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Tectonics of Volcanogenic Massive Sulphide (VMS) Deposits at Flores Back Arc Basin: A Review Noor Cahyo Dwi Aryanto; Hananto Kurnio
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.679

The bathymetry, petrology, marine magnetic, and seismic-SBP data have identified the northwest-southeast direction submarine ridge that shows hydrothermal activity. This activity occurred through Mount Baruna Komba, Abang Komba, and Ibu Komba. The volcanic rocks are andesite basaltic lava flows, tuff, and pumice. The andesite basaltic lava shows porphyritic, intergranular, intersertal to glomeroporphyritic textures. The rock composes anhedral minerals of k-feldspar, plagioclase, and pyroxene. These minerals present in small-sized, short prismatic dispersed in very fine groundmass minerals or glasses. Most of the volcanic rocks have experienced various degrees of alteration. The k-feldspar and plagioclase are most dominantly transformed into sericite, clay mineral, carbonate, epidote and oxide mineral, opaque mineral, and secondary plagioclase through the albitization process, while pyroxene replaced by chlorite. Other minerals are biotite and quartz, and base metals are present Cu, Zn, Ag, As, Pb, and gold. Mineralization categorizes as the phyllic zone, sub-prophylithic zone, and phyllic-potassic zone that formed at a temperature range of 250-400oC. The submarine hydrothermal alteration in the Komba Ridge is associated with a volcanogenic sulphide deposit controlled by crust thinning due to the crust rifts in the back-arc tectonic setting.Keywords: volcanic rocks, submarine hydrothermal alterations, Komba ridge, volcanogenic massif sulphide (VMS), back-arcData batimetri, petrologi, magnetic laut dan seismic-SBP telah memetakan dan mengidentifikasi suatu punggungan bawahlaut berarah baratlaut-tenggara yang memperlihatkan aktifitas hidrotermal bawah laut. Aktifitas tersebut muncul melalui Gunung Baruna Komba, Abang Komba dan Ibu Komba. Batuan gunungapi penyusun adalah aliran lava andesit basaltic, tuf dan pumis. Lava andesit basaltik memperlihatkan tekstur porfiritik, intergranular, intersertal to glomeroporfiritik. Mineral penyusun berupa k-felspar, plagioklas, dan piroksen dalam bentuk mineral anhedral, prismatik pendek berukuran kecil yang berada dalam masa dasar mineral sangat halus atau gelas. Batuan vulkanik telah mengalami ubahan dalam berbagai tingkat, dimana k-flespar dan plagioklas paling dominan terubah menjadi serisit, lempung, karbonat, epidot dan mineral oksida, opak atau plagioklas sekunder melalui proses albitisasi sedangkan piroksen mengalami proses ubahan digantikan oleh klorit. Mineral ubahan lainnya adalah biotit dan kuarsa dan logam dasar seperti Cu, Zn, Ag, As, Pb, dan emas. Mineralisasi dikategorikan sebagai zona filik, zona sub-profillitik, dan zona filik-potasik yang terbentuk pada kisaran suhu 250-400oC. Alterasi hidrotermal bawah laut di Punggungan Komba berasosiasi dengan suatu endapan sulfida volkanogenik yang dikontrol oleh penipisan kerak akibat peregangan kerak dalam tatan tektonik busur belakang.Keywords: batuan gunungapi, alterasi hidrotermal bawah laut, punggungan Komba, sulfida massif vulkanogenik, busur belakang

Elemental Analysis on Marine Sediments Related to Depositional Environment of Bangka Strait Pungky Sampurno; Rina Zuraida; Nazar Nurdin; Luli Gustiantini; Noor Cahyo Dwi Aryanto
BULLETIN OF THE MARINE GEOLOGY Vol 32, No 2 (2017)
Publisher : Marine Geological Institute of Indonesia

