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Geochemical Evidence of Island-Arc Origin for Sumatra Island; A New Perspective based on Volcanic Rocks in Lampung Province, Indonesia

Indonesian Journal on Geoscience Vol 6, No 4 (2011)
Publisher : Geological Agency

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Abstract

DOI: 10.17014/ijog.v6i4.128Since decades, Sumatra Island is considered as the Eurasia continental margin where the Indian Ocean plate has been subducted oblique beneath the continental plate of Sumatra. But, the occurrences of volcanic rocks in almost all areas of Lampung Province in the southernmost of Sumatra Island, as the presence of the Quaternary Tanggamus Volcano in the western part of the province together with the Quaternary Rajabasa Volcano in the eastern area cannot be justified using the consideration. Spider diagrams of trace and rare earth elements of volcanic rocks from the western and eastern areas of the province reveal that the rocks come from three different tectonic settings, namely island-arc, active continental margin (ACM), and intra continental plate. All basalt and one dacite of western volcanic rocks show a character of island-arc origin, while the eastern volcanic rocks are reflecting characters of ACM and intra continental plate. Plot of the rocks in the diagram of Ta/Yb versus Ce/P and in Ta/Yb versus Th/Yb confirmed the tectonic environments and specifically classify the intra continental plate into Within Plate Volcanic Zone (WPVZ). The island-arc group is characterized by Ta/Yb ratio of less than 2.0 and Ce/P less than 1.8. The ACM group is recognized having Ta/Yb ratio between 2 and 4 with Ce/P more 1.8, while the WPVZ group is defined as a group having Ta/Yb more than 6 and Ce/P more than 1.0. The result indicates that the western part of Sumatra is an island-arc fragment and the eastern part belongs to the Eurasia continental margin. The concentration of volcanics having ACM character from areas around the Sumatra Fault System to the east indicates that the collision zone between the Sumatra island-arc fragments with the Eurasia continental margin is probably located along the SFS. More statistical data is still needed from other Sumatra volcanics to confirm this conclusion.

Geochemical Signature of Mesozoic Volcanic and Granitic Rocks in Madina Regency Area, North Sumatra, Indonesia, and its Tectonic Implication

Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

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http://dx.doi.org/10.17014/ijog.vol4no2.20094Five samples consisting of two Permian-Triassic basalts, two Triassic-Jurassic granitic rocks, and a Miocene andesite were collected from the Madina Regency area in North Sumatra that is regionally situated on the West Sumatra Block. Previous authors have proposed three different scenarios for the geological setting of West Sumatra Permian Plutonic-Volcanic Belt, namely an island-arc, subduction related continental margin arc, and continental break-up. Petrographic analysis of the Mesozoic basaltic samples indicates that they are island-arcs in origin; however their trace element spider diagram patterns (Rock/MORB ratio) also show the character of back-arc marginal basin, besides the island-arc. Furthermore, their REE spider diagram patterns (Rock/ Chondrite ratio) clearly reveal that they were actually generated in a back-arc marginal basin tectonic setting. Meanwhile, the two Mesozoic granitic rocks and the Miocene andesite reflect the character of an active continental margin. Their spider diagram patterns show a significant enrichment on incompat- ible elements, usually derived from fluids of the subducted slab beneath the subduction zone. The high enrichment on Th makes their plots on Ta/Yb versus Th/Yb diagram are shifted to outside the active continental margin field. Although the volcanic-plutonic products represent different ages, their La/Ce ratio leads to a probability that they have been derived from the same magma sources. This study offers another different scenario for the geological setting of West Sumatra Permian Plutonic-Volcanic Belt, where the magmatic activities started in a back-arc marginal basin tectonic setting during the Permian-Triassic time and changed to an active continental margin during Triassic to Miocene. The data are collected through petrographic and chemical analyses for major, trace, and REE includ- ing literature studies.  

Petrogenesis batuan vulkanik daerah tambang emas Lebong Tandai, Provinsi Bengkulu, berdasarkan karakter geokimianya

Indonesian Journal on Geoscience Vol 3, No 2 (2008)
Publisher : Geological Agency

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http://dx.doi.org/10.17014/ijog.vol3no2.20081Lebong Tandai is a village in the Napal Putih Sub-regency, North Bengkulu Regency, that can be accessed only through the local people train called “molek”. The area is well known as a gold mine since the Dutch time. Volcanic rocks in the area belong to the Hulusimpang Formation that are dominated by andesitic rocks with small amount of dacite and basalt. They show an affinity as a transition between calc-alkaline and tholeiite. Its trace elements and REE patterns show that they are derived from “magma one”, one of the two magma sources producing volcanic rocks in Bengkulu. “Magma one” is derived from a magma source with adakitic composition due to the most primitive sample among the “magma one” samples. The Lebong Tandai magma activity has occurred since more than 30 million years ago in a back-arc side tectonical environment, and they were enriched on incompatible elements during an upper crust penetration. The occurrence of gold mineralization in this area indicates that the “magma one” is a gold bearing mineralized magma in this region. It seems to be reasonable when it is corresponded with an investigation result reported from the Phillippine that adakitic rocks contain higher gold concentration than calc-alkaline rocks. This paper is written using a geochemical approach based on major elements, trace elements and rare earth elements (REE) that are plotted into general and specific classifications in a petrological discussion.  

