VOLCANOSTRATIGRAPHY AND PETROGENESIS KELIMUTU VOLCANO AND SURROUNDING AREA, ENDE DISTRICT, EAST NUSA TENGGARA

• Main Author: Bahrun Najah, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69672
• Institution: Institut Teknologi Bandung

Kelimutu volcano has a highest point is 1639 masl, located in the Ende Regency, East Nusa Tenggara, with its characteristic in the form of three crater lakes at the summit. The volcano is located on the southern part of Flores Island, East Nusa Tenggara. The volcano formed by the interaction between the Indo-Australian Plate and the Eurasian Plate. The distribution of the rocks has not been mapped specific. The previous research only discussed the lake water geochemistry and geothermal potential around Kelimutu Volcano. However, in terms of petrogenesis it is not well defined. Thus, this aims of study to map the rocks on Kelimutu Volcano and its surroundings with the principle of vulcanostratigraphy, along with the geological history of its formation and the evolution of magma that occurred on Kelimutu Volcano and its surroundings. Then, define the tectonic environment of Kelimutu Volcano and its surroundings with petrogenesis approach. Remote sensing analysis and field observations were conducted to study of the geological aspects, such as geomorphology, stratigraphy, and geological structures that control the research area. Petrographic and geochemical analysis of rocks used to explain the evolution of magma and tectonic setting. Based on the previous research, the research area included in the volcanic landscape which divided into 12 units of the Earth's surface. The geomorphological units were defined and combined with field observation data, four khuluk were identified, namely the Khuluk Kelimutu Complex, Khuluk Sokoria, Khuluk Kelibara, and Khuluk Kelimutu. Khuluk Kelimutu consists of Gumuk Ata Mbupu, Gumuk Koofai, and Gumuk Ata Polo. The Khuluk and Gumuk are in the Bregada resulting from the eruption of the Kelimutu Complex. The identified materials resulting from volcanism in the study area are lava, pyroclastic breccia, tuff, lapilli and ash deposits. The material is produced from four phases, namely the Kelimutu Complex phase, Sokoria, Kelibara, and the young Kelimutu phase. The geological structure in the study area divided into the primary structures in the form of columnar joints, sheeting joints, laminates and parallel beds, autobreccia, and vesicular. The secondary structures in the form of faults and joints. Magma differentiation processes such as crystal fractionation, magma injection, mixing due to convection, decompression due to primitive magma, and eruption processes. Those features are reflected in fluctuations in anorthite content, plagioclase microtextures, rock texture in general, Harker diagrams, and fluctuations in oxide compounds. Furthermore, several analyzes have mentioned that each khuluk has its shallow magma chamber. Especially for the Khuluk Kelimutu, each Gumuk has a shallower magma chamber. Analysis of geochemical data using diagrams with major and trace elements shows that the magma affinity is classified as toleitic-calc-alkaline originating from an island arc magmatism.