KARAKTERISTIK BASAL DAERAH TANJUNG AGUNG

Research on crystalline rocks in Lampung has been carried out by various researchers, but this research still does not cover other areas, such as Tanjung Agung village, Katibung District, South Lampung. Therefore, this research aims to analyze the characteristics of basalt rocks in the Tanjung Agung area, South Lampung, which is important for expanding understanding of the geological diversity in the region. These rocks are found in the form of entablature-type columns formed from basalt lava flows. The methods used include literature studies, field observations, and laboratory analysis, especially petrographic analysis, to identify mineral content and rock structure to understand the crystallization process and formation of columnar joints. The results of the petrographic analysis show a porphyritic texture with plagioclase, pyroxene, and hornblende phenocrysts, as well as a finer groundmass. These rocks show gradual crystallization and textural variations such as trachytic, sieve, glomeroporphyritic, and zoning, which reflect processes of decompression, pressure reduction, and magma mixing. Based on the mineral composition, this rock is classified as basalt which undergoes a gradual crystallization process, namely the formation of large crystals (phenocrysts) at depth and the formation of a finer groundmass at the surface. This research also opens up opportunities for geochemical analysis to understand the origin and evolution of magma in the region. Thus, this research provides further insight into the dynamics of magmatism and rock formation in the Tanjung Agung area.