/* Style Definitions */table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin:0cm;mso-para-margin-bottom:.0001pt;mso-pagination:widow-orphan;font-size:10.0pt;font-family:"Calibri","sans-serif";} Bulletin of the Geological Society of Malaysia, Volume 59, November 2013, pp. 53 – 58
1Program Geologi, Pusat Pengajian Sains Sekitaran dan Sumber Alam, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor
2Jabatan Mineral dan Geosains Malaysia, Selangor
3Jabatan Geologi, Fakulti Sains, Universiti Malaya, 50603 Kuala Lumpur
*Email address: mahat@jmg.gov.my
Abstrak: Semenanjung Malaysia secara tradisinya telah dibahagikan kepada tiga jalur mineral, iaitu Jalur Barat untuk bijih timah, Jalur Tengah bagi emas dan Jalur Timur untuk kedua-dua bijih timah dan emas. Walaupun Jalur Barat diterima sebagai jalur bijih timah, penyiasatan terperinci peta dan laporan-laporan geologi mendedahkan bahawa emas juga berlaku di pelbagai tempat di dalam lingkaran timah ini. Di Tapah-Bidor, Perak dan Batu Cave, Selangor, emas telah dikumpul sebagai hasil sampingan dari perlombongan bijih timah plaser. Longgokan bijih timah dijumpai meluas di Jalur Barat, sedikit di Jalur Timur manakala tiada di Jalur Tengah. Satu kajian geokimia sedimen sungai di kawasan Tapah telah dijalankan untuk melihat corak taburan kedua-dua unsur tersebut. Konsentrat mineral berat yang didulang dari sedimen sungai dikaji melalui mikroskop binokular. Batuan dasar di kawasan tersebut terdiri daripada granit dan metasedimen.
Di kawasan Tapah, kepingan halus emas dan butiran kasiterit adalah biasa dan pelbagai diperhatikan dalam hampir semua konsentrat mineral berat yang dikutip. Apabila nilai geokimia unsur-unsur diplotkan di atas peta, emas dan bijih timah mempunyai corak taburan berbeza. Konsentrat dengan kepingan emas terbatas kepada kawasan metasedimen manakala kasiterit didapati di kawasan metasedimen dan juga granit. Ini mudah dijelaskan kerana telerang kasiterit, yang berasal dari jasad batuan granit, boleh merentasi kedua-dua batuan granit dan batuan metasedimen setempat. Kasiterit berasal dari cecair magma lewat dan dibawa oleh cecair hidroterma dari magma dan dimendap dalam telerang-telerang tanpa mengira jenis batuan dasar. Emas berasal daripada batuan sedimen. Ia dirembes keluar dari batuan metasedimen dan diuraikan oleh air hidroterma yang beredar didorong oleh haba semasa penerobosan batuan igneus dan dimendap di dalam telerang. Oleh kerana ia tidak berasal dari bendalir granit, ia didapati jauh dari batuan granit.
Abstract: Peninsular Malaysia has traditionally been divided into three mineral belts, viz the Western Belt for tin, the Central Belt for gold and the Eastern Belt for both tin and gold. Although the Western Belt is accepted as the tin belt, close examination of geological maps and reports revealed that gold do occur in various places in this tin belt. In Johor and Negeri Sembilan gold has been mined and in Tapah-Bidor, Perak and Batu Cave, Selangor gold has been recovered as a byproduct in placer tin mining. Tin deposits are widespread in the Western belt, some in the Eastern Belt and absent in the Central Belt. A study of heavy mineral concentrates in the stream sediments in Tapah area in Perak was carried out to determine their distribution patterns. The heavy mineral concentrates were panned from the streams and studied under a binocular microscope. Bedrock geology is underlain by granite and metasediments.
In Tapah area, fine gold flakes and cassiterite grains are common and variably observed in almost all heavy mineral concentrates collected. When their respective geochemical values were plotted on a map, gold and tin have dissimilar distribution patterns. Concentrates with gold flakes are confined to the metasedimentary areas, whereas cassiterite bearing concentrates are found both in the metasedimentary areas as well in the granite areas. This is because cassiterite veins originated from the granite bodies can cut across both the granite and the metasediment country rock. Cassiterite originates from late magmatic fluids and being carried by hydrothermal solution from the magma and deposited in veins regardless of the bedrock type. Gold on the other hand originates from the sedimentary rocks. It is being squeezed out from the metasedimentary rocks, dissolved by circulating hydrothermal fluids and deposited in the veins. Since it originates not from granitic fluid, it is found away from the granite.
Keywords: gold and tin mineralization, Western Belt, heavy minerals, geochemistry
https://doi.org/10.7186/bgsm59201309
