British Geological Survey

TECHNICAL REPORT WC/94/26R Overseas Geology Series

ENVIRONMENTAL GEOCHEMISTRY OF THE MENGAPUR AND SUNGAI LUIT MINING AREAS, NEAR KUANTAN, PAHANG, MALAYSIA

N BREWARDl, T M W I W S AND C CUMh41NS2

* British Geological Survey, Mineral and Geochemical Surveys Division Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Cambridge

A Report prepared for the Overseas Development Administration under the ODNBGS Technology Development and ResearchProgramme, Project 9 216

ODA clasdmdon : Subsector: Others Subject: Geoscience Theme: Mineral resources Project title: Environmental impact of gold and complex sulphide mining Reference number: R5553

Bibliographic reference : B r e d N and others 1994. Environmental geochemistry BGS Technical Report WCl94126R

Icqrwordr : Malaysia; geochemistry; environment; mining; arsenic; toxic element; aquatic biota.

Front cozler i2lustration : Alluvial gold processing plant at Sungai Luit, near Mengapur

0 NERC 1994

Keyworth, Nottingham, British Geological Survey, 1994

CONTENTS

SUMMARY

INTRODUCTION

PHYSIOGRAPHY

GEOLOGICAL SETTING Regional Geology Geology of the Mengapur/Sungai Luit area Structure

METALLIFEROUS MINERALISATION

EXPLORATION AND MINING

MINERALOGICAL INVESTIGATIONS Primary assemblages Tailings/spoil investigations

REGIONAL GEOCHEMICAL SURVEY

HYDROGEOCHEMICAL SURVEY

STREAM SEDIMENT GEOCHEMISTRY Bulk geochemistry Solid-phase partitioning

SOIL GEOCHEMISTRY Soil transects Do wn-pro file geoc hemical variation Solid-p h ase partitioning

BIOLOGICAL MATERIALS

DISCUSSION AND CONCLUSIONS

ACKNOWLEDGEMENTS

REFERENCES

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LIST OF FIGURES

Fiaure 1: Simplified outline of the Malay Peninsular, showing the location of the Meng apur/Su ng ai Lu i t area.

Fiaure 2: Conventional geological and metallogenic sub-division of Peninsular Malaysia showing approximate boundaries of the Western, Central and Eastern belts.

Fiaure 3: Sketch map of the Hulu Lepar area including Mengapur and S. Luit.

Fiaure 4: Outline geological map of the Mengapur and S. Luit areas.

Fiaure 5: Regional geochemistry: Distribution of Arsenic.

Fiaure 6: Regional geochemistry: Distribution of Lead.

Fiaure 7: Regional geochemistry: Distribution of Copper.

Fiaure 8: Regional geochemistry: Distribution of Zinc.

Fiaure 9: Arsenic in Mengapur and Sungai Luit stream waters.

Fiaure 10:

Fiaure 11 :

Mengapur and Sungai Luit stream waters pH measurements.

Stream sediment XRF data.

Fiaure 12: Mercury in stream sediments.

Fiaure 13: Flow sheet for sequential extraction scheme.

Fiaure 14: Phase distribution pie-diagrams for Mengapur stream sediments.

Fiaure 15:

Fiaure 16;

Fiaure 17: Main soil line: Mn and Fe oxides.

Fiaure 18:

Main soil line: Cu, As and Pb.

Main soil line: Zn, MO and Bi.

Main soil line outliers: a). Cu, As and Pb. b). Zn, MO and Bi.

Fiaure 19: Main soil line outliers: Mn and Fe oxides.

Fiaure 20:

Fiaure 21:

Mengapur South soil transect.

Sungai Luit soil transect.

Fiaure 22: Mengapur soil profiles.

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LIST OF PLATES

Plate 1:

Plate 2:

Plate 3: - The Bt. Mengapur - Bt. Batu ridge. Karstic limestone scenery .

Mengapur base camp and Bt. Botak.

Alluvial gold mine, S. Luit valley.

Abandoned alluvial workings, Sungai Luit.

LIST OF TABLES

Table 1: Outline geological succession in the Hulu Lepar area.

XRF trace element analyses for Mengapur and Sungai Luit stream sediments.

Table 3; OES Arsenic analyses of sequential leaching extracts, Mengapur and Sungai Luit stream sediments.

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SUMMARY

In April 1992, the UK Overseas Development Administration (Engineering Division)

approved funding for a three year study under the BGS/ODA Technical Development and

Research (TDR) programme to address specific environmental aspects of gold mining,

including studies of the release, dispersal and bioassimilation of potentially toxic trace

elements (notably As and Hg) in a variety of climatic, geological and technological

development settings. The ultimate aim is to provide a clear scientific basis for the

development of site remediation and pollution abatement strategies.

A field visit to Peninsular Malaysia was carried out in October 1992 by BGS and ITE staff

to examine the geochemistry of a number of former gold mining sites in order to establish

typical patterns of concentration and dispersion of As, Hg and other trace heavy metals.

The two principal areas chosen were the Penjom mining area near Kuala Lipis, Pahang; and

the Mengapur/Sungai Luit area near Kuantan, Pahang. The work at Penjom is the subject of

an earlier report (Williams et al., 1993) and the Mengapur results are described here. A

similar study was carried out in Eastern Malaysia (Williams et al., 1994b).

The Mengapur and Sungai Luit areas occupy the southern part of the Hulu Lepar district,

about 50 km to the west of Kuantan, Pahang, West Malaysia. Mengapur is a prospective

complex sulphide porphyry-skarn mineral deposit with potential for Cu and associated Au,

whereas the nearby Sungai Luit valley is a site of formerly extensive alluvial gold

workings, currently continuing on a small scale. Rocks, soils, stream sediments and

surface waters were collected for analysis, along with a suite of biological samples

(mostly of fish) to establish any uptake of As into the food chain.

The results show that very high levels of As and other toxic elements such as Pb are

present in the soils over the orebody and in some stream sediments at Mengapur. However,

the geochemical distribution patterns suggest that the elements at these anomalous high-

level sites are largely immobile, either due to their being held in insoluble primary minerals

or, more likely, being very strongly bound to the secondary iron oxide fraction of the soils

and stream sediments. Sequential extraction data from the stream sediments generally

supports the latter explanation.

At present, therefore, the Mengapur prospect is not a significant environmental risk, but

mining the ore could raise other difficulties. The major problem with any development in

the area, however, would be the disturbance of the soil which could release substantial

amounts of fine-grained As and Pb-rich material into the streams. In the Sungai Luit, no Hg

contamination was discovered despite a long history of alluvial Au working.

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INTRODUCTION

In April 1 992, the UK Overseas Development Administration (Engineering Division)

approved funding for a three year study under the BGS/ODA Technical Development

and Research (TDR) programme to address specific environmental aspects of gold

mining, including studies of the release, dispersal and bioassimilation of potentially

toxic trace elements (notably As and Hg) in a variety of climatic, geological and

technological settings (Project 92/6, R5553). Most of the work was carried out by

BGS, but some ecotoxological aspects were covered by the Institute of Terrestrial

Ecology. The ultimate aim is to provide a clear scientific basis for the development of

site remediation and pollution abatement strategies. Detailed models of the geochemistry and dispersal of elements such as As (widely used as a gold 'pathfinder' element on account of its common association) may also prove of value for the

interpretation of high-resolution exploration data.

