The Petrology and Volcano-Stratigraphyof The Muria-Peninsula High-K Volcanic Rocks, Central Java, Indonesia

Mulyaningsih, Sri and Bronto, Sutikno and Kusniadi, Arie and Apriyanti, Lilis and Budianto, L and Wiloso, Danis Agoes (2022) The Petrology and Volcano-Stratigraphyof The Muria-Peninsula High-K Volcanic Rocks, Central Java, Indonesia. Journal of Geoscience, Engineering, Environment, and Technology, 7 (2). pp. 69-80. ISSN E-ISSN : 2541-5794, P-ISSN : 2503-216X

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The Muria-Peninsula is a Quaternary volcanolocated in the northern Sunda arc. Its activitywas controlled under high potassic and very high potassic magma series resulting in leucite-rich trachyte and pyroxene-rich basaltic-andesite. It is a strato-type volcanothatis composed of lava,breccia, and tuff layers, and some dikes havesome volcanic cratersand maars varying in age and composition. The study area is covering the volcanoes of Muria,Genuk, and Patiayam. This paper aims to describe the petrology,mineralogy, and volcano-stratigraphyof the different volcanic materials. The data and materials were sourced from the primary and secondary data. The methods are field mapping, stratigraphy measurements, collectingsamples, thin section analyses, and major element geochemistryusing X-Ray fluorescence (XRF). The results describe two groups of volcanic rocks consisting of pyroxene-rich andesitic-basaltic volcanic materials and leucite-rich trachyticvolcanic materials. Augitepresents in the andesitic basalt together with small grains of olivine and a few anorthite and foid minerals.Aegirine (Na-Pyroxene) is present in the leucite-rich trachyte that is often associated with biotite and hornblende. Na-Ca Plagioclase such as labradorite-andesine is often present in the basaltic-trachy-andesite that is usually rarely leucite. The major elementsshow high-K volcanic rocks with % K2O is 4-5.9% and very high-K volcanic rocks (with % K2O is between 6-8.24%) and low-K volcanic rocksthat contain % K2Ois2-3,9%.There are two groups of high-K to very high-K volcanic materials consisting of silicic-rich volcanic materials (~57-64%of SiO2) and low-silicic volcanic materials (~46-50%).The TAS diagram identifies tephrite, phonolite, and trachyte. Stratigraphic data identifies calcareous sediments of the Bulu Formation as the basement rocks of the Muria trachyandesite. Beds of pumice-rich volcanic breccia of the Ujungwatu Formation are the basementrocks of the basanite-tephrite of the Genuk Volcano, and the tuff of the Ujungwatu is also exposed consisting of the basanite-tephritic-phonolite of the Patiayam Volcano. The leucite-like feldspars are very common in the andesite lava and dikes that compose the crater of Muria. Most of the Muria volcanic materials are rarely in leucite, while some maars contain pumice-rich pyroclastic flows and basaltic lava.The results of the major elemental analysis of the Muria materials indicate that the rock tends tobe of medium to high K affinity (~2% K2O).The Genuk and older Muriaare consisting of leucite-rich tephrite-phonolite. It was two periods of magmatic series developed in the Muria-Peninsulathat was resulting in the high-K to very high-K magmatism and the medium K Kalk-alkalinemagmatism.

Item Type: Article
Uncontrolled Keywords: petrology, mineralogy, stratigraphy, high-K volcanic rocks, very high-K volcanic rocks, and characteristics.
Subjects: Q Science > QE Geology
Divisions: Fakultas Teknologi Mineral > Teknik Geologi (S1)
Depositing User: sri mulyaningsih
Date Deposited: 05 Jul 2022 02:59
Last Modified: 05 Jul 2022 02:59

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