Lithogeochemistry and XRD Mineralogy of Martin Group and Related Rocks, Greater Beaverlodge Area, Saskatchewan

David H. Quirt1

Quirt, D.H. (1990): Lithogeochemistry and XRD mineralogy of the Martin Group and related rocks, greater Beaverlodge area, Sas­katchewan; in Summary of Investigations 1990, Saskatchewan Geological Survey; Saskatchewan Energy and Mines, Miscel­laneous Report 90-4.

Along the north shore of Lake Athabasca are found the remnants of several Proterozoic red-bed dastic succes­sions: the Athabasca, Martin, and Thluicho Groups (Langford, 1980, 1981). These roci<s were initially grouped together as a single unmetamorphosed to weakly metamorphosed sedimen1ary unit overlying the highly deformed and metamorphosed Tazin Group rocks (Hale, 1953, 1954, 1955; Koster, 1968, 1970). Map­ping of this area by Scott (1978) allowed the sub­sequent subdivision of these cover rocks into the Athabasca, Martin, and Thluicho Groups.

The Martin Group in general has been extensively studied (Tremblay, 1972; Macey, 1973) and detailed sedimen1ological studies on this unit have also been car­ried out by researchers at the University of Sas­katchewan (Langford, 1980, 1981 ; Elliot, 1982; Hendry, 1983; Mazimhaka and Hendry, 1984, 1985, t986). The nomenclature and subdivision of the Martin Group roci<s in this report follows that suggested by Langford (1981) and used in Mazimhaka and Hendry (1984, 1985, 1986). The Thluicho Group has not been covered as ex­haustively as the Martin Group, with rocks of this group having been mapped by Koster (1968) and Scott {1978) and a reconnaissance sedimentological investigation having been conducted on these rocks during the Mar­tin Group study of Mazimhaka and Hendry (1985).

As uranium is associated with the Martin Group (Hoeve, 1982) as well as with the overlying Athabasca Group (Hoeve and Quirt, 1984), a lithogeochemical study was initiated to evaluate the major and trace element content and distribution in the Martin Group rocks. In addition, whole-rock and <5µm fraction mineralogical analyses were carried out using x-ray diffraction (XRD) with the aim of correlating the geochemical data with mineral­ogy, stratigraphic position, and possible sediment source areas. P. Mazimhaka of the University of Sas­kachewan supplied 102 samples of powdered rock. Par­tial funding for the geochemical analyses was provided by the Saskatchewan Geological Survey. The samples represent all of the Martin Group formations, as well as the underlying Thluicho Group.

1. General Geology The Martin Group rocks are found in several isolated basins within a 50 km radius of Uranium City, the best exposed being in the immediate vicinity of the townsite. These rocks lie unconformably on the highly deformed

and metamorphosed basement rocks of the T azin Group which consist primarily of metasedimentary and metavolcanic units. A number of igneous complexes are also present in the region.

The Martin Group consists of up to 6000 m of texturally immature sediments (Tremblay, 1972). A basal con­glomerate up to 750 m thick is followed by up to 2400 m of arkosic sandstone which contains up to 1000 m of volcanic flows intercalated with the upper portion of the unit. Overlying these volcanic rocks is up to 2100 m of arkosic sandstone, in turn being overlain by up to 1800 m of siltstone. Only in the Martin Lake area is a com­plete section preserved.

Conditions of deposition were continental as indicated by the presence of cross-bedding, raindrop imprints, mudcracks, and grain size variations {Tremblay, 1972). Transport distances were short and deposition was rapid into several basins having a rugged, block-faulted terrain. Basin deepening, controlled by active faults, oc­curred as the basin filled, allowing the accumulation of great thicknesses of material (Tremblay, 1972; Hendry, 1983). The typical red colour of most of the Martin Group rocks is due to hematite, which is found in several forms including cement in siltstone and arkosic sandstone, as coloring in feldspar grains, and in the matrix of the conglomerate. Conglomerate clast com­positions in the Martin and T azin Lake areas indicate that the main sediment source was the unweathered granitic basement immediately underlying the Martin rocks or in adjacent fault blocks (Tremblay, 1972; Mazimhaka and Hendry, 1986). Clasts in the Charlot Point Formation were mainly derived from sedimentary sources.

The Martin Group has been divided into a number of for­mations by Langford (1981) and Mazimhaka and Hendry (1985). Four formations are found in the Martin Lake area while only the basal succession remains in areas away from the Martin Lake basin. For detailed descriptions of the Martin Group rocks, see Tremblay (1972), Langford (1981), Elliot (1982), Hendry (1983), and Mazimhaka and Hendry (1984, 1985, 1986), and for the Thluicho Group rocks, see Scott (1978) and Mazim­haka and Hendry P985).