Study of elemental composition in sediment has been proven useful in interpreting the depositional environmental changes. Multi Sensor Core Logger (MSCL) is a non-destructive analysis that measures several parameters in sediment core including magnetic susceptibility and elemental composition. Magnetic susceptibility and elemental analysis were measured in four selected marine sediment cores from western part of Bangka Strait (MBB-67. MBB-119, MBB-120 and MBB-173) by using magnetic susceptibility and X-ray Fluorescence (XRF) sensors attached to the MSCL. The data was collected within 2 cm interval. Scatter plots of Y/Zr and Zr/Ti show singular trend demonstrated by sediments from MBB-173 and two groups that composed of MBB-67 (Group 1) and MBB-119 + MBB-120 (Group 2). MBB-67 that is located adjacent to Klabat Granite shows upward changes in mineralogy, slight increase of grain size and negligible change in Y concentration. Cores MBB-119 and MBB-120 are inferred to be deposited during regression that resulted in the accummulation of Y-bearing zircon in MBB-119 before the mineral could reach MBB-120. Core MBB-173 is interpreted to be the product of plagioclase weathering that is submerged by rising sea level. This core contains a horizon of rich Y-bearing zircon at 60 cm.Keywords: Multi Sensor Core Logger, X-Ray Fluorescence, magnetic susceptibility, depositional environment, Bangka Island Studi tentang komposisi unsur kimia dalam sedimen telah terbukti bermanfaat dalam interpretasi perubahan lingkungan pengendapan. Multi Sensor Core Logger (MSCL) adalah sebuah analisis yang non-destructive, untuk mengukur beberapa parameter dalam bor sedimen termasuk suseptibilitas magnetik dan kandungan unsur. Suseptibilitas magnetik dan kandungan unsur diukur dari 4 bor sedimen laut yang terpilih di bagian barat Selat Bangka (MBB-67. MBB-119, MBB-120 and MBB-173) dengan menggunakan sensor suseptibilitas magnetik (MS) dan X-ray Fluorescence (XRF) yang terpasang pada MSCL. Pengukuran dilaksanakan dengan interval 2 cm. Plot Y/Zr dan Zr/Ti menunjukkan satu trend yang diperlihatkan oleh sedimen bor MBB-173 dan dua grup yang terdiri atas MBB-67 (Grup 1) dan MBB-119 + MBB-120 (Grup 2). Bor MBB-173 ditafsirkan sebagai hasil pelapukan plagioklas yang kemudian terendam air laut. Bor ini memperlihatkan horizon yang kaya akan zirkon pembawa yttrium pada kedalaman 60 cm.Kata kunci : Multi Sensor Core Logger, X-Ray Fluorescence, suseptibilitas magnetik, lingkungan pengendapan, Pulau Bangka

DISTRIBUTION OF SUBSURFACE QUATERNARY SEDIMENT IN SOUTH BINTAN ISLAND WATERS AS A POTENTIAL HEAVY MINERAL PLACER OR RARE EARTH ELEMENT DEPOSIT BASED ON SEISMIC INTERPRETATION Muhammad Zulfikar; Nazar Nurdin; Noor Cahyo Dwi Aryanto; Ildrem Syafri; Budi Muljana; Andi Agus Nur
BULLETIN OF THE MARINE GEOLOGY Vol 36, No 1 (2021)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.36.1.2021.705

Bintan Island is one of the areas traversed by the Southeast Asian granitoid belt which is known to have the potential for heavy mineral placer deposits. Due to the dwindling presence of heavy mineral placer deposits in land areas, it is necessary to look for the potential presence of heavy mineral placer deposits in water areas. Searching for placer heavy mineral deposits accomodation in these waters requires subsurface mapping.The method used in this subsurface mapping is a single channel seismic method with a total of 179 lines in the direction of northeast – southwest and west – east. The results of this seismic recording are then interpreted the boundaries of the seismic facies unit and distributed using the kriging method. Furthermore, the thickness calculates by using the assumption velocity 1600 m/s.Based on the facies unit boundaries that have been interpreted, the quaternary sediments that formed in the study area are divided into 2 types of units, namely: Unit 2 which is estimated to be fluvial – transitional sediment, and Unit 1 which is estimated to be transitional sediment – shallow sea. There is also a difference in thickness patterns in these two units, where unit 2 shows a pattern of sediment thickening that resembles a paleochannel trending northeast – southwest, while unit 1 is relatively uniform.From the results of this study, it can be said that the area that has potential for heavy mineral placer deposits is in the west - center of the southern waters of Bintan Island. Where the potential for heavy mineral placer deposits should be in the paleochannel deposits that are part of Unit 2.