Mining activities account for approximately 10% of Malaysia's total GDP (1 991

figures) and are of major importance for employment and infrastructure

development. Continued investment in the minerals sector is officially encouraged,

alongside increasing recognition of the need for effective site monitoring and post-

extractive remediation strategies to minimise the adverse impacts of mining on the environment, the non-mining economy and, ultimately, human health.

Problems of acid-drainage and the attendant mobilisation of potentially toxic metals

due to the mining and oxidation of auriferous- and complex heavy-metal sulphides are well documented (e.g. Alpers and Nordstrom, 1991; Plumlee et al., 1993; see UNEP 1991 for summary). Additional contaminants, including mercury (Hg) and

cyanide compounds, may be released during the processing of primary and alluvial gold. Such problems are often accentuated in humid tropical environments, where rates of chemical weathering (and possibly Hg methylation) are particularly high.

Field studies of gold localities in Pahang, Peninsular Malaysia were undertaken with

logistic assistance from the Geological Survey of Malaysia in October 1992. Areas of

investigation included an extensive porphyry-skarn system at Mengapur, 50km west of Kuantan, and the nearby alluvial workings at Sungai Luit, for which results are presented here. Surveys around an area of bedrock, alluvial and eluvial workings

at Penjom, south-west of Kuala Lipis form the subject of an independent report

(Williams et al., 1994a). The Mengapur prospect is currently under investigation

by the Malaysia Mining Corporation, with a view to mining should the economic and technical problems be overcome. Additional sampling was conducted in the floodplain

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of the Sungai Luit river system to the south-west of Mengapur, an area of formerly extensive alluvial gold workings and currently small-scale mining operations.

PHYSlOGRAPHY

The Mengapur and Sungai Luit areas are within the Hulu Lepar district some 50 km

west of the east coast city of Kuantan, in the state of Pahang in central Peninsular Malaysia. Access to the study areas is via a well-graded unmetalled track starting at Kg. Seri Jaya on the main Kuantan-Kuala Lumpur road and running northwards for a

further 40 km. Numerous subsidiary tracks serve well-established rubber and palm oil plantations and logging sites on the west side of the S* . Lepar valley, and one branch crosses the watershed into the S. Luit valley, then runs southwards alongside

the Luit, rejoining the main highway south-west of Kg. New Zealand. Between the

broad valleys of the S. Lepar and S. Luit a marked ridge of high ground culminates in

the steep-sided karstic limestone scenery of the Bt. Mengapur and Bt. Batu hills (Plate 1). The Mengapur Prospect lies just to the north of these, on the flanks of

another very steep feature (Bukit Botak) which mostly consists of limestone with a rhyolitic tuff cap on top of a granitic intrusion. The S. Luit catchment also has

rubber and palm oil plantations on its eastern slopes, but the broad alluvium-filled floodplain has been extensively worked for gold and shows the scars of a long history of alluvial gold workings, with numerous shallow lakes and tailings dumps partly reclaimed by secondary jungle growth. The normal soil cover has obviously been removed from such areas, but elsewhere typical residual soils about Im thick are present, showing an organic-rich dark-brown A horizon of 5-20 cm thickness overlying an orange-yellow silty-clay B horizon, often becoming mottled at depth

and with occasional ferruginous concretions. Exposure of the low-lying

metasediments and volcanic rocks is typically poor, but the limestones on the steep flanks of the hills are well exposed and there are also short lengths of 'ephemeral' limestone-floored streams over the limestone outcrop in which the bedrock is also

well exposed.

Note the following Malay (Bahasa) words and abbreviations are * frequently used in the text:

Sungai = stream, small river. Bukit = hill e.g. Bt. Botak Kampung = village, settlement e.g. Kg. Seri Jaya

e.g. S. Lepar

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GEOLOGICAL SETTING

Regional Geology

Tectonically, Peninsular Malaysia forms part of the Sunda Shield. Its fold-mountain system (the predominant trend of which is northerly or north-westerly) is a

continuation of that extending from eastern Burma, through Thailand and south-

eastwards into Indonesian Borneo.

The Malay Peninsula has conventionally been described in terms of three discrete belts (Fig. 2), differentiated on the basis of their distinctive styles of mineralisation (Scrivenor, 1928). The boundary delineations (and overall validity) of this

classification have been widely questioned (Hutchinson, 1977; Tan, 1984), but it's

use remains widespread as a framework for discussion. The present survey area lies within the Central Belt, which is characterised by a predominance of gold and base- metal mineralisation. The bordering Western and Eastern belts are dominated by

alkaline and calc-alkaline granites, with widespread Sn mineralisation (for greater detail see Cobbing et al., 1992).

The Central Belt comprises mainly shallow marine and continental margin sediments

of Palaeozoic age. Volcanic and volcaniclastic rocks of acid to intermediate

composition are also widely developed. The western margin of the belt is defined by the Raub-Bentong suture, a zone, up to 20 km wide, of melange incorporating tectonised metasediments and basic-ultrabasic rocks. Adjacent to the suture are continental rudaceous and arenaceous sediments of Devonian age, passing eastwards

into Permian marine sediments. The nature of this suture, and hence the fundamental tectonic evolution of the Central Belt, is disputed (see Williams et al., 1994a)

Geology of the Mengapur-Sungai Luit area

The geology of the Hulu Lepar area, which includes the Mengapur and S. Luit areas, is described in detail on the GSM 1:63 360 geological map sheets 81 and part of 82 and

in the associated memoir (Lee, 1990). The geological succession is summarised in

Table 1.

The oldest rocks in the district are the Kambing beds, a sedimentary formation of early Carboniferous age, which crop out in the north-east of the map area. They are intruded by the late Carboniferous/early Permian Dagut Granite and followed

unconformably by the Seri Jaya beds and Luit Tuffs, a sequence of interbedded

argiilaceous, less abundant arenaceous, calcareous and volcanic rocks of Permian

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age. These beds include the Mengapur limestones and underlie most of the Mengapur

and S. Luit areas.

The Seri Jaya beds are unconformably overlain by the Buluh sandstones, Tekam and Serentang Tuffs, a sequence of early Triassic arenites and volcanics, and the

Semantan Formation, a group of mid-Triassic argillaceous sedimentary and pyroclastic rocks. The Hulu Lepar beds, a sequence of rudaceous, arenaceous and

argillaceous sedimentary rocks with minor vulcanicity, of post mid-Triassic to early Cretaceous age, follow. These sedimentary formations were then intruded by

two phases of granitoids (the Lepar Granodiorite and the Berkelah Granite) with attendant thermal metamorphism such as that producing the skarns at Mengapur, and

subjected to a major phase of folding and faulting in the mid Triassic to late Cretaceous period.

Post-Mesozoic uplift, folding and faulting during the Cenozoic was followed by the

formation of several types of alluvium during the Quaternary.

Structure The dominant structural elements of the area are a series of folds with axial trends varying from NW-SE to NNE-SSW which were imposed on the rocks of the area mainly during the mid-Triassic and early Cenozoic tectonic events. Faulting is also widespread, mostly along similar trends to those of the fold axes but also with a less

common, but important, east-west and north-south trend set. The fault type, age and direction are linked: the north-south elements are early normal faults, the NW-SE

group are wrench faults, the east-west suite are later wrench faults, and the youngest are the NNE-SSW group which are also mainly wrench faults.

