Geochemical characteristic of volcanic rocks in the Karaha – Talagabodas fields related to Galunggung Volcano

Abstract

The Karaha-Talagabodas field is located on the east side of the ancient Bandung-Garut caldera and adjacent to the Galunggung volcano in West Java, Indonesia. Karaha-Talagabodas are two distinct locations separated by approximately 10 km. Geochemical analysis including major, trace and rare earth elements has been done using Fusion ICP-MS to find out how the different composition of volcanic rocks in the two regions (Karaha and Talagabodas). The volcanic rocks of the Karaha-Talagabodas field were composed of pyroxene andesite, andesite basaltic, basalt, highly altered pyroclastic and tuff breccia. The identified alteration minerals are indicated by the presence of kaolinite, halloysite, silica, sericite and chlorite. Geochemically, these volcanic rocks contain SiO2 variable (49.94%-62.27%), Na2O (3.02%-3.83%) and K2O (0.46%-1.78%). Based on the major element diagram of rock chemistry (Na2O+K2O vs SiO2). It shows rocks consisting of calc-alkaline for andesite from Karaha basalt, basaltic andesite and andesite formed in tholeiitic environments on Talagabodas volcanic rocks. Trace element data for host volcanic rocks are provided by this study to identify the magmatic arc system and distribution of subduction components. The normalized REE diagram of N-Morb shows the similarity of the pattern of all Talagabodas volcanic rocks, only Karaha andesite rocks show slight REE enrichment and europium depletion.