Ciri Petrologi dan Geokimia Batuan Terobosan Gunung Sepikul, Trenggalek, Jawa Timur
DOI:
https://doi.org/10.33332/jgsm.geologi.v25i2.742Abstract
Gunung Sepikul di bagian selatan Jawa Timur berkaitan dengan proses magmatisme yang berumur Miosen. Maksud penelitian ini untuk mengetahui karakteristik petrologi dan geokimia batuan beku Gunung Sepikul. Tujuannya mengungkapkan gambaran tektonik dan melengkapi data petrologi lajur magmatisme Jawa bagian selatan. Singkapannya berupa stock terdiri atas diorit dan granodiorit. Percontoh batuan dianalisis menggunakan metode petrografi, XRF dan ICP-MS. Data lapangan dan hasil analisa laboratorium berupa komposisi mineral serta geokimia batuan dapat menunjukkan proses magmatisme batuan Gunung Sepikul. Batuan diorit berwarna kelabu, tekstur inequigranular terdiri atas mineral plagioklas, kuarsa, piroksen, hornblenda dan mineral opak. Batuan granodiorit berwarna kelabu cerah, tekstur porfiritik dengan fenokris plagioklas, hornblenda, kuarsa dan mineral opak pada masadasar feldspar dan kuarsa. Berdasarkan analisa geokimia, batuan terobosan ini berafinitas magma Medium-low K series yang berhubungan dengan magmatisme di lingkungan tektonik orogenic.
Kata Kunci: terobosan, stock, diorit, granodiorit, magmatisme
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