The junction of the Mengapur limestones with the non-calcareous Seri Jaya beds is transitional and suggests that the limestones were originally a reef structure, subsequently (in part) thermally metamorphosed by the intrusion of the Lepar Granodiorite. The Mengapur Prospect itself (Bukit Botak) consists of limestones and

shales of the Seri Jaya beds which are intruded by a cupola of the Lepar Granodiorite which is capped by a rhyolitic tuff.

M ETALLl FEROUS MI NE R ALlSATlON

Bedrock and alluvial gold, tin and tungsten are known in and around the area and are

either directly associated with, or derived from, the granites or the effects of the

granite intrusions on the country rock. Resistate minerals such as ilmenite,

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monazite and xenotime are also present in the alluvial cover, but probably not in economic quantities.

Many mineral veins associated with the faulting carry galena, while porphyry- skarns (Lee and Chand, 1980) produced by reaction of the limestones with intrusive

granites carry magnetite and a complex sulphide mineral suite with Cu-MO-Au enrichment in association with As, Zn and Pb.

EXPLORATION AND MINING

The Hulu Lepar area has had a long history of exploration and mining, dating back to prehistoric workings in the S. Lembing area just outside the Lepar area. Tin was mined from the mid-eighteenth century, initially from opencast workings but below

adit level from the 1890's. Tin mining finally ceased in 1988 when low world tin prices made further working uneconomic. Since 1891, some 125,000 tonnes of tin

concentrates had been produced.

Gold, with silver as a by-product, was mined from alluvial placer deposits in the Sungai Luit area from the early 1800's by a mainly Chinese workforce. Although the gold was largely worked out by the 193O's, small-scale operations continue at

present in the upper reaches of the S. Luit.

During the gold-working period several galena-bearing lodes were discovered in the S. Luit. Several of these were worked on a very small scale by a local company in the 194O's, but have not been exploited since, although applications for licences are

sometimes made.

The skarn-type magnetite mineralisation in the Mengapur area was the target of a prospecting programme in the 1960's and reserves of around 700,000 tonnes of ore with an average grade of 60.7% Fe were indicated by diamond drilling. Unfortunately

the ore proved to be unsaleable due to the very high level of base metals present.

Geochemical work by Lee and others of the Geological Survey of Malaysia in the late 1970's and early 1980's (Lee and Chand, 1980; 1982) led to the quasi-

governmental (now privately owned) Malaysia Mining Corporation, in association with the Pahang State government, being granted authority to carry out further detailed investigation, including drilling and metallurgical tests, with a view to working the deposit for Cu. Although large amounts of ore have been proven, and

detailed plans for mining the deposit have been made (including an environmental

impact study) the mineralogical complexity of the deposit would necessitate a

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complex ore treatment procedure, and at current world metal prices mining would

pro bab I y be eco no rn ical I y m a rg in al.

MINERALOGICAL INVESTIGATIONS

Primary ore assemblages

The complex sulphide assemblage at the Mengapur prospect includes chalcopyrite as the primary copper-bearing mineral, in association with pyrrhotite, pyrite, arsenopyrite, and magnetite. Copper minerals such as bornite, azurite, chrysocolla

and malachite are locally present in gossan. Molybdenite is present in the same areas as the Cu minerals but not always in intimate association. Although the presence of

gold has been proved by analysis, it is not in a visible form and is probably occluded within the sulphide minerals. Other minerals present in small amounts in the 'core

zone' of the skarn-porphyry system include scheelite, native bismuth and tetradymite, while Pb and Zn minerals (galena, sphalerite etc.) are present in the

outer zone.

Alluvial minerals (S. Luit)

Detrital pyrite is abundant in parts of the Sungai Luit, especially downstream of the

cur rent sm al I-scale m i n i ng operations.

Gold particles, mostly irregular elongated and flattened grains up to a maximum length of 2mm, can still be readily panned from stream sediments in the S. Luit but estimated typical yields of less than 0.2 g/tonne (Lee, 1990) are well below the

margin for economic mining at a larger scale than that currently active. The source

of the gold has been the subject of much discussion. The predominantly shale bedrock

is rich in pyrite and this is a likely host, but the volcanic rocks are also possible sources. In either case, it is important to note that there is no genetic relationship

between the Mengapur and S. Luit gold mineralisation.

REGIONAL GEOCHEMICAL SURVEY

A regional geochemical survey of the Hulu Lepar area carried out by Lee et al. for the

Geological Survey of Malaysia provided stream sediment data for several elements, including As, Cu, MO, Pb, Sn, W and Zn (see also Lee et al., 1980, 1982)). This data, generously supplied to the authors by GSM, was used to create the geochemical maps for As, Pb, Cu and Zn shown in Figs. 5 to 8, using the BGS standard methods

given in Breward et al; (1992). These maps correspond approximately to the area

shown in Fig. 3, with the Mengapur area just below the centre of the maps, giving a

major anomaly foe each element.

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Arsenic (Fig. 5)

With 95% of the data below 10 ppm the area is clearly not regionally enriched in As,

but a number of clear patterns can be observed. The As anomalies (values above the 95th percentile are mostly restricted to the Permo-Carboniferous metasediments of

the Kambing and Seri Jaya beds, with relatively low levels over the major granitoids

and the Mesozoic sediments. However, a NW-SE trending line of enrichment, cutting

across several lithologies including the granitoids, and terminating NE of Mengapur,

may be associated with mineralisation along the Lepar Fault zone. The highest As

values in the area are associated with zones of contact metamorphism, such as the Hulu Kuantan-S. Dagut area in the North-east of the map sheet and the 'skarn-

porphyry' system at the Mengapur prospect, where As values A5000 ppm are locally present in soils.

Lead (Fig. 6)

The major Pb anomaly in the area is clearly centred on the Mengapur and Sungai Luit districts, though lesser anomalies are also present in the north of the area over both the Lepar Granodiorite and the Permo-carboniferous metasediments. In the south, a

broad area of above-background Pb values spreads eastwards from Mengapur across

the S. Lepar valley and may be linked to mineralisation associated with the Lepar and

Dagut fault zones.

Copper (Fig. 7)

Copper anomalies are present in the north of the area, in the S. Song and S. Dagut catchments where Sn-Cu mineralisation is associated with the Berkelah granite. In

the south-west, a broad area of Cu enrichment runs west from the Bt. Mengapur limestone area and just to the east of the Mengapur Prospect itself to encompass the headwaters of the S. Jempul and a large part of the S. Luit valley. The mineralisation

is probably linked to both the thermal metamorphism effects of the Lepar Granodiorite (as at the Mengapur Prospect) and the presence of the N-S trending

Cedung Fault zone.

Zinc (Fig. 8)

Anomalies are again present in the Hulu Kuantan district in the north of the map

area, but the most significant feature is the large area of elevated Zn values centred on Mengapur and the upper S. Luit valley. The greater area of the Zn anomaly

compared to that of Cu clearly reflects the higher dispersion characteristics of Zn

under the prevailing conditions, but it is important to note that, although the

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primary anomalies of Zn and Pb are similar in shape and extent, the broad eastern

extension shown by Pb is not clearly defined for Zn.