(f ) Mtnerals/Gtoundwater Program. Resources Technology DMslon, Saskatchewan Research Council, Seska1oon, Sasklltcllewan

Saskatchewan Geological Survey 129

2. X-ray Diffraction Mineralogy Mineralogical data were obtained using XRO techni­ques. Whole-rock bulk mineralogy is tabulated by forma­tion and rock type (Table 1). The mineralogy of the <&um fraction was determined from the remaining material following centrifugal extraction of the >&um fraction (Table 2).

The Martin, Charlot Point, and Thluicho sediments are composed of quartz and feldspar with minor mica/clays, carbonate, and ubiquitous hematite (Table 1). Potassium feldspar generally exceeds plagioclase with quartz and feldspar being approximately equal in abundance, as for most arkoses (Pettijohn et al., 1972; van de t<amp et al., 1976). This relationship is likely due to inheritance of the feldspar ratio present in the source area. The carbonate is predominantly calcite but dolomite is present in some samples. The clays are composed of illite/sericite and Fe-Mg trioctahedral chlorite. Only trace amounts of aluminous di,trioc­tahedral chlorite (sudoite), as found in the Athabasca

Basin, and kaolinite have been detected in these rocks. Mixed-layer illite-smectite is rare. Trace amounts of pyrite have been noted in several hand samples of grey sandstone. Two samples of Beaverlodge Formation (grey sandstone and breccia) contain traces of hornblende. Rock fragments and conglomerate clasts in­clude sandstone as well as metamorphic and igneous lithologies.

The clay content in the arkoses is generally less than 10 percent of the rock. Most of the clay minerals are in the matrix as siltstone fragments are sparse. Biotite is rare, likely having been chloritized, and the presence of am­phibole was not detected by XRD. Calcite cement is lo­cally present.

Rock fragments are variably present, usually in lesser quantity than feldspar. As the quartz content is far less than 75 percent, the rocks are predominantly arkoses ac­cording to the Pettijohn classification scheme (Pettijohn et al., 1972). The low matrix content of the arkose clas­sification separates this lithology from that of greywacke.

Table 1 - Whoi.rock mineralogy for formation and rock type. Pl, plagioc/ase; Ct, trioctahedral chlorite; K, kaolinite; Do, dolomite; Kl, potassium feldspar; Cc, calcite; I, i/lite; Cd, di,trloctahedral chlorite; nd, not detected.

Formation n or rock· e

Thluicho 4 Taz Bay 7 Beaverlodge 36 Charlot Point 18 Gillies Channel 13 Seaplane Base 15 Melville Lake 9 Siltstone/fine - grained

sandstone 13 Sandstone 43 Coarse • grained

sandstone 9 Conglomerate/breccia 31 Coarse • grained

conglomerate/breccia 5 Volcanic 1

Q

42 26 41 46 38 32 36

32 41

38 41

31 15

pt

14 25 17 15 17 22 12

15 18

24 17

7 2

Kf 0/ F PI/ Kf Cc

24 1.11 0.58 2 29 0.48 0.86 2 23 1.03 0.74 3 14 1.59 1.07 <1 23 0.95 0.74 8 29 0.63 0.76 3 25 1.33 0.48 7

27 0.76 0.56 6 22 1.03 0.82 3

11 1.09 2.18 5 22 1.05 o.n 3

51 0.53 0.14 2 42 0.34 0.05 nd

Do

nd nd

2 5

nd nd

2

2 1

4 2

1 10

Table 2 - Clay mineralogy of the <5µm fraction for formation and rock type. I, illite; K, kaolinite; C, total chlorite; Ir, i/lite 1002/1001 peak af9a ratio; Ki, Kubler index; PC, percent­age of sample in fraction; nd, not detected; nc, not calculated.

