Internal Field Trip-Mt.Gupit

      The internal field trip of SEG UGM SC was held in Gupit, Kebonsari, Magelang at 23rd April 2016. The fieldtrip was guided by Mrs. Dian Yesy Fatimah, S.T. Fieldtrip started at 10 am until 2.30 pm. The first observation placed on Dusun Ngadiharjo. The first location was interpreted by the previous observer as high sulfidation epithermal deposits. High sulfidation epithermal deposits is result from hydrothermal fluid activity in the hipabisal depth at 1-1,5 kilometers, with low temperature that about 50-300 C.  High sulfidation epithermal deposits controlled by geological structural in this zone because, the hydrothermal fluid can move upward through the weak zone and usually the weak zone is fault. High sulfidation epithermal deposits is characterized by vuggy silica texture and clay mineral that formed in high temperature condition such as dickite, alunite, pyrofilit. The hydrothermal alteration that happened in Gupit Hill is consisting of Propilitic, Argilic, Advance Argilic and silicification alteration.

      In the first STA, we can see the Propylitic alteration that has some typical mineral, such as chlorite, epidote. In the first STA, there is a body rock that already controlled by geological structure, that is joint. The joint caused the hydrothermal fluid move upward, so the wall rock’s texture and minerals are replaced and become new minerals. In the first STA, we saw the altered rock that consist some minerals like chlorite and epidote, also oxide mineral that have black red color.


Figure 2. The outcrop of propylitic alteration

      In the second STA, about 500 meters from first STA, we met the Argilic-Advance Argilic Alteration.  In this STA, we met the altered rock that consist some composition of clay mineral group. The rock consists of alunite, dickite, and kaolin group. To determine the type of clay mineral, we should do the SEM test. The alteration in this STA didn’t look good because the strong of clay weathering.


Figure 3. Advance argilic alteration outcrop that consist of clay mineral such as dickite, alunite

      In the third STA, about 1 kilometer from second STA, we met the host rock of alteration. The host rock of high sulfidation epithermal in Gupit area mostly hornblende andesite. The host rock have already altered to propylitic alteration that characterized by chlorite and epidote, but the alteration only selective. The selective alteration happened because the distance far from source and the temperature is low. STA 4 is located about 300 meters from third STA. In fourth STA, we can see the traditional gold mining which being neglected by the miners. In this STA we found some type of altered rock.   There is lignin in this STA that belong to Nanggulan Formation. The intrusion pass the low rank coal and then the low rank coal become medium rank coal because heat transfer.  There is silicication and silicification alteration in this zone. This type of alteration made from some mineral that change into silica mineral. This alteration type was made in high temperature. In hydrothermal process, silica came from circulation fluid or leaching of host rock. The silica gel deposited in low pressure zone and fills the crack of the rock.


Figure 4. The quartz vein on STA 4, that probably consist Au element


Figure 5. Lignin that breached by intrusion

Tin Deposits in Indonesia

      Indonesia  became the second largest tin mine in the world. Most of Tin Deposit in Indonesia was produce by placer deposit. Placer deposit  is mineral deposits formed by the mechanical concentration of resistant minerals, which are released by weathering from source rocks. A mineral with a high specific gravity will become concentrated by flowing water.


Figure 1. Principal of placer deposit formation

      The only mineral of commercial importance as a source of tin is Cassiterite (SnO2). Cassiterite has been an important ore of tin for eons and is still the greatest source of tin today. Most sources of cassiterite today are not primary deposts but alluvial deposits containing weathered grains. There are three distinct types of cassiterite placers:

(1) residual eluvial concentrationson interfluves and valley side slopes;

(2) para-allochthonous placers, which directly overlythe mostly weathered country rocks of valley bottoms; and

(3) allochthonous alluvialdeposits interbedded in the sedimentary valley fill.


Figure 2. Hand specimen of cassiterite mineral as the main source of tin deposits

      Type 1 and 2 placers are directly relatedto nearby primary mineralization associated with granite intrusions, whereas type 3 depositsconsist primarily of reworked type 1 and 2 material. Most tin is used as a protective coating or as an alloy with other metals such as lead or zinc.  Tin is used in coatings for steel containers, in solders for joining pipes or electrical/electronic circuits, in bearing alloys, in glass-making, and in a wide range of tin chemical applications. Secondary, or scrap, tin is an important source of the tin supply. The potential area that consist tin in Indonesia dominantly appear on Bangka and Belitung Island which have tin from ilmenite series of granitic magma. The tin mining discovered at Sungai Liat (Bangka Island), Manggara ( Belitung Island ), Dabo (Singkep Island) and Karimun Island.