HYDROGEOCHEMICAL SURVEY

Surface water samples were collected from 16 sites within the Mengapur and Sungai Luit areas, as marked on the map in Fig. 4. At each site 30 ml of water was drawn

into a hypodermic syringe and passed through a 0.45 Fm Millipore filter into a

Sterilin storage tube. Acidification of samples was carried out within 4 hours of collection through the addition of 0.3 ml of concentrated HNO3 (ARISTAR grade). By

reducing the pH of samples to c. 1.0, adsorption of dissolved metals to the interior tube walls was assumed to be precluded and microbial alteration processes minimised.

Initial analysis of water samples involved the direct determination of dissolved As by

ICP-AES. Samples yielding values of 4 0 ppb were then re-analysed by hydride-

generation ICP-AES, giving improved low-level precision to a minimum practical

detection limit of 0.2 ppb.

Surface water pH was determined at each site using a temperature-compensated

electrode and Radiometer Instruments meter. Calibration of the electrode was undertaken prior to each measurement using a series of commercial buffer solutions

(pH 4, 7 and 9).

Data for dissolved As and stream water pH are shown graphically in Figs. 9 and 10.

The pH values show relatively little variation, all values being between pH 5.5 and

pH 7.0 characteristic of the well-buffered nature of the limestone and base-rich tuffaceous and sedimentary bedrock. There is little evident correlation between the

stream water pH and As content. With the exception of site Men204, all As values are below 15ppb - below the current WHO and EPA maximum limits for drinking water (although these are under revision)- showing the very low dispersion and solubility

of As in stream waters even in an area where thousands of ppm of arsenic are locally

present in soils (see below). The anomalous site Men204 is a sample from a spring overflowing from a test borehole drilled into the Mengapur ore body and would therefore be expected to give a markedly higher value. Even so, a value of 82 ppb is

not particularly high in such circumstances, and the relatively low levels are certainly a consequence of the near-neutral pH due to the high buffering capacity of

the bedrock.

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STREAM SEDIMENT GEOCHEMISTRY

Sedirnents for use in the present study were obtained from 17 streams in the Mengapur and Sungai Luit area. Sample/location numbers (coded Men)' mostly

correspond to those used for water samples and are thus discernible from Figure 4. Sampling procedures followed those outlined by Plant and Moore (1979) and entailed

wet sieving of approximately 100 g (dry wt.) of -100 BSI mesh (e150 pm) detritus at each site, using a minimal volume of water to avoid the loss of fine silt

and clay fractions. Excessive drying and oxidation during transportation was

minimised by sealing all samples in polythene bags. On reaching the laboratory, three splits were taken from each sample, for use in multi-element XRF, Hg and As-

speciation analyses.

Bulk geochemistry Results for six important elements (Cu, Zn, As, MO, Pb and Bi) determined by XRF analysis of the 17 stream sediments are shown in Table 2 and Fig.11. Not

surprisingly, the sites located over the Mengapur prospect and its immediate surroundings (sites Men201 -205 and Men21 4-21 8 inclusive) show higher values

of most trace elements than those in the Sungai Luit catchment. Exceptions to this

rule are the high Pb values at sites Men208 and Men211 which may reflect the

observed presence of Pb-bearing vein mineralisation in the S. Luit. and the low levels of all the trace elements at site Men215, which lies to the north of the

Mengapur prospect and does not receive any drainage from the mineralised area.

High levels of As and Pb dominate the trace element content of the stream sediments

over the Mengapur prospect, with levels up to nearly 3000 ppm Pb at site Men204

and 2300 ppm As at site Men216. High Cu levels are more restricted, but reach 1000 pprn at site Men204 and 2700 ppm at site Men218. Perhaps significantly, both sites Men204 and Men218 are located on ephemeral streams over the limestone and skarn hosting the ore body, and both sites were dry when sampled. (The water sample corresponding to site Men204 was taken from a nearby overflowing borehole). Clearly, with such high trace element levels present locally in the

stream sediments but only relatively low levels (at least of As and probably the

others too) in solution in the stream waters, the dispersion of such elements from the mineralised sites is clearly limited. Accordingly, speciation studies using a sequential leaching system were used to determine the chemical form and host phases for As.

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Determination and distribution of mercury (Hg).

Liquid metallic mercury is often used in the processing of gold-bearing ores to concentrate fine-grained particulate gold by the formation of amalgams (liquid mercury alloys) from which gold may be recovered by evaporation or distillation. In small-scale mining operations, where pollution controls are limited, such

processes can be inefficient and may result in significant contamination of the local environment. Since the Mengapur area has not been mined the levels of Hg in the

local sediments can probably be relied upon as representing the natural background level. Amalgamation was probably used extensively in the historic alluvial Au mining

in the S. Luit, and its use continues in the current operations, though probably under greater control than before. To check for contamination the stream sediments were

analysed for Hg using a vapour-generation Atomic Absorption Spectrometry technique. The data are shown as a bar graph in Fig.12. Mercury levels around

Mengapur (sites 201-205 and 214-218) are, as expected, low, with typical Hg values I 0.15 ppm. Even in the S. Luit, the highest value (at site Men209) is only

0.45 ppm indicating that mercury contamination is not significant in this area despite its history of gold mining.

Solid-phase partitioning Sequential extractive procedures formulated by Breward and Peachey (1 983) were applied to all the stream sediment samples to determine the partitioning of As among the common geochemical phases. Oxidation of sample material was carefully avoided prior to analysis, to preclude adjustments of speciation during storage. The sequence of operation stages in this scheme is shown in Fig.13.

The initial stage of the leaching sequence entailed shaking 1 g of sediment (dry wt.)

in 25ml 1M ammonium acetate solution (NaOAc) at pH 7 for one hour to remove

adsorbed or exchangeable cations. Organic components of the residue were then removed with 1 M ammonia solution (NH40H) and subsequently separated into fulvic

and humic fractions by hydrochloric acid (HCI) precipitation at pH 1. The precipitated humic acid fraction was subsequently taken into solution by using a hot (80oC) leach with acidified hydrogen peroxide (H202) solution (1 00 vol. strength). The inorganic residue remaining after the NH40H application was leached for 1 hour with 0.1M hydroxylamine solution (NH2OH.HCI) acidified to pH 3 by dilute nitric

acid, to remove Mn-oxide bound As phases. A Tamm's Reagent (oxalic acid- ammonium oxalate mixture) application was then utilised for the dissolution of Fe- oxide phases, samples being given a 2-hour leach in the absence of light as the

system is photosensitive. Washing of the residue was undertaken between each stage of the leaching sequence, to avoid cross-contamination of extractants. With the

1 5

exception of the hydrogen peroxide attack on the humic material, all extractions

were carried out at room temperature, nominally 25* C. The abundance of As held in resistate (silicate and non-volatile sulphide) minerals was estimated using a sixth stage hot mineral acid attack on the residue from the Tamm’s Reagent extraction and is given as the ‘residual’ phase in the pie diagrams in Fig. 14. The alternative method, in which the residual phase is calculated by subtracting the sum of adsorbed,

organic, Mn-oxide and Fe-oxide bound As from the total value obtained by XRF analysis, is also valid but is prone to summing errors at low As levels.

Full sequential As data for all samples are provided in Table 3 (page 14). The data were also used to prepare the pie diagrams in Fig. 14, in which the proportion of the

As content of the nominally geochemically active phases (i.e. those extracted by the leaching scheme) are compared with the total As content of the sediment. In

consequence these diagrams should always be interpreted with the total As levels (Fig. 11) in mind.

