Analisis Petrografi dan Geokimia Batuan Diorit-Granodiorit-Granit di Daerah Gorontalo, Sulawesi
DOI:
https://doi.org/10.33332/jgsm.geologi.v23i4.718Abstract
Petrografi dan geokimia batuan granitoid didekati dari aspek petrografi dan whole-rock X-ray fluorescence (XRF) serta pemodelan data geokimia unsur utama menggunakan perangkat lunak GCDkit berbasis bahasa pemrograman R. Kelompok batuan Gorontalo diorit-granodiorit-granit (DGG) merupakan kelompok batuan beku plutonik bersifat menengah-asam yang dapat dibedakan jenisnya berdasarkan persentase kehadiran mineral kuarsa, alkali feldspar dan plagioklas serta komposisi geokimia. Secara fisik, batuan tersebut menunjukkan struktur masif, tekstur holokristalin dengan bentuk kristal umumnya euhedral-subhedral dengan ukuran kristal fanerik sedang hingga sangat kasar. Analisis pada batuan Gorontalo DGG menunjukkan kecenderungan sifat magnesian dengan indeks saturasi aluminium seluruhnya adalah metalominous dan memilik seri magma dengan tipe kalk-alkalin yang berasosiasi dengan lingkungan subduksi dengan perkiraan kedalaman peleburan sebagian magma terjadi pada kedalaman antara 114 hingga 160 km. Material batuan yang mengalami peleburan berasal dari dua jenis yang berbeda, yaitu low dan high-K mafic rocks. Selanjutnya, proses diferensiasi magma Gorontalo DGG setidaknya mengalami proses magma mixing, gravitational settling mineral, dan fraksionasi.
Katakunci: DGG, geokimia, Gorontalo, petrografi.
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