VOLCANOSTRATIGRAPHY AND PETROGENESIS OF LASEM VOLCANO REGION, REMBANG DISTRICT, CENTRAL JAVA

• Main Author: DISANDO (NIM : 12012035), TABEGRA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31208
• Institution: Institut Teknologi Bandung

<p align="justify">Mount Lasem is an inactive volcano located behind of Java Magmatic Arc. The parameters are includes the analysis of geomorphology, volcanostratigraphy, structural geology, and rock geochemistry. The methods are used in this research includes remote sensing (Landsat-8 and ASTER GDEM), petrographic analysis, and rock geochemistry analysis by XRF (XRay Fluorescence). Geomorphology of the research area are divided into 8 geomorphology units, Plain <br /> Denudational Unit, Pyroclastic Flow Slope Unit, Lava Flow Slope Unit, Volcanic Caldera Unit, Mass Flow Unit, Residual Volcanic Hills Unit, Intrusion Hills Unit, and Alluvial Plain Unit. Volcanostratigraphy of the research area are divided into 2 khuluk (Lasem Khuluk and Senjong Khuluk) and 2 units of shallow marine sediments. Lasem Khuluk consists of Ngargo Gumuk, Gunturgeni Gumuk, Kedung Gumuk, and Lengis Gumuk. Senjong Khuluk consists of Senjong Gumuk, Genderuwo Gumuk, Genuk Gumuk, Brenjang Gumuk and Nganten Gumuk. Lasem Khuluk and Senjong Khuluk volcanic products consist of pyroclastic flows, andesitic lava flows and andesite intrusions. Geologic structure of the research area was divided into primary structure and secondary structure. The primary structure includes <br /> sheeting joint, columnar joint, and auto breccia, while the secondary structure includes Kali Kebonan Anticline, Kali Tempur Anticline and Caldera of Mount Lasem Normal Fault. Based on the result of petrographic analysis and rock geochemistry analysis, Mount Lasem Complex Volcano showed magma differentiation, i.e. assimilation and magma mixing. The magma mixing process continued by magma fractionation with Calc-alkaline magmatic series as the end product in Active Continental Margin tectonic environment.<p align="justify">