Figure 3. Tin deposits distributions in Indonesia

Course 2-Exploitation, Economic Assessment and Environmental Countermeasure in Gold Group Mining

      Production geology is an applied science which combines the principles of economic geology and mining engineering to the development of a defined mineral resource.Production geology is responsible to keep the gold production achieve the target with good understanding geology,  and characteristic of ore due to metallurgical process,ensure the minerals are efficiently extracted from the deposit, and  give information to engineer where the good grade ore places.

Figure 1. Mr. Seno Aji is giving the explanation about production and processing overview in gold mining

      There are some terms in ore deposit, such as ore loss  is ore that mistaken classified as waste ore throw away due to bad peformance of blasting.Dilution is waste that mixed to ore are and classified as ore.Contamination,usually in grade. High grade mixed to low grade area due to poor mining practice. In production geology , the grade control is the most critical one. Because  all missclassification leads to financial loss.

      Production geology in organization is under Geology Department and Mining Department. The processes that have to be done in production geology are :

  1. Resource model

  2. Drilling. There are 3 kind of drilling such as reverse circulation drilling, tamrock drilling, and diamond/ore drilling which have their own risks and benefits.
  3. Sampling method using manual splitter or cone splitter.
  4. Geology mapping has to be done by geologist. There are 2 kinds of geology mapping: wall mapping and floor mapping. Wall maping goals are to help interpretating the mineralization constantly on subsurface or not and to help geologist to detail structure mapping that show if there are mineralization outside the pit or not. Meanwhile, floor mapping is to show the engineer what mineralization that will come up and to help the geologist to domain the area due to estimation model
  5. Assaying to control the quality before inserted to routine sample.
  6. Ore control model using resource estimation, using geological data and using geostatistical approach (Variogram).
  7. Blasting
  8. Excavating (the removal of waste) and hauling
  9. Ore storage
  10. Reconciliation is to compare resource model and actual production.

      To result the metal from mineral extraction, ores must to be crushed to the smaller size, grinding ore into finer powder, mineral separation and help leaching. Working on mining has typical risk. Therefore the thing that has to be main concern is work safety. Work safety here is based on UU number 1 year 1970,  “Bahwa setiap tenaga kerja berhak mendapat perlindungan atas keselamatannya dalam melakukan pekerjaan untuk kesejahteraan hidup dan meningkatkan produksi serta produktivitas Nasional;  bahwa setiap orang lainnya yang berada di tempat kerja perlu terjamin pula keselamatannya; bahwa setiap sumber produksi perlu dipakai dan dipergunakan secara aman dan effisien;   Pembinaan norma-norma perlu diwujudkan dalam Undang-undang yang memuat ketentuan umum tentang keselamatan kerja yang sesuai dengan perkembangan masyarakat, industrialisasi, teknik dan teknologi.

 Figure 2. Mr. Sujarwo is giving the explanation about safety supervisory training

       However, the assurance of work safety is only available for those legal mining company. Those legal mining company should be led by KTT (Ketua Teknik Tambang). Based on KEPMEN NO:555.K/26/M.PE/1995 -1 article 1 paragraph (6)  “KTT adalah seseorang yang memimpin dan bertanggung jawab atas terlaksananya serta ditaatinya peraturan perundang-undangan  K3  pada suatu kegiatan usaha pertambangan di wilayah yg menjadi tanggung jawabnya.”

      KTT is helped by safety committee and safety manager also supervises Technical Controller and Operational Controller. They are liable to the external and internal audit and K3 Committee. Technical Controller takes control the mining tools meanwhile the Operational Controller takes control the worker safety. Also they do inspection frequently, analyze the accident, make a report etc. Every legal mining company has mining book which legalized by Mining Inspector. K3 Committee is obeyed to analyze the accident. In order to process the accident report, there are several conditions that have to be accomplished:

  • The accident is really happened
  • The accident happens to mining worker or identified person
  • The accident happens because of mining activity
  • The accident happens at work hour
  • The accident happens in the mining area

      The mining accident statistic consists of the frequency rate of the accident in 1 million hours and the rate of serious accident in 1 million hours. The mining accident statistic should be sent by KTT before a month after the end of the year. Also KTT is responsible to follow-up the dangerous incident such as explosion of pressured tube, broken machine, leakage of dangerous substance etc. to KAIT.

Figure 3. Momento giving to the Mr. Adi Tarwoco as the 3rd speaker about environmental control

      Besides the protection of work safety, the protection of mining environment is also be the main concern. The management of mining environment is regulated on Kepmen PE No. 1211.K/008/M.PE/1995 about Prevention and Handling of Devastation and Contamination to Mining Activity and UU number 32 year 2009 about protection and management of natural environment. Before do mining activity all that have to do is ask for permission. Mining activity is one of activity that should be had AMDAL. Kind of activity that should have AMDAL are mining and coal activity, metallic mineral, nonmetallic mineral and rocky mineral; the management of purities.

Figure 4. Photo session with all participants and speaker also the committee at the end of session