Bulletin of the Geological Society of Malaysia, Volume 72, November 2021, pp. 223 – 232

Petrography and field study of andesitic ignimbrite in Temangan, Kelantan

Nur Shafiqah Shahman^1,2,*, Elvaene James³, Arham Muchtar Achmad Bahar³, Muhammad Irfan Hadhi³, Norazif Anuar^1,2

1 Department of Geoscience, Universiti Teknologi PETRONAS (UTP),32610, Seri Iskandar, Perak, Malaysia
2 Centre of Excellence in Subsurface Seismic Imaging & Hydrocarbon Prediction (CSI), Universiti Teknologi PETRONAS (UTP),32610, Seri Iskandar, Perak, Malaysia
3 Faculty of Earth Science, Universiti Malaysia Kelantan Kampus Jeli, Locked Bag 100, 17600 Jeli, Kelantan, Malaysia
* Corresponding author email address: nurshafiqah_hafish94@yahoo.com

Abstract: The volcanic rocks in Temangan, Kelantan consist of felsic to intermediate volcanic rocks, that is mainly of pyroclastic with rhyolitic, dacitic, and andesitic tuff. A geological review has been carried out in Kampung Bukit Besi, Temangan, in Kelantan, Malaysia, which is composed of schist, shale, andesite, and ignimbrite. In Temangan, andesite and ignimbrite show an intimate relationship, as the ignimbrite exists as the fragments and andesite as the matrix. The methodology used in this study are petrography and X-ray Diffraction (XRD) analyses, to determine the mineralogical composition of andesitic ignimbrite. Andesite shows aphenitic and porphyritic textures and consist of pyroxene, plagioclase, alkali feldspar, quartz, biotite and iron oxides. A range of plagioclase textures indicate imperfect equilibrium condition from andesite, reflecting plagioclase dissolution and regrowth. The structural analysis suggest that thrust fault occurred in the study area. Andesite and ignimbrite of the two stages are suggested to have derived from the andesite magma eruption which produced pyroclastic flow eruptions in small amount in most caldera volcanoes at high temperature gradient.

Keywords: Andesitic ignimbrite, petrography, Temangan, Kelantan
Abstrak: Batuan gunung berapi di Temangan, Kelantan terdiri dari batuan gunung berapi felsik hingga pertengahan, yang terdiri daripada batuan piroklastik dengan riolit, dasit, dan tuf andesit. Kajian geologi telah dilakukan di Kampung Bukit Besi, Temangan, di Kelantan, Malaysia, yang terdiri dari syis, batuan lempung, andesit, dan ignimbrit. Di Temangan, andesit dan ignimbrit menunjukkan hubung rapat, kerana ignimbrit wujud sebagai fragmen dan andesit sebagai matriks. Metodologi yang digunakan didalam kajian ini ialah kajian petrografi dan sinar-X Difraksi yang digunakan untuk menentukan komposisi mineralogi ciri-ciri ignimbrit andesit. Andesit menunjukkan tekstur afenitik dan porfiritik serta mengandungi komposisi mineralogi seperti piroksen, plagioklas, feldspar alkali, kuarza, biotit dan oksida besi. Pelbagai tekstur plagioklas menunjukkan keadaan keseimbangan yang tidak sempurna daripada andesit, yang mencerminkan pembubaran dan pertumbuhan semula plagioklas. Berdasarkan kepada kajian struktur menunjukkan sesar sungkup terdapat di kasawan kajian. Andesit dan ignimbrit terdiri daripada dua tahap mencadangkan kemungkinan berasal daripada letusan magma andesit yang menghasilkan letusan aliran piroklastik dalam jumlah yang sedikit di kebanyakan gunung berapi kaldera pada kecerunan suhu tinggi.

Kata kunci: Andesit ignimbrit, petrografi, Temangan, Kelantan

DOI: https://doi.org/10.7186/bgsm72202118