Analisis Studi Morfologi dan Geokimia untuk Identifikasi Kerucut Skoria Studi Kasus Lereng Utara Kompleks Gunung Bromo-Tengger

Hawan, Shofi Iqtina (2020) Analisis Studi Morfologi dan Geokimia untuk Identifikasi Kerucut Skoria Studi Kasus Lereng Utara Kompleks Gunung Bromo-Tengger. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kompleks Gunung Bromo-Tengger merupakan kompleks gunungapi yang termasuk dalam Sub Zona Gunungapi Kuarter. Di lereng utara kompleks ini ditemukan berbagai bentang alam vulkanik, salah satunya kerucut skoria. Kerucut skoria adalah kerucut monogenetik yang tersusun atas material vulkanik (lava dan skoria) yang umum ditemukan pada kaki gunungapi strato. Pada penelitian ini dilakukan identifikasi kerucut skoria pada Kompleks Bromo-Tengger berdasarkan analisis morfologi, pengukuran densitas dan porositas batuan skoria, serta analisis geokimia. Identifikasi kerucut skoria dilakukan berdasarkan citra DEM dan Google Earth. Analisis geokimia menggunakan parameter unsur mayor dan jejak yang ditampilkan dalam bentuk diagram Harker dan Spider. Sedangkan nilai densitas dan porositas batuan skoria didapat dari studi referensi mengenai kerucut skoria yang pernah dilakukan sebelumnya. Dari hasil identifikasi morfologi, didapat sepuluh kerucut skoria yang tersebar di lereng utara Kompleks Bromo-Tengger dengan kerucut terkecil memiliki diameter 329 meter dan ketinggian 13,75 meter dan kerucut terbesar memiliki diameter 1.195 meter dan ketinggian 169 meter. Berdasarkan analisis diagram Harker dan Spider, diketahui bahwa skoria pada SC 6 memiliki afinitas Medium K dan jenis batuan basalt. Sedangkan skoria pada kaldera Lautan Pasir memiliki afinitas High K dan jenis batuan basaltic-andesit. Penentuan nilai densitas dan porositas mengacu pada penelitian sebelumnya mengenai kerucut skoria di Volcan de Colima (VdC) Mexico, dimana gunungapi ini memiliki tatanan tektonik yang menyerupai Kompleks Bromo-Tengger, yaitu zona subduksi lempeng samudera terhadap lempeng benua. VdC memiliki afinitas magma Medium K – High K dengan jenis batuan basaltic-andesit, dengan kandungan SiO2 52,52 – 58,32%, dimana kandungan SiO2 pada Kompleks Bromo-Tengger adalah 51,5 – 56,2 %. Berdasarkan kesamaan ini, diperkirakan nilai densitas dan porositas skoria Kompleks Bromo-Tengger berada pada rentang nilai yang sama dengan skoria pada Volcan de Colima, yaitu 1,3 – 1,4 gr/cm3 dan 44,9 – 48,1%. ================================================================================================================== The Bromo-Tengger Mountain Complex is a volcanic complex that belongs to the Quaternary Volcano Sub Zone. On the north slope of this complex are found various volcanic landscapes, one of it is the scoria cone. Scoria cone is monogenetic cone composed of volcanic material (lava and scoria) that commonly be found at the foot of the strato volcano. In this study, the identification of the scoria cone at the Bromo-Tengger Complex is carried out based on morphological analysis, measurement of the density and porosity of the scoria rocks, and geochemical analysis. Scoria cone identification is based on DEM imagery and Google Earth. Geochemical analysis uses the parameters of major and trace elements which are displayed in Harker and Spider diagrams. While the value of the density and porosity of the scoria rocks were obtained from a reference study that had been done before. From the morphological identification, we obtained ten scoria cones scattered on the northern slope of the Bromo-Tengger Complex with the smallest’s diameter is 329 meters and a height of 13.75 meters and the largest’s diameter is 1,195 meters and a height of 169 meters. Based on the analysis of the Harker and Spider diagrams, it is known that SC 6 has a Medium K magma affinity and basaltic rock type. While the scoria on the Sand Sea caldera has High K affinity and basaltic-andesite rock types. Determination of density and porosity values refers to previous study on the scoria cone in Volcan de Colima (VdC), Mexico. Where this volcano has a tectonic setting that resembles the Bromo-Tengger Complex, which is a subduction zone of oceanic plates against continental plates. VdC has a Medium K – High K magma affinity with basaltic-andesite rock types. Based on this similarity, it is estimated that the density and porosity scoria of the Bromo-Tengger Complex are in the same range as the scoria on Volcan de Colima, which are 1.3 – 1.4 gr/cm3 and 44.9 – 48.1%.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: kerucut skoria; morfologi; diagram harker; diagram spider; studi referensi scoria cone; morphology; harker diagram; spider diagram; reference study
Subjects: Q Science > QD Chemistry > QD75.2 Chemistry, Analytic
Q Science > QE Geology > QE571 Sedimentation and deposition. Sediment transport.
Q Science > QE Geology > QE601 Geology, Structural
T Technology > TA Engineering (General). Civil engineering (General) > TA441 Aggregates
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User: Shofi Iqtina Hawan
Date Deposited: 25 Aug 2020 13:00
Last Modified: 25 Aug 2020 13:00
URI: http://repository.its.ac.id/id/eprint/78326

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