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ISSN 0126-5539 PERSATUAN GEOLOGI MALAYSIA NEWSLETTER OF THE GEOLOGICAL SOCIETY OF MALAYSIA KANDUNGAN (Contents) CATATAN GEOLOGI (Geological Notes) Ng Tham Fatt: Layered microgranite-pegmatite complexes of the Kuala 129 Lumpur Granite, Peninsular Malaysia PERTEMUAN PERSATUAN (Meetings of the Society) Jon Noad: From limestone to sandstone: The sedimentology of the 139 Gomantong Limestone and Tanjong Formation in Northeast Borneo Site Visit - LRT2 Tunnel Site (Sultan Ismail Station) - Report 141 Annual Geological Conference 1997 - Report 143 Ucapan Aluan Pengerusi Penganjur Persidangan, Dr. Ahmad 144 Tajuddin Ibrahim Ucapan Perasmian oleh Y.A.B. Dato' Seri Amar DiRaja Haji Wan 145 Mokhtar bin Ahmad, Menteri Besar Terengganu Programme 147 Abstracts of Papers & Posters 155 BERITA-BERITA PERSATUAN (News of the Society) Keahlian (Membership) 201 Pertukaran Alamat (Change of Address) 202 Pertambahan Baru Perpustakaan (New Library Additions) 202 BERITA-BERITA LAIN (Other News) Local News 203 International Workshop: Tectonics, stratigraphy and petroleum systems 213 of Borneo Department of Petroleum Geoscience at Universiti Brunei Darussalam 215 Delta '98: Modern & Ancient 216 Oil & Gas West Asia 217 Kalendar (Calendar) 218 Majlis (Council) 1997/98 Presiden (President) KhalidNgah Naib Presiden (Vice-President) Khoo Kay Khean Setiausaha (Secretary) Ahmad Tajuddin Ibrahim Penolong Setiausaha (Asst. Secretary) S. Paramananthan Bendahari (Treasurer) Lee Chai Peng Pengarang (Editor) Teh Guan Hoe Presiden Yang Dahulu (Immediate Past President) : FatehChand AHli .. Ahli Majll$(Counciliors) 1997-99 1997-98 Tan Boon Kong Abd. Ghani Mohd Rafek Azhar Hussin Abdul Rahim Samsudin KK Liew Abdul Hadi Abd. Rahman Kadderi Md. Desa Sia Hok Kiang Jawatankuasa Kecil Pengarang (Editorial Subcommittee) Teh Guan Hoe (PengerusilChairman) Fan Ah Kwai Ng Tham Fatt J.J. Pereira Lembaga Penasihat Pengarang (Editorial Advisory Board) AwPeckChin Foo Wah Yang Mazlan Madon P.H. Stauffer Azhar Hj. Hussin C.A. Foss Ian Metcalfe Tan Boon Kong KR. Chakraborty N.S. Haile S. Paramananthan Tan Teong Hing Choo Mun Keong C.S. Hutchison John Kuna Raj Teoh Lay Hock Chu Leng Heng Lee Chai Peng Senathi Rajah H.D. Tjia Denis N.K. Tan Leong Lap Sau Shu Yeoh Khoon Yeap Cheng Hock The Society was founded in 1967 with the aim of promoting the advancement of earth sciences particularly in Malaysia and the Southeast Asian region. The Society has a membership of about 600 earth scientists interested in Malaysia and other Southeast Asian regions. The membership is worldwide in distribution. Published by the Geological Society of Malaysia, Department of Geology, University of Malaya, 50603 Kuala Lumpur. Tel: 603-757 7036 Fax: 603-756 3900 E-mail: [email protected] Printed by Art Printing Works Sdn. Bhd., 29 Jolon Rlong, 59700 Kuala Lumpur. Layered microgranite-pegmatite complexes of the Kuala Lumpur Granite, Peninsular Malaysia N G TRAM FAT!' Institute of Advanced Studies University of Malaya 50603 Kuala Lumpur Abstract: The Kuala Lumpur Granite is cut by late magmatic microgranite-pegmatite complexes that occur as gently to moderately dipping and weakly curved composite sill-like bodies. They display prominent grain size layering defined by alternating layers of pegmatite and microgranite. Mineral zoning is conspicuous in the pegmatites. The microgranites exhibit a fine scale, 5 to 100 mm thick, internal rhythmic compositional layering. The microgranite-pegmatite complexes are probably formed by multiple injection of volatile-rich granitic magma, each injection was initially homogeneous and subsequently segregated into pegmatite and microgranite. The rhythmic layering originated from in-situ local fractionation of granitic magma and the variation of volatile pressures during crystallization has probably played an important role. INTRODUCTION hypiodiomorphic groundmass. The major minerals are alkali feldspar, quartz and Microgranite dikes and pegmatite bodies plagioclase, while biotite, muscovite and are common in the granitic rocks of Peninsular tourmaline usually occur in minor amounts. Malaysia. These late stage differentiates often The Kuala Lumpur Granite consists of several form discrete bodies, however, they are observed textural and mineralogical varieties or units, to form composite microgranite-pegmatite and the main units are megacrystic biotite complexes displaying grain size and rhythmic granite; megacrystic muscovite-biotite granite; compositional layering in several places, and equigranular tourmaline-muscovite granite including Kuala Lumpur, Bukit Mor in Johor, (Fig. 1). These granitic rocks are cut by late Sungai Siput Selatan in Perak, and near Gunung phase differentiates including the microgranite Jerai in Kedah. Among these