West Coast Malaysia Tin Belt - Kinta Valley, Kuala Lumpur District, Gopeng, Bidor, Sungei Besi
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The West Coast Malaysia tin belt corresponds to the Triassic Main Range Granite batholith and the strip of Middle to Late Palaeozoic and Triassic sedimentary rocks between the batholith and the west coast. Alluvial, eluvial and minor lode deposits are found over the granite and to the west of it, while virtually none is known to the east of the batholith. Of the more than 2 million tonnes of tin Malaysia produced until the dramatic decline in the country's production by the mid 1990's to date, around 90% had come from the West Coast Belt. Within the belt two districts stand out, namely the northern and more significant Kinta Valley centred on Ipoh in Perak, and the slightly less important area around Kuala Lumpur in Selangor e.g., Sungei Besi. Other areas of mineralisation are distributed from the far north-west to south of Melaka.
For an overview of the broader setting of the East Coast Malaysia tin belt, see the separate South-east Asian Tin-Tungsten Belt, Thailand, Myanma/Burma, Malaysia, Indonesia.
The main geological elements of the West Coast Malaysia tin belt are as follows:
• The Main Range Granite - This batholith extends for some 500 km from near the north coast of the Thai-Malay Peninsular, between Songkhla and Kota Bharu, trending in a general north-south direction to near Melaka on the south western coast. It ranges from 30 to 100 km in width and is believed to have been emplaced in the Middle to Late Triassic. The granites of the batholith are usually coarse- to very coarse-grained and almost always porphyritic, commonly being very coarsely porphyritic with phenocrysts up to 5 cm long. Finer varieties are encountered however. They are grey biotite granites.
The granites of this batholith are believed to be deep seated as they give strongly discordant Rb-Sr and K-Ar age dates.
To the west, they intrude Silurian, Devonian and Triassic sediments, while to the east, in addition, they cut Permian sedimentary and volcanic rocks which are not found to the west.
Granites of the Main Range yielded Rb/Sr isochrons and ages ranging from 360 to 140 Ma, with pronounced statistical modes around 300 and 210 Ma (Bignell, 1972). Some older dates of ~450 Ma have been obtained from peculiar labradorite granodiorite rocks in the Main Range between Kuala Lumpur and Bentong. In strong contrast, the K/Ar dates for the same granites range from 210 to 40 Ma, with a statistical mode ~190 Ma (Bignell, 1972). The K/Ar dates are taken to be related to the main period of uplift, rather than the cooling of the granites (Armstrong, 1966), indicating that the Main Range Belt granites were emplaced over
an extended period from Late Carboniferous to Late Triassic, and uplifted during the Jurassic and Cretaceous.
• Silurian - Silurian deposition appears to have been restricted to the west coast tin belt and mainly comprises inter-bedded calcareous and argillaceous strata, with minor arenaceous beds within the latter. Acid volcanic rocks, mainly rhyolitic to rhyodacitic tuffs, are found associated with Lower Silurian limestones, shale and quartzite in northern Perak State.
Cross-cutting ultrabasic rocks are also found in this sequence. Upper Silurian sediments are largely absent from the northern part of the Malaysia, although significant Middle to Upper Silurian limestones are found in the Kuala Lumpur area. These are underlain by probable Lower Silurian carbonaceous phyllites and schists. To the north east of Kuala Lumpur, on the eastern margin of the Main Range Granite, a series of quartz and graphitic schists, phyllites and slates with lesser interbeds of amphibole schist, which conformably underlie Early Devonian Beds, are assumed to be Silurian.
• Devonian - Devonian sedimentary rocks flank the Main Range granite on both margins, from Ipoh south. In general, they comprise argillaceous beds with arenaceous interbeds, and locally extensive carbonates. The most significant development of carbonates are those of the Kinta Valley around Ipoh. In this area, limestones and marbles, with much lesser inter-bedded shale, schist, phyllite and minor quartzite, form the floor of a broad valley bounded to the east and west by granitic ranges. The limestone is generally a white, pale grey or slightly yellowish rock. It is usually coarse grained and massive, but in some areas is finer and well bedded with laminations of carbonaceous material. The inter-bedded sedimentary rocks include minor tourmaline and carbonaceous schist. A deeply dissected karst topography has subsequently formed over these carbonates and sediments.
