Electronic Theses and Dissertation

Kecamatan kota jantho, kabupaten aceh besar, provinsi aceh merupakan daerah yang memiliki kondisi geologi kompleks akibat aktivitas tektonik regional pulau sumatera. berdasarkan peta geologi regional lembar banda aceh, lokasi penelitian tersusun oleh beberapa satuan batuan, salah satunya formasi anggota padangtiji (tuktp) yang didominasi oleh batuan sedimen. namun, hasil observasi lapangan menunjukkan adanya singkapan batuan granitoid pada formasi tersebut. keberadaan singkapan tersebut memerlukan kajian lebih lanjut untuk mengetahui karakteristik dan klasifikasi batuannya. oleh karena itu, penelitian ini bertujuan mengidentifikasi kondisi geologi daerah penelitian yang meliputi geomorfologi, litologi, stratigrafi, dan struktur geologi, serta menentukan karakteristik petrografi dan klasifikasi mineralogi maupun geokimia batuan granitoid. penelitian ini menggunakan metode pemetaan geologi skala 1:25.000, analisis petrografi, serta analisis geokimia menggunakan x-ray fluorescence (xrf) dan inductively coupled plasma mass spectrometry (icp-ms). hasil penelitian menunjukkan bahwa daerah penelitian tersusun atas bentang alam fluvial (f1), denudasional dataran (d5), perbukitan denudasional (d1), dan struktural (s1), dengan pola aliran sungai rektangular dan subdendritik yang dikontrol kuat oleh struktur geologi berarah barat laut–tenggara (nw–se). litologi penyusun daerah penelitian terdiri atas satuan endapan lanau–pasir, endapan pasir–kerikil, batupasir karbonatan anggota padangtiji, batupasir anggota padangtiji, batu peridotit terserpentinkan, batugamping meucampli, batulanau meucampli, dan batupasir meucampli. berdasarkan analisis petrografi, batupasir karbonatan anggota padangtiji dan batupasir meucampli diklasifikasikan sebagai lithic wacke, sedangkan batuan peridotit mengalami serpentinisasi sedang berdasarkan klasifikasi babineau (2002). hasil klasifikasi granitoid menggunakan diagram qap menurut streckeisen (1967) menunjukkan bahwa batuan tersebut termasuk syenogranite. berdasarkan klasifikasi geokimia granitoid, granitoid diklasifikasikan sebagai granitoid tipe s (s-type) yang bersifat peraluminous berdasarkan xrf, sementara itu granitoid ini diinterpretasikan terbentuk pada lingkungan volcanic arc granite (vag), sesuai dengan tatanan tektonik regional pulau sumatera yang dikontrol oleh sistem subduksi lempeng indo-australia di bawah lempeng eurasia. kata kunci: pemetaan geologi, petrografi, granitoid, geokimia, lithic wacke, syenogranite

Kota Jantho District, Aceh Besar Regency, Aceh Province is an area with complex geological conditions due to regional tectonic activity on Sumatra Island. Based on the Banda Aceh Regional Geological Map, the research location is composed of several rock units, one of which is the Padangtiji Member Formation (Tuktp) which is dominated by sedimentary rocks. However, field observations indicate the presence of granitoid rock outcrops in the formation. The existence of these outcrops requires further study to determine the characteristics and classification of the rocks. Therefore, this study aims to identify the geological conditions of the research area including geomorphology, lithology, stratigraphy, and geological structure, as well as to determine the petrographic characteristics and mineralogical and geochemical classification of granitoid rocks. This study uses a 1:25,000 scale geological mapping method, petrographic analysis, and geochemical analysis using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The results of the study indicate that the study area is composed of fluvial (F1), denudational plains (D5), denudational hills (D1), and structural (S1) landforms, with rectangular and subdendritic river flow patterns strongly controlled by Northwest–Southeast (NW–SE) trending geological structures. The lithology of the study area consists of silt–sand sedimentary units, sand–gravel sedimentary units, carbonate sandstones of the Padangtiji Member, sandstones of the Padangtiji Member, serpentinized peridotites, Meucampli limestones, Meucampli siltstones, and Meucampli sandstones. Based on petrographic analysis, the carbonate sandstones of the Padangtiji Member and Meucampli sandstones are classified as Lithic Wacke, while the peridotites have experienced moderate serpentinization based on the Babineau (2002) classification. The results of granitoid classification using the QAP Diagram according to Streckeisen (1967) indicate that the rocks are Syenogranites. Based on the geochemical classification of granitoids, they are classified as S-type granitoids with peraluminous properties based on XRF. They are interpreted to have formed in a Volcanic Arc Granite (VAG) environment, consistent with the regional tectonic setting of Sumatra Island, which is controlled by the subduction system of the Indo-Australian Plate beneath the Eurasian Plate. Keywords: Geological Mapping, Petrography, Granitoid, Geochemistry, Lithic Wacke, Syenogranite