Top Ten Finalist of International Student Paper Contest UGM 2015 MiŶiŶg aŶd EĐoŶoŵiĐ Geology iŶ “ustaiŶaďle DeǀelopŵeŶt STRUCTURAL CONTROL ON HIGH GRADE GOLD MINERALIZATION IN PROSPECT ‘A’, NORTH SULAWESI : Back to Basic! Considering Geological Structures as One of the Most Important Aspect for Gold Mineralization to Answer the Challenges of Future Gold Exploration Aditya Pratama 1*, Seno Aji Kowara 2 , Gerry Mokoginta 2 1 Geological Engineering Department, Universitas Gadjah Mada, Yogyakarta 2 P.T. J-Resources Bolaang Mongondow *Corresponding author: aditya.pratama@mail.ugm.ac.id ABSTRACT This paper discusses the structural control on gold ŵiŶeralizatioŶ iŶ prospeĐt A, ďased oŶ priŵary field study aŶd laďoratory aŶalysis. ProspeĐt A is loĐated iŶ North “ulaǁesi ProǀiŶĐe, Indonesia. The research area is covered by vulcanic rocks, called as Plio-Pleistocene sequences (Hardjana, 2012). Gold ŵiŶeralizatioŶ iŶ prospeĐt A is hosted ďy hydrothermal breccia, tuff, tuff breccia, and maar unit deposits. Silicic alteration as the core of mineralization is characterizied by vuggy-massive silica which outward to silica-alunite/dickite and alunite/dickite-clay assemblages. The mineral assemblages show that ore deposit in this area is categorized to high sulphidation epithermal deposit. Fire assay analysis show that this area has high grade Au mineralization until 10,7 ppm. Faults and joints in this area are mostly oriented in NNE-SSW and NE-SW with high dipping where the latest trend is the most favourable for gold mineralization. The faults are strike-slip system in transpressional environment and interpreted as conjugate transfer type of regional structural. Strike- slip with NNE-SSW orientation is the feeder of gold mineralization, as long as geological time in its dilation part, reactivated as normal fault with NE-SW orientation. NE-SW shows the increasing of grade in this fault system, shown by fire assay analysis in this area. As the feeder of mineralization, geological structures are righteously considered as one of the most important aspect for exploration and exploitation evaluatioŶ. ProspeĐt A shoǁs that high grade gold mineralization is hosted by flexure in the strike slip fault system. The next exploration target hopefully can be shown by the other dilation pattern as shown by Riedel shear model in this transpressional environment. Keywords: Gold mineralization, high sulphidation epithermal, flexure, strike-slip system, transpressional environment, prospeĐt A I. PREFACE Geological structures play very crucial and important role for the mineralization in general, playing as the pathways for hydrothermal bearing metal and as the spaces for ore deposition (Blewett, 2012; Bonson et al., 2012). The accomodation jogs or extentional structures act as the main fluid pathways (Weinberg et al., 2004 at Blewett, 2012). Besides, jogs are believed as the reason of mineralization clustering. Because of its importances, understanding the genetics and characteristics of geological structures will lead to the mineralization facts. Important structures for the mineralization, not obviously, can be inferred from the regional datasets (Blewett, 2012). The datasets include metamophic assemblages, stratigraphic associations, intrussions, lineaments, drainage patterns, and map patterns. These structures can also guide to tectonic processes and it will shown in this paper using the three latest datasets mentioned above. Indonesia is a country that regarded as one of the biggest metal producer in the world and categorized as the primary player in metal industries. It is caused by the geological setting of Indonesia which mentioned as