places, the pegmatite complexes. microgranite-pegmatite complexes is best exposed in the quarries and road cuts in eastern The Kuala Lumpur Granite was emplaced Kuala Lumpur. This paper describes the during the Late Triassic (199-215 Ma) (Bignell interesting and unique layered structures in and Snelling, 1977; Liew, 1983; Darbyshire, the microgranite-pegmatite complexes in the 1988). The Kuala Lumpur Granite like the Kuala Lumpur Granite, and discusses their other granites of the Main Range batholith, possible origins. exhibits typical S-type features such as being tin-bearing, and having peraluminous 3 THE KUALA LUMPUR GRANITE composition, high ~O/Na20 ratios, low Fe +/ Total Fe ratios, a restricted compositional range The Kuala Lumpur Granite is a large dominated by high Si02 granites and high initial granitic body which is predominantly 87Sr/86Sr ratios (Liew, 1983). On the basis of megacrystic consisting of alkali-feldspar S-type features and other evidence like absence megacrysts set in an allotriomorphic to of associated mafic magmatism, negative eNd ISSN 0126-5539 Warta Geologi, Vol. 23, No.3, May-Jun 1997, pp. 129-138 + + + + + + + + + + + + +Host + G+ram ' t+e + + --' -,_: - ' _. _- --' -~ - .---- . -. + + + '- - •.. • I \ I I t _,. _. _-.--;_,_~:.;-J_::-- . _~ ___ .-'_: _ .. - ........... _.: ~ . ~.---=- - .- ... ~- "', -::..::-:: "': - tA Single -c.. --.,. - -./ ------- .- -. _ .. ___ -~. __ microgranite- § tT.J.,--,.,-r--,--, o ~~~~~ '- .' , pegmatite body .~ Cti E g> t.":..:"r'"_ ~=r--'--_ D.. 2 'Conformable 'c P=~-:-:::~""""''-'''--';--:-:-''''--'TT''l..;,.:........::::>..... ,contacts ~ - ~. '- -- --- Meg~crystic biotite - eo D granite --,,"-- -' ~ Megacrystic muscovite __ Unconformable D biotite granite contact Equigra~ular tou,rmaline ~ • muscovite gramte + + + + + + + + + 1 m + + + + + + + 2A ~FAULT ~ I, IROAD e 5 km 2 '~ E en Q) CL ~, , 3.N \_ PWD Quarry I _. Cheras Quarry 28 Figure 2. A) Simplified field sketch of a microgranite-pegmatite complex cutting megacrystic muscovite-biotite granite in Dayapi Quarry. The 101 microgranite-pegmatite complex is made up of subparallel microgranite pegmatite bodies. The contacts of the microgranite-pegmatite bodies are often Figure 1. Map showing the distribution of the three main units of the conformable, but may also be unconformable. B) Sketch of part of the Kuala Lumpur Granite and the location ofthe quarries where microgranite micro granite-pegmatite complex shown in (A) illustrating a microgranite pegmatite complexes were observed and studied. pegmatite body. Grain size layering is formed by the pegmatite andmicrogranite with contrasting grain size. The microgranite layer also has internal rhythmic modalla ering. LAYERED MICROGRANITE-PEGMATITE COMPLEXES OF THE KUALA LUMPUR GRANITE 131 values and the presence of U-Pb zircon the microgranite-pegmatite complexes are 0.5 inheritance features, Liew (1983) concluded m to more than 5 m thick and up to tens of that the Main Range batholiths are derived meters long. from partial melting of underlying old continental crust. Each microgranite-pegmatite body is made up of an upper pegmatite layer and a lower microgranite layer. These two subparallel layers GENERAL FEATURES OF THE may be regarded as well developed grain-size MICROGRANITE-PEGMATITE layering (i.e. the pegmatite forms a coarse COMPLEXES grained layer, and the microgranite a fine The microgranite-pegmatite complexes are grained one, Fig. 2B). Within the microgranite observed in the Perkuat Quarry, Dayapi Quarry, layers, rhythmic layering is frequently observed Bt. Sg. Besi Quarry and km 23 of Karak (Fig. 2). Individual microgranite-pegmatite Highway. They form composite sub-horizontal bodies within a microgranite-pegmatite complex sill-like bodies cutting the main Kuala Lumpur are usually parallel with conformable contacts. Granite. They are often confined to the contacts However, unconformable contacts (truncation between equigranular granites and megacrystic structures) with apparent angle of discordance granites (Fig. 1). ranging from a few degrees to 30° are not uncommon (Figs. 2A and 4). Truncation The microgranite-pegmatite complexes structures mostly occur towards the outer margin commonly form gently to moderately dipping of a microgranite-pegmatite complex, which and weakly curved composite tabular bodies. according to Duke et al. (1988), is suggestive of Each composite complex may contain 5 to tens a general upward addition of new magma pulses. of microgranite-pegmatite bodies, each ranging from 5 cm to 1 m thick, and this gives them a In summary, there are three types of layered appearance (Figs. 2 and 3). Generally layering of different scales in the microgranite- + + + "" "'" + + + ~ -+ -+ I -+ -+ + -+ -+ -+ + -+ 1" + -+ -+ -+ -t + + + -t -+ -+ -+ .. -+ -+ 1"