ORGANIC GEOCHEMISTRY, PETROGRAPHY AND MINERALOGY …
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PROSIDING PERTEMUAN ILMIAH TAHUNAN IAGI KE-37 HOTEL HORISON BANDUNG, AGUSTUS 2008 630 ORGANIC GEOCHEMISTRY, PETROGRAPHY AND MINERALOGY OF WUNGKAL-GAMPING MUDSTONE IN BAYAT AREA, KLATEN, CENTRAL JAVA Noviar Hendriyanto 1 # , Hendra Amijaya 2 , 1,2 Department of Geological Engineering, Gadjah Mada University, Jalan Grafika 2 Yogyakarta 55281, Telp/Fax. 0274-513668, Email: [email protected]ABSTRACT The Geology of Bayat Area in Klaten, Central Java, which is regionally part of Southern Mountain, is very interesting to be researched. Near Pendul Hill, Bayat, dark grey mudstone of Wungkal-Gamping Formation can be found. The color of mudstones indicates that this mudstone is probably rich in organic contents and has potential to be a source rocksof hydrocarbon. This research has objectives to know how much organic material contained in Wungkal-Gamping mudstone and its potential to be source rock of hydrocarbon. TOC analysis and organic petrography analysis has been done to attain that objectives. TOC analysis result shows that 8 samples of mudstone in research area have range of 0.16 % to 0.42 % weight of TOC. Organic petrography analysis also shows that the organic materials occured in each sample are not more than 6 % volume. This results conclude that mudstone in research area does not have potential to be source rock of hydrocarbon. Organic petrography using spore fluorescence color analysis, shows that sporinite in rock sample has moderate orange to red or brown color which is equivalent with Ro of aprroximately 0.6 – 1 % and shows peak mature to late mature in maturity. Furthermore, XRD analysis indicates that clay minerals contents of fresh dark grey mudstone are dominated by chlorite, while clay minerals contents of weathered yellowish to whitish light grey mudstone are dominated by smectite. All of that indicates that dark grey color of mudstone in research area does not show large amount of organic material but shows the occurence of clay mineral, especially chlorite. Keywords: organic geochemistry, mineralogy, mudstone, Wungkal-Gamping Formation SARI Geologi daerah Bayat, Klaten, Jawa Tengah, yang merupakan bagian dari Geologi Regional Pegunungan Selatan sangat menarik untuk diteliti. Di Gunung Pendul, Bayat, ditemukan batulumpur (mudstone) berwarna abu-abu gelap dari Formasi Wungkal- Gamping. Warna batulumpur tersebut mengindikasikan adanya kemungkinan bahwa batuan tersebut kaya akan kandungan material organik dan berpotensi menjadi batuan induk hidrokarbon. Penelitian ini bertujuan untuk mengetahui besarnya kandungan material organik yang terkandung dalam batulumpur Wungkal-Gamping dan potensinya sebagai batuan induk hidrokarbon, serta tingkat kematangan batuannya. Analisis TOC dan analisis petrografi organik dilakukan untuk mencapai tujuan tersebut. Hasil analisis TOC menunjukkan bahwa 8 sampel batulumpur di daerah penelitian memiliki nilai antara 0.16 % - 0.42 % berat TOC. Analisis petrografi organik juga menunjukkan bahwa material organik yang terdapat dalam setiap sampel tidak lebih dari 6 % volume. Hasil tersebut dapat menunjukkan bahwa batulumpur di daerah