KUALITAS MIKROBIOLOGIS SUSU KAMBING FERMENTASI MENGGUNAKAN STARTER Lactobacillus fermentum strain NCC2970 PADA PENYIMPANAN SUHU REFRIGERATOR

Jurnal Ilmu dan Teknologi Terapan Pertanian Vol 3 No 1 (2019): Journal of Applied Agricultural Science and Technology
Publisher : Payakumbuh State Polytechnic of Agriculture

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Abstract

Penelitian ini bertujuan untuk mengetahui kualitas mikrobiologis susu kambing yang difermentasi dengan Lactobacillus fermentum strain NCC2970 dengan waktu penyimpanan susu fermentasi yang berbeda. Metode yang digunakan adalah metode eksperimen rancangan acak lengkap dengan 4 perlakuan waktu penyimpanan susu kambing fermentasi pada suhu refrigerator 4oC yaitu selama0, 5, 10 dan 15 hari dengan 5 ulangan. Hasil penelitian menunjukkan nilai pH mengalami penurunan berkisar antara 4,09-4,04. Total asam tertitrasi mengalami peningkatan selama penyimpanan dengan nilai 0,80 hingga mencapai 1,52% sampai penyimpanan 15 hari. Total koloni bakteri asam laktat berkisar antara 4.8 x 108cfu/ml sampai 21.6 x108 cfu/ml. Nilai Total Plate Count selama penyimpanan mengalami penurunan dari 219.4 x 102cfu/ml sampai 106.4 x 102cfu/ml. Berdasarkan hasil penelitian ini dapat disimpulkan bahwa susu kambing fermentasi dengan Lactobacillus fermentum strain NCC2970 dapat mempertahankan kualitas sampai masa penyimpanan 15 hari dengan viabilitas bakteri asam laktat yang memenuhi kategori sebagai probiotik.

Leptospirosis at Dr. Cipto Mangunkusumo and Persahabatan Hospitat Review of 104 cases

Medical Journal of Indonesia Vol 9, No 4 (2000): October-December
Publisher : Faculty of Medicine Universitas Indonesia

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Abstract

[no abstract available]

Studi Penyusunan Kriteria Perencanaan Pelestarian Kawasan Bersejarah Sunda Kelapa Menggunakan Metode Analytical Hierarchy Process (AHP)

Jurnal Planesa (Planologi) Vol 1, No 1 (2010)
Publisher : Universitas Esa Unggul

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Semenjak awal tahun 1990, Pemerintah Provinsi DKI Jakarta sebenarnya sudah membuat studi, kajian dan kegiatan revitalisasi bagi kawasan kota tua. Namun usaha tersebut terkesan seperti jalan di tempat. Hal ini dikarenakan banyak hal, salah satunya adalah tidak adanya kriteria bagi perencanaan pelestarian kawasan bersejarah yang bisa dijadikan acuan bagi penyusunan rencana pelestarian itu sendiri. Untuk itu perlunya disusun kriteria perencanaan pelestarian kawasan bersejarah yang diharapkan dapat dijadikan acuan arahan dalam membuat rencana pelestarian kawasan bersejarah, sehingga bias menjadi komitmen bagi setiap stakeholders, dimana penanganan kawasan dan bangunan bersejarah dapat lebih optimal. Dalam penyusunan kriteria pelestarian kawasan bersejarah dalam studi ini menggunakan Analytical Hierarchy Process (AHP) sebagai metode pengambilan keputusan yang komprehensif dengan metode expert choice yaitu metode yang dilakukan untuk mengolah masukan dari informan yang diperoleh dengan menggunakan indeep interview. Penelitian ini adalah bertolak dari adanya permasalahan yang timbul pada kawasan kota lama Batavia khususnya kawasan Sunda Kelapa. Sebagai kawasan potensial yang dapat dikembangkan menjadi suatu kawasan yang lebih bernilai, pada saat ini permasalahan yang timbul adalah permasalahan sirkulasi dan kondisi jalan, pembongkaran bangunan-bangunan kuno dan pertumbuhan bangunan baru secara sporadis, dan berkurangnya ruang-ruang terbuka kota baik secara jumlah maupun ukuran. Ketiga permasalahan tersebut dikhawatirkan akan merubah dan memudarkan pola kota lama yang khas. Berdasarkan hasil analisis dalam studi ini, diperoleh 13 kriteria pelestarian kawasan dan bangunan bersejarah. kriteria-kriteria tersebut diperoleh dari hasil studi literatur yang kemudian diuji cobakan kepada stakeholders dengan menggunakan metode AHP. Hasil analisis menunjukan bahwa kriteria utama yang harus diperhatikan adalah aspek peraturan dan tujuan dari kegiatan pelestarian, dengan demikian diharapkan pelestarian kawasan dan bangunan bersejarah dapat lebih terarah dan sesuai dengan harapan banyak pihak.Kata Kunci: Kawasan Bersejarah, Sunda Kelapa, Analytical Hierarchy Process

