QUANTITATIVE GEOCHEMICAL ANALYSIS OF THE MAGMATISM PROCESS BASED ON POST-CALDERA LAVA ROCK DATA IN IJEN VOLKANIC COMPLEX USING PETROGRAM

• Main Author: Noorhaqqur Rosyadi, Nauval
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/54438
• Institution: Institut Teknologi Bandung

The Ijen Volcanic Complex is located in the Banyuwangi Regency, Indonesia. Ijen Volcanic Complex is an old mountain caldera which has a diameter of about 20 km and has about 22 postcaldera eruption centers in it. This post-caldera complex consists of caldera-rim, intra-caldera, and young mountains, namely Mount Blau and Ijen Crater. The research objective in this final project is to make an analysis of the magmatism process based on the geochemical data of the Ijen Volcanic Complex using a Microsoft Excel-based petrology program, namely PetroGram. PetroGram can approach and calculate the magmatism process and approach forward and inversion calculations. Analysis of the magmatism process includes the character of geochemical variations, initial mantle sources and partial melting, assimilation and crystallization, and magma mixing. The variation of the major elements shows that the Ijen Volcanic Complex has a certain trend where the content of Fe2O3, TiO2, and CaO forms a positive trend, while the content of Na2O, SiO2, and K2O forms a negative trend towards the MgO content. For the variety of trace elements, the majority of the more incompatible elements are more enriched than the more compatible elements. For isotope variations, data tends to be more diffuse and do not form relationships. In the Europium anomaly, there are two groups based on the Ca content. The trace element and isotope ratios tend to be relatively between I-MORB and Java Sea sediments. The source of magma comes from partial melting of the mantle such as I-MORB which has added fluid and assimilates the sediment, then forms several magma storage sites before erupting to the surface.