OPHIOLITE: Jurnal Geologi Terapan

Asosiasi Skandium dan Potensi Logam Tanah Jarang pada Profil Laterit Nikel di Daerah Palangga Selatan, Konawe Selatan, Sulawesi Tenggara

2026-06-07T06:05:32+00:00

This study examines the association between scandium (Sc) and rare earth elements (REE) in a nickel laterite profile within the concession of PT Generasi Agung Perkasa, Watumbohoti Village, South Palangga, Southeast Sulawesi. Nine samples were collected from six observation points on the pit face, representing limestone, clay, limonite, saprolite, and bedrock layers between 5 and 35 m depth. Sc and fourteen REE were determined by ICP-MS and ICP-OES, major oxides by XRF, and relationships among variables were tested using Pearson correlation. Sc ranges from 0.9 to 76 ppm and total REE from 4.4 to 60.1 ppm. The highest Sc contents occur in the limonite zone, 76 ppm in USN LP06 and 71 ppm in USN LP04, whereas the highest total REE occur in the clay zone, 60.1 ppm in USN LP02 and 60.0 ppm in USN LP03. Sc correlates strongly with Cr₂O₃ (r = 0.952), Fe (r = 0.949), and Co (r = 0.917) at p < 0.001, while ΣREE correlates significantly only with Al₂O₃ (r = 0.771, p < 0.05). Sc correlates with neither ΣREE (r = 0.161) nor Ni (r = 0.158), whereas Ni correlates with MgO (r = 0.707, p < 0.05). These results confirm two separate enrichment controls within one profile, the iron oxide fraction for Sc and aluminium-bearing clay for ΣREE. REE contents are too low to justify exploration in their own right, whereas Sc in the limonite zone merits testing as a nickel by-product through regularly spaced drilling and mineralogical analysis.

Identifikasi Struktur sebagai Jalur Migrasi Sistem Panas Bumi Gunung Ciremai Berdasarkan Analisis dan Pemodelan Gaya Berat

2026-05-21T02:55:25+00:00

The Mount Ciremai area is a Quaternary volcano that developed within the tectonic framework of the Java volcanic arc and is controlled by magmatic activity and regional fault structures, indicating significant geothermal potential. This study aims to characterize subsurface structures and specifically identify geothermal fluid migration pathways based on the analysis of satellite gravity data from the Global Gravity Model Plus (GGMPlus). The gravity data were processed to obtain the Complete Bouguer Anomaly (CBA), separated into regional and residual anomalies, and subsequently analyzed using gravity field derivatives, namely the First Horizontal Derivative (FHD) and the Second Vertical Derivative (SVD), and further modeled through three-dimensional gravity inversion. The results indicate that the CBA values range from −45.4 mGal to +29.7 mGal, with low-anomaly zones concentrated in the central part of the study area, forming a low-density basin-like pattern. The regional anomaly suggests the presence of deep geological structures and possible influences of magmatic systems, whereas the residual anomaly reveals shallow-to-intermediate density contrasts interpreted to be associated with fracture zones and geothermal alteration. The FHD and SVD analyses consistently identify possible fault systems, including reverse and normal faults with dominant orientations related to sharp gravity anomaly gradients. The 3D inversion modeling indicates a spatial correlation between low-density zones and these fault structures, which are interpreted as the main migration pathways for geothermal fluids. These findings confirm that the integration of derivative analysis and 3D inversion based on GGMPlus data is effective for the preliminary delineation of controlling zones within the geothermal system of Mount Ciremai.

Integrasi Pemodelan Muka Airtanah dan Penggunaan Parameter Hidrogeologi dalam Penentuan Kualitas Airtanah di Daerah Imogiri, Bantul, Yogyakarta

2026-05-23T14:13:23+00:00

Penelitian ini memodelkan sebaran muka airtanah (MAT) dan mengevaluasi kualitas airtanah di Selopamioro, Imogiri, Bantul, Yogyakarta. Survei lapangan mencakup pengukuran MAT dan pengambilan sampel air pada 80 sumur gali untuk pengujian suhu, pH, TDS, dan daya hantar listrik (DHL). Pemrosesan data menggunakan ArcGIS untuk pemetaan spasial serta Leapfrog untuk pemodelan tiga dimensi MAT. Hasil menunjukkan bahwa muka airtanah dikontrol oleh kondisi morfologi; kawasan selatan berfungsi sebagai zona imbuhan sementara aliran airtanah bergerak ke dataran rendah di utara. Nilai pH (6,06–8,86), TDS (54,13–549,98 mg/L), dan DHL (19,9–1.096 µS/cm) sebagian besar sesuai baku mutu nasional, namun beberapa titik menunjukkan nilai TDS tinggi dan pH rendah yang membutuhkan perhatian. Temuan ini mendukung perlunya pemantauan spasial berkala dan integrasi aspek hidrogeologi–geologi dalam strategi pengelolaan airtanah berkelanjutan di kawasan karst dan vulkanik Yogyakarta.