Referat C Simada Sembiring

Pembentukan cekungan sangat dikontrol oleh adanya gejala tektonik,
sehingga banyak cekungan di kulit bumi yang pembentukannya berhubungan
dengan sesar, utamanya sesar turun, namun hubungan antara 2 sesar geser
mendatar (strike slip fault) juga dapat mengakibatkan terbentuknya cekungan
pengendapan. Hubungan antara struktur kompresif dan ekstensi penting untuk
dipelajari lebih dalam, terutama pembentukan struktur inverse. Geometri dari
cekungan tipe ini dapat sangat bervariasi sesuai dengan pola tegasan yang terjadi.
Deformasi (Ramsay dan Huber, 1983) merupakan perubahan geometri suatu
material karena terkena suatu gaya. Sebagai studi kasus, batas selatan Zona
Kendeng pada awal terbentuknya merupakan sesar turun, kemudian mengalami
kompresi dan pada sesar turun tersebut akan mengalami inversi.
Kata kunci : deformasi, sesar turun, inversi, cekungan. read more

The 2010 eruptions of Merapi Volcano in Indonesia, began in late   October 2010 when Merapi Volcano in Central Java, Indonesia began an increasingly violent series of eruptions that continued into November.
Beside respiratory health effect to human health, volcanic ash may result in short-term physical and chemical changes in water quality. The addition of volcanic ash to water supplies can lead to a change in
water quality. The most common ash-contamination problems result from a change in turbibity and acidity, but these usually last a few hours to a few days unless the ash fall occurs for prolonged periods of time. For longer period, the effect of pyroclastic flow was also suspected to efect of surface water, in fact the material of pyroclastic flow consist of fresh volcanic material which can carry a variety of metals and other potentially-pathogenic trace elements. In this study, thirty water samples were obtained from several water supplies including groundwater, surface water, waterworks company, and spring, which collected on the day after eruption. The result showed that some of some water samples has been contaminated by volcanic ash.
Some parameters including Total Suspended Solid, Color, pH, Iron, Mangan, Nitrate, Lead, Cadmium, Selenium were detected above the threshold. Especially for Selenium, it was considered high and the source of selenium was considered from sulfur composition in volcanic ash sample. On the other hand, the impact of pyroclastic flow for water supplies has been carried out, by sampling five location of  surface water in two month after eruption. Water quality data obtained from several rivers in study area indicated Iron, pH, turbidity and Total Suspended Solid were above the threshold. In particular, the suspension of ash in water can block intake filters and cause wear and tear on components of water treatment plants due to its abrasive and corrosive nature. High turbidity levels can compromise the effectiveness of disinfection of pathogenic micro-organisms. Other effects are high water demand for cleanup depleting water storage in reservoirs, and the leaching of soluble components, particularly acidity, into receiving waters.*** read more

he study area is located in the western part of Kalimantan, between the latitude 2º 15’S to 2º 15’N, and longitudes 108º 55’ and 113º 10’E. The six administrative districts within the study area are administered respectively from the towns of Sanggau, Singkawang, Sambas, Pontianak, Ketapang and Nangapinoh. Kalimantan can be divided into several roughly E-W trending tectonic provinces. The northern portion of the island is dominated by the Cretaceous and Eocene to Miocene geological units. The Schwaner Batholith itself is a triangular exposure of Cretaceous granitic rocks which intrude into Paleozoic and Mesozoic volcanics, volcaniclastics, and marine sediments.
The main purpose of this research work is to understand the geology and geochemical characteristics of granitoid rocks of the area and to establish the relation of its rocks with association of mineralization in the area. The analytical methods such as petrography, ore mineralogy, X-ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) have been conducted for this research.
The granites, granodiorites, tonalites, quartz monzonites, and quartz monzodiorites of the western Kalimantan area have calc-alkaline fractionation trends that are consistent with magmas formed at volcanic arc setting. Characteristics vary slightly between samples but generally have I-type signatures. Normalized trends and tectonic comparisons for REE suggest that the granitoid rocks from the area are the crystallization product of an initial partial melting of any combination of volcanic-arc environment and active continental margins.
Mineralizations are mostly associated with Cretaceous granites bodies and some are related with younger Miocene intrusive rocks which are mostly occured along the marginal parts of granite plutons. It is also related with structural control that can be seen at the deposit scale. This mineralization displays both of the shallow level to deep level environments. Potential mineralizations have the highest copper grade of 26,500 ppm, zinc 369,000 ppm, lead 216,000 ppm, silver 1,580 ppm, cassiterite 31,200 ppm and manganese 10,100 ppm. Other base element nickel (Ni) and chromite (Cr) have low contents, in which the highest grade for nickel is only 20 ppm and chromite is merely 290 ppm. read more

