Sutarto, Sutarto (2020) Karakteristik dan Pembentukan Batuan Beku di Pegunungan Jiwo, Bayat, Jawa Tengah. Jurnal Mineral, Energi, dan Lingkungan, 4 (2). pp. 18-31. ISSN ISSN 2549-7197 (cetak) ISSN 2549-564X (online)/vol.4/no.2
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15.Karakteristik dan Pembentukan Batuan Beku di Bayat.pdf Download (1MB) | Preview |
Abstract
Pegunungan Jiwo, merupakan salah satu dari tiga wilayah di Jawa yang memperlihatkan singkapan batuan-batuan
metamorf Pra-Tersier yang tidak selaras diatasnya diendapkan batuan sedimen Tersier dan diterobos oleh batuan-batuan
beku seperti gabro, diabas, basalt, dan diorite. Penelitian ini bertujuan untuk mengetahui karakteristik mineralogi dan
tekstur, serta hubungan pembentukan antar batuan beku. Metode yang digunakan adalah pendekatan petrografi serta
pentarikhan umur dari data peneliti terdahulu. Batuan beku hasil kegiatan magmatisme tesebut di atas, hadir sebagai
intrusi (stok, retas) maupun ekstrus (lava). Kenampakan mikroskopik, gabro dan gabro mikro atau diabas umumnya
memperlihatkan tekstur equigranular, kumulus, ofitik, subofitik, dan diabasik disusun oleh mineral-mineral primer
plagioklas (±52-66%), olivin (±0-14%), piroksen (±4-18%), mineral opak (±2-12%). Sebagian besar gabro mengalami
ubahan hidrotermal lemah-sedang, dicirikan oleh terubahnya beberapa mineral primer menjadi mineral-mineral klorit,
silika, epidot, karbonat, serpentin, dan aktinolit. Basalt secara mikroskopik, memperlihatkan tekstur inequigranular,
porfiritik-porfiroafanitik, disusun oleh mineral-mineral primer plagioklas, olivin, piroksen, mineral opak dengan mineral
sekunder seperti klorit dan karbonat. Batuan-batuan beku tersebut, diperkirakan merupakan hasil magmatisme yang
berumur Eosen Akhir-Miosen Awal (39,82±1,49 Ma sampai 13.852±5.45 juta tahun) dan merupakan bagian dari busur
kepulauan Sunda-Banda, terbentuk karena subduksi kearah utara lempeng Hindia-Australia di bawah bagian tenggara
lempeng Eurasia.
Kata Kunci: batuan beku; basalt; gabro; gabro mikro; magmatisme
ABSTRACT
The Jiwo Hills are one of three regions in Java that show pre-Tertiary metamorphic rock outcrops that are
unconformably underlain the Tertiary sedimentary rocks and intruded by igneous rocks such as gabbros, diabases,
basalts, and diorites. This study was aimed to determine the mineralogy and texture characteristics, as well as the
igneous rocks formation. The method used were petrographic approach and age dating from previous research data.
Igneous rocks in the research area present both as intrusion (stock, dyke) and extrusion (lava). Microscopically, gabbro
and micro gabbro or diabas generally shows an equigranular, cumulus, ophytic, subophytic, and diabasic textures
composed of primary minerals such as plagioclases (± 52-66%), olivines (± 0-14%), pyroxenes (± 4 -18%), and opaque
minerals (± 2-12%). Most of the gabbro show a weak-moderate hydrothermal alteration, characterized by the
replacement of several primary minerals into secondary minerals such as chlorites, silicas, epidote, carbonates,
serpentines, and actinolites. Petrographically, basalt showing inequigranular texture, porphyritic and porphyroaphanitic, composed of primary minerals plagioclases, olivines, pyroxenes, opaque minerals with secondary minerals
such as chlorites and carbonates. These igneous rocks are thought to be the result of the Late Eocene-Early Miocene
magmatism (39.82 ± 1.49 to 13,852 ± 5.45 Ma) and are part of the Sunda-Banda Arc, due to subduction towards the
north of the Indian-Australian plate under the southeastern part of the Eurasian plate.
Keywords: basalt; gabbro; igneous rocks; magmatism; micro gabbro
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | batuan beku; basalt; gabro; gabro mikro; magmatism, basalt; gabbro; igneous rocks; magmatism; micro gabbro |
| Subjek: | Q Science > QE Geology |
| Divisions: | x. Faculty of Engineering, Science and Mathematics > School of Engineering Sciences |
| Depositing User: | Dr.Ir. MT SITI UMIYATUN CHOIRIAH |
| Date Deposited: | 16 Mar 2022 05:05 |
| Last Modified: | 16 Mar 2022 05:06 |
| URI: | http://eprints.upnyk.ac.id/id/eprint/28678 |
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