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Widi, Bambang Nugroho
Buletin Sumber Daya Geologi
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Kajian Endapan Pasir Besi di Daerah Pantai Selatan Kabupaten Ende, Flores, Provinsi Nusa Tenggara Timur Widi, Bambang Nugroho; Kisman, Kisman
Buletin Sumber Daya Geologi Vol 1, No 1 (2006): Buletin Sumber Daya Geologi
Publisher : Buletin Sumber Daya Geologi

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Iron as One of primary raw material in steel and construction industry, its presence and potencies in Indonesia have an important role. Genetically, known 3 formation of iron deposits (1) Primary, (2) Lateritic, (3) Secondary/reworking process.Based on the survey conducted in Ende in 2005, the typical of iron deposits in this area is classified into sedimentary iron deposits (due to leaching, transporting, accumulating and depositing in somewhere). The accumulation of magnetite grains suggested is due to by leaching, washing in the long term and occurs intensively, so that produce high magnetite concentration in certain area. The interesting area is spread in four sectors; Rapo Rindu, Bheramari, Ruku Ramba and Ondorea sectors.The result of physical laboratory analysis (in concentrate) show the magnetite degree (MD) is vary from 10% to 50%, whereas from chemical analysis known the highest grade reach 37.10% and lowest grade is around 4.4%. However, the everage grade, in general are from 10 to 25 %.The potential of the deposits is obtained from combination between field work laboratory analysis and for those areas mentioned above the total hypothetics resources is 57.134.358,4 ton (concntrate). It seem the deposits of this area is not economic in mining view because very small (under 100 millions tonnes). 
PROSPEK ENDAPAN KROMIT PADA LATERIT DOSAY, PEGUNUNGAN CYCLOOP, SENTANI BARAT, JAYAPURA, PAPUA Widi, Bambang Nugroho
Buletin Sumber Daya Geologi Vol 12, No 1 (2017): Buletin Sumber Daya Geologi
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Keterdapatan mineral kromit di Wilayah Dosay, Kecamatan Sentani Barat,Provinsi Papua, merupakan temuan baru yang menarik untuk di kaji secara lebih jauh.Adanya indikasi tersebut telah memberikan gambaran kondisi mineralisasi  yang belum terungkap oleh penyelidik sebelumnya, terutama terutama berkaitan dengan keterdapatan kromit di wilayah ini.   Secara geologi Jalur Pegunungan Cycloop dimana indikasi kromit ditemukan memiliki ciri yang karakteristik. Kromit ditemukan dalam batuan ultrabasa kelompok ofiolit Pegunungan Cycloop. Batuan ofiolit merupakan batuan induk (host rock) dari kelompok mineral logam jenis kobalt (Co), nikel (Ni), besi laterit (Fe), platinum (Pt), Paladium (Pd) dan kromit (Cr).Dari hasil penyelidikan oleh Pusat Sumber Daya Mineral, Batubara dan Panas Bumi, Badan Geologi th 2016, di daerah Sentani Barat diketahui anomali kromit ditemukan cukup signifikan yaitu dari kisara 1,3% hingga 4,7% dari soil hingga lapukan batuannya (saphrolit). Anomali ini mencapai grade tertinggi sekitar 130 kali lipat kelimpahan unsur kromit di kerak bumi. Sementara dari kelompok mineral logam lainnya seperti kobal, nikel dan besi kehadirannya tidak begitu signifikan.Adanya indikasi kromit yang kuat di horizon soil bagian atas hingga saphrolit pada bagian bawah diharapkan akan menjadi suatu temuan baru yang menarik dan berharga baik secara “scientific”c maupun ekonomi diwilayah ini dimasa mendatang
MINERALISASI BESI TIPE SKARN DI DAERAH BUKIT GADANG LANGE, DESA TARUNG TARUNG, KECAMATAN RAO, KABUPATEN PASAMAN, PROVINSI SUMATERA BARAT Widi, Bambang Nugroho; ., Sukaesih
Buletin Sumber Daya Geologi Vol 11, No 3 (2016): Buletin Sumber Daya Geologi
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Abstract

