Buletin Sumber Daya Geologi

ANALISIS ALTERASI DAN MINERALISASI BERDASARKAN PENGAMATAN MEGASKOPIK DAN MIKROSKOPIK PADA DAERAH PROSPEK X KABUPATEN BOLAANG MONGONDOW, SULAWESI UTARA

2024-07-02T00:40:12+00:00

The North Arm of Sulawesi Island is a gold-rich metallogenic belt. The study area is located in Bakan Village, Bolaang Mongondow Regency, North Sulawesi in the IUP area of PT J Resources Bolaang Mongondow. Exploration to obtain new prospect areas is still being carried out. Therefore, research on alteration and mineralisation characteristics is expected to be a reference for the discovery of new prospects. The research was conducted by identifying surface and subsurface data megascopically and microscopically. Microscopic observations with petrography and mineragraphy. To obtain surface data, alteration observations, channel sampling and grab sampling were carried out, while subsurface data were obtained from core drilling. The purpose of the study was to determine the alteration, mineralisation, oxidation, and deposits type. The study area has lithologies of hydrothermal breccia, diatreme breccia, fault breccia, and tuff breccia. Alteration developed in the form of vuggy sillica, massive sillica, advanced argillic, and argillic. Mineralisation includes gold and silver and sulphide minerals such as pyrite, chalcopyrite, sphalerite, enargite, covellite, and oxide minerals such as goethite, jarosite and hematite. The epithermal high sulphidation deposit type was formed at medium depth, with oxide-type ore.

KETERDAPATAN DAN GENESA CEBAKAN BIJIH BESI DAERAH KAPAYANG, KABUPATEN TANAH BUMBU, KALIMANTAN SELATAN

2024-07-02T00:40:11+00:00

The occurences of iron mineralisation in upper part of Kusan River, Kapayang, Regency of Tanah Bumbu are still indicative and required more research to reveal the characteristic and potency of iron ore deposits. The research was conducted with reconnaissance survey using methode of geological mapping, sampling of rock, iron ore, lateritic soil, and panning concentrate of crushed ore material. The laboratory analyses involve petrographic, mineragraphic, grain mineralogy and geochemical assay. Iron ore in the research area consist of two deposit type are primary iron and lateritic iron. The genetic is related to procces of magmatism, metamorphism/metasomatic and hydrothermal. The primary iron ore mineral in altered dunite and gneiss-schist rocks are dominated by magnetite and hematite, some chromite and garnet. While in lateritic iron as resulted from weathering of pyroxenite-peridotite rock consist of hematite magnetite and goetit. Potency of exploration target of lateritic iron is 158,264 wmt and the grade of Fe_tot ranging from 49.45 to 54.89%. Grid soil geochemical exploration is suggested for follow up work using hand auger to collect soil sample in laterisation zone to obtain more optimize reource potency.

KARAKTERISITIK ENDAPAN POLIMETALIK EMAS DAN LOGAM DASAR DAERAH DOLOK PANGKURUHAN, KECAMATAN PEGAGAN HILIR, KABUPATEN DAIRI, PROVINSI SUMATERA UTARA

2024-07-02T10:08:35+00:00

Several previous investigative activities in the Dolok Pangkuruhan area, Dairi Regency, North Sumatra Province have discovered several locations of gold and base metal mineralization. This article discusses the characteristics of alteration and mineralization of gold and base metals based on the results of investigations in 2023 with the aim of determining the characteristics of alteration and mineralization as well as a deposit type model. The research methods used include semi-detailed geological mapping, alteration and mineralization, XRD analysis, spectral analysis, mineralography, and fluid inclusion analysis. The alteration that develops consists of: argillic, advanced argillic, phyllic-pyrite and phyllic-silicification. There are four types of mineralization: a. Au-galena veins (Dolok Pangkuruhan) which are characterized by the presence of native gold and crystalline and colloform vein textures; b. Galena mineralization, sphalerite (Aek Sulfi), with massive and banded texture characteristics; c. quartz-silicification-sphalerite-galena vein (Sembilin River); d. quartz-bornite-chalcopyrite vein (Sikiring- kiring River). The results of fluid inclusion analysis are interpreted as epithermal deposits with mineralization formation temperatures ranging from 240°C – 346°C. Based on paragenetic sequence analysis, the mineralization characteristics can be interpreted as a model of polymetallic deposits (Au-Pb and Zn-Pb-Cu) of medium - high sulphide epithermal vein type.