One other problem with these diagrams is that at very low levels of total As, the

extracted phase content may be very near or below the analytical detection limit. In the latter case, if the value for the practical detection limit is used instead of the real value, then the proportion of As in the extracted phases relative to the total will be exaggerated. This is the case in all of the samples from the S. Luit catchment, so Fig. 14 concentrates on the Mengapur samples which show a range of features at realistic

As detection levels.

Clearly two groups of pie diagram types can be observed in Fig. 14. Samples Men203

and Men215 were taken from streams away from the mineralised area and have ‘background’ total levels of As and trace metals. Here, the extractable As-bearing phases form a significant proportion of the total As content. In sample Men203, the

secondary Mn and Fe phases together host more than 50% of the total As, with lesser amounts in the Absorbed and organic-bound forms, such that only about 25% of the

total As is in the residual forms. In sample Men215 the Absorbed and Fe-oxide

phases dominate the extractable portion, with about 50% in the residual forms.

A very different picture is presented by the other Mengapur samples. The residual phases account for some 80-90% of the total As, showing the preponderance of As

either in primary minerals (such as FeAsS) or low-solubility secondary forms.

There is some variation in the dominant extractable phase at the other sites, with the

Fe-oxides usually the most prominent (except at Men21 4), but with variable proportions of the other phases. At site Men205, 47 ppm As is present in the

1 6

ammonium acetate extractable phase (cf. 46 ppm in the Fe-oxide phase) while at site Men204, 45 ppm in the 'Humic' phase compares with 48 ppm in the Fe-oxide phase. At site Men214, 39 ppm is present in the fulvic phase (values in the other extracted phases all being c l 0 ppm, while at Men201 and Men216 'Fulvic' and Mn-

oxide values are both significant. The lack of consistency in the phase distribution

patterns is curious, but the actual As levels in the extracted phases are all relatively low, a few tens of ppm being typical.

The most important conclusion that can be drawn is that, under the prevailing

conditions at Mengapur, the As released by weathering of the orebody is held in relatively geochemically inactive (low-solubility) phases and as such are also likely to be of low bioavailability and consequently of limited ecotoxicity. However, a change in conditions such as a major fall in pH could liberate As from the substantial total reserves in the sediments, but as long as the high buffering capacity of the local bedrock and groundwater is not exceeded, this remains unlikely. Problems of this kind are more likely to arise if the sulphide ore is mined, and processed in an area of

much lower buffering capacity.

SOIL GEOCHEMISTRY

A number of traverses were made across the Mengapur and S. Luit areas to determine the spatial variation of As and other elements. In addition, down-profile samples were taken from specially-dug pits to monitor the geochemical variation with soil horizon. At a number of sites, grain-size separations, with subsequent determination of As, were carried out to examine possible As associations with particular size

fractions. Sequential extractions similar to those carried out on the stream

sediments were performed on selected soils to establish the solid-phase partitioning of As and other elements present.

Soil transects. Three soil transects were made in the area and their positions can be seen on Fig. 4.

The major 1 km line was intended to cross Bukit Botak and the associated orebody

from SE to NW, but its original course had to be modified due to the excessive

gradients and impenetrable forest, so the line was taken SW from the highest point of the transect on the southern slope of Bk. Botak. Along this line samples were taken every 25 m, with 'outliers', i.e. samples taken 50 m either side of the line, every 100 m. To the south of this line, a shorter (200 m) transect was taken running

eastwards from a road junction east of Bukit Mengapur through an oil palm plantation, in order to establish a local 'baseline' for As and trace metal levels away from the mineralised area. In the S. Luit catchment, a 400 m N-S line was

1 7

established in an area of floodplain which had been recently clear-felled prior to the extension of workings of an alluvial gold mine.

1. Main transecf

The profile for Cu, As and Pb (the principal 'trace' elements in the soil samples) for the main Mengapur line (excluding the outliers) is shown in Fig. 15, that of the less abundant but still significant trace metals (Zn, MO and Bi) in Fig. 16 and the major oxides (manganese and iron) in Fig. 17. Profiles of the outlying samples 50 m either side of the main line are shown separately in Figs. 18 and 19. For these samples, (+50) indicates a sample on the north side of the main line and (-50) one to the south.

Very high levels, especially of As and Pb, are clearly present over the skarn orebody

to the south of Bt. Botak, with up to maxima of 13 182 ppm As and 11 694 pprn Pb present at site Men600 +50, and several other sites showing As values >4000 ppm

and Pb levels >2000 ppm. Copper is less abundant than As and Pb, but reaches a maximum value of 3434 ppm at site Men600 +50 (again!) and is >2000 ppm at a number of sites between Men600 and Men750. In contrast, Zn levels are highest in

the southeastern part of the traverse, with levels up to 900 ppm at site MenO5O. Molybdenum reaches its maximum value of 179 ppm at site Men200 -50 and shows

a well-defined peak on the main line around site Menl50. Bismuth more closely follows the As and Pb pattern, with its maximum ~(333 ppm) at site Men600 -50.

The differences in the distribution of these elements is probably tightly controlled

by the strongly-zoned nature of the porphyry-skarn orebody, as proved by MMC's

test drillings and soil geochemistry sudies, while the relatively low dispersion of the

elements in the soil is indicated by the good resolution of the anomalies at such a high sampling density.

It is instructive to compare the trace element distributions with those of manganese and iron (Fig. 17). Iron is abundant in primary minerals in the orebody, mostly as

sulphides (pyrite) and oxides (magnetite); and both elements also form secondary oxide phases in the soils which are important controllers of subsequent trace metal mobility owing to their sorptive and binding properties. Manganese shows two sharply-defined high-level zones above a background level of around 0.1% MnO, the first in the southeast below site Men200 which broadly coincides with the zone of

high Zn levels and the second around site Men675 and Men600+50 which corresponds with the major As anomaly. Iron also shows peak values (up to 44% Fe2O3) in the Men675-Men700 and Men600+50 area and probably indicates the

presence of the weathering arsenopyrite-rich orebody close to the surface at this

1 8

point. Although levels are slightly above background over the southeastern part of

the traverse, below site Men200, there is not the well-defined zonal break shown by manganese.

2. Menaapur Sout h transect. (Fia. 201

A short east-west line to establish the local background levels for the area. High As

and Pb levels near the track are most probably due to the use of mineralised

aggregate in the road construction rather than local mineralisation, as the levels fall

to steady background levels (ca. 30ppm Cu, 50ppm As and 100ppm Pb) within 50

metres of the road.

3. Sunrrai Luit transect. (Fia. 21)

Copper, As and Pb values are mostly similar to, or below, the 'background' levels

established at Mengapur South except for the northern extremity of the line, where

levels of up to 500ppm Pb and elevated As levels probably reflect the presence of local Pb vein mineralisation which is known to be widespread in the area.

Down-profile geochemical variation.

Soil samples were collected at various depths by digging pits at three selected sites

on the main Mengapur soil transect. Pit 2 is adjacent to site Men500, Pit 3 is at site Men250 and Pit 4 is at the SE end of the line at Men000. The profiles at each site were fairly similar, with an organic 'A' layer about 5 cm thick at the top, a red-

brown clay-rich 'B' horizon up to about 35 cm depth and an increasingly stony red clay 'C' horizon below this going down to at least 100 cm depth. Samples were taken

at depths of 5 cm, 30 cm and 10 cm and analysed for trace element content as for the other soil samples. Although three sample sites represent only a very limited dataset

and the trends shown in Fig. 22 are inconclusive, it is interesting to compare the levels of As and Pb in each profile, and note especially the very high levels (>5000 ppm) of As and Pb in the 'C' horizon of Pit 3 (= Men5OO).

