<> "The repository administrator has not yet configured an RDF license."^^ . <> . . . "THE GENESIS OF VOLCANIC SANDSTONES ASSOCIATED WITH BASALTIC PILLOW LAVAS : A CASE STUDY AT THE JIWO HILLS, BAYAT AREA (KLATEN-CENTRAL JAVA)"^^ . "Asosiasi batupasir gunungapi, lava bantal basalt dan batuan sedimen gampingan tersingkap baik di perbukitan Jiwo dan kaki utara Pegunungan Selatan, Klaten-Jawa Tengah. Batuan tersebut termasuk Formasi Kebo-Butak (Surono drr., 1992; Samudra & Sutisna, 1997). Penyelidik terdahulu (missal, Rahardjo, 1983; Suryono & Setyowiyoto, 2001 ) menyatakan bahwa batupasir. gunungapi itu merupakan bagian endapan turbidit yang diendapkan di lingkungan kipas bawah laut. Batupasir gunungapi itu berasosiasi dengan lava bantal berkomposisi basalt berwarna abu-abu gelap sampai hitam sekalipun bagian yang lapuk dan teralterasi berwama coklat sampai coklat kehijauan. Di bawah mikroskop batupasir gunungapi itu tersusun oleh butiran sangat meruncing, terpilah baik, kemas tertutup, berbentuk pipih dan berstruktur massif hingga berlubang sangat jarang. Hampir semua bahan batupasir gunungapi itu tersusun oleh fragmen gelas gunungapi, sebagian memperlihatkan struktur radier dan pecahan konkoidal. Kristal sangat halus dan sangat jarang (3%) memperlihatkan tekstur pendinginan sangat cepat, terdiri dari klinopi- roksen diopsidik dan plagioklas basalt yang hal ini sebanding dengan komposisi lava bantal basalt. Analisa geokimia juga mendukung kesamaan komposisi tersebut dengan memberikan kandungan Si02 sebesar ± 52 %. Data tersebut mengindikasikan bahwa batupasir gunungapi itu di endapkan sangat dekat dengan sumbemya yang berupa suatu gunungapi bawah laut. Kegiatan gunungapi itu baik yang bersifat non eksplosif maupun erupsi eksplosif lemah menghasilkan piroklast basalt yang masuk ke dalam air laut dengan temperatur sangat tinggi (± 10000C). Kondisi ini menyebabkan proses pendinginan sangat cepat sehingga membentuk fragmen gelas gunugapi berbentuk sangat meruncing. Studi ini memberikan implikasi bahwa tidak semua batupasir gunungapi di sana merupakan endapan turbidit epiklastik yang berasal dari luar cekungan pengendapan. Dalam rangka memperbaiki model fasies di daerah penelitian, pembedaan antara fasies gunungapi bawah laut, fasies gunungapi darat dan fasies non gunungapi sangat penting. Studi lebih lanjut untuk mendapatkan fasies pusat erupsi gunungapi bawah laut diharapkan dapat menunjang eksplorasi mineral vulkanogenik di lautan dan prospek hidrokarbon. \r\n\r\nAbstract\r\nIn the Jiwo Hills and northern foot of the Southern Mountains, Klaten-Central Java, association of volcanic sandstones, basaltic pillow lavas and calcareous sediments are exposed. Those rocks are grouped into Kebo-Butak Formation (Surono et al., 1992; Samodra & Sutisna, 1997) and previous studies (eg Rahardjo, 1983; Suryono & Setyowiyoto, 2001) stated that the volcanic sandstone is a part of turbidite deposited in submarine fan environment. The volcanic sandstone associated with basaltic pillow lavas is dark grey to black in color although the weathered and altered parts are brown to greenish brown. Under the microscope the volcanic sandstone shows very angular grains, well sorted and grain supported, massive to very little vesicularity with platy shards in shape. Nearly all material is composed of volcanic glass fragments, some of them showing radiated structures and conchoidal fractures. Crystals are very rare (< 3%) showing quenching textures and consisting of diopsidic clinopyroxene and calcic plagioclase which are comparable with the composition of basaltic pillow lavas. Geochemical analyses also support the similar composition by having about 52% SiC> 2 content. These data suggest that the volcanic sandstone was deposited very close to the source, that is a submarine volcano. Volcanic activities there, either non-explosive or weakly explosive eruptions produced basaltic pyroclasts having high temperature (ca. 1000 C) into (deep?) sea water that has very low temperature and high hydrostatic pressure. This condition caused very rapid cooling process of the material to form very angular fragments of volcanic glass. This study implies that not all volcanic sandstones there are epiclatic turbidites coming from outside of the basin. In order to revise the facies modek there it is necessary to duffer between submarine volcanic facies, on land volcanic facies and non-volcnic facies. Further study to obtain the central facies of submanrine volcanoes will probably help in exploration of marine volcanogenic mineral deposits and hydrocarbon prospects."^^ . "2002-11-01" . . "XII" . "131" . . "Badan Penelitian dan Pengembangan Energi Sumber Daya mineral departemen Energi dan Sumber daya Mineral"^^ . . . "Jurnal Geologi dan Sumberdaya Mineral / Journal of Geology & Mineral resources"^^ . . . "08539634" . . . . . . . . . . . . . . . . "S."^^ . "Bronto"^^ . "S. Bronto"^^ . . "S."^^ . "Pambudi 052426101"^^ . "S. Pambudi 052426101"^^ . . "Hill Gendoet"^^ . "Hartono"^^ . "Hill Gendoet Hartono"^^ . . "D."^^ . "Purwanto"^^ . "D. Purwanto"^^ . . . . . . "THE GENESIS OF VOLCANIC SANDSTONES ASSOCIATED WITH BASALTIC PILLOW LAVAS : A CASE STUDY AT THE JIWO HILLS, BAYAT AREA (KLATEN-CENTRAL JAVA) (Text)"^^ . . . "JGSM 2002.pdf"^^ . . . "THE GENESIS OF VOLCANIC SANDSTONES ASSOCIATED WITH BASALTIC PILLOW LAVAS : A CASE STUDY AT THE JIWO HILLS, BAYAT AREA (KLATEN-CENTRAL JAVA) (Other)"^^ . . . . . . "indexcodes.txt"^^ . . 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