Seismic Facies of Pleistocene–Holocene Channel-fill Deposits in Bawean Island and Adjacent Waters, Southeast Java Sea Ali Albab; Noor Cahyo Dwi Aryanto
BULLETIN OF THE MARINE GEOLOGY Vol 32, No 1 (2017)
Publisher : Marine Geological Institute of Indonesia

The late Pleistocene-Holocene stratigraphic architecture of the Bawean Island and surrounding waters, southeast Java Sea has been analyzed by using sparker seismic profiles. Geological interpretation of these seismic profiles revealed the widespread distribution of paleochannels with different shape and size in the present-day Java Sea. Two channel types can be distinguished based on its morphology: U-shaped channels in the western part and V-shaped channels in the eastern part. The stratigraphic successions were grouped into two major seismic units separated by different seismic boundaries. Characters of marine and fluvial deposits were determined based on seismic boundaries and internal reflectors. Three seismic facies can be identified within late Pleistocene – Holocene incised channel fills associated with SB2. The internal structure of incised-channels consist of chaotic reflector at the bottom, covered by parallel–sub parallel and almost reflection-free indicating the homogenous sediment deposited during the succession.Keywords : Pleistocene-Holocene channel fills, sparker seismic profiles, seismic boundaries, incised–channel, Java Sea. Rekaman seismik sparker digunakan untuk menganalisis endapan stratigrafi berumur Plistosen Akhir–Holosen di Perairan Pulau Bawean dan sekitarnya. Berdasarkan interpretasi geologi dari rekaman seismik tersebut teridentifikasi sebaran alur purba yang berbeda bentuk dan ukuran dengan kondisi Laut Jawa sekarang. Berdasarkan morfologinya, dua tipe alur purba yang terdentifikasi adalah alur purba berbentuk U di bagian barat dan berbentuk V yang terbentuk di bagian timur daerah penelitian. Suksesi stratigrafi kemudian dibedakan menjadi dua grup unit seismik utama yang dibatasi oleh perbedaan batas seismik, yaitu endapan asal darat dan laut yang ditentukan berdasarkan batas sikuen dan reflektor internal. Pada unit Pleistosen–Holosen teridentifikasi tiga tipe fasies seismik yang berkorelasi pada batas sikuen SB2. Struktur internal alur purba yang tertoreh terdiri dari reflektor kaotik yang di bagian bawah, kemudian ditutupi oleh reflektor paralel - sub paralel sampai hampir bebas refleksi yang mengindikasikan terendapkannya sedimen homogen selama suksesi tersebut.Kata kunci : Pengisi alur Plistosen - Holosen, penampang seismik sparker, batas seismik, alur tertoreh, Laut Jawa.

Study of Granitoid Distribution at Toboali Waters, Bangka Belitung Province: Seismic data interpretation approach Muhammad Zulfikar; Noor Cahyo Dwi Aryanto; Andi Agus Nur; Ildrem Syafri
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.681

Bangka Island is one of the islands in Indonesia which is traversed by Southeast Asia granitoid belt. This belt stretches from Burma (Myanmar) to Bangka Belitung. This granitoid has potential as a source rock of mineral that carrying tin and rare earth element. At present, mapping of granitoid rocks to the waters area is rarely published, so acoustic basement mapping is necessary to do in order to determine the distribution of granitoids in Toboali waters. The research method used is a single channel seismic with an energy source of 300 joules. The sound source uses a single plate boomer, so it has a high enough resolution but the penetration is not deep enough. Acoustic basement in Toboali waters varies in depth from 15 - 75 ms or getting deeper south. When viewed from the continuity of the acoustic basement, it is estimated that the granitoid is 7 km from the nearest coastline.Key words: single channel seismic, seismic interprtation, granitoid distribution, Toboali Waters, Bangka Belitung ProvincePulau Bangka merupakan salah satu pulau di Indonesia yang dilalui oleh jalur granitoid Asia Tenggara. Jalur ini membentang dari Burma (Myanmar) hingga Bangka Belitung. Granitoid ini memiliki potensi sebagai batuan sumber pembawa mineral timah dan unsur tanah jarang. Pada saat ini pemetaan batuan granitoid pada daerah perairan jarang dipublikasikan, sehingga pemetaan batuan dasar akustik perlu dilakukan dalam rangka mengetahui sebaran granitoid di Perairan Toboali. Metode penelitian yang digunakan yaitu seismik single channel dengan sumber energi yang dikeluarkan sebesar 300 joule. Sumber suaranya menggunakan boomer single plate, sehingga memiliki resolusi yang cukup tinggi akan tetapi penetrasinya tidak cukup dalam. Batuan dasar akustik di Perairan Toboali memiliki kedalaman bervariasi mulai dari 15 – 75 ms atau semakin ke selatan semakin dalam. Jika dilihat dari kemenerusan batuan dasar akustiknya diperkirakan granitoid tersebut berada 7 km dari garis pantai terdekat.Kata kunci: Seismik single channel, interpretasi seismik, distribusi granitoid, Perairan Toboali, Provinsi Bangka Belitung

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