Daerah penyelidikan terletak di Kecamatan Rao, Kabupaten Pasaman, Provinsi Sumatera Barat, secara geologi disusun oleh batuan metamorf (sabak, gneis), granodiorit, batuan vulkanik (lava andesit, breksi vulkanik), batuan sedimen dan endapan aluvium. Secara tektonik wilayah Rao berada dalam zona sesar Semangko yang berarah baratlaut-tenggara, sedangkan pola struktur lokal berarah timurlaut-baratdaya. Alterasi yang yang teramati pada batugamping marmeran ditandai dengan hadirnya epidot, garnet, karbonat dan urat-urat kuarsa akibat dari adanya intrusi granodiorit. Kehadiran mineral tersebut menunjukkan bahwa mineralisasi yang terbentuk mempunyai tipe skarn. Asosiasi mineralisasi logam berdasarkan analisis mineragrafi terdiri dari magnetit, hematit, kalkopirit, bornit, kovelit, kalkosit dan pirit dengan tekstur mineral yang beragam. Mineral mangan teridentifikasi secara megaskopis. Hasil pengamatan dengan menggunakan Scanning Electron Microscope (SEM) menunjukkan bahwa jenis mineral garnet di daerah Tarung Tarung diinterpretasikan berupa spessartit (Mn3Al2(SiO4)3) dan andradit (Ca3Fe(SiO4)3). Di bagian barat intrusi dijumpai kandungan besi tinggi dengan Fe total antara 59,39% s.d. 64,04%, nilai P sangat rendah (0,1%), TiO2 nilai tertinggi 0,84%. Magnetit yang berasosiasi dengan garnet ditemukan pada zona kontak antara intrusi granodiorit dengan batugamping marmeran di Bukit Gadang Lange. Hal ini menunjukkan adanya pengaruh larutan hidrotermal bersuhu tinggi yang masuk ke dalam batuan karbonat sehingga terbentuk mineralisasi tipe skarn.
Review Of The Small Scale Gold Mining Practices At Cineam, Tasikmalaya Regency, West Java, Indonesia Hutamadi, Hutamadi; Widi, Bambang Nugroho; Suprapto, Sabtanto Joko
Buletin Sumber Daya Geologi Vol 2, No 1 (2007): Buletin Sumber Daya Geologi
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Abstract

Gold deposit at Cineam area is an epithermal gold deposit of low sulphidation type which lies about 180 km southeast of Bandung at an elevation of 400 meter above the mean sea level. The Cineam deposit is administratively belongs to Cineam Subdistrict , Tasikmalaya Regency, West Java Province, which dominantly occurred within volcanic rocks unit of Jampang Formation. Alterations developed in this area namely propylite, argillic, sericitation, and silisification, occurred in andesitic lava, volcanic breccia, and andesitic to dacitic tuff. The thickness of gold bearing quartz veins are commonly from few cm up to > 20 cm, while for the veins of higher grade of gold content the thickness are about 5 cm or less. The average grade of gold content is around 6 - 10 gr/t Au. Although Cineam gold deposits can not be classified as a big scale deposit, itsmineral genesis has an interesting characteristic to be further studied. The Cineam area representing one of the most prospect areas of gold found in the eastern part of West Java Southern Mountain Range. As the Cineam gold deposit is proportionally suitable for a small scale gold mine, the local government had already gave a mining license to a Family Firm in the form of a Village Unit Cooperation or “KUD” such as KUD Mekarjaya which had also been updated to become a B class of Exploitation License category that permitted for the realization of metallic exploitation. This action was in line with the implementation of Autonomy Policy since the year of 2001.Although KUD Mekarjaya’s mining production is relatively so small but in fact the mining activity is still being maintained to be daily earnings for the local gold miners to rely on. Within the long run of the local gold miners activity at Cineam which has been working since 1968, this condition can give rise to many well skilled and experienced labors in seeking for gold ores, in handling small scale gold mining works, and in obtaining for the bullions. In other side, on thecontrary, there are some negative actions must be kept under control such as the disposal of the waste or tailing directly into the river and the unsafely process of heating the amalgam to obtain the bullion including other improper ways done during the handling of their mining activities. Since the whole mining operation so far generally financed by individual investors it is very likely that small scale gold mining lacks of the capital needed for the mining operation. This condition is what the KUD always facing with so that management and financial matters can be a very serious problem affecting the progress of the KUD Mekarjaya From some presentation given by the CCOP-CASM Meeting in Bandung we can compare the condition of small scale mining in Indonesia. and that from other countries which have conducted good management in mining regulation and policy in relation with licensing, mining workers, tax payment and awareness of environment live in the vicinity of mining areas On account of that event this can be expected to motivate and encourage the policy anddecision makers either locally or centrally throughout Indonesia in giving more attention related to the guidance, monitoring and inspection of the implementation of small scale mining activities which is actually growing in numbers.
Co-Authors ., Sukaesih Hutamadi, Hutamadi Kisman Kisman Sabtanto Joko Suprapto