Electronic Theses and Dissertation

Formasi Gunungapi Breueh di Kecamatan Pulo Aceh, Kabupaten Aceh Besar, Provinsi Aceh merupakan kawasan yang belum banyak diteliti secara geologi, padahal terletak di gunungapi tersier. Kurangnya data mengenai petrogenesa batuan beku pada Formasi Gunungapi Breueh menjadikan wilayah ini penting untuk diteliti. Penelitian ini dengan luas area sekitar ±24 km². Wilayah ini secara geologi terdiri atas tiga satuan utama: Formasi Gunungapi Breueh (Tlvb), Formasi Diorit (Tir), dan Formasi Aluvium (Qh). Penelitian ini bertujuan untuk memahami kondisi geologi, kondisi geomorfologi, serta mengetahui petrogenesa batuan beku pada Formasi Gunungapi Breueh (Tlvb) hasil analisis geokimia meliputi jenis magma, asal magma, dan tatanan tektonik. Metode yang digunakan meliputi pemetaan geologi skala 1:25.000, observasi lapangan pada 73 titik singkapan, serta analisis laboratorium menggunakan Petrografi, X-Ray Flourencence (XRF), dan Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Secara geomorfologi, wilayah ini terdiri Satuan Vulkanik dengan bentuk lahan kerucut vulkanik (V2) dan bentuk lahan lereng kaki gunungapi/lereng bawah gunungapi (V6), Satuan Denudasional dengan bentuk lahan dataran atau peneplain (D5), dan Satuan Marine dengan bentuk lahan marine wave cut platform (M1) dan bentuk lahan pantai (M3), dengan pola aliran sungai sentripetal. Hasil analisis litologi menunjukkan terdapat enam satuan batuan, yaitu: Satuan Basal (Tlvbb), Satuan Andesit (Tlvba), Satuan Dasit (Tlvbd), Satuan Tuf-lapili (Tlvbt), Satuan Diorit (Tird), dan Satuan Endapan Pantai (Qb). Hubungan stratigrafi antara Formasi Tlvb, Tir dan Qh bersifat tidak selaras, mengindikasikan peran aktivitas vulkanisme, dan sedimentasi pantai. Struktur geologi berupa kekar dengan arah dominan timur laut - barat daya (NE-SW) dan barat laut–tenggara (NW-SE) dan struktur batuan beku dalam berupa dike. Analisa petrogenesa menunjukkan bahwa sampel batu beku RY14, RY28, dan RY43 dikategorikan sebagai batuan beku yang pembentukannya berkaitan dengan Active Continental Margin (ACM), berada pada tatanan tektonik Destructive Plate Margin yang terletak pada zona konvergen dimana antara dua lempeng (subduksi samudra dengan benua) yang saling bertumbukan menghasilkan magma, dengan ditandai dengan jenis magma Calc-Alkaline Series - Alkaline Series. Magma mengalami perubahan komposisi (diferensiasi), magma dengan jenis Calc-Alkaline Series - Alkaline Series, karena lelehan sebagian kerak samudra dan kerak benua, magma mengalami perubahan seiring dengan naiknya magma tersebut ke atas permukaan, akibat pengaruh dari batuan yang dilewatinya serta pengaruh perbedaan suhu dan tekanan.
Kata Kunci : Gunungapi Breueh, Petrografi, XRF, ICP-MS, Petrogenesa

The Breueh Volcanic Formation in Pulo Aceh Subdistrict, Aceh Besar Regency, Aceh Province is an area that has not been extensively studied geologically, even though it is located on a tertiary volcano. The lack of data on the petrogenesis of igneous rocks in the Breueh Volcanic Formation makes this area important for research. This study covers an area of approximately ±24 km². Geologically, this area consists of three main units: the Breueh Volcanic Formation (Tlvb), the Diorite Formation (Tir), and the Alluvium Formation (Qh). This study aims to understand the geological and geomorphological conditions and determine the petrogenesis of igneous rocks in the Breueh Volcano Formation (Tlvb) through geochemical analysis, including magma type, magma origin, and tectonic structure. The methods used include 1:25,000 scale geological mapping, field observations at 73 outcrop points, and laboratory analysis using petrography, X-Ray Fluorescence (XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Geomorphologically, this region consists of Volcanic Units with volcanic cone landforms (V2) and volcano foot/lower volcano slope landforms (V6), Denudational Units with peneplain landforms (D5), and Marine Units with marine wave-cut platform landforms (M1) and coastal landforms (M3), with centripetal river flow patterns. The results of lithological analysis show that there are six rock units, namely: Basal Unit (Tlvbb), Andesite Unit (Tlvba), Dacite Unit (Tlvbd), Tuff-lapilli Unit (Tlvbt), Diorite Unit (Tird), and Coastal Deposit Unit (Qb). The stratigraphic relationship between the Tlvb, Tir, and Qh formations is discordant, indicating the role of volcanism and coastal sedimentation. The geological structure consists of fractures with a dominant northeast-southwest (NE-SW) and northwest-southeast (NW-SE) direction and igneous rock structures in the form of dikes. Petrogenetic analysis shows that igneous rock samples RY14, RY28, and RY43 are categorized as igneous rocks whose formation is related to the Active Continental Margin (ACM), located in the Destructive Plate Margin tectonic system in a convergent zone where two plates (oceanic subduction with continental) collide, producing magma characterized by the Calc-Alkaline Series - Alkaline Series type. Magma undergoes compositional changes (differentiation), specifically the Calc-Alkaline Series - Alkaline Series type, due to the partial melting of oceanic and continental crust. As the magma rises toward the surface, it undergoes changes influenced by the rocks it passes through, as well as differences in temperature and pressure. Keywords: Breueh Volcano, Petrology, XRF, ICP-MS, Petrogenesis