Pemanfaatan geologi yang diketahui pertama kali untuk penilaian medan peperangan terjadi di Katzback pada 1813 dan berkonstribusi dalam mengalahkan Tentara Napoleon. Semenjak itu, sebagian besar kegiatan militer besar mulai memanfaatkan ahli siasat geologi untuk mengevaluasi medan dan roman-roman atau menjalankan aksi peperangan secara langsung. Nilai pengalaman ahli geologi dikenal dalam buku-buku seperti penerapan militer geologi pada 1859 dan 1885 dan terbitnya “Militargeologie” pada 1913 oleh perwira Angkatan Darat Jerman.
Selama Perang Dunia I, data geologi mulai tersedia pada peta-peta khusus untuk
lalu-lintas dan pergerakan perbekalan, kendaraan dan personil, mengidentifikasi air dan sumber material-material konstruksi, merencanakan dan mendesain benteng pertahanan di permukaan tanah dan di bawah tanah, dan memimpin peperangan bawah tanah dengan susur terowongan. Angkatan Bersenjata Amerika Serikat (1917–1918) menyiapkan peta geologi teknik pertama kali untuk keperluan peperangan dan konstruksi bangunan lapangan. Seluruh pasukan menyatakan pentingnya geologi terkait perang untuk sesumber, strategi, dan pemahaman karakteristik medan peperangan untuk siasat dan penyerbuan.
Petunjuk lapangan tertulis bagi Geologi Militer (Wehrgeologie) diterbitkan oleh Angkatan Darat Jerman pada 1938. Penilaian geologi untuk wilayah peperangan yang potensial dan roman-roman startegis menjadi makin bertambah penting selama Perang Dunia II, sebagai contoh, peta topografi Jerman sebelum perang
yang memuat Afrika Utara dengan lokasi sumber air dan wadi, rintangan berupa dinding curam yang mempengaruhi pergerakan kendaraan bermesin. Satuan Geologi Militer Amerika Serikat menyiapkan folio-folio geologi untuk kegiatan di Eropa Selatan dan seluruh wilayah Kepulauan Pasifik. Satuan Geologi Militer Inggris menyediakan peta dan penasehat geologi untuk kegiatan di Eropa Barat.
Perbaikan infrastruktur-infrastruktur geologi tanpa henti membantu sejumlah kegiatan seperti pemilihan lokasi pendaratan pesawat dan lapangan terbang, pelabuhan pantai dan pendaratan darurat, lokasi dan konstruksi instalasi  perlindungan permukaan dan bawah tanah. Hal yang serupa dengan pekerjaan ini,
sebagai contoh, pelabuhan untuk pendaratan Normandy. Geofisika militer menjadi penting bagi tujuan kelautan, sebagai contoh, pengembangan magnetik dan ilmu bunyi bagi tambang aktif, menelusuri Kapal Selam U milik Jerman dan menyediakan peta bawah samudera dan endapan-endapan, teknik-teknik
pengindera panas udara dalam mengidentifikasi pergerakan pada Era Vietnam di bawah lebatnya hutan. Selama 1940-an dan 1950-an, prinsip-prinsip dan teknik- teknik ilmu kebumian dimanfaatkan pada suatu skala baru bagi tujuan militer dan keteknikan.
Penelusuran terowongan yang berhasil dilakukan oleh Angkatan Bersenjata Serikat pada Perang Sipil dan oleh Inggris pada Perang Dunia II, meginspirasi suatu persenjataan dalam penyerangan besar Korea Utara pada 1950-an.
Terowongan penyusupan banyak ditemukan pada saat ini di bawah Zona Demiliterisasi atau Demilitarized Zone (DMZ) dan Korea Selatan. Cabang Geologi Militer tetap, Badan Survei Geologi Amerika Serikat (1946),
mempelajari lokasi uji atom di Pasifik dan Nevada. Penelitian oleh Kesatuan Insinyur Angkatan Darat Amerika Serikat dan Kesatuan RAND memimpin desain dan konstruksi instalasi-instalasi bawah tanah pada 1960-an. Ahli kebumian menginterpretasi peledakan nuklir Rainier (1957) dan membedakan antara
ledakan nuklir dan peristiwa gempa. Proyek Keamanan Nasional ini (1957–1966) bergantung pada sejumlah prinsip-prinsip dan teknik-teknik ilmu kebumian, dan program Plowshare dari 1960-an yang menyesuaikan database ini untuk sejumlah kekuatan militer dan keperluan industri.
Upaya geologi selama Era Vietnam dalam perang gerilya yang tersebar luas mengharuskan suatu kelompok membentuk pendekatan dengan membuat foliofolio dan peta topografi oleh satuan geologi terpusat. Fungsi-fungsi geologi secara luas terfokus kembali dari kekuatan pertempuran angkatan bersenjata terhadap
Agen Intelijen Pertahanan pada 1970-an. Banyak Proyek Keamanan Nasional melayani penegakan militer dan bergantung pada prinsip-prinsip ilmu kebumian. read more

