PETROLOGY AND MINERALOGY OF LAVA BARUJARI VOLCANO IN RINJANI VOLCANO COMPLEX LOMBOK, NUSA TENGGARA BARAT

• Main Author: Setiawan, Alvin
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/47217
• Institution: Institut Teknologi Bandung

The study was carried out on the Lava of Rinjani Volcano, which are products of the Barujari Volcano in Rinjani Volcano Complex eruptions. It consists (from old to young) Lava 1944 (L44), Lava 1966 (L66), Lava 1994 (L94), Lava 2004 (L04), Lava 2009 (L09). Detailed investigation of petrology and mineralogy using polarisation microscope and SEM-EDS from the oldest lava unit to the youngest lava unit were carried out in order to determine the characteristics (affinity, temperature, and pressure) and the change of mineral composition rock forming minerals which can explain the magmatic evolution of the Lava Rinjani Volcano. Petrology analysis show that Lava of Barujari Volcano in Rinjani Volcano Complex is andesite olivine have phenocrysts consists of plagioclase, pyroxene, olivine, and opaque mineral then have matrix consists of volcanic glass, plagioclase microlites, pyroxene, and opaqe minerals. Based on calcic-clinopyroxene analysis, the magmatic affinity of Rinjani Volcano is calc-alkaline. The magmatic evolution initiated by magma with temperature 980 – 1110.4oC which was influenced by convection zone and formed Lava 1944 (L44). Then, magma temperature of Lava 1966 (L66) was increase to 1010 – 1120oC was caused by more primitive magma injection with Mg and Ca-rich. In Lava 1994 (L94) magma temperature was decreased 1000 – 1090.3oC caused by convection process. Magma still in convection process and continue until Lava 2004 (L04) and magma temperature still decrease to 950oC. For the youngest lava unit, Lava 2009 (L09) was form caused by magma injection and affected magma temperature was increase become 1080 – 1127oC.