Formation or rock • type

Thluicho Taz Bay Beaverlodge Charlot Point Gillies Channel Seaplane Base Melville Lake

Siltstone /fine.grained sandstone

Sandstone Coarse11rained sandstone

Conglomerate /breccia Coarse.grained conglomerate jbreccia

Volcanic

130

n

4 7

36 18 13 15 9

13 43

9 31

5 1

54 23 32 67 52 61 80

62 49

50 53

8 17

c

46 77 66 27 42 39 20

38 47

50 44

92 83

K

nd nd

2 6 6

nd nd

nd 4

nd 3

nd nd

Ir

0.27 0.40 0.33 0.33 0.30 0.35 0.28

0.32 0.35

0.30 0.31

0.45 nc

Ki

2.5 3.7 4.9 4.3 4.3 4.4 3.7

3.7 4.6

4.7 4.2

3.1 nc

PC

3.3 3.3 3.2 4.4 4.2 2.8 3.3

3.7 3.4

3.4 3.6

2.2 5.0

H Cd

7 7 nd 7 4 nd 5 3 <1

10 8 < 1 4 5 < <1

11 3 < 1 13 3 < < 1

12 5 nd 7 4 <1

8 8 < 1 8 4 <1

3 < 1 nd 19 8 nd

Ct K

4 7 4 2 4 1 1

3 3

3 3

5 4

nd nd <1

1 2

nd nd

nd 1

nd <1

nd nd

The preservation of the feldspars, as illustrated by the low quantity of clay minerals present, indicates that only mild chemical weathering of the source rocks had oc­curred. This evidence agrees with the interpretation of Hendry (1983) and Mazim­haka and Hendry (1984) that the arkoses were derived from areas of high relief such as oc­curs during long periods of scarp retreat in a fault· bounded graben environment. The abundance of feldspar and the relatively low amount of quartz indicates that the arkoses are likely a result of first-cycle sedimentation.

Summary of Investigations 1990

On the basis of formation, a number of differences in mineralogy appear between the samples used in this study. Samples of Charlot Point formation tend to be more quartz-rich (Q/F > 1.5), dolomitic, hematitic illitlc and less chloritic than the other basal sandstone' form~­tions (Taz Bay, Beaverlodge), but are

1

similar to those of the silty Melville Lake formation in some aspects. The ~lagioclase to potassium feldspar ratio (1.07) is also dis­tinctly different from the other formations, indicating that the source area for the Charlot Point sediments was like­ly different than for the other formations.

~he Taz Bay Formation is quartz-poor (Q/ F <0.50) rela­tive to the other formations. It is distinctly different from the ~eaverlodge formation, having less quartz, more plag1oclase and no dolomite.

The Gillies Channel and Melville lake formations are dis­ti~ctly more calcic _than the other formations. The sig­nificances of the differences between the formations are low due to small sample populations.

Minor amounts of dolomite are only found in the Beaver­lodge, Mel~lle lake,. and to a somewhat greater degree, Charlot Point formations. The Thluicho rocks are similar in bulk mineralogy to the basal Martin lithologies. Both the Thluicho and Charlot Point formations appear to be more illitic than the Martin lithologies.

The clay-size fraction mineralogy of these formations are also similar (Table 2) although Thluicho Group illite tends to be less aluminous (lower Ir value) and slightly more crystalline (lower Ki value). The minor amounts of kaolinite present may be due to pre-Athabasca Group pal9?weathering. In general, the clay mineralogy of the M~in Group appears to become illCfeasingly illitic up ~ct1on from the Beaverlodge formation, through the Gil­lies Channel and Seaplane Base formations, to the Mel­ville Lake formation.

For the fine- to medium-grained elastic classifications, the Q/ F ratio is approximately unity. This feature ap­pears to be typical of arkose derived from unweathered sources (van de Kamp et al., 1976). The very fine­grained and very coarse-grained sediments contain sub­stantially less quartz than feldspar, with O / F values of less than 0.76. Only one volcanic rock was included in th~ sample set. This sample revealed a very low Q/F ratio (0.34). Both quartz and plagioclase contents are low, while the potassium feldspar content is high (PI/ Kf .. 0.05), as are the dolomite and hematite proportions. The high PI/Kf value (2.18) for the coarse-grained sandstone remains unexplained as no control on sam­pling was ~vailable. The bulk clay mineralogy appears to be consistent between rock types with only the poorly :epresented very coarse-grained sediment group differ­ing by having a relatively low illite proportion.

The clay mineralogy of the clay-size fraction (Table 2) reveals a trend of decreasing iltite proportion with in­creasing grain size. Total chlorite proportion varies inver­sely to that of illite. Only minor kaolinite was detected. The sample of Martin Group volcanic material showed a dominance of illite over chlorite in the whole rock analysis yet revealed a much higher proportion of

Saskatchewan G&o/ogicaJ Survey

chlorite than Ulite in the clay-size fraction. This trend, also observed to a lesser extent for the elastic rocks is 1ikely due to the presence of coarser-grained musco~ite in these samples in addition to illite/ sericite. The chlorite is likely an alteration product of biotite and hornbl911de. Crystallinity and composition of illite appears to be similar for the elastic rock types, but the amount of clay­size fraction material is significantly lower in the very coarse-grained sediments.

