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Quantification Model of Qualitative Geological Data Variables for Exploration Risk Assessment in Prospect Cu-Au Porphyry Deposit Randu Kuning, Wonogiri, Central Java Nurkhamim Nurkhamim; Arifudin Idrus; Agung Harijoko; Irwan Endrayanto; Sapto Putranto
UNEJ e-Proceeding 2016: Proceeding The 1st International Basic Science Conference
Publisher : UPT Penerbitan Universitas Jember

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Abstract

Almost geological data variable contain some degree of uncertainty. Most decisions in mineral exploration was based on geological reports, measurements, calculations as well as ignorance of the geological uncertainty underlies all natural risks of the exploration effort. Risks affecting mineral exploration activities, among others caused by several things. Inherent natural variability in the process of geology and geological objects. Uncertainty on the conceptual and models, associated with incomplete knowledge and subjective interpretations of processes and geological objects. Errors can also occur when observing, measuring or evaluating samples or mathematical analysis of geological data. Data from exploration activities, can be grouped into two types of data, namely quantitative data (e g; grade) and qualitative data (geological data). Geological data variables still largely a qualitative data, resulting between some geologists are not infrequent errors of judgment (assessment of subjective data). This leads to misinterpretation of results of exploration that will ultimately impact on the exploration risk assessment. Currently, the quantification of qualitative data variable is one parameter which is becoming a necessity, because it will be easier in terms of interpretation, communication and measurable. Porphyry Cu - Au deposit in the Randu Kuning Prospect, Wonogiri has the characteristic geometry and grade distribution are quite complex. It is characterized by the appearance of some kind of vein and stockwork with different characteristics. Quantification of geological variables will result in a value that allows the quantification in quantifying exploration risk. For quantitative variables data (grade) using geostatistical methods, while for qualitative variables geological data using canonical correlation and multivariable regression.
Hydrothermal Alteration and Mineralization of the Randu Kuning Porphyry Cu-Au and Intermediate Sulphidation Epithermal Au-Base Metals Deposits in Selogiri, Central Java, Indonesia Sutarto Sutarto; Arifudin Idrus; Agung Harijoko; Lucas Donny Setijadji; Franz Michael Meyer; Sven Sindern; Sapto Putranto
Journal of Applied Geology Vol 1, No 1 (2016)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (23220.401 KB) | DOI: 10.22146/jag.26951

Abstract

The Randu Kuning Porphyry Cu-Au prospect area is situated in the Selogiri district, Wonogiri regency, Central Java, Indonesia, about 40 km to the South-East from Solo city, or approximately 70 km east of Yogyakarta city. The Randu Kuning area and its vicinity is a part of the East Java Southern Mountain Zone, mostly occupied by both plutonic and volcanic igneous rocks, volcaniclastic, silisiclastic and carbonate rocks. Magmatism-volcanism products were indicated by the abundant of igneous and volcaniclastic rocks of Mandalika and Semilir Formation. The Alteration zones distribution are generally controlled by the NE–SW and NW–SE trending structures. At least eight types of hydrothermal alteration at the Randu Kuning area and its vicinity had been identified, i.e. magnetite + biotite ± K-feldspar ± chlorite (potassic), chlorite + sericite + magnetite ± actinolite, chlorite + magnetite ± actinolite ± carbonate (inner propylitic), chlorite + epidote ± carbonate (outer propylitic), sericite + quartz + pyrite (phyllic), illite + kaolinite ± smectite (intermediate argillic), illite + kaolinite ± pyrophyllite ± alunite (advanced argillic) and quatz + chlorite (sillisic) zones. The Randu Kuning mineralization at Selogiri is co existing with the porphyry Cu-Au and intermediate sulphidation epithermal Au-base metals. Mineralization in the porphyry environment is mostly associated with the present of quartz-sulphides veins including AB, C, carbonate-sulphides veins (D vein) as well as disseminated sulphides. While in the epithermal prospect, mineralization is particularly associated with pyrite + sphalerite + chalcopyrite + carbonate ± galena veins as well as hydrothermal breccias. The Randu Kuning porphyry prospect has copper gold grade in range at about 0.66–5.7 gr/t Au and 0.04–1.24 % Cu, whereas in the intermediate sulphidation epithermal contain around 0.1–20.8 gr/t Au, 1.2–28.1 gr/t Ag, 0.05–0.9 % Zn, 0.14–0.59 % Pb and 0.01–0.65 % Cu.