DamaraMining Company Uranium Proposition.Grant M46/3/399. Unpubl. rep., Gold FieldsProspecting (Pty) Ltd.

Labuschagne, A.N. 1979. The Anomaly 26Uranium Prospect and its EnvironmentsValencia 122. Prospecting Grant M46/3/449.Unpubl. rep., Trekkopje Exploration andMining Co. (Pty) Ltd, 68 pp.

Linning, K. 1973. Annual report 1972 -Prospecting Grant M46/3 334 (MYL 72).Unpubl. rep., General Mining and FinanceCorp. Ltd.

Linning, K 1976a. Exploration Progress ReportLanger Heinrich Uranium Deposit. Unpubl.rep., General Mining and Finance Corp. Ltd,3 pp.

Linning, K 1976b. Progress Report SourceMaterial Grant M46/3/670. (Namib Park IV).Unpubl. rep., General Mining and FinanceCorp. Ltd.

Linning, K. 1977. Progress Report on theExploration for source materials in the Elspeconsession, portion of prospecting grantM46/3/431, South of the Swakop River.Unpubl. rep., General Mining and FinanceCorp. Ltd.

Marlow, A.G. 1983. Geology and Rb-Srgeochronology of mineralised andradioactice granites and alaskites, Namibia.Spec. Publ. geol.Soc. S.Afr., II, 289-248

Marsh S.C.K 1984. Final Grant Report - Oryx.Grant M46/3/430. Unpubl. rep., AngloAmerican Prospecting services Namibia(Pty) Ltd, 72 pp.

Meyer K. 1973. Uran-Prospektion vorSudwestafrika. Erzmetal, 26, 313-317.

Misiewitcz, J.E. 1984. Valencia uraniumAnomaly 26. Correlation of boreholes atproposed prospect shaft. Unpubl. rep., GoldFields of S.A.

Mouillac, J. 1976. Half-yearly prospectingreport for the period ending 30th June, 1976- Goanikontes Grant. Unpubl. rep.,

Acquitaine Namibia.Mouillac, J. 1978. Gobabeb Grant M46/3/534.

Technical Report. Unpubl. rep. OmitaraMines, 3pp.

Mouillac, J.L., Valois, J-P., and Walgenwitz, F.1986. The Goanikontes uranium occurrencein South West Africa/Namibia. In:Anhaeusser, C.R. and Maske, S. (Eds),Mineral Deposits of Southern Africa, II,Spec. publn geol. Soc. S. Afr., 1833-1843.

Nash, C.R. 1971. Metamorphic petrology of theSJ area, Swakopmund District, Namibia.Bull. Chamber Min. Precambr. Res. Unit,Univ. Cape Town, 9, 77 p.

Pienaar P.J. 1975. Final Prospecting ReportM46/3/398. Horebis Area, RegistrationDivision “G” South West Africa. Unpubl.rep., Anglo American Prospecting Services.

Quoix J. 1980. Prospecting Grant M46/3/867“Auris” South West Africa. Final QuarterlyReport for the Period 31-10-1980 to 31-12-1980. Unpubl. rep., Omitara Mines, 4 pp.

Ransom A.H. 1978. Interim Report on the CapeCross Grant M46/3/794. Unpubl. rep.,Falconbridge of S.W.A. (Pty) Ltd, 6 pp.

Ransom A.H. 1980. Final Report on the GelukUranium Prospect- Damaraland, South WestAfrica/Namibia Grant M46/3/717. Unpubl.rep., Falconbridge of S.W.A. (Pty), Ltd, 16pp.

Ransom A.H. 1981. Interim Report onProspecting Grant No M46/3/738. TumasProject No. 53. Namib Desert Park SWA/Namibia. Unpubl. rep., Falconbridge ofS.W.A. (Pty) Ltd, Bulletin No 2267, 3pp.

Smith, D.A.M. 1965. The geology of the areaaround the Khan and Swakop Rivers inNamibia. Mem. geol. Surv. S. Afr. (S.W.A.Series), 3, 113 p.

Veldsman, H.G. 1980. Report in support of anApplication for renewal for grant M46/3/664.Unpubl. rep., Trekkopje Exploration andMining Company (Pty) Ltd.

Wagener G.F. 1977a. Husab Uranium JointVenture, Prospecting grant M46/3/444 SouthWest Africa. Unpubl. rep. SwakopExploration (Pty.) Ltd (Anglo AmericanCorporation of South Africa Limited).

Wagener G.F 1977b. Prospecting Grant M46/3/433 Prospecting report for the period 24/6/75/to 31/12/76. Unpubl. rep., Tubas Mining (Pty)

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Ltd, 7 pp.Wagener G.F 1983. Tubas Uranium Joint

Venture Prospecting Grant M46/3/433Prospecting report for period 24/6/80 to 31/3/83. Unpubl. rep., Anglo AmericanProspecting Services Namibia (Pty) Ltd, 4pp.

Wilson, P.A. 1978. Final prospecting ReportMeob Bay Grant No M46/3/768. Unpubl.rep., Anglo American Prospecting Services(Pty) Ltd, 56 pp.

Documents

Uranium - gsn.gov.na · Uranium occurrences in and associated with plutonic rocks comprise both potentially economic deposits and source rocks for uranium deposits in pedogenic and