3. Lithogeochemistry

All rock samples were analyzed by several methods fol­lowing crushing by steel jaw crusher and grinding using an motorized agate mortar. Most elements were analyzed by atomic absorption spectrophotometry (AAS) or inductively coupled plasma emission spectros­copy (ICP) following total digestion using HF / HN03/ HCIQ4. Exceptions are as follows: FeO analysis was by titration following HF / H2S04 digestion; LOI was determined after heating to 900°C; C02 and S by use of an induction furnace; As and Se by hydride generation and AAS analysis; U by fluorometry; Au by fire assay with AAS completion; Pt and Pd by instrumen­tal neutron activation analysis (INAA). Only selected samples underwent analysis for S, Pt, and Pd. The oxides Si02, F82{)3, and Hi) were calculated by dif­ference. Group mean values by formation and rock type are presented in Tables 3 and 4, respectively.

Clastic rocks can be classified by chemical composition in order to show relationships between elemental com­position, mineralogy, and rock type (Pettijohn et al., 1972). A number of classification schemes to relate chemical compositions to common sandstone classifica­tio~s have been devised, with the most commonly used being the log (N820/K20) versus log (Si02/ A12<)3) plot o_f ~ettijohn et al. (1972). Herron (1988) has proposed a s1m1lar plot (Sand Class format) using (total iron as F~03/ 1<2(}} rather than (NaO/ K20) as the ordinate parameter. The Si02/Al20a ratio is used as an indicator of mineralogical maturity (Pettijohn et al., 1972) while the N820/1<20 ratio is used to differentiate lithic sandstone from arkose and greywacke. The F~03/1<2() ratio is used as an indicator of mineralogical stability (Herron, 1988}. As the use of the Sand Class format bet­ter classifies these analyses with respect to their petrographic classification (Quirt, 1990), only the Sand Class format was used in this study for classification pur­poses.

The chemistry of the Martin arkoses does not vary great­ly with respect to the Si02/Al203 ratio, most of the varia­tion on the Sand Class plot being in Fe203/ K20 . The samples fall primarily into the arkose field, however, a number fall into the wacke, lnharenite, Fe-sand, and Fe­shale fields with increasing F9203/ K20 ratios (Quirt, 1990). This feature is likely due to the abundant hematite present in the majority of these samples. No dif­ferentiation can be made on the basis of rock type, as each rock type reveals a substantial spread of F~03/ 1<2(} values. A similar situation prevails for the values of the N820/1<20 ratio. Grouping of the samples by formation tends to reveal the same snuation as for

131

Table 3 - Awrage Chemical Compositions by Formation. Major oxide concentrations are similar to those of com·

Thluicho Taz Bay Beavertodge Chllflot Gillies Seaplane Melville mon granitic and metamorphic Point Channel Base Lake rocks (cf. Taylor, 1972; Ross,

1972}. Values for Si02, C02, Si02c 71 .23 70.40 73.28 74.11 71.12 75.40 68.68 and H20 appear to be Al203 11.80 12.61 10.43 10.62 10.46 10.74 10.16 elevated in the Martin Group Fe203t 3.40 3.55 3.33 2.84 2.97 2.26 2.74 arkoses with respect to FeO 1.15 2.02 1.95 0.78 1.47 0.72 0.50 F1120:ic 2.12 1.30 1.16 1.97 1.32 1.48 2.19 average Canadian Shield MgO 2.03 1.52 1.92 1.n 1.35 0.67 1.11 material {cf. Shaw, 1967),

eao 1.70 1.33 1.84 1.39 3.55 1.59 4.95 whereas concentrations of 1<20 3.66 4 .49 2.83 3.77 3.00 3.42 2.90 Al203, and to a lesser extent Na2') 2.36 3 .22 2.54 1.55 2.64 3.41 3.17 Cao and N~O. are lower. The Ti02 0.27 0 .21 0.26 0.32 0 .35 0.19 0.25 lower CaO and Na20 values P2~ 0.11 0.11 0.10 0.18 0.15 0.09 0.13 probably result from LOI 3.27 2.32 3.22 3.25 4.16 2.00 5.61 plagioclase alteration and non-C02 1.40 0.84 1.65 1.49 2.37 1.12 4.41 H20c 1.87 1.48 1.57 1.75 1.78 0.88 1.20 incorporation in clay minerals.

