ALTERATION, MINERALIZATION AND CHARACTERISTICS OF QUARTZ CURSOR SECTION 090 (WEST-EAST) BATU HIJAU OPEN MINE, WEST SUMBAWA, WEST NUSA TENGGARA.

• Main Author: Aji Frans Jaya, Ryan
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70503
• Institution: Institut Teknologi Bandung

Batu Hijau is one of the copper and gold mining area located in the western part of Sumbawa Island, West Nusa Tenggara Province, Indonesia. PT. Amman Mineral Nusa Tenggara (PT. AMNT) is currently hold contract in Batu Hijau with an area of approximately 12 km x 6 km. This study was conducted to determine the geological setting, alteration, mineralization with special studies of density and quartz vein types as well as its relationship to Cu and Au distribution along section 090 (west–east) of the Batu Hijau open pit mining. Primary data were obtained from the description of seven drill core wells, petrographic analysis of 20 thin sections and five polished sections, XRD (X-Ray Diffraction) and supported by secondary data in the form of Cu and Au assay data. The data processing and analysis is done qualitatively through overlay method. In general, the study area is an intrusion complex consist of several units (Late Miocene – Early Pliocene), they are: Andesite, Quartz Diorite, Intermediate Tonalite and Young Tonalite. Alteration zone is divided into 4 zones, they are: Biotite - Actinolite – Quartz Zone, Chlorite - Calcite - Epidote – Actinolite Zone, Sericite - Chlorite - Calcite - Quartz Zone, and Kaolinit - Quartz Zone. The main mineralization of the research area can be divided into 3 zones based on the dominant presence, they are: Bornit Zone, Chalcopyrite Zone and Pyrite Zone. The vein density zone based on its abundance at each measurement interval is divided into 4 classes, they are: abundant (> 10%), moderate (5-10%), rare (1-5%) and very rare (<1%). The quartz vein type of study area consists of Mt, A, B, C and D type. The results of the analysis show that alteration and mineralization occur in 3 stages, they are: early, transitions, and late stage which is controlled by the intrusion of Intermediate Tonalite. The development of the Mt quartz veins is controlled by the Young Tonalite, while the other vein types are controlled by the development of alteration. There are correlations between Cu and Au grade with the density and distribution of certain quartz vein type. High dense quartz veins are locally occur between Intermedier Tonalite and Quartz Diorite and the density is positively correlated with copper and gold grades. “A” veins also correlated with the high grade of Cu and Au, which associated with Biotit – Actinolite – Quartz Alteration Zone.