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Peningkatan Aktivitas Vulkanik Gunung Api Slamet dan Pengaruhnya Terhadap Sistem Panas Bumi Mamay Surmayadi; Hanik Humaida; Cahya Patria; Adjat Sudrajat; Nana Sulaksana; Mega Fatimah Rosana
Jurnal Lingkungan dan Bencana Geologi Vol 6, No 3 (2015)
Publisher : Badan Geologi

ABSTRAKSejak awal Maret 2014 status aktivitas Gunung Api Slamet di Jawa Tengah dinaikkan dari normal (level I) menjadi waspada (level II) seiring dengan peningkatan jumlah gempa vulkanik. Seismisitas Gunung Api Slamet yang dipantau melalui empat stasiun seismik memperlihatkangempa letusan terekam sebanyak 1.106 kejadian dengan rata-rata 73 kejadian per hari, gempa hembusan terekam sebanyak 6.857 kejadian dengan rata-rata 457 kejadian per hari, sedangkan gempa vulkanik dalam (VA) hanya terekam sebanyak 2 kali selama periode Maret – Agustus 2014. Sumber gempa tersebut berada pada kedalaman antara 1 - 2 km di bawah kawah Gunung Api Slamet sebagai indikasi gempa permukaan. Peningkatan aktivitas magmatik tersebut menghasilkan pelepasan gasCO2 yang berpengaruh terhadap fluida panas bumi yang ditunjukkan dengan terjadinya perubahan keasaman air dari normal menjadi alkalin, pembentukkan bualan gas CO2 pada air panas Pancuran 3 di Baturraden, dan peningkatan saturasi kalsit. Bualan gas CO2 pada air panas Pancuran 3 menjadi indikasi terjadinya proses pendidihan pada temperatur 273° C pada elevasi kedalaman 454 m dibawah permukaan laut. Kondisi ini menjadikan temperatur reservoar menjadi lebih tinggi sebagai indikasi bahwa sistem panas bumi Gunung Api Slamet merupakan sistem panas bumi aktif (active geothermal system) bertemperatur tinggi (high enthalpy).Kata kunci : bualan gas, fluida panas bumi, gempa permukaan, saturasi kalsitABSTRACTSince the beginning of March 2014 the activity status of The Slamet Volcano in Central Java has been declared from normal (level I) to become alert (level II) due tosignificant increase in the number of volcanic earthquakes. The Slamet Volcano seismicity monitored by four seismic stations shows eruption earthquakes as many as 1,106 events with an average of 73 events per day, gas emission earthquakes as many as 6,857 events with an average of 457 events per day, whereas the deep volcanic (VA) earthquake recorded only 2 times during the period of March to August 2014. The hypocentre of these earthquakes was at a depth of 1-2 km below Slamet Volcano crater as an indication of surface earthquakes. Increased magmatic activity resulted in the release of CO2 gas effect on the geothermal fluid indicated by changes in water acidity from normal to alkaline, formation of CO2bubblegas on Pancuran 3 hot springat Baturraden area, and calcite saturation enhancement. The presence of CO2 bubble gas on Pancuran 3 hot springis an indication of a boiling process at the temperature of 273° C at a depth of 454 m below sea level. This condition makes the reservoar temperature becomes higher as an indication that the geothermal system of The Slamet Volcano is an active geothermal systemwith high temperature (high enthalpy).Keywords: bubble gas, geothermal fluid, surface earthquake, calcite saturation

Age and Depositional Environment of the Sandstone Unit of Ciletuh Formation in Ciletuh-Palabuhanratu Geopark Winantris Winantris; Mega Fatimah Rosana; Katon Sena
Indonesian Journal on Geoscience Vol 10, No 1 (2023)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.10.1.73-82

Sandstones form part of the Cenozoic Ciletuh Formation which is widely exposed in The Ciletuh Palabuhanratu Geopark, Indonesia. This study aims to establish the age of these sandstone units, and to evaluate their depositional environment based on palynological data. Five samples from Ciletuh sandstones were collected for palynomorph analysis. Exposed sections were measured and sampled to determine the stratigraphic position, with palynomorphs being separated from the sediment using acetolysis. Cluster analysis was applied to the resultant palynomorph assemblages and interpreted using plant association model, which refered to the depositional environment of different taxa. Two distinct clusters were identified, characterized by different environmental markers. The first cluster is dominated by Proxapertites operculatus and Proxapertites cursus, while the second cluster is dominated by Podocarpus pollen. While the Proxapertites cluster includes Dicolpopollis kalewensis, Palmaepollenites kutchensis, foraminiferal test linings, dinoflagellates cysts, plant debris, deposited in the marine environment. The Podocarpus cluster consists of Podocarpus pollen, plant debris, foraminiferal test linings, and dinoflagellate cysts, that was deposited in a more distal marine environment. All samples were deposited during the end of Middle Eocene (E6-zone), as defined by the age markers of Proxapertites. cursus, P. operculatus, Restioniidites punctulatus, and Podocarpus pollen.

