Benom Complex: Evidence of magmatic origin

Abstract

The study area is underlain predominantly by syenite, monzonite and gabbro. The area lies on the western flank of Benom batholith. Field mapping has proven the intrusive nature of the suite of rocks into the surrounding country rocks. The country rocks were contact metamorphosed into various hornfelses of hornblende hornfels facies. The occurrence of a crystal settling layer within the suite of rocks is particularly convincing of an igneous origin. Moreover, the occurrence of accidental xenoliths in these igneous rocks, which correspond to the aureole rocks, indicate that the xenoliths were incorporated during magma intrusion. The presence of different types of cognate xenoliths ranging from pyroxinite to gabbroic and syenitic in composition, is also widespread in the study area. The occurrence of planar flow structure in the syenite and monzonite defined by megacrystic K-feldspar, is evident of magmatic flow. Petrographic studies reveal that igneous foliation in the suite of rocks is made up of euhedral to subhedral plagioclase and K-feldspar crystals. Abstrak: Kawasan kajian terdiri daripada batuan syenit, monzonit dan gabro. Kawasan ini terletak di sebelah barat Komplek Benom. Pemetaan lapangan menunjukkan batuan ini menerobos batuan sekelilingnya yang terdiri daripada metamorfisma hornfel daripada fasis hornblende hornfel. Kewujudan lapisan pemendapan hablur di dalam suit batuan ini mencadangkan asalan igneus. Tambahan lagi kewujudan xenolit yang mempunyai ciri-ciri persamaan dengan batuan sekeliling mencadangkan xenolit tersebut telah terjatuh ke dalam magma semasa penerobosan magma tersebut. Kewujudan pelbagai jenis xenolit kognat berjulat daripada piroksinit ke gabroik dan syenitik juga banyak dijumpai di kawasan kajian. Kajian petrografi menunjukkan bahawa foliasi igneus di dalam batuan ini dibentuk oleh plagioklas yang berbentuk euhedral to subhedral plagioclase dan alkali feldspar.

Petrogenesis of Malaysian granitoids in the Southeast Asian tin belt: Part 1. Geochemical and Sr-Nd isotopic characteristics

“…These syenites are Permo-Triassic in age (Ng et al, 2015), containing K-feldspar, plagioclase, hornblende, pyroxene, quartz, and biotite, in decreasing abundance. They are interpreted as the fractionated product of alkali basalt (Ghani, 2001(Ghani, , 2003Yong et al, 2004;Ghani, 2006). COMPARISON BETWEEN CHAPPELL AND WHITE'S (1974) I-AND S-TYPE GRANITES (CHAPPELL AND WHITE, 1974MCCULLOCH AND CHAPPELL, 1982;CLARKE, 1992;COBBING ET AL., 1992;PITCHER, 1997 …”

Geochemistry and petrology of syenite, monzonite and gabbro from the Central Belt of Peninsular Malaysia

“…Mohd Rozi Umor & Syed Sheikh Almashoor (2000) considered that the same rock types from the northern part of the study area (Benta Complex) were derived from the melting of eclogite from the mantle and could not have derived from the continental crust. The interaction with mantle material is supported by the occurrences of mafic enclaves and synplutonic dykes in the studied rocks (Yong et al, 2004). The Benom granite has yielded an initial 87 Sr/ 86 Sr ratio of 0.7079 (Cobbing et al, 1992), which points to an origin in highly enriched lithospheric mantle.…”

High Ba igneous rocks from the Central Belt of Peninsular Malaysia and its implication

“…Green and Wallace, 1988;[onov et al, 1993;Rudnick, 1993). Evidence of the interactions with mantle material are provided by the occurrence of mafic enclaves and mafic synplutonic dykes everywhere in this area (Shafari Muda, 1992;Yong, 1998;Ramesh, 1999). More work has to be done in order to support the existence of mantle plume beneath this region during Permo-Triassic time.…”

“…1) near to the Raub township. The area has been studied by several workers and different interpretations have arisen (Scrivenor, 1931;Richardson, 1939;Khoo, 1968;Hutchison, 1971;Jaafar, 1979;Khoo & Tan, 1983;Shafari Muda, 1992;Tan & Khoo, 1993;Yong, 1998;Ramesh, 1999;Mohd Rozi Umor & Syed Sheikh Almashoor, 2000). The main controversy is either the rock in this area represents a migmatite complex or the product of igneous differentiation.…”