Elevated C02 and H20 values NI 22.5 22.5 19.8 16.4 18.4 11.4 25.1 are a result of matrix mineral Cr 49.2 36.7 41.5 45.0 47.0 23.8 53.0 formation. When plotted on an Ba 532.2 758.8 647.9 664.9 879.6 851.6 696.6 AFM diagram, commonly Sr 81 .7 85.4 105.2 118.1 174.3 148.1 181 .6 used to illustrate trends in ig-v 54.2 45.8 47.0 47.7 39.2 25.1 34.2 neous differentiation series, ZI 198.5 156.0 138.3 154.3 180.6 1344 162.S the study samples plot along Th 33.0 15.4 13.7 13.6 17.4 14.8 13.7 u 4.7 3.6 3.6 2.6 3.5 3.1 4.2 and in the vicinity of a calc-hJ 10 4 7 3 7 6 9 alkaline trend line. This might Pt 5 5 5 5 5 5 s suggest that the source rocks Pd 5 5 5 33 5 6 5 were calc-alkaline plutonic

rocks.

Table 4 - A~,age Chemical Compositions by Rock Typt,. A, siltstone and finflilrain9d Trace element concentrations sandstDnt1; B, sandstone; C, coarse-grained sandstone; D, canglofTltlrate and fine-grain9d

breccia; E, C041Hilrain9d conglomerate and breccia; F, 110lcanic. are similar to those given for granitic to granodioritic rocks

A B c D E F {Taylor, 1972; Ross, 1972} and to those given for the average

Si02c 69.65 74.22 73.45 73.12 70.00 49.02 composition of the Canadian Al203 11.09 10.40 9.73 10.82 12.54 13.80 Shield (Shaw, 1967). Strontium Fe203t 3.36 2.72 2.26 3.09 3.91 9.92 content is low (BO to 180 ppm), FeO 1.24 1.35 0.83 1.22 2.54 5.20 likely a reflection of the PI/Kf F~30 2.00 1.22 1.33 1.73 1.08 4.14 MgQ 1.52 1.38 1.66 1.54 1.79 6.76

ratio (Table 1). The Ti02 con-

CaO 3.16 1.98 2.79 1.86 1.56 5.20 tent is also low due to the reta-1<20 3 .28 3.27 3.95 3.37 1.17 2.81 tively small quantities of clay ~o 3.01 2.49 1.61 2.42 5.48 2.10 minerals in these lithologies. T102 0.31 0.23 0.18 0.27 0.34 1.98 p~ 0.14 0.11 0.09 0.10 0.19 1.26 Ni and Cr are strongly corre-LOI 4.18 2.98 4.07 3.19 2.74 6.50 lated and show a scattered but CXn 2.73 1.60 2.44 1.59 1.28 3.30 positive relationship to the Nig-H20c 1.45 1.38 1.63 1.60 1.48 3.20 gli mg parameter ( = mol.

NI 26.4 17.9 14.4 16.2 13.2 83.0 MgO/(mol. MgO + FeO + Cr 58.3 36.4 34.6 39.8 22.2 151 .0 MnO + 2 F9203)] (Quirt, Ba 753.1 656.3 674.0 674.8 1011 .6 3160.0 1990}, which are to be ex-Sr 148.7 121.8 88.3 103.3 163.2 1000.0 pected inigneousrocks (van v 44.9 35.6 37.5 48.2 42.6 184.0 de Kamp et al., 1976). The Zr 158.5 145.2 153.8 144.7 207.4 256.0 lack of, or low negative correfa-Th 13.2 21 .8 17.6 16.1 21 .8 18.0 tion between Si02 and Niggli u 4.4 3.0 3.9 3.3 5.4 3.6 mg is also characteriS1ic of ig-Au 6 5 8 6 8 3 Pt 5 5 5 5 5 na neous suites (van de Kamp et Pd 5 5 5 23 5 na al., 1976). The independent b&-

ha11ior of Zr with increasing the grouping by rock type, however, Fe-shale and Fe- Si02 that these rocks exhibit sands are found only in the Beaverlodge and Gillies (Quirt, 1990) does not fit the fan-like sedimentary Zr-Channel formations. The Seaplane Base and Melv~le Si02 pattern (van de Kamp et al. , 1976) of the maxi-lake formation samples tend to cluster in and close to mum Zr value rising and the minimum Zr value falling

the arkose field, not having a large range of F9203/K20 with increasing silica content. Tamey's (1976) dis-ratio values. criminant plot of Ti02 versus Si02 indicates that most of

132 Summary of Investigations 1990

the study samples fall within the field representing an ig­neous origin (Quirt, 1990). Those samples that do fall into the sedimentary field are close to the boundary with the igneous field. The slightly higher Si02 values of these samples possibly result from quartz enrichment caused by minor mechanical and chemical reworking of the detritus, which may also explain the relatively low Cao and Na:20 values.