Solid phase partitioning

No partitioning studies by means of selective extractions equivalent to those carried

out on the stream sediments were carried out on the Mengapur soils, but given the similar Eh-pH conditions and bulk geochemistry, the speciation profile is likely to be similar to that shown by the soils at Penjom (Williams et al., 1994a). Due to the nature of the soils, high Fe203 levels are present with or without high levels of As

or other potentially toxic elements, but although only a small fraction of the 'total'

iron oxide content may be derived from arsenopyrite weathering, the oxide phase clearly hosts and retains much of the As released from the primary ore. Without

1 9

disturbance of the soil, the release of As to the environment is probably controlled

and strongly limited by this iron oxide phase sorption. However, this fine-grained

arsenic-bearing iron-oxide material is readily dispersed in suspension from

exposed soil, and may enter the drainage in this form. Under normal stream

conditions the As will probably remain bound to the low-solubility iron oxide

matrix, but under certain conditions, for example those of low Eh and pH (perhaps

generated by microbial activity in anoxic environments such as stagnant, organic- rich lake bottoms) the equilibrium position would change and this material could

release As into solution, becoming available for incorporation into the biosphere and

could therefore constitute a hazard.

BIOLOGICAL MATERIALS

Systematic sampling of aquatic biota was undertaken of streams in the Mengapur and

S. Luit areas. Sampling of filamentous algal species was carried out by use of a c lmm

mesh net, while fish and invertebrate samples were collected using a casting drag- net with a diameter of approximately 2 metres. Sub-sampling of fish was carried out

within two hours of collection, by removal of the principal muscle tissue. The

sample was subsequently preserved by immersion in 70% ethanol solution. All biological samples were analysed for 'total' As by ICP-AES following cold acid digestion. Although some 30 samples were taken and analysed, only at site Men201

(see equivalent water and stream sediment site map, Fig. 4) was an arsenic value above the ITE As analytical detection limit of 0.05 pprn observed. This value of 43 pprn was given by filamentous algae and could be due as much to entrained As-rich particulate matter as to As sorbed by the algae. However, the ~0.05 pprn As levels in

the other samples amply demonstrate the low level of As uptake into the biota in this system.

A much more detailed overview of As and Hg in aquatic biota generally, and the biological data from both Penjom and MengapurEungai Luit, can be found in a separate ITE report (Cummins and Wyatt, 1994).

2 0

DISCUSSION AND CONCLUSIONS

The mobilisation of fine (~0.45pm) colloidal or dissolved As into surface or groundwater systems is a potentially significant hazard associated with the exploitation of arsenical gold deposits. Human responses to persistent external contact or ingestion of waters holding As at levels of 50-500 ppb are well documented (e.g. Chen, 1988) and range from losses of nervous response, gastro-

intestinal irritation, peripheral circulatory damage and dermaVinternal

carcinomas. Notably, carcinogenesis is specifically a human response, other mammals and reptiles being apparently unaffected.

The Mengapur prospect has not yet been mined so there are no extensive spoil heaps of the type and range found at Penjom (Williams et al., 1994a). Consequently,

surface contamination by waste material is not a problem. However, very high

levels of As and other toxic elements such as Pb are present in the soils over the orebody and in some stream sediments. The geochemical distribution patterns suggest

that the elements at these anomalous high-level sites are largely immobile, either

due to their being held in insoluble primary minerals or, more likely, being very strongly bound to the secondary iron oxide fraction of the soils and stream sediments. The sequential extraction data from the stream sediments generally supports the

latter explanation.

As a consequence of the strong binding of As and Pb to the secondary iron oxide fraction in the soils and sediments, levels of these elements in the stream waters is very low, generally well below the WHO exposure guidelines for potable waters.

This situation is also assisted by the relatively high pH of the stream waters (26.0)

which ensure that any solution equilibria involving hydrogen ion transfer are strongly inhibited. The high stream pH levels are mainly a consequence of the base- rich limestone-skarn bedrock which possesses a high buffer capacity capable of

neutralising the acidity generated within the soil profile.

At present, therefore, the Mengapur prospect is not a significant environmental

risk, but mining the ore could raise other difficulties. With a limestone-skarn host rock, acid generation in waste dump material is not likely to be such a problem as it is at sites with poor bedrock buffering capacity, and good design would further

minimise this problem. However, siting any waste dumps or tailings ponds on the less well-buffered granites or metasedimentary bedrock could lead to acid waters high in As and Pb leaching into the streams and groundwater. Again, good design and

planning based on geological and hydrogeological data would minimise the

environmental impact of such development.

2 1

The major problem with any development in the area, however, would be the disturbance of the soil. While the soil is vegetated, there is little outwash of fine

material into the drainage, but forest clearance and earthworks could release more substantial amounts of fine-grained clay and iron oxide material into the streams. In

the Mengapur area, this fine material can be strongly enriched in As and Pb and could

create a long-term contamination problem, even at a considerable distance from the

source. If the arsenic and lead remain strongly bound to the clay and iron oxides then there is little environmental concern, but if this material is subjected to a reducing environment such as a stagnant, organic-rich lake bed, then microbial reduction

could conceivably release As and Pb in biologically available forms into solution and be an environmental health risk. In a high-rainfall tropical climate, soil outwash is difficult to prevent, but can be reduced by minimising the amount of devegetation and

ground disturbance.

Alluvial gold working inevitably leads to major disturbance as large areas of alluvium are cleared and quarried, and the Sungai Luit catchment shows abundant evidence of past and current workings. However, despite the dramatic disturbance during active working (Plate 3), natural revegetation is relatively rapid and since

the levels of toxic elements such as As and Pb in the soils and alluvium are fairly low there is little long-term health risk from these natural sources. Alluvial gold

processing in the area has used amalgamation with mercury as a standard recovery method and some contamination from past workings might be expected. Little evidence of elevated Hg levels was found in the catchment, however, and even though the currently-active mines also use amalgamation there is no evidence of high Hg levels in the tailings ponds suggesting that the process is being diligently operated

and leaks minimised.

The Mengapur-Sungai Luit dataset provides a valuable insight into the natural and post-extractive behaviour of As, Hg and other trace elements from a complex polymetallic sulphide orebody and alluvial gold workings. Selected data from the study will later be included in a comparative assessment of several geological/metallogenic settings, aimed at characterising the contaminant hazard potential of a wide range of deposit types and host lithologies. This approgch has predictive applications and should therefore be of value for future Impact Assessments and environmental planning within the minerals sector in Malaysia and

elsewhere.

r’

2 2

ACKNOWLEDGEMENTS

The authors wish to extend their gratitude to the Geological Survey of Malaysia for

the provision of data, vehicles, equipment, support personnel and local expertise throughout the 1992 BGS field visit. In particular, Mr. Lee Ah Kow provided valuable guidance based on his personal knowledge of the Mengapur and S. Luit area.

Thanks are also due to the management and field staff of the Malaysia Mining

Corporation, especially Dr. Jaafar Ahmad and Mr. Fauzi Zainuddin, for permitting

access to concessions and providing valuable guidance during sampling.

