GEOLOGY AND ALTERATION STUDY of GARUMUKTI REGIONAL PAMULIHAN SUB-DISTRICT, GARUT DISTRICTS GARUT JAWABARAT PROVINCE
Raden Reza Dwi Yana, Mirzam Abdurrachman, Melky B. Rondonuwu dan Daniel Jefri H.

Sekolah Tinggi Teknologi Mineral Indonesia
Institut Teknologi Bandung

Abstract

This study aims to identify and examine geological aspects, in the form of Lithology, Geological Structure and Alteration Zone. The research area is located in Garumukti and its surroundings, Pamulihan District, Garut Regency, West Java Province. Tectonically, it is included in the volcanic arc zone of the southern part of western Java, in the study area there are rocks of late Miocene to Holocene age divided into nine units namely the Sembung Lava Unit, Sembung Pyroclastic Flow Unit, Kendeng Lava Unit, Mandalagiri 1 Lava Unit, Mandalagiri Lava Unit 1, Mandalagiri 2 Lava Unit, Mandalagiri 2 Pyroclastic Unit, Diorite Intrusion Unit and Papandayan Lava Unit.
The geological structure of the study area has seven faults in Late Pleistocene faults, namely Cipanyairan Left Fault, Cipaningeu Right Fault, Cicadas Left Fault, Ciangkrong Right Fault, Cibitung Normal Left Fault, Cipeundeuy Normal Left and Sawer Normal Left Fault.
The research area is an area that has three alteration zones, namely Advanced Argillic Zone (Quartz, Kaolinite and Carbonate), Subpropylithic Zone (Quartz, Chlorite, Illite and Carbonate) and Phylic Zone (Sericite, Quartz and Chlorite). Judging from the mineral associations, it is formed at a temperature of 200 to 320 Celsius which indicates a low sulfidation epithermal system. There are also metallic minerals in the form of pyrite, chalcopyrite, galena and sphalerite, which are formed at temperatures of 200 to 250 Celsius with a pH of 4 to 5. The distribution of Alteration zones in the study area is generally controlled by lithology in the form of andesite and breccias as well as horizontal fault structures that arise as a result of subduction the Eurasian plate beneath Indo-Australian plate.

Keywords: Garumukti, Alteration, Low Sulfidation Epitermal

Topic: Solid Earth Sciences