Shaw (1972) developed a discriminant function (OF) to distinguish between igneous and sedimentary protoliths of an amphibolite facies biotite-quartz-feldspar gneiss. Positive values of this function indicate an igneous origin, negative values a sedimentary origin. This func­tion classified only approximately half of the samples as igneous. For the Martin rocks, tlie relatively high Si(h and Fe2<)3t values, and low Na;iO values found for these samples are reflected in low, commonly negative, values for the OF. Increasing 'igneous' signature up­wards in the Martin stratigraphy appears to reflect reworking of the detrital inflow to the basin. Van de Kamp et al. (1976), do not consider this function to be a reliable means of determining the origin of arkosic rocks and tlie ambiguous results from the Martin rocks appear to confirm this opinion. However, the data in Table 5 do appear to allow some discrimination of the uppermost Martin formations from the basal lithologies, likely due to an increased volcanic component in these forma­tions.

Table 5 - Mean values for Shaw's (1972) discriminant function.

Formation Mean value Percentage of samples of function classified as 'i~neous'

Thluicho -1 .1 25 Taz Bay 0.9 86 Beaverlodge -1.6 31 Charlot Point ·2.6 17 Gillies Channel 0.6 46 Seaplane Base 0.9 80 Melville Lake 2.9 89

The sedimentary source strongly indicated by the OF for the Charlot Point fonnation is in agreement with the sedimentological evidence. For Charlot Point rocks, illite correlates well with K20 (as does potassium feldspar) and H20. Chlorite correlates well with MgO, FeO, Al20a, Ti02, and a number of trace elements including Mn, Zn, Ni, Co, and U. Chlorite also correlates with plagioclase and correlates negatively with hematite and quartz. llfite correlates negatively with plagioclase. Both K and Rb are present in the clay minerals, likely illite, but varia­tions in the feldspar compositions that dominate the mineral assemblage cause scatter in the illite-1<2() relationship. As expected CaO correlates well with C02 with both occurring in calcite, and a good CaO and P20s correlation indicative of apatite. Dolomite is repre­sented by a strong MgO and C02 correlation. The dolomile-C02 relationship has two trends because C02 is in dolomite and calcite, these minerals being negative­ly correlated. Similarly, the dolomite-MgO relationship has of two trends with MgO present in both dolomite and chlorite. Ferric iron correlates strongly with hematite and negatively with ferrous iron, which correlates well

Saskatchewan Geological SuMy

with S in pyrite. Zinc also correlates with S and chlorite. Copper is associated with As, Ni, Co, MgO, FeO, and Ti02 in chlorite, kaolinite, and potassium feldspar. Heavy minerals are represented by correlations between Zr-U-Pb-REE (zircon) and Ti02-Zr (rutile).

The range of mean gold values obtained for the groups of Martin samples (0.003 to 0.010 ppm) is similar to that for shales as well as for falsie plutonic rocks (0.001 to 0.050 ppm and 0.002 to 0.061 ppm, respectively: Mason, 1966; Garett, 1983). The highest gold value ob­tained was 46 ppb (M-11-1), however, the formations with the highest mean Au values (Thluicho: 9.6 ppb, Mel­ville Lake: 8.8 ppb) had relatively narrow ranges, with no values greater than 18 ppb. Gold correlates with only U and Cu, and correlates negatively with Pb. Mineral as­sociations with Au are poor with only low positive cor­relations with potassium feldspar and calcite.

Similar to gold, the range of mean uranium values for the Martin formations is similar to those for shales and falsie plutonic rocks. Uranium correlates well with Zr and Al20a and to a lesser degree with MnO, FeO, Ti02, Zn, Co and P20s. The U-Zr association reflects uranium present in zircon and that of U-P20s reflects uranium in­cluded in apatite. A moderate U-chlorite correlation is supported by the U-FeO-Ti()z-Zn-Ce>MnO association.

Only a few representative samples were analysed for Pt and Pd, most of which were at or below the detection limit of 5 ppb. One sample of hematitic Charlot Point conglomerate (M4022) had 60 ppb Pd. The low con­centration levels precluded element correlations.