DwikoritaKarnawati(1), Eric. G. Frost(2), T. Faisal Fathani(1), Subroto(1), Budi Andayani(3)
1) UniversitasGadjahMada, Faculty of Engineering, Yogyakarta, Jl. Grafika no 2, 55281, Indonesia
2) San Diego State University, Geological Sciences and Visualization Center, San Diego, California, USA
3) UniversitasGadjahMada, Faculty of Psychology, Yogyakarta, Bulaksumur, 55281, Indonesia

Abstract: Smart Grid is a participatory cyber-based communication and information system, developed to support the communication-monitoring of landslide hazard and the coordination for landslide early warning, via participatory on-line web and/ or various type of social media. To test the effectivity ofthe Smart Grid performance, a pilot implementation of this system is now under preparation. A specific landslide hazard area in Karanganyar Regency will be selected as a pilot implementation site. Prior to and after the trial implementation of this system, a psycho-social survey will be carried out, in order to evaluate the limitations of such system and community response during the trial. read more

The copper-gold skarn mineralization occurred at the Batu Hijau deposit, a world class porphyry copper-gold deposit, is located in the southwestern corner of Sumbawa Island, Indonesia. The deposit mainly consists of three major rock types: andesitic volcaniclastic unit (Early to Middle Miocene) and equigranular quartz diorite (Late Miocene to Middle Pliocene), which are intruded by the three phases of copper-gold bearing tonalite porphyries (Early to Middle Pliocene). The tonalite porphyries were emplaced along the lithological contacts of two pre-mineralization wall rocks. Skarn were newly found at the contact of calcium rich andesitic volcanic layer and intermediate tonalite porphyry intrusion. Skarn can be classified as calcic-exoskarn, and it consists of a Fe-rich and oxidized skarn locally controlled by faults and fractures. Although no limestone is known in the Batu Hijau deposit, Ca-rich volcanic host rocks favoring to become skarn alteration within the Batu Hijau deposit.
Based on the mineral assemblages, the skarn forming process can be divided into two major stages such as prograde and retrograde stages consisting of four sub-stages. Prograde skarn consists of clinopyroxene (diopside) and garnet (mainly andradite) ± magnetite formed at relatively high fO2 and fS2 and temperature of 340 ̊-515 ̊C while retrograde skarn alteration is dominated by Fe- rich minerals such as amphibole and epidote formed at lower fO2 and fS2 , temperature down to 200 ̊-396 ̊C. Opaque minerals include chalcopyrite, pyrite, sphalertite, minor galena and bismuth-telluride. Gold precipitates in the retrograde alteration associated bismuth-telluride minerals. A decrease in SiO2 corresponds to increase FeOt from porphyry intrusion towards skarn zones. CaO and FeOt behave comparably in the skarns suggesting that the ore mineralization is coincident with carbonization of prograde assemblages during retrograde alteration. Chemical analysis shows the concentration of gold mineralization of 4.15 g/t and 2.7 g/t from
the high grade ore zone.
Based on the result of fluid inclusion and δ34S value, the evolution of fluid origin can be suggested that the origin of skarn and porphyry from the Batu Hijau deposit was largely of an igneous sulfur source of magmatic origin caused by the early anhydrous skarn assemblage is dominated by denser and more saline, and has very high temperature and salinity. The Batu Hijau deposit evidently shows a porphyry-related skarn mineralization that is mineralogically and metallogenically zoned and that transition from one style to the next can be relatively rapid. The result of this research has indicated that the range of porphyry-related deposits, skarn (calc-silicate-magnetite rocks) and porphyry (potassic altered rocks) can form during a single prolonged hydrothermal event. read more

