FLUID INCLUSION STUDY ON EPITHERMAL DEPOSITS IN MALASARI AREA, BOGOR REGENCY, WEST JAVA PROVINCE

• Main Author: Eka Pradana, Rizka
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69691
• Institution: Institut Teknologi Bandung

The research area located in Malasari Village, Nanggung District, Bogor Regency, West Java Province is a Mining Business License managed by PT. Antam. The research area is in the Mount Halimun Salak National Park. Research was conducted to determine the geological conditions, alterations, mineralization, and character of hydrothermal fluids. The methods used are geological mapping and alteration, petrography analysis, mineragraphic analysis, specTERRA analysis, XRD analysis, Assay AAS analysis, and fluid inclusion analysis. The analysis was carried out on samples of alterred rocks and quartz veins. The research area is composed of the Brexit Tuff Unit. The geological structure in the research area is in the form of a shear fault with the direction of NW-SE and NE-SW. The alteration zone is divided into two zones, namely the Quartz + Kaolinite ± Smektite ± Ilit-Smektite ± Ilit (argilic) Alteration Zone and the Quartz + Chlorite ± Albit ± Smektite ± Ilit-Smektit (propicitic) Alteration Zone. The vein textures present are massive textures, crustiform-colloform, and bladed lattice in the Quartz + Kaolinite Alteration Zone ± Smektit ± Ilit-Smektit ± Ilit (argilic). Fluid inclusion analysis showed that the fluid characteristics in crustiform-colloform textured veins have homogenization temperatures ranging from 180 – 260 °C and salinity ranging from 2.13 – 5.46 wt. % NaCl eq. And in vein textured lattice bladed has a homogenization temperature ranging from 150 – 225 °C and salinity ranges from 1.95 – 5.29 wt. % NaCl eq. The temperature of homogenization and salinity indicates the characteristics of epithermal deposits. Alteration and mineralization in the research area is divided into three stages, namely the first stage in the form of meteoric water infliteration to the bottom of the surface. The second stage of the fluid undergoes a boiling process at a depth of 180 – 185 m with a temperature of 196 - 198 °C. The third stage of the fluid rises to the surface and continues to cool to 150°C through fracturing formed by ne - SW directional shear faults and forming altered minerals and precipitating metal minerals.