Limited sampling of Martin formations allows only generalizations to be made on the geochemical charac­terization of the individual formations (Table 3). The Thluicho Group rocks, with lower Ba values and higher Th and Au values, appear to reflect a different source area than the other units. The Taz Bay formation tends to contain substantially more 1<20 than the others and tends to have more FeO than Fe203. Samples of the Gil­lies Channel and Melville lake formations are CaO-COz­Sr-Ba-rich due to calcite cement, whereas the Seaplane Base formation samples tend to have less clay matrix than tlie other formations. The lack of clay is reflected in lower H20. MgO, Ni, Cr, and V contents relative to the other units. The Charlot Point formation does not ap­pear to be geochemically distinguishable from the other formations, except through Shaw's ( 1972) discriminant function.

4. Summary The Proterozoic elastic successions found along the north shore of Lake Athabasca exhibit many similarities in mineralogy and lithogeochemistry. In general, the mineral assemblage consists of quartz and feldspar with minor mica/clays, carbonate and hematite. Potassium feldspar content usually exceeds that of plagioclase, both being typically well preserved. Quartz content ap­proximates that of total feldspar, indicating a relatively unweathered source area. This mineral assemblage is typical of an arkose. The Charlot Point assemblage dif­fers from the other units with respect to quartz and

133

dolomite contents, as well as the plagioclase to potas­sium feldspar ratio.

The clay minerals present are illite (sericite), chlorite, kaolinite, and mixed-layer illite-smectite. lllite content nor­mally exceeds that of chlorite, while kaolinite is only lo­cally present. Most chlorite is Fe-Mg-rich trioctahedral chlorite, likely a result of degradation of biotite, with only trace amounts of aluminous di,trioctahedral chlorite (sudoite) being observed. Generally speaking, Martin Group clay mineralogy becomes increasingly illitic up section. Thluicho Group illite is less aluminous and more crystalline than that of the other formations.

Accessory minerals are scarce and include trace amounts of pyrite, noted in greyish, reduced sandstone, and carbonate (calcite, dolomite) which forms the cementing agent in some samples.

Major oxide and trace element concentrations and trends are similar to those described for common granitic and meta-igneous rocks of calc-alkaline charac­ter. Shaw's (1972) discriminant function indicates that the Charlot Point formation is probably derived from a sedimentary source, perhaps second-cycle sedimenta­tion. Thluicho Group material differs from the other for­mations with respect to Ba, Th, and Au content, probal> ly reflecting a different source. Gold, uranium, platinum and palladium are found in low concentration in all the rocks. Au is poorly correlated with other elements and minerals (U, CaO, potassium feldspar, calcite), but U correlates well with the heavy minerals zircon (Zr) and apatite (P20s), and with chlorite (Al203, MgO, FeO, Ti(h, Zn, Co).

5. Conculsions

From this investigation it is concluded that the forma­tions of the Martin Group possess minor differences in mineralogy and geochemistry which reflect variations in source relief and depositional processes, as noted in previous sedimentological studies. Both the Charlot Point formation and the Thluicho Group are distinguish­able from the other units with respect to mineralogy and geochemistry.

The relative lack of clay minerals and the presence of unaltered feldspars in these rocks indicates that the source area for the Martin Group and related rocks had undergone only mild chemical weathering before erosion. First-cycle sedimentation is indicated by the quartz to feldspar ratio.

The minor quantities of kaolinite found in the samples taken for this study possibly relate to pre-Athabasca Group paleoweathering. Minor quantities of sudoite in the Martin Group rocks may be an indication of the proximity of these rocks to the sub-Athabasca unconfor­mity and related basement - Athabasca sandstone fluid Interaction associated with uranium mineralization. Mar­tin Group formations become increasingly iliitic up-sec­tion.

Shaw's (1972) discriminant function does not appear to be of great use in determining the provenance of these

1:U

arkoses. The strong indication of sedimentary source area given by this function for the Charlot Point forma­tion does, however, indicate some utility for dis­criminators of this type.

Gold, uranium, platinum and palladium are not seen to be anomalous in the Martin arkoses. Due to the lack of diagenetic alteration exhibited by these rocks and the u­biquitous, albiet low concentrations of these elements, the possibility that the Martin lithologies may host syn­genetic gold and uranium mineralization in the area is discounted. Later epigenetic processes have, however, formed mineralization in these rocks (eg, uranium at the Martin Lake Adit).

6. References Elliot, C. G. (1982): A description of the Gillies Channel Forma­

tion, Martin Group; in Summary of Investigations 1982, Sask. Geot. Surv., Misc. Rep. 82-4, p31-38.

Garett, G.J.S. (1983): Handbook of Exploration Geochemistry, Volume 3: Rock Geochemistry in Mineral Exploration; El­sevier, New York, 461p.

Hale, W. E. (1953): Black Bay map area, Saskatchewan (preliminary report); Geol. Surv. Can., Pap. 53-15, 18p.

