Buletin Sumber Daya Geologi

KARAKTERISTIK ALTERASI DAN MINERALISASI BERDASARKAN PENGAMATAN INTI BOR DENGAN METODE ANALYTICAL SPECTRAL DEVICES (ASD) DAN CORESCAN DI AREA PIT A DAN PIT C DAERAH TUMPANGPITU, KABUPATEN BANYUWANGI, JAWA TIMUR

2025-05-27T06:58:32+00:00

The research area is located within the Mining Bussines Licence-Operation Production (IUP-OP) of PT Bumi Suksesindo in the Tumpangpitu area, Pesanggaran District, Banyuwangi Regency, East Java. The research area covers two areas, namely Pit A and Pit C. In Tumpangpitu, there are two types of ore deposits: porphyry copper and high-sulfidation epithermal gold. The aim of this research is to determine the types of lithology, alteration, mineralization, and ore deposit types in the research area. The research methods used include detailed core logging, analytical spectral devices (ASD) measurement, corescan, and mineragraphy analysis. The research was conducted using data from 10 drill holes: GTD-719, GTD-727, GTD-728, GTD-735, GTD-778, GTD-781, GTD-782, GTD-785, GTD-786, and GTD-792. The correlation results of the drill holes in the research area indicate that the lithology consists of andesite volcanic, preatomagmatic phase 1 breccia, dacite volcanic, diorite, preatomagmatic phase 2 breccia, and dacite intrusion dome. Based on the set of alteration minerals, pH, and temperature, there are 7 alteration zones: silica, silica ± alunite, pyrophyllite ± diaspore ± alunite, alunite ± pyrophyllite ± dickite ± kaolinite, alunite ± kaolin, kaolinite ± dickite ± montmorillonite-illite, chlorite ± montmorillonite-illite. The mineralization found includes pyrite (FeS₂), enargite (Cu₃AsS₄), and sphalerite ((ZnFe)S). The type of deposit in the research area is high-sulfidation epithermal deposit with a depth of 500-1,000 meters (intermediate).

KARAKTERISTIK FISIK, GEOKIMIA DAN SEBARAN ENDAPAN NIKEL LATERIT DAERAH LOJI BEACH, PULAU OBI, KABUPATEN HALMAHERA SELATAN, PROVINSI MALUKU UTARA

2025-05-27T07:10:00+00:00

Indonesia is one of the largest nickel producing countries in the world. One of the nickel producing areas in Indonesia is in the Loji Beach area. This research area is located on Obi Island, South Halmahera Regency, North Maluku Province. Geologically, the research area is composed of ultramafic rocks. This research aims to determine the characteristics of nickel laterite and its relationship with geological conditions in the research area using petrographic methods of rock samples and XRF (X-Ray Fluorescence) geochemistry of drilling samples. Geochemical data in the form of Ni content from drill data was interpolated using the IDW method using ArcGIS software. Based on research results, Ni-laterite is abundant in the morphology of gentle hills with a slope of 0-7%. The base rock bearing Ni-laterite is thought to be serpentinite from the serpentinization of harzburgite and dunite. Based on petrographic analysis, the bedrock is composed of >85% serpentine, the rest is relict minerals olivine and orthopyroxene, as well as other minerals such as talc, oxide minerals and opaque. The results of geochemical analysis show that in the limonite zone there is an abundance of Fe elements, while in the saprolite zone the Ni element is enriched with levels of 1.5% -2.8%.

GEOLOGY AND STRUCTURAL CONTROL ON MINERALISATION OF THE ARINEM AREA, GARUT, WEST JAVA

2025-06-29T14:22:34+00:00

Exploration by PT Aneka Tambang in 1981 identified several promising mineral prospects in West Java, categorized as low- to high-sulfidation epithermal types. One such prospect is the Arinem area in Garut, which became the focus of this study. Spanning 0.46 km², this area is located 45 km from Garut city.

The data used in this research include field data and core samples from seven boreholes provided by PT ANTAM Tbk. This study aims to understand the geological and hydrothermal alteration processes of the region using field work measurements, petrographic, mineralographic, and ASD specTERRA

The study area consists of volcanic and volcaniclastic units, intruded by Pyroxene Andesite and Hornblende Andesite, with prominent hydrothermal alteration zones. The geological structures include the Left-Lateral Arinem Fault and the Right-Normal Arinem Fault, both of which control hydrothermal processes. Minerals such as pyrite, chalcopyrite, galena, and sphalerite were identified, with mineral veins trending north – south. The results suggest that Arinem is a part of an en-echelon structure arrays part of a larger left lateral strike slip system in West Java that cross-cut by the younger NE – SW dextral faults. This provides crucial insight into the geology, subsurface alteration and mineralization distribution, highlighting its significance for ongoing exploration efforts.