Sedimentary Exhalative Deposite

Sedimentary exhalative (SEDEX) deposits are bedded or laminated, tabular sulfide–rich bodies in carbonaceous shales or other, fine-grained clastic rocks. (Carne and Cathro, 1982). These deposits are an economically important source of lead, zinc, and silver. It is interpreted to have been formed as a result of hydrothermal activity which are released in a basin on the sea floor, resulting in the precipitation of stratiform ore. The host rocks are generally shales, siltstones, and carbonates. The host sediments represent both low and high energy depositional environments with locally derived breccias becoming important in the latter (Large, 1983 in Evans, 1993). The ores are finely layered and often interbanded with rock material, with both being affected by soft sediment deformation suggestive of a syn-sedimentary origin of the sulphides.

Large (1983) categorized the setting of sedex deposits into three order in terms of a hierarchy of sedimentary basins of decreasing size. First order basins with lateral extents of hundreds of kilometres may be either epicratonic embayment into continental margins or, less importantly as hosts, intracratonic basins. Second order basins are tens of kilometres in size, occur within first order basins and contain third order basins. Third order basins have less than 10 kilometres in diameter, within which the stratiform sulphides are accumulated. Both second and third order basins are bounded by syn-sedimentary faults leading to rapid changes in lithological thicknesses and the development of decris-flow breccias. The environments within the third order basins appear to have varied from deepwater, sediment-starved, and anoxic, with a high sediment input of turbidites and shales, to shallow water, oxygenated, carbonate-filled basins, which may even contains anhydrite beds indicating evaporitic environments, or even to lacustrine environments (Sangster, 1990). These third order basins acted as morphological traps into which dense, metal-bearing brines appear to have flowed from distant vents to form brine pools, which then lost heat and salt to the overlying sea water, leading to the precipitation of fine-grained, layered sulphides. The majority of sedex deposits do not appear to be underlained by stockwork feeder zones and are therefore regarded as distal exhalative, unlike the volcanogenic massive sulphides which are dominantly proximal exhalative.

Russel et al. (1981) explains how metal-bearing brines generated. Exhalations were formed by sea water convection cells similar to those shown in Figure 1. which dissolved base metals from the rocks they traversed. Such cells would only have to penetrate a few kilometres into the oceanic crust in order to be heated to and sustained at the necessary temperatures, if supplied with the latent heat of crystallization from a magma chamber (Cann & Strens, 1982).

sedex

Figure 1. Diagram showing how sea water circulation through the crust might give rise to the formation of an exhalative, sediment-hosted, stratiform ore deposit. (After Russel et al. 1981 dalam Evans, 1993)
 

Sedex deposits can be found throughout the world from the west to the east. More than half of the world’s Zinc and Lead has come from sedex deposits like Mt. Isa in Australia, Red Dog in Alaska, Sullivan Mine in Canada, Broken Hill in Australia, Howard’s Pass in Yukon, Mehdiabad in Iran, Black Mountain in South Africa, etc. In Indonesia, sedex deposit can be found in Sopokomil, North Sumatera, currently held bt PT. Dairi Prima Mineral with zinc sulfide ore as the primary target, and galena which is the mineral form of lead sulfide and silver as the secondary target. This area has been explored and also the reserves and resources have been counted, but until this article published (April 17th 2016) there are still no news about when will the mining activities in this area begin.

References:

Emsbo, Paul. 2009. Geologic Criteria for the Assessment of Sedimentary Exhalative (Sedex) Zn-Pb-Ag Deposits. Virginia: USGS

Evans, A. M. 1993. Ore Geology and Industrial Minerals: An Introduction. USA: Blackwell.

Minnovation 2015

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 MINNOVATION IS COMING BACK!!

Apa itu Minnovation?

Minnovation adalah sebuah kegiatan yang dilaksanakan oleh salah satu badan independen di Jurusan Teknik Geologi UGM yaitu Society Of Economic Geologist Student Chapter (SEG UGM-SC).

Pada kegiatan di tahun ini SEG bekerja sama dengan IGLO (Indonesia Gems Lover), yaitu suatu komunitas yang aktif dalam dunia Gemstone dan perkembangannya khusunya di Indonesia.

Oleh karena itu, seminar kali ini akan membahas aspek hard rock dengan tema yang kita angkat pada tahun ini adalah Gemstones dan segala aspek yang berhubungan dengan gemstone yaitu identifikasinya, gemstone testing, dan laboratorium uji gemstones.