--...---, (1954): Gulo Lake, Saskatchewan; Geol. Surv. Can., Pap. 54~.

- ....... - (1955): Forcie Lake map area, Saskatchewan; Geo!. Surv. Can., Pap. 55-4.

Hendry, H. E. (1983): Sedimentological study of the Martin Group; in Summary of Investigations 1983, Sask. Geol. Surv., Misc. Rep. 83·4, p46-48.

Hoeve, J. (1982): Perspective on uranium mineralization at Beaverlodge; Sask. Res. Counc., Publ. No. G7451 E82, 23p.

Hoeve, J. and Quirt, 0. H. (1984): Mineralization and hos trock alteration in relation to clay mineral diagenesis and evolu­tion of the middle Proterozoic Athabasca Basin, northern Saskatchewan, Canada; Sask. Res. Counc., Tech. Rep. No. 187, 187p.

Koster, (1968): The geology of the Zin Bay area, Sas­katchewan; Sask. Dep. Miner. Resour., Rep. 121, 40p.

--,-.,...,.... (1970): The geology of the Burchnall Lake area, Sas· katchewan; Sask. Oep. Miner. Resour., Rep. 131, 24p.

Langford, (1980): Successor basins in the Beaverlodge area; in Summary of Investigation 1980, Sask. Geo!. Surv., Misc. Report 80-4, p29.

-~~ (1981): The Martin Group in the greater Beaver­lodge area; In Summary of Investigation 1981, Sask. Geol. Surv., Misc. Rep. 81-4, p38-43.

Macey, G. J. (1973): A sedimentologlcal comparison of two Proterozoic red-bed successions (the South Channel and Kazan Formations of Baker Lake, NWT, and the Martin Formation at Uranium City, Saskatchewan); unpubl. M.Sc. thesis, Carleton University, Ottawa, Ontario.

Mason, B. (1966): Principles of Geochemistry, third ed., John Wiley & Sons, New York, 329p.

Summary of Investigations 1990

Mazimhakam P. and Hendry, H.E. (1984): The Martin Group, Beaverlodge area; io....Summary of Investigation 1984, Sask. Geol. Surv., Misc. Rep. 84-4, p5~2.

(1985): The Martin Group: Tazin Lake, Charlot Point --a-n ... d ..... Jug Bay areas; in Summary of Investigation 1985,

Sask. Geol. Surv., Misc. Rep. 85-4, p67-80.

--~ (1986): Conglomerate composition, source areas and dispersal in the depositional basin of the Martin Group; in Summary of Investigation 1986, Sask. Geol. Surv., Misc. Rep. 86-4, pl 14-120.

Pettijohn, F.J., Potter, P.E. and Siever, R. (1972): Sand and Sandstone; Springer-Verlag, New York, 618p.

Quirt, D.H. (1990): Mineralogy and lithogeochemis1ry of samples from the Martin and Thluicho Groups, Beaver­lodge area, Saskatchewan; Sask. Res. Counc., Publ. No. R12301E90.

Ross, D.C. {1972): Petrographic and chemical reconnaissance study of some granitic and gneissic rocks near the San Andreas Fault from Bodega Head to Cajon Pass, Califor­nia; U.S. Geol. Surv., Prof. Pap. 698.

Saskatchewan Geological Survey

Scott, B.P. (1978): The geology of an area east of Thluicho Lake, Saskatchewan; Sask. Dep. Miner. Resour., Rep. 167, 51p.

Shaw, O.M. (1967): An estimate of the chemical composition of the Canadian Precambrian Shield; Can. J . Earth Sci., v4, p829-S35.

_____ (1972): The origin of the Apsley gneiss, Ontario; Can. J. Earth Sci., v9, p18-35.

Tarney, J . (1976): Geochemistry of Archean highgrade gneis­ses, with lmpllcations as to the origin and evolution of the Precambrian e<ust; in Windley, B.E. (ed.), The earty hi&­tory of the earth John Wiley & Sons, London, p405-417.

Taylor, S.R. (1972): Geochemistry of andesites: origin and dis­tribution of the elements; in Ahrens, L.H. (ed.), Physics and chemistry of the earth Pergamon Press, New York, p559-583.

Tremblay, LP. (1972): Geology of the Beaverlodge mining area, Saskatchewan; Geol. Surv. Can., Mem. 367, 265p.

van de Kamp, P.C., Leake, B.E. and Senior, A (1976): The petrography and geochemistry of some Californian arkoses with application to identifying gneisses of metasedimentary origin; J . Geol., v84, p195-212.

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