Tertiary Petroleum System along Sorong Fault in the Bird Head of Papua to South of Halmahera Area, Indonesia
Surjono, S.S^1,2 , Toha, B² & Winardi, S²

^{1, 2} Geological Engineering Department, Faculty of Engineering, Gadjah Mada University

Jalan Grafika No.2, Yogyakarta, 55281, INDONESIA

¹(sugengssurjono@gmail.com)

Abstract

Sorong Fault occurred in the northern part of Papua Island westward to the eastern part of Sulawesi Island is the boundary of Australian Continental and Pacific Oceanic Crusts. Close to the fault zone, there is the Salawati Basin that proofed as prolific tertiary basin in the eastern Indonesia developed among the Paleozoic and Mesozoic Basins. Sorong Fault which have initiated in the Late Miocene deformed northern part of Papua westward to form transtensional basin including Salawati. Several explorations in Sorong Fault zones have been done following the successful of Salawati which their petroleum system rely on the Miocene Carbonate reservoir of Kais Formation with the younger Klasafet shale as the sources rocks. Juxtaposed stratigraphic position is the main petroleum play for this basin. read more

Oleh: Salahuddin Husein, Ph.D.

Gempabumi besar di dasar kerak samudera (lebih tepat lagi: di bagian atas mantel litosfer) lempeng Indo-Australia tanggal 11 April 2012 telah banyak diulas. Skalanya duh Gusti: 8,6 Mw dan disusul 8,2 Mw.
Meski sudah banyak gempabumi sebelumnya pada patahan yang sama, terutama setelah Gempabumi Lepas Pantai Aceh 24 Desember 2004, gempa tempohari itu tetap saja mengejutkan dalam hal intensitas.

Bagi para peneliti gempabumi (atau pembelajar gempabumi, seperti juga penulis) Pulau Sumatera memiliki 4 karakter gempabumi tektonik mengacu pada mekanisme pemicunya, dimana dua kelompok pertama terkait pada datangnya lempeng Indo-Australia dan konvergensinya dengan Paparan Sunda, yaitu: (1) terpicu patahan geser sinistral berarah U-S di kerak samudera Indo-Australia, yang mendekati Palung Sunda dengan kecepatan sekitar 6 cm/tahun; (2) terpicu patahan anjak di kisaran Palung Sunda hingga daerah prisma akresi akibat gaya kompresif sangat kuat dari konvergensi lempeng di sepanjang palung; kelompok ini dipopulerkan oleh Prof. Kerry Sieh dkk sebagai megathrust Sunda/Sumatera.
Dua kelompok berikutnya berada di Pulau Sumatera, namun pada kedalaman dan mekanisme berbeda, yaitu:
(3) gempabumi dalam, umumnya sesar normal, terpicu oleh pergerakan turun lempeng samudera Indo-Australia akibat tarikan gravitasi (slab-pull) dibawah Pulau Sumatera; dan (4) gempabumi dangkal di sekitaran Bukit Barisan akibat pergeseran dekstral Sesar Sumatera.
Keempat kelompok mekanisme tersebut saling mempengaruhi satu sama lain, namanya juga masih keluarga gempa, bisa akrab juga seperti keluarga Cemara? 😀 read more