VOLCANOSTRATIGRAPHY AND PETROGENESIS OF MERBABU MOUNTAIN AREA AND AROUND, BOYOLALI, MAGELANG, AND SEMARANG DISTRICT, CENTRAL JAVA PROVINCE

• Main Author: RIZKI AZMI (nim : 1201118), WAHYU
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31543
• Institution: Institut Teknologi Bandung

<p align="justify"> Mount Merbabu is one of the Quartenary volcano located in three districts in Central Java: Boyolali, Magelang, and Semarang Districts. It is located in 428000 - 445000 mT and 9171000 - 9185000 mU (zone 49S) UTM coordinate. Mount Merbabu classified as B type volcanoes (the dormant mountain). The aim of this project was to analyze the geological system and volcanic rock characteristic of Mount Merbabu and its surrounding area. Geomorphological unit in the studied area is divided into 5 units. The Peak of Volcano Unit (V3), Body of Volcano Unit (V4), Foot of Volcano Unit (V6), Volcanic Plain Unit (V11), and Denudated Volcanic Hill Unit (V14). The Volcano-stratigraphy of the studied area from the eldest to the youngest units consist of the Andong Khuluk composed of Andong Basaltic Lava Unit (A11) and Andong Andesitic Lava Unit (A12). The Merbabu Khuluk composed of three gumuks: <br /> The Old Merbabu Gumuk, Young Merbabu Gumuk, and Puasa Gumuk. The Old Merbabu Gumuk consists of Old Merbabu Basaltic Lava Unit 1 (Mtl1), Old Merbabu Pyroclastic Flow Breccia Unit 1 (Mta1), Old Merbabu Pyroclastic Fall Breccia Unit (Mtj), Old Merbabu Pyroclastic Flow Breccia Unit 2 (Mta2), Old Merbabu Basaltic Lava Unit 2 (Mtl2), Old Merbabu Basaltic Lava Unit 3 (Mtl3), Old Merbabu Andesitic Lava Unit 1 (Mtl4), Old Merbabu Andesitic Lava Unit 2 (Mtl5), Old Merbabu Andesitic Lava Unit 3 (Mtl6), Old Merbabu Andesitic Lava Unit 4 (Mtl7), and Old Merbabu Andesitic Lava Unit 5 (Mtl8). Young Merbabu Gumuk consists of Young Merbabu Basaltic Lava Unit 1 (Mml1), Young Merbabu Basaltic Lava Unit 2 (Mml2), Young Merbabu Andesitic Lava Unit 1 (Mml3), Young Merbabu Andesitic Lava Unit 2 (Mml4). Puasa Gumuk consists of Puasa Basaltic Lava Unit (Pl). There is also Sumberrejo Lahar Breccia Unit found in surface. Geological structures found in the studied area consist of the primary structures such as columnar joints and sheeting joints. Several secondary structures such as crater structure, Tempel Normal Fault, Kenteng Normal Fault, and volcanic lineaments. According to the petrography and geochemistry data processed in the laboratory, Mount Merbabu's petrogenesis are affected by magma differentiation; crystal fractionation, magma mixing, and assimilation. <p align="justify">