Pada seminar kali ini SEG UGM-SC dan IGLO akan mengundang speakers yang telah berpengalaman dan handal dalam bidang hard rock dan gemstone, serta akan dibahas beberapa topik utama yang sangat erat kaitannya dengan dunia gemstones antara lain:

1. Bagaimana Cara Mengidentifikasi Suatu Gemstones?

Pembicara ( Keynote Speakers ) :

  • Lucas Donny Setijadji ( Geological Engineering Lecturer, UGM)
  • Sumarni Paramitha ( Gemologist Adamas Gems Laboratory )

2. Peralatan Lab Standar Pengujian Gemstones dan Hubungannya Dengan Sumber Daya Manusia

Pembicara ( Keynote Speakers ) :

  • Nugroho Imam Setiawan ( Geological Engineering Lecturer, UGM )
  • Adam Harits ( Gemologist GRI Labs )

3. Asosiasi Lab dan Lab Penelitian Teknik Geologi Universitas Gadjah Mada 

Pembicara ( Keynote Speakers ) :

  • Nugroho Tri Putranto ( Gemologist SKYLAB )

Rangkaian kegiatan seminar Minnovation akan dilaksanakan pada :

Tanggal : 19 September 2015

Tempat : Jogjakarta Exhibition Center, Jalan Janti, Banguntapan, Jogjakarta

 

Fasilitas apa saja yang akan peserta peroleh? Fasilitas tersebut yakni :

  • Certificate
  • Coffee Break
  • Seminar Kit

serta ilmu pengetahuan yang baru mengenai gemstones.

 

Adapun cara pendaftaran sebagai peserta seminar dapat dilakukan melalui :

DeskStand pendaftaran selasar KPFT (Kantor Pusat Fakultas Tenik) Universitas Gadjah Mada atau dengan membuka link berikut : http://ugm.id/registrasiminnovation2015

Harga Tiket :

  1. Umum         : Rp 300.000,-
  2. Mahasiswa : Rp 100.000,-

Jika memiliki pertanyaan anda dapat menghubungi :

  • Rezha Ramadhika (0899-7636-906)
  • Hendra Maulana Irvan (0878-3935-2797)

So, what are you waiting for? Let’s join us and get new knowledge here!

 

Internal Course – Technical Upgrade For Paper Writing

This internal course was held on March 12, 2015 with our special instructor Mr. Fahmi Hakim, S.T. He is our former vice president of Society Economic Geology UGM SC with high experiences on paper making. One example of his paper is “Ore And Alteration Mineralogy OfPaningkaban-Cihonje Gold Prospect, Gumelar Sub-District, Banyumas Regency, Central Java: A New Discovery Of Carbonate Base Metal Gold Ephitermal Deposit” with author Arifudin Idrus, Jochen Kolb, Peter Appel, and himself. Now he is opening gemstone gallery and doing exploration about economical minerals in some areas in Indonesia.

Mr. Fahmi Hakim explain about paper writing

Before the presentation given by Mr. Fahmi Hakim, there were an opening speech by our president Kresna Kustrianugraha, he told that this is our special moment to learn from the master, and hope that someday we could make research paper. Then at 4 o’clock the course began. The first stage of writing a paper is having logic about theme that we want to create. It means that we have to interest in the subject that we want to make its paper. Then we must collect data from field. He also said that you can use other people data as your modal to made a paper, but it must under restriction and in a deal communication. The next step is analysis and data interpretation. You must do the laboratory observation in this step. When you think that your data and your interpretation is enough, you can made a conclusion. This conclusion is about the paper content that you have made. And the last step you must publish it and let the world knows about your name. This publication can be spoken on scientist forum presentation, scientist publication through preceding, or publication through book. But there were any one big problem among research scientist, that was many “predator paper” that liked to take other people and publish it without any permission.

Enthusiast of course participants

When you really interested to make a paper, don’t ever try to be lazy person if you wanti to make it through. Don’t think that if you want to make a paper is always a high quality paper with thousand research and much money spent on it. No, you are wrong, you can make a good paper with only simple data, with only simple knowledge that you had gotten. Don’t turn off your spirit on making research

Photo session at the end of course

SEG’s President Election

On January 9th 2015, SEG UGM SC had a president election. After a year passed under the leadership of Aditya Pratama, the time had come to choose a new leader. There were four candidates, that are Kresna Kustrianugraha, Anggara Widyastanto, Reza Ramadhika, and Taufiq Bakhtiar.

The election took place in Racik Desa, a restaurant located at Jalan Kaliurang, Yogyakarta. This event was attended by all SEG members, started at 05. 30 p.m. The conductor of this event was Muhammad Syesar as the head of internal division.

The first agenda was presentation by the candidates. Every candidates had 10 minutes to present his vision and mission for the next period of leadership.

The next session were asking and answering. This session was kind of convincing session for the candidates and judging time for the audience.

The second session had to be ended at 9 p.m due to limited time.The candidates left the room while allmembers discussed the best one to be chosen as new president. It was rough to choose one of the four since they all were capable.

Finally, a decision had been made. The congratulation word went to Kresna Kustrianugraha as the elected president

The last session was inaugurating the new president. A memento was given by Aditya Pratama to Kresna Kustrianugraha which officially symbolized a new period of leadership and the end of the previous period. The previous president then gave a little advice for all members.

“Right foot for learning and left foot for contributing. So the organization can run well and every member can take the benefit. Because to walk and run we need not just one foot, but we need feet.”

In the end of the event all members had a photo session. The event was ended at 10 p.m.