East Coast Malaysia Tin Belt - Bukit Besi, Machang Setahun, Pelepah Kanan, Sungei Lembing
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The East Coast Malaysia tin belt is restricted to a zone about 70 km wide, bounded to the east by the South China Sea, and to the west by line that closely parallels the coast line. It includes stratabound magnetite and/or sulphide Deposits such as Bukit Besi, Machang Setahun and Pelepah Kanan and lode deposits such as Sungei Lembing. Bukit Besi, Pelepah Kanan and Sungei Lembing are the subject of separate records.
For an overview of the setting of the East Coast Malaysia tin belt see the separate South-east Asian Tin-Tungsten Belt, Thailand, Myanma/Burma, Malaysia, Indonesia.
The East Coast Malaysia tin belt is coincident with the Eastern Granite Belt, the oldest of three alignments of tin granites that occur within and parallel the Malay Peninsula and young to the west. The Eastern Granite Belt comprises a series of Late Permian to Lower Triassic high level granite batholiths, which intrude Carboniferous and Permian sedimentary rocks and are bounded to the west by a Mesozoic sequence. Minor late Mesozoic sedimentary rocks cap both the Palaeozoic sequences and the granites, while along the coast there are extensive Quaternary deposits.
Based on a series of mine visits, discussions with local geologists and available literature in 1978, the main geological elements of the area may be summarised as follows:
• The East Coast Granite Belt - This belt comprises two groups of granitic batholiths, each covering an area of around 70 x 250 km elongated in a NNW-SSE direction. The southern group is offset to the south west by about 50 km from the trend of the northern segment. The major Sungei Pahang (river) flows through this gap. There are two phases of granitic emplacement recognised in the northern segment. These comprise an older central stanniferous granite type which yields age dates of 240 to 260 Ma, flanked on either side by younger barren granites with ages of around 215 Ma. Both are reasonably potassic and are regarded to be high level intrusive. They have significant granodiorite components. The younger granites are very similar in composition to the Permo-Triassic intermediate to acid volcanics found immediately to the south west.
The granites are, in general, coarse grained and non-porphyritic to only weakly porphyritic. Towards the south, the granite is very even grained with local porphyritic micro-adamellite phases. The east coast granites are present as both grey and pink varieties which are closely associated in any one area. In the northern segment the granites often have a pronounced aureole, in some cases up to 3 km wide, which stands out as prominent hills. The older granite tends to be subdued, due to deeper erosion.
• Carboniferous - The oldest sediments in the area are of Carboniferous age. These are restricted to the area at the northern segment of the east coast Granite Belt. The sequence comprises Lower Carboniferous carbonaceous shales, phyllites and siltstones, with lesser quartzites and minor carbonates, and acid to intermediate volcanics, overlain by an Upper Carboniferous arenaceous sequence. The Lower Carboniferous shales, phyllites and siltstones are often well laminated where seen in fresh exposures along the coast.
Inland, where weathering is more intense, this fine bedding is not as obvious, which may or may not be a consequence of the weathering. There are significant sections of the sequence, such as that seen underground at Sungei Lembing, where the shales of this sequence overall are fairly massive with only a coarse bedding being obvious. However, within this mine area there are also beds of finely laminated shale and siltstone (see the separate Sungei Lembing record).
The coastal outcrops at Kemasik, south of Dungun, included finely banded siltstone to shale with laminations from 0.5 to 1 mm thick within beds 1 cm to 30 cm thick. Within this there are minor massive quartzite units up to 2 m thick. The sequence exhibits some cross bedding, scour and fill structures and minor slumping. There are a few ferruginous and calcareous beds 1 to 2 cm thick, scattered through the sequence.
Elsewhere in the belt there are well developed quartzite facies, as at the Bukit Besi tin-iron mine. 25 km to the north of Bukit Besi and at a slightly higher stratigraphic level, andesitic to rhyolitic volcanics are developed over a strike length of up to 10 km and thickness of several hundred metres. Some 70 km to the south of Bukit Besi, similar but more restricted rhyolitic to rhyodacitic volcanics are developed as a number of lenses of the order of 2 to 3 km long and a few hundred metres thick. In this area lenses of limestone 3 to 4 km long and 500 to 600 m thick are found at a similar stratigraphic horizon to the volcanics. At Bukit Besi, a stratabound magnetite pyrrhotite-pyrite body which carries tin rich lenses is associated with a carbonate unit which has minor accompanying lenses of what may be a rhyolitic tuff.
The Upper Carboniferous arenaceous sequence was deposited either unconformably or transgressively over the Lower Carboniferous sediments. These are mainly grey cross-bedded and laminated quartzites with lesser interbeds of dark siltstone. The shales occasionally have worm burrows. n some areas, units of conglomerate with a sandy to shaly matrix, and grits are found.
• Permian - Within the east coast tin belt the Permian is present on the western margin of the eastern granite belt and occurs as the main rock type embracing the granites of the southern segment of the belt. Along the western margin of the northern half of the eastern granite belt, the Permian is mainly limestone with associated shales, siltstones and quartzite, with a significant component of acid to intermediate volcanics. Similar rocks are found on the eastern margin of the southern segment of the granite belt.
The volcanic rocks, although mainly rhyolitic, comprise andesitic to rhyolitic tuffs, which are mainly ignimbritic, with lesser fine lapilli and vitric to lithic tuffs and inter-layered lavas. To the east, in both Johore and Trengganu states, the volcanics and limestones are not as well developed and the sequence is largely shales and quartzites. The Pepelah Kanan magnetite-tin deposit is associated with calc-silicates within this sequence in southern Johore.
