Karakterisasi Petrologi dan Geokimia Batuan Gunungapi Adang dan Kaitannya dengan Kelimpahan Unsur Tanah Jarang Di Daerah Botteng Kabupaten Mamuju, Provinsi Sulawesi Barat

Abstract: The Adang Volcanic Formation in Mamuju Regency, West Sulawesi, is a volcanic complex consisting of eruptive, intrusive, and altered rocks with potential rare earth element (REE) content. This study aims to characterize the petrology and geochemistry of rocks and their relationship to REE distribution across three key blocks: Botteng, North Botteng, and Ahu Pasabu. Analytical methods applied include petrographic analysis, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), and ICP-MS on rock and soil samples. The lithology is primarily basalt, with SiO₂ content ranging from 30% to 60%. Alteration minerals such as chlorite, analcime, and calcite indicate hydrothermal alteration processes. The highest REE concentration was detected in soil drill samples from depths of 1–2 meters, reaching up to 4,803 ppm, and is dominated by light REEs (La, Ce, Nd). Based on integrated petrological and geochemical data, the REE occurrences are classified as lateritic deposits, where rare earth elements are adsorbed onto clay mineral surfaces formed through volcanic rock weathering. This study reinforces the strategic exploration potential of the Botteng area and offers valuable insights into the sustainable development and management of Indonesia’s mineral resources, particularly in relation to REE-bearing volcanic terrains. Abstrak: Formasi Gunungapi Adang di Kabupaten Mamuju, Sulawesi Barat, merupakan kompleks vulkanik yang tersusun atas batuan hasil erupsi, intrusi, dan alterasi, serta memiliki potensi keterdapatan unsur tanah jarang (REE). Penelitian ini bertujuan mengidentifikasi karakter petrologi dan geokimia batuan serta hubungannya dengan sebaran REE pada tiga blok utama: Botteng, Botteng Utara, dan Ahu Pasabu. Metode analisis meliputi petrografi, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), dan ICP-MS terhadap sampel batuan dan tanah. Hasil menunjukkan bahwa litologi didominasi oleh basalt dengan kandungan SiO₂ antara 30–60%. Kehadiran mineral ubahan seperti klorit, analsim, dan kalsit mengindikasikan proses alterasi hidrotermal. Kandungan REE tertinggi ditemukan pada sampel tanah bor di kedalaman 1–2 meter dengan total konsentrasi mencapai 4.803 ppm, yang didominasi oleh unsur LREE (La, Ce, Nd). Berdasarkan hasil integrasi data petrologi dan geokimia, endapan REE diklasifikasikan sebagai tipe laterit, di mana unsur tanah jarang teradsorpsi pada permukaan mineral lempung hasil pelapukan batuan vulkanik. Studi ini menegaskan potensi eksplorasi strategis di wilayah Botteng serta memberikan kontribusi bagi pemanfaatan dan pengelolaan sumber daya mineral yang berkelanjutan di Indonesia.