2 3

REFERENCES

Abers. C N and Nordstom. D A: 1991 : Evolution of extremely acid mine-waters at

Iron Mountain, California. Are there any lower limits to pH? in Proceedings

of 2nd International Conference on the Abatement of Acidic Drainage. MEND, Ottawa, Canada, 2, 321 -342.

Preward. N.. Green. P.M and Hennev. P.J: 1992: Analysis and processing of regional

geochemical imagery using a Macintosh I I microcomputer for geochemical

map production. BGS Technical Report WP/92/16.

Breward. N. and Peachev. D: 1983: The development of a rapid scheme for the

elucidation of the chemical speciation of elements in sediments: The Science of

the Total Environment 29, 155-1 62.

Chen. C J : 1988: Arsenic and cancers. Lancet I (8575/6), 414-415.

Cobb ina. E J. Pitfield. P E J. Da rbvshire. D P F and Mallick. D I J. 1992: The

granites of the South-East Asian tin belt. Overseas Memoir of the British Geological Survey, No. 10

Cumrnins. C.P. and Wvatt. C .L.: 1994: Environmental Geochemistry of the Penjom

and Mengapur mine areas, Peninsular Malaysia: Preliminary studies of arsenic and mercury in aquatic biota. Institute of Terrestrial Ecology.

Hutchinson. C S : 1977: Granite emplacement and tectonic sub-division of Peninsular

Malaysia. Bulletin of the Geological Society of Malaysia, 9, 187-207.

Lee Ah Kow and Chand. F: 1980: A detailed pedogeochemical investigation of the

Mengapur Prospect in the Mengapur base metal district of Pahang. Unpublished Regional Mineral Exploration project report, Geological Survey

of Malaysia, no. EMR 03/1980.

Lee Ah Kow and Chand. F: 1982: A follow-up geochemical survey of the Mengapur

halo area in the Mengapur base metal district, Pahang. Unpublished report, Geological Survey of Malaysia, no. EMR 01/1982.

2 4

Lee Ah Kow; 1990: The geology and mineral resources of the Hulu Lepar area, Pahang.

Geological Survey of Malaysia. District Memoir 22.

Plant. J A a nd Moore. P J; 1979: Regional geochemical mapping and interpretation in

Britain. Philosophical Transactions of the Royal Society of London, 288, B95-112.

Plurnlee. G S : Smith. K S: Ficklin. W H : Briags. P H and McHuah. J B ; 1993:

Empirical studies of diverse mine drainages in Colorado. Mined Land

Reclamation Symposium, Billings, Montana, Proceedings.

Scrivenor. J B : 1928: The Geology of the Malayan Ore Deposits. (Kuala Lumpur,

Government Printing Office).

Tan. B K; 1984: The tectonic framework and evolution of the Central Belt and it's

margins. Bulletin of the Geological Society of Malaysia, 17, 307-322.

JJNEP; 1991 : Environmental Aspects of Selected Non-ferrous Metal Mining: A

Technical Guide.

Williams. T M : Breward. N.. Gunn. A G and Cummins. C 1994a Environmental

Geochemistry of the Penjom Mine area, Kuala Lipis, Pahang, Malaysia: Preliminary results with particular reference to Arsenic. British Geological

Survey Technical Report WC/94/20R.

Williams. T M: Breward. N and Smith. R 199 4b; Environmental Geochemistry of

the Mamut Coppper Mine, Sabah, East Malaysia: A preliminary study. British Geological Survey Technical Report WC/94/9R.

2 5

GEOLOGICAL SEQUENCE SEDIMENTS VOLCANICS

PERIOD ERA

Allwium - Uncomolidated fluviatile clay, sik sand and gnwl ' F I and raidualsoil

TERTIARY

FOLDING SW NE -

I

E I- m

% E El

CRETACEOUS BR &rapit sandstones - Basal polymin conglomerate overlain

by red sandnom/mudstone interbeb. ancl grey arenites with subordinate interbedded pelites and rudites

Mangking sandswnes - Argillrceous red beds (shale. mudstone. minor siltstone. sandstone. conglomerate and volcanics) overlain by grey ucnites with minor pekes. rudites and volcanics.

MG

DISCONFORMIM

BK

SM

BL

MN

JM

TR

KL

BcrkeWl conglometata - Red polymict. p;lra

conglomentes and interbedded s a n d s m d m u d l e

FOLDING

Semanmn formation - Grbonaceous shale and CUH I TRlASSlC TK

SR P

Tdam N f f ~ - F&c ( h ~ l i r i c and daciric)tuffs with minor siltscone

Buluh sandstoms - Well-bedded sandstone with minor intercalated silrsrone . mudscone and shale. c Serenrwg ruffs - Felsic pyrocLrrics (&vitrified. lithic

tu%) interbedded with minor agglomcnte. wndnone. silmone and shale

Mengapur limescones - Massive marble with subordinate slate. phyilite. schii and quartzite.

jempul slates - P e l i (hornfels. slate and phyllite) with

interbedded minor metatuff. quurzite and meprudites.

FOLDING

COMYtmePmOrphOKd

Tenpai mpsilrscones - Mepsiltsmnes and quamite with minor pelitetlumites Keliu slates - Pelices (homfek, slate and phyllite) intercalated Wcr-ucnitcz (metrtlut.one and quartzite) and rare rudites

c o n r m - m e ~

LT Luit cuffs - Mecunorphosed (rhyoiitic to andesitic) vdcanics PERMIAN

CARBONIFEROUS

INTRUSIVES

Fine - gtained

Medium -grained

Coarse -grained

Fine -grained

Medium -grained

COVK - gnined

Fine - gnind

Medium -grained

Coarse - p ined

1 TRlASSlC

Berkelah Granite-Pink fine to GM medium-grained alkali granite

7

Pink alkali granite

Lepar Granodiorite - Dark grey

gnnodiorite cD" medium-grained hornblende-biotite

7

Dark grey hornblende- biotite gtanodiorite

7 cffi &gut Gnnite- Grey. porphyritic granite PERMO-CARBONIFEROUS Grey porphyritic biocite granite

Simplified stratigraphic column for the Hulu Lepar area. (after Lee, 1990)

Table 1

Table 2. XRF trace element analyses for Mengapur and Sungai Luit stream sediments (all values in pprn).

Sample

Men201 Men202 Men203 Men204 Men205 Men206 Men208 Men209 Men21 0 Men21 1 Men21 2 Men21 3 Men21 4 Men21 5 Men21 6 Men21 7 Men21 8

cu 21 6 184 46

99 1 262

18 24 47 3 0 16 33 1 2

204 41 399 473

2655

zn 235 456 254 360 801

83 133 245 103 24 1 182 54

26 1 151 179 904 601

As

1033 768 161

670 28 45 4 6 2 0 9 8 2 4 4 7

828 170

2333 1373 2237

1635 +

MO

156 78 16

603 79 1 5 7 8 5 8 7

14 7 0 11

392 40

160

Pb

1361 1750 384

2967 1563

181 868 236

76 506 189 101

1200 285

1735 1794 1876

Bi

70 27

4 349

41 3 1 1 1 1 1 3

34 4

142 64 323

Table 3. ICP-OES arsenic analyses of sequential leaching extracts, Mengapur and Sungai Luit stream sediments (all values in P P m m

Fraction Men201 Men202 Men203 Men204 Men205 Men206 Men208

Absorbed F u Iv ic.. Humic

Mn-Oxide Fe-oxide Residual

Absorbed Fulvic Humic

Mn-Oxide Fe-oxide Residual

10 58 26 47 66

834

Men209 1 0 10 10 1 0 10 -

1 0 10 10 1 0 67 661

Men21 0 10 10 10 10 10 -

10 10 47 10 1 0 10 10 45 10 36 10 10 53 48 46 42 1512 547

Men21 1 Men21 2/21 3 Men214 10 10 10 10 1 0 39 10 10 10 10 10 10 10 1 0 10 48 - 749

39 1 0 10 10 10

10 10 10 10 10

Men21 5 27 10 10 10 29 84

Men21 6 10 43 10 45 69

21 56

Fiaure 1 ; Simplified outline of the Malay Peninsular, showing the location of the Mengapur/Sungai Luit area.

