Penentuan Tipe Batuan Granitik Berdasarkan Analisis Geokimia Di Daerah Kulawi Kabupaten Sigi Provinsi Sulawesi Tengah

Research on geochemical characteristics for determining the type of granitic rock in the Central Sulawesi Region is still very rarely carried out, especially in the southern part of Palu, Kulawi Region, Sigi Regency, Central Sulawesi Province. Granitic rock sampling has not been carried out in detail, so further research is needed. This study aims at determining the mineral composition of granitic rock, the chemical element content of granitic rock and to determine the type of granitic rock at the research site. The method used in this research was field research related to outcrop observation and megascopic determination of rock types, and laboratory analysis in the form of petrographic and XRF analysis. Based on the petrographic analysis, granitic rocks in the research area consisting of granite and granodiorite rocks with a mineral composition consisting of quartz (Qtz), orthoclast (Or), plagioclase (Pl), biotite (Bt), hornblende (Hbl), opaque minerals (Op) and mineral accessories in the form of zircon (Zr). Based on the results of geochemical analysis of granitic rocks, the chemical element content of granite rocks shows the affinity of the Shoshonite or High-K series magma and the granodiorite rocks show the High-K Calc-alkaline magma affinity, where this magma affinity identifies the addition of K2O which is formed through the involvement of the crust component continent which is granitic in nature. Granitic rock types found in the research area were I-type (infracrustal) and S-type (supracrustal), where these two types of granitic rock are peraluminous which is characterized by the presence of mafic minerals in the form of biotite.

Keywords: geochemical analysis, granitic rock, I-type, S-type, peraluminous.