To the east of the Main Range Granite the Devonian comprises conglomerates, grits, quartzites, phyllites and lesser cherts with minor associated pyroclastics and basic to ultrabasic intrusives.
• Carboniferous - Within the West Malaysian Tin Belt, Carboniferous rocks are largely restricted to three small areas. These are found to the west of both Kuala Lumpur and the Kinta Valley, and in far northwestern Malaysia. In general, they comprise argillaceous and arenaceous sedimentary rocks with some Lower Carboniferous limestones being developed on the south western margin of the Kinta Valley adjacent to the Devonian carbonates of the area. In far north western Malaysia, sedimentation was continuous from Late Devonian to Lower Carboniferous and comprised non-calcareous siltstones and shales. A minor, possible Upper Carboniferous, limestone has been found in this area.
• Triassic - Within the area under description, the Triassic is largely confined to the northern third of the area. Triassic rocks occur extensively to the east of the Main Range Granite. In the north of the country, Middle to Upper Triassic inter-bedded arenaceous and argillaceous sediments directly overlie both Carboniferous and Silurian rocks.
• Quaternary - Extensive Quaternary deposits are found along the coastal strip of much of the west coast of Malaysia. These are largely alluvial flood plain deposits, admixed with marine sediments along the coast. In places the older alluvium is fluvio-deltaic and cyclic, related to the Pleistocene glacial periods, and is often semi-consolidated. In many areas the older deposits are overlain by younger unconsolidated gravel, sand, silt and clay. Both the younger and older alluvium carry the major secondary tin deposits of the area. The main source of the detritus of the Quaternary alluvium is the deeply decomposed granites of the Main Range which were uplifted along a series of north-south faults. These exhibit a markedly youthful topography which changes abruptly on their western margin to more mature flood plains, broad valleys and mangrove swamps.
Distribution of Mineralisation
Of the approximately 2 million tonnes of tin Malaysia has produced to the early 1990s, around 90% has come from the West Coast Belt. Within the belt two districts stand out, namely the northern and more significant Kinta Valley centred on Ipoh in Perak, and the slightly less important area around Kuala Lumpur in Selangor.
Other areas of mineralisation are distributed from the far north-west to south of Melaka. The tin deposits of the West Malaysia Tin Belt can be sub-divided as follows.
Alluvial - These deposits are by far the most important and comprise the majority of occurrences in the Kinta Valley and Kuala Lumpur area. They fall into three main groups, namely:
• The large dredging operations - These are based on deep alluvium usually developed over a non-limestone bedrock. Carbonate rocks are hard and usually have very uneven karst topography developed on them, thus hampering dredging operations, whereas argillaceous and arenaceous sediments and schists are more easily worked over and into if necessary. These deposits can support a large dredge with grades of 120 g/m3. Depths of up to 50 m have been worked.
Examples of this type of operation visited are the Sri Timah Dredge south of Kuala Lumpur, in the Kuala Lungut Field, and the Bidor Malaya Tin Sdn Bhd operation in the southern reaches of the Kinta Valley.
• Hydraulic operations - These range in size from the Gopeng Consolidated Mine which produces up to 2000 tonnes of tin metal a year, to the small Chinese family mines. Operations of this kind are developed on alluvium too shallow for a dredge or those developed in too rugged a karst topography. They are worked by breaking up the alluvium with a number of monitors, and pumping the resultant slurry with a gravel pump to a central treatment plant.
The larger operations of this type are found in the mid to upper reaches of the Kinta Valley, while hundreds of small Chinese workings are scattered throughout the belt working any available alluvium or old tailings dumps. These small Chinese workings, usually with only one or two gravel pumps, produced up to 50% of Malaysia's production.