• Mesozoic - To the west of the eastern granite belt Triassic calcareous strata are found with minor shales and rhyolitic to rhyodacitic tuffs. These are overlain by the Jurassic continental red-bed sequence. To the north, minor Triassic sedimentary rocks overlie the granite belt while small areas of terrestrial Cretaceous sediments are also evident.
• Tertiary - Minor Tertiary basalt caps the sequence near Kuantan.
• Quaternary - Extensive alluvium and coastal deposits occur along the coast of the South China Sea.
Distribution of Mineralisation
The east coast tin belt is not as significant from the point of view of production as its western counterpart. Of the approximately 2 million tonnes of tin produced in Malaysia to 1978, only about 200 000 have come from the east coast. Of this, around 110 000 tonnes were extracted from the quartz lodes of Sungei Lembing. The east coast is notable for the number of significant hard rock deposits while no large alluvial accumulations have been worked to that date. The deposits of the east coast tin belt can be subdivided as follows:
• Lode Deposits - The most outstanding of these is Sungei Lembing which is described in detail in a separate record. It comprises quartz lodes, averaging 1.2 m thick, which crosscut Lower Carboniferous sedimentary rocks in a zone parallel to the margin of the adjacent granite. Tin is developed within the veins and on their selvages. There is a suggestion that the rocks hosting the veins have an elevated tin background of 25 to 50 ppm. These lodes are persistent over lengths of hundreds of metres and occur as swarms. A few other lode systems similar to, but not approaching, the size of Sungei Lembing are known along the east coast. Deposits of this type sometimes have associated tungsten. See the separate Sungei Lembing record for more detail.
• Stratabound Magnetite and/or Sulphide Deposits - Examples include Bukit Besi, Machang Setahun and Pelepah Kanan. Bukit Besi and Machang Setahun are within Lower Carboniferous sedimentary rocks and comprise either: i). massive magnetite with the basal portion of the lens being tin rich and the remainder barren, as at Machang Setahun, or ii). a series of magnetite pyrrhotite lenses as at Bukit Besi.
At Bukit Besi, three deposits are found over a strike length of around 5.5 km. The central lens is magnetite rich and completely barren of tin, while the two pyrrhotite-pyrite rich lenses to the north and west carry tin. Bukit Besi has associated calc-silicates and marbles.
At Pelepah Kanan, in Johore State, a massive banded magnetite unit with accompanying tin overlies a calc-silicate unit which carries cassiterite both in a vein system and as extremely fine disseminations developed in a planar zone below the iron oxide unit. To the north and south within 2.5 km, stanniferous magnetite lenses at Susor Rotan and Pelepah Kiri overlie 'metamorphosed' shales which carry low grade tin levels. These three deposits are embraced by Permian sediments.
See the separate Bukit Besi and Pelepah Kanan records for more detail.
The Machang Setahun deposit was first mined for iron by the Japanese just before the Second World War and for a short period after 1945. A total of around 1 million tonnes of ore were removed, while an estimated 400 000 tonnes remained. The associated tin ore lens has subsequently been exploited by a small local operation. The iron orebody, which comprised hematite and magnetite, was a single lens which dipped steeply to the east. It was up to 30 m thick, and was completely barren of tin, although in the footwall of the main iron lens, there is a small discrete tin-rich lens with sharp grade cutoffs, a strike length of ~50 m and down dip extent of at least 50 m. It appears to have had a thickness of from 1 to 5 m and probably carried around 1% Sn. The remaining material of this bed is massive, powdery black and, in places, crystalline, ex-magnetite which has reverted to martite. The footwall and hanging wall rocks are decomposed, yellow to red, well bedded, shale (1 to 2 cm thick beds). The iron lens is concordant with these sedimentary rocks. About 1 km to the north is a ferro-manganese pit on the same horizon. A bit further to the north again is a manganese rich lens. To the south, the prospective zone is masked by a thick, extensive, alluvial plain. These deposits and occurrences are some 20 km to the south of Bukit Besi and possibly at a higher stratigraphic position. The host sequence is mapped as being near the top of the lower Carboniferous succession, near the overlying upper Carboniferous arenites.
Other magnetite and magnetite-manganese lenses are distributed regionally in the district to the south of Bukit Besi and roughly along strike. Some are barren of tin while others have yielded minor amounts. These deposits are sometimes found in association with limestone lenses and minor acid volcanic units (as at Bukit Bangkong). Elsewhere in the district Pb-Zn and Cu mineralisation occurs in similar stratigraphic positions. These deposits are in Trengganu and Pahang States.
In Kelantan State the Mansons Lode which appears to comprise a series of stratabound cassiterite bearing stannite, pyrrhotite, sphalerite, galena, cinnabar lenses occurs within Permian acid volcanics.
• Alluvial Deposits - Alluvial tin accumulations are scattered along the east coast tin belt. None has to date been proven to be big enough to support a large dredge, although a deposit CRM is testing near Kuantan in Pahang could well be. The east coast alluvial deposits are mainly worked by small Chinese gravel pump mines.
• Eluvial Deposits - Some small eluvial gravel pump operations are found in the area. These are developed over zones of granite which carry fine cassiterite bearing quartz vein stockworks and minor lodes. The upgrading factor between the eluvium and the primary rock is around 3:1, giving a mining grade of around 0.2 to 0.3 kpcy, ie. 155 to 230 g/m3.
The most recent source geological information used to prepare this summary was dated: 1978.
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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