Perangkat Soal Berbasis Konflik Kognitif

Jurnal Pendidikan Matematika Vol 1, No 1 (2013)
Publisher : Jurnal Pendidikan Matematika

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Konflik kognitif adalah kesadaran individu tentang adanya ketidaksesuaian antara struktur kognitif mereka dengan informasi yang mereka hadapi. Konflik pada siswa dapat muncul secara  alami dan dapat juga direncanakan secara bermakna oleh guru, yang ditujukan untuk mengatasi kesalahan konsep siswa.  Memunculkan konflik kognitif dapat dilakukan diantaranya dengan menyajikan data ganjil. Dalam pembelajaran matematika, data ganjil dapat berupa soal-soal dengan struktur tidak lengkap (ill-structure).  Makalah ini mengetengahkan beberapa materi dalam topik aljabar  kelas sepuluh  yang berpotensi memunculkan  konflik kognitif disertai  beberapa contoh soalnya. Contoh-contoh soal ini dapat dijadikan  sebagai instrumen guna mengukur kemampuan pemahaman relasional

Short course treatment of Typhoid fever with 400 mg fleroxacin OD a preliminary report

Medical Journal of Indonesia Vol 7 (1998): Supplement 1
Publisher : Faculty of Medicine Universitas Indonesia

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Abstract

[no abstract available]

NEW GEOCHEMICAL DATA OF ISLAND-ARC ORIGIN FOR SUMATERA: THE BENGKULU CASE.

JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 22, No 1 (2012)
Publisher : Indonesian Institute of Sciences

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ABSTRACT Sumatera is always recognized as margin of Eurasia continental plate, where the Indian oceanic plate is considered to be subducted beneath continental materials. The subduction system has produced volcanic or magmatic rocks on Sumatera at least since Cretaceous. Chemical analytical results of volcanic rocks in Bengkulu Province on major, trace and rare earth elements reveal that the volcanic rocks are derived from two different tectonic settings where the western side showing island-arc character and the eastern side represents an active continental margin (ACM). The island-arc group is characterized by lower ratio of (Ce/P)N varying between 1.1 to 2.4 and wider range of (P/Zr)N ratio varying from 1.0 to 1.7, while the ACM group show wider variation with (Ce/P)N ratio more than 3.4 and has narrower range of (P/Zr)N ranging from 0.3 to 0.6. The REE pattern of the island-arc in spider diagram shows steady decreasing in rock/chondrite ratio from La to Lu, while the ACM type is characterized by flat trend from Eu to Lu. The results suggest that it is not the whole Sumatera showing continent character, but it is island-arc in origin from Sumatera Fault Zone to the west and becomes ACM to the east.

Menyingkap Arena Kuasa Simbolik Islam Ideologis (Studi Lapangan di Yogyakarta)

SOSIOLOGI Vol 1, No 1 (2009): Jurnal Society Mei 2009
Publisher : Universitas Bangka Belitung

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The researcher discusses the symbolical power field of Hizbut Tahrir Indonesia (HTI) and Majelis Mujahidin Indonesia (MMI) which fight the strategic arena as the political tools to achieve the substantive power after the order regime. HTI and MMI as ideological Islam organizations which struggle Islamic Syariah formalization in state and nation order can be analyzed using Pierre Bordieu conceptual framework. It consists of three key concepts as follow: habitus, champ and symbolic power. Those key concepts are formulated in political dakwah and jihad which invite personnel’s or among members to change an old paradigm to a new paradigm (fully syariah) to create a uniformity and habitus reproductions.Field of struggles are directed to dominate political fields which institutional based, community based, and governmental institutions through an economic capital hegemony, a culture, a social and symbolic powers. The economic capital can be means of production possession, materials, and money changes as inherited investment in a long period. Culture capitals are accumulated into intellectual hegemony, discourses, and argumentations to get social positions. The culture capitals are directed to social networks (cooperation’s) ownership and authorities in relation to an other stakeholder or power holders. Symbolic capitals is the accumulation of economic, culture and social capitals which deal with a prestige, status, authority and legitimacy from other stakeholders. A symbolic capital hegemony is the centre of field of struggles domination and requirements to get symbolic powers.