Conventional geological and metallogenic sub-division of Peninsular Malaysia showing approximate boundaries of the Western, Central and Eastern belts.

Figure 3. Simplified sketch map of the Hulu Lepar area.

Hulu Lepar Beds (Mesozoic)

VI Q) S 0 c,

P rn U 3

P c, .- c m

v)

0

C Q v)

c, Q

P P B z

v) Q) S 0

c rn v)

8 s I- E Q Y

Seri Jaya Beds (Permian)

c, .- 3

v) Q) 4J Q v) -

ln t rusives

Q) c, .-

0

0

0

e 0 c e

0

Figure 4. Area detail for Mengapur and Sungai Luit areas, showing geology, drainage and sample site numbers.

/

U

c 0 - U - 8 e

Figure 9.

100

80

a 6o e U

20

0

8.0

7.5

7.0

6.0

5.5

5.0

Arsenic in Mengapur and S. Luit stream waters

Determination by Hydride-generation/lCP. Limit of detection 0.2ppb

Sample Site

Mengapur and S. Luit stream water pH.

Sample Site

0

0 0

0

0 0

a 0 0 0

a 0 0

0 0 a a 0

0 0

0 0

0 0 0 0 0 0

0 0

0 0 a 0

Figure 11

n U) (II

0

I

c,

c, Y

U) E 6)

c,

U)

E L (0

c, U)

L J e (II m C 6)

I

OOOE 00% oooz 00s 1 000 1 00s 0

L a s E I z

e 0

0

0 e 0

0

0 e 0

0 0 0 0

0 0

0

0

0

0

0

0

0 0

0 0 0

0

0

Figure 12.

0 0

0

0

0

Figure 13. Flowsheet for sequential extraction system

Liquid Shake for 1 hr with 1M ammonia solution

Fresh, moist ' &ry weight sample

Acidify to pH I Liquid *with concentrated

hydrochloric acid

Exchangeable Shake for 1 hr with 1M ammonium acetate solution

Liquid

_j

Liquid Shake for 1 hr with 1M ammonia solution

Acidify to pH I Liquid *with concentrated

hydrochloric acid

Heat to 80 C with acidified hydrogen

Solid

Humic fraction Liquid

Solid

Shake for 1 hr with

in 0.001 M HN03 0.1 M NH20H.HCI manganese Liquid

1 peroxide I

Mix with Tamm's Reagent and allow to stand in dark for 2 hrs.

I So'id

Secondary Liquid

W

c

a 0 0

0

0

0

0

0 0 0

0 0

0

0 0

0 0

0 0

0

0 0

0

0

0

0

0

0

0 0

a 0

Sample Men201 Figure 14. Sample Men202

Absorbed

Fulvic Humic Mn-Oxide Fe-oxide

Resid ua I

Sample Men203 Sample Men204

Absorbed

Fulvic Humic M n-Oxide Fe-oxide

Residual

Sample Men205 Sample Men214

Absorbed

Fulvic Humic M n-Oxide Fe-oxide

Residual

Sample Men21 5 Sample Men21 6

Absorbed

Fulvic Humic Mn-Oxide Fe-oxide

Residual

a 0

0

0

e 0 e 0

0 0

e 0

0

0

0

0

a 0

0

a a 8 0 0

e 0

e 0

0 0

0 0

0 0

0 0 0 El

Figure 15.

0 0 0 00

0 0 0 CO

udd

0 0 0 w

0 0 0 cu

0

0 0 0

Figure 76.

0 0 CO

0 0 CO

udd

0 0 *

0 0 (U

0

Figure 17a. Mengapur Soil Line I = Manganese

1 .o

0.8

0.6

0.4

0.2

0.0

<Southeast> <Bt. Botak>

Figure17b- Mengapur Soil Line I = Iron (Fe203)

L

&out hwesb

Figure 18a. Mengapur Soil Line 1 Outliers

15000 J

.

10000 -

E & .

5000 -

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Z Z E E 2 2 % 2 Z Z 2 2 Y ? Z E 2 2 Z % ? s s s 8 8 8 8 9 8 $ 9 s s $ ~ s ! $ k s 8

<Southeast> <Bt. BotaK> <Southwest>

Figure 18b. Mengapur Soil Line 1 Outliers

0 0 0 c 1

0 0 0 c 8

0 0 c 7

2 0 0 cu c 2

0 0 cu c s

0 0 m c 2

0 0 m c s

0 0 e c s

0 0 * C

2 0 0 v) c 2

0 0 Lo c 3

0 0 CO c 9

0 0 a c 2

0 0 b c 8

0 0 03 c 8

0 0 Qo c 8

0 0 Q) c 8

0 0 Q) c 8

cS ou t heast> <Bt. Botak> <Southwest>

Figure 19a.

0

e

Mengapur Line 1 Outliers 2.0

0 0 0 t

9

0 0 0 c 8

0 0 c F

8

0 0 c F

2 0 0 cu c 8

0 0 cu c 5

0 0 $2 2

0 0 2 8

0 0 * c 8

0 0 w c 3

0 0 v) c s

0 0 v) c= 2

0 0 CD C

8 <southeast> <Bt. Botak>

Figure 19b. Mengapur Line 1 Outliers

0 0 CO t

8

0 0 h c 2

0 0 h c 3

0 0 a3 c 9

0 0 CO c 3

0 0 Q, c 8

0 0 Q, C

9 <Southwest>

50

40

30

20

10

0

0 0 0 C

8

0 0 0 c 2

0 0 c 7

8

0 0 c - s

0 0 cv c 2

0 0 cu C

8

0 0 m c s

0 0 m c 5

0 0 d c 8

0 0 c s

0 0 v) c 5

0 0 v) c 2

0 0 CO C

8

0 0 CQ c s

0 0 h c s

0 0 h c 2

0 0 CO c 2

0 0 CO c f

0 0 Q, c 5

0 0 Q, c 9

<Southeast> <Bt. Botak> <Southwest>

E Q Q

E Q e

Figure 20. Mengapur soil line E

1000 1

800

600

400

200

0 101 102 103 104 105 106 107 108 109

Sample No.

Figure 21 Sungai Luit soil line

400 4

200 3001 Sample No.

Figure 22.

U)

e c, rn

I rn

0 U)

L 3

1

0 0 0 <D

0 0 0 rc)

0 0 0 v

0 0 0 m

0 0 0 (U

0 0 0 T-

O

E P P