Characteristics of quaternary volcanic rocks based on petrographic analysis in Belandang Area, Ulu Ogan, Ogan Komering Ulu

Abstract

Administratively the research area located in Belandang, Ogan Komering Ulu District, South Sumatra Province. The astronomical located at coordinates 04, 04’ 6.9 ″-04 07’ 54.2″ LS - 103 45’ 15.1 ″- 103 49’ 1.4″ BT. The research area included in the territory of the Bukit Barisan formed on the Late Oligocene-Early Miocene and controlled by Semangko Fault Northwest-Southeast oriented accompanied by an increase in the rate of volcanic activity. Then in the Plio-Pleistocene compression and removal process occurs that causes volcanism, so that at the end of the deposition of South Sumatra Basin filled by volcanic materials. The research area is dominated by volcanic deposits consisting of, Andesite Lava, Lapilli Tuff Unit, and Agglomerates. The method used is the petrographic analysis of the 9 rock samples were considered to represent the extent of the study area, consisting of 2 samples of Andesite, 1 sample of Lapilli Tuff, and 6 samples of Agglomerate. The results are show that volcanic rocks in the study area has undergone a change that is characterized by the presence of alteration minerals such as Carbonates, Chlorite, Sericite, Quartz and Clay minerals. The presence of alteration minerals indicate that the volcanic rocks in the study area belongs to the type of alteration Phyllic and Outer/Sub Propyllitic. Based on lithological characteristics, the research area enter into the Central and Proximal Facies.