Karakteristik Geokimia Batuan Unsur Jejak dan Unsur Tanah Jarang Gunung Api Kaba untuk Interpretasi Tatanan Tektonik Berdasarkan Analisis ICP-MS
DOI:
https://doi.org/10.54082/jupin.1674Kata Kunci:
Active Continental Margin, Geokimia, Gunung Kaba, Island Arc, Unsur Jejak, Unsur Tanah JarangAbstrak
Gunung Kaba yang terletak di bagian timur Provinsi Bengkulu merupakan bagian dari jalur gunung api aktif di sepanjang zona subduksi barat Pulau Sumatra. Penelitian ini bertujuan untuk mengungkap karakteristik geokimia unsur jejak dan unsur tanah jarang (rare earth elements/REE) guna menafsirkan asal-usul magma serta tatanan tektoniknya. Sebanyak tujuh sampel batuan dari Gunung Kaba dianalisis menggunakan metode ICP-MS dan hasilnya dipresentasikan dalam bentuk diagram laba-laba yang dinormalisasikan terhadap primitive mantle, N-MORB, dan chondrite. Hasil analisis menunjukkan pola pengayaan unsur LILE dan LREE, serta penipisan unsur HFSE dan HREE, yang merupakan ciri khas magmatisme pada zona subduksi. Selain itu, terdapat indikasi transisi pola dari tatanan tektonik island arc menuju active continental margin (ACM), yang tercermin dari variasi kandungan unsur jejak. Temuan ini mendukung hipotesis bahwa bagian barat Pulau Sumatra terbentuk bukan hanya dipengaruhi oleh tatanan tektonik busur kepulauan (island arc), tetapi juga dipengaruhi oleh tatanan tektonik tepi benua aktif (active continental margin). Penelitian ini memberikan data geokimia baru terkait pemahaman mengenai interpretasi tatanan tektonik dan evolusi magma di zona subduksi Sumatra.
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