• Dry Mining by open cut - This type is relatively rare and restricted to deposits too deep to work by large dredge. The best example is the Sungei Besi Mine near Kuala Lumpur, which was visited. The main No. 2 pit at Sungei Besi was to be completed at a depth of 132 m.
The important alluvial deposits at the West Malaysian Tin Belt are found either over a karst topography developed on Silurian or Devonian limestone bedrock, or in meandering channelways on flood plains over other Palaeozoic sediments. The latter are more removed from the source area. Rich deposits often form in deep depressions found at the contact of granites and Devonian or Silurian limestones, eg. Sungei Besi and Gopeng Consolidated.
The source of the alluvium is largely the granites of the Main Range Batholith. These granites normally have a tin background at around 5 ppm throughout but do carry numerous zones of fine cassiterite bearing quartz vein stockworks (as described at Gopeng Consolidated). Elsewhere, as at Sungei Besi, small pods of siliceous, and sulphidic cassiterite are found within the granite near the alluvial deposits.
The Kinta Valley is the largest single alluvium-covered valley that has been worked to date. It extends for some 70 km, being only a few kilometres in width in the north, to around 20 km wide to the south. At least 50% of this valley is being or has been worked. The northern half of the area is too shallow and has too irregular a base to allow dredging, while the downstream reaches are being, or have been, dredged.
The alluvial fields elsewhere in the belt and near Kuala Lumpur comprise smaller valleys or groups of valleys. In the Kuala Lumpur area, the main dredging operations are in the Sungei Selangor to the north of the city and in the Kuala Lungut Tin Field where Sri Timah operates.
• Eluvial - These are less important than the alluvial deposits and are largely only worked by the small Chinese mines. They usually form over small stockwork zones of cassiterite bearing fine quartz veinlets within the Main Range Granite. Grades of 0.2 to 0.3 kpcy or 155 to 230 g/m3 are worked, representing about a three times upgrading of the primary grade in the granite. These deposits are also occasionally found over small quartz lodes or massive cassiterite beds similar to those described at Sungei Besi.
• Lode Deposits - Small, impersistent cassiterite bearing quartz lodes are known within the Main Range Granite, although to date none have been encountered that are large enough to support a significant operation as at Sungei Lembang on the east coast.
The other form of lode is the massive cassiterite beds with minor ex-sulphide limonite, as at Sungei Besi.
• Limestone Pipe Deposits - A number of sulphide bodies have been found developed within the Devonian Limestone of the Kinta Valley. The most famous of these are the Lahat and Beatrice Pipes. The Lahat Pipe had surface dimensions of 0.6 x 2.1 m and persisted undiminished to 100 m vertically, where technical considerations caused mining to cease. At the surface, it comprised cassiterite and iron oxide cemented by secondary calcite. Below the level of oxidation the iron oxide became arsenopyrite. The Beatrice Pipe had dimensions of approximately 23 x 6 m at the surface. At depth, it ranged from 17 x 10 m at 65 m below the surface, to 30 x 4.6 to 10.5 m at 90 m, and to 14 x 3.6 m at 110 m. It ended abruptly at a depth of 119 m, truncated by granite. The body dipped to the west at around 75°, shallowing to 30° near the surface. The pipe had a total down dip dimension of 260 m and produced 8885 tonnes of tin ore. The ore comprised cassiterite, arsenopyrite, chalcopyrite and bornite in a gangue of tremolite with traces of fluoborite, talc, fluorite and dolomite. The ore was sometimes banded parallel to the lodes walls.
The most recent source geological information used to prepare this summary was dated: 2009.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
References to this deposit in the PGC Literature Collection:
Hosking, K.F.G., 1977 - Known relationships between the hard-rock tin deposits and the granites of Southeast Asia: in Geological Society of Malaysia, Bulletin 9, pp. 141-157|
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