Electronic Theses and Dissertation

Nikel laterit banyak dimanfaatkan dalam industri stainless steel, baterai, dan sektor lainnya. Pada tahun 2024 Indonesia memiliki cadangan nikel terbesar di dunia, yaitu sekitar 55 juta ton atau lebih dari 20 persen total cadangan global. Salah satu wilayah konsesi nikel laterit yang prospektif di Indonesia adalah Kecamatan Pomalaa, Sulawesi Tenggara, yang dikelola oleh PT ANTAM Tbk. Daerah penelitian berada di wilayah IUP PT ANTAM Tbk. dengan luas sekitar 24 km² dan secara geologi tersusun oleh Kompleks Ultramafik ofiolit Sulawesi yang telah mengalami pelapukan intensif hingga membentuk endapan nikel laterit. Penelitian ini bertujuan untuk mengetahui kondisi geologi daerah penelitian serta hubungan batuan dasar terhadap pengayaan unsur Ni pada zona saprolit. Metode penelitian meliputi pemetaan geologi permukaan, analisis geomorfologi dan struktur geologi, analisis petrografi pada 4 sampel batuan dengan tingkat serpentinisasi berbeda, serta analisis geokimia menggunakan X-ray Fluorescence (XRF) pada 9 titik bor. Data geokimia diolah melalui analisis korelasi dan statistik deskriptif berdasarkan nilai rata-rata kadar Ni pada zona batuan dasar, saprolit, dan limonit. Hasil penelitian meliputi peta geologi, peta geomorfologi, peta kelurusan, serta peta isopach dan peta isograde kadar Ni menggunakan metode Inverse Distance Weighting (IDW). Hasil pemetaan menunjukkan bahwa daerah penelitian tersusun atas dua satuan geologi, yaitu Kompleks Ultramafik (Ku) dan Formasi Aluvium (Qa). Litologi utama pada satuan Kompleks Ultramafik berupa batuan peridotit, khususnya harzburgit terserpentinisasi. Secara geomorfologi, daerah penelitian didominasi oleh bentang alam denudasional dan struktural dengan morfologi perbukitan hingga dataran. Struktur geologi berorientasi tenggara–barat laut dan timur laut–barat daya. Secara geokimia, kadar Ni meningkat dari sekitar 0,3% pada zona batuan dasar menjadi 1,42% pada zona saprolit, kemudian menurun pada zona limonit sekitar 1,14%. Unsur Fe₂O₃ dan Al₂O₃ menjadi indikator proses lateritisasi pada zona saprolit hingga limonit. Hasil ini menegaskan bahwa batuan dasar berupa harzburgit terserpentinisasi berperan sebagai sumber Ni, sedangkan zona saprolit merupakan zona utama pengayaan Ni di daerah penelitian, Kecamatan Pomalaa, Kabupaten Kolaka, Provinsi Sulawesi Tenggara.

Kata Kunci : Batuan Dasar, Nikel, Laterit, Ultramafik, Pengayaan

Laterite nickel is widely utilized in the stainless steel industry, batteries, and other sectors. In 2024, Indonesia possessed the largest nickel reserves in the world, amounting to approximately 55 million tons or more than 20 percent of the total global reserves. One of the prospective laterite nickel concession areas in Indonesia is Pomalaa District, Southeast Sulawesi, which is managed by PT ANTAM Tbk. The study area is located within the Mining Business License (IUP) of PT ANTAM Tbk, covering an area of approximately 24 km², and is geologically composed of the Sulawesi ophiolite ultramafic complex that has undergone intensive weathering, resulting in the formation of laterite nickel deposits. This study aims to determine the geological conditions of the study area and to evaluate the relationship between the bedrock and Ni enrichment in the saprolite zone. The research methods include surface geological mapping, geomorphological and structural geological analyses, petrographic analysis of four rock samples with different degrees of serpentinization, and geochemical analysis using X-ray Fluorescence (XRF) on nine drill holes. The geochemical data were processed through correlation analysis and descriptive statistical analysis based on the average Ni grades in the bedrock, saprolite, and limonite zones. The research outputs include geological maps, geomorphological maps, lineament maps, as well as isopach and isograde maps of Ni grades generated using the Inverse Distance Weighting (IDW) method.The mapping results indicate that the study area is composed of two geological units, namely the Ultramafic Complex (Ku) and the Alluvium Formation (Qa). The main lithology of the Ultramafic Complex unit consists of peridotite, particularly serpentinized harzburgite. Geomorphologically, the study area is dominated by denudational and structural landforms with hill to plain morphologies. The geological structures generally trend southeast–northwest and northeast–southwest. Geochemically, Ni grades increase from approximately 0.3% in the bedrock zone to 1.42% in the saprolite zone, followed by a decrease to about 1.14% in the limonite zone. Fe₂O₃ and Al₂O₃ contents serve as indicators of lateritization processes in the saprolite to limonite zones. These results confirm that serpentinized harzburgite bedrock acts as the source of Ni, while the saprolite zone represents the main zone of Ni enrichment in the study area, Pomalaa District, Kolaka Regency, Southeast Sulawesi Province. Keywords: Bedrock, Nickel, Laterite, Ultramafic, Enrichment