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Bulletin of the Geological Society of Malaysia, Volume 58, Decemberf 2012, pp. 43 – 48

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Batuan volkanik Formasi Semantan di sekitar Gunung Benom, Pahang

Mohd Rozi Umor¹, Azman Abd. Ghani² & Hamzah Mohamad³

¹Program Geologi, Pusat Pengajian Sains Sekitaran dan Sumber Alam, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor
²Jabatan Geologi, Fakulti Sains, Universiti Malaya, 50603 Kuala Lumpur
³Pusat Penyelidikan Arkeologi Global, Universiti Sains Malaysia 

Abstrak: Batuan volkanik Formasi Semantan yang terdapat di sekitar Gunung Benom, Pahang telah dikaji secara petrografi dan geokimia untuk mengetahui kandungan mineral dan jujukan penghabluran yang berlaku. Tiga jenis batuan dikenali sebagai tuf riolit, tuf riolit porfiri kuarza dan trakit-andesit telah dijumpai. Kajian petrografi menunjukkan ketiga-tiga batuan mempunyai tekstur batuan yang berbeza, iaitu tuf riolit bertekstur isogranular dan bersaiz halus. Tuf riolit porfiri kuarza pula bertekstur porfiri sangat baik. Sementara itu batuan trakit andesit bertekstur porfiri agak jelas dan mempunyai komposisi mineral pelbagai saiz mewujudkan tekstur seriat. Geokimia menunjukkan batuan ini dikelaskan sebagai siri sub-alkali atau tholitik.

Volcanic rocks of the Semantan Formation in the vicinity of Gunung Benom, Pahang 

Abstract: Petrographic and geochemistry studies were carried out on volcanic rocks within the Semantan Formation at the vicinity of Gunung Benom, Pahang to reveal their mineral composition and sequence of crystallization. Three rock types were identified. They are rhyolite tuff, porphyritic quartz rhyolite tuff and trachyte andesite, and they have different textures. The rhyolite tuff shows an isogranular texture and fine-grained, while the porphyritic quartz rhyolite tuff has well developed porphyritic texture. The trachyte andesite is moderately porphyritic with seriate texture indicated by minerals with various grain size distribution. The geochemistry of these rocks indicates that they can be classified as sub-alkali series or the tholeiitic series.

Keywords: volcanic rocks, petrography, geochemistry, Semantan Formation

 https://doi.org/10.7186/bgsm58201207