PETROLOGY OF VESICULAR BASALT OF YOUNG SLAMET VOLCANO, BANYUMAS REGENCY, CENTRAL JAVA

Abstract

Vesicular basaltic rocks are exposed on the southern slope of Slamet Volcano, forming part of the Young Slamet Volcano system. Due to the lack of detailed studies on these vesicular basalts, this research aims to describe their petrology and mineral composition. Field observation methods and direct descriptions of outcrops and rock samples were conducted, along with petrographic analysis to determine the mineral composition. Petrologically, the basalt outcrops are dark gray, ranging in dimensions from 30 cm to 3 meters, and extend along the river. The rocks exhibit an aphanitic texture with a vesicular structure, composed of plagioclase, olivine, and pyroxene as phenocrysts with a porphyritic texture and vesicular structure. Specific textures such as zoning and sieve textures provide evidence of magma mixing, while the presence of glomerocrysts indicates fractional crystallization processes.