Geokimia Endapan Nikel Laterit di Tambang Utara, Kecamatan Pomalaa, Kabupaten Kolaka, Provinsi Sulawesi Tengara Riko Ardiansyah Indra Kusuma; Hashari Kamaruddin; Mega Fatimah Rosana; Euis Tintin Yuningsih
Jurnal Geologi dan Sumberdaya Mineral Vol. 20 No. 2 (2019): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v20i2.418

Pomalaa is administratively located in Kolaka Regency, Southeast Sulawesi Province. The nickel mining business area in Pomalaa is managed by State-Owned Enterprises and Private Enterprises. Pomalaa is a sub-district that has natural resources in the form of nickel. Nickel Laterite deposits is a result weathering of ultramafic rock that is leaching process and accumulates in the supergen enrichment zone. The lateritization factor is controlled by lithology, morphology, and structure. In general, the profile of laterite nickel deposits in the North Mine area from top to bottom consists of top soil, limonite, saprolite, and bedrock zones. The laterite nickel precipitate in the North Mine shows varying thickness, based on color, texture, size and mineral composition. Laterite deposits from drilling results reaches an range of 25 - 30 meters. Soil and rocks sampling from each laterite zone every meter resulting from drilling are carried out by laboratory testing using XRF (X-Ray Fluorescence) analysis method with 283 total sample. High Ni element show enrichment in the saprolite zone, whereas in the high Fe (iron) element in the limonite zone.Keywords: nickel, laterite, geochemical, Pomalaa

Karakteristik dan Petrogenesis Batuan Beku di Kecamatan Cisolok (Daerah Geopark Ciletuh-Palabuhanratu), Kabupaten Sukabumi Asti Gindasari; Mega Fatimah Rosana; Agus Didit Haryanto
Jurnal Geologi dan Sumberdaya Mineral Vol. 23 No. 3 (2022): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v23i3.692

Lokasi studi yang terletak di daerah Ciletuh merupakan bagian dari Unesco Global Geopark dicirikan oleh batuan beku intrusif dan ekstrusif berumur Miosen. Batuan beku ini tersebar di sepanjang pantai dan sebagian membentuk perbukitan kecil. Tujuan studi ini adalah untuk mengkarakterisasi dan mengetahui petrogenesis dari batuan beku yang ada di daerah Cisolok. Metode kegiatan yang dilakukan menggunakan analisis petrografi, geokimia, XRF dan ICP-MS. Secara petrografis batuan dapat dikelompokkan menjadi batuan andesit porfiri dan dasit porfiri. Analisis kimia menunjukkan bahwa karakteristik batuan beku dibedakan menjadi jenis dasit, andesit, andesit basaltik, dan basal. Magma sebagai sumber pembentukan batuan beku memiliki komposisi metaluminous dari jenis magma seri calc alkaline, kecuali untuk contoh dari Pasir Randu yang merupakan jenis high-K calc alkaline series. Batuan tersebut terbentuk pada zona lingkungan subduksi dengan posisi continent arc, yang termasuk dalam tepi kontinen aktif.Katakunci: Batuan beku, Cisolok, geopark Ciletuh Palabuhanratu.

Age and Depositional Environment of the Sandstone Unit of Ciletuh Formation in Ciletuh-Palabuhanratu Geopark Winantris Winantris; Mega Fatimah Rosana; Katon Sena
Indonesian Journal on Geoscience Vol. 10 No. 1 (2023)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.10.1.73-82

Sandstones form part of the Cenozoic Ciletuh Formation which is widely exposed in The Ciletuh Palabuhanratu Geopark, Indonesia. This study aims to establish the age of these sandstone units, and to evaluate their depositional environment based on palynological data. Five samples from Ciletuh sandstones were collected for palynomorph analysis. Exposed sections were measured and sampled to determine the stratigraphic position, with palynomorphs being separated from the sediment using acetolysis. Cluster analysis was applied to the resultant palynomorph assemblages and interpreted using plant association model, which refered to the depositional environment of different taxa. Two distinct clusters were identified, characterized by different environmental markers. The first cluster is dominated by Proxapertites operculatus and Proxapertites cursus, while the second cluster is dominated by Podocarpus pollen. While the Proxapertites cluster includes Dicolpopollis kalewensis, Palmaepollenites kutchensis, foraminiferal test linings, dinoflagellates cysts, plant debris, deposited in the marine environment. The Podocarpus cluster consists of Podocarpus pollen, plant debris, foraminiferal test linings, and dinoflagellate cysts, that was deposited in a more distal marine environment. All samples were deposited during the end of Middle Eocene (E6-zone), as defined by the age markers of Proxapertites. cursus, P. operculatus, Restioniidites punctulatus, and Podocarpus pollen.

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