YOGYAKARTA - Lecturer of Geology University of Yangon, Myanmar, May Thwe Aye, succeeded to gain doctorate at UGM after defending her dissertation on skarn mineralization in deposits of gold and copper in Batu Hijau mining, Sumbawa, West Nusa Tenggara.
In her research, she found that in Batu Hijau mining area there is no limestone being found. However, gold deposits are generally covered by four lithologies, namely limestones, sandstones, meta-sandstones, diorite intrusive rocks - andesitic porphyry, and andesite rock dikes. "Although there is no limestone found in Batu Hijau deposit, its presence is replaced by volcanic rocks rich in calcium which were formed through mineralization in form of skarn type," May Thwe Aye said in her doctoral examination in Geology Science at Faculty of Engineering UGM, Friday (10/2).
According to May Thwe Aye, skarn is found in contact between andesitic volcanic rocks and intermediate tonalit porphyry intrusion. Skarn deposit type can be classified as Classical-eksoskarn, which consists of Fe-rich skarn and locally oxidized controlled by faulting and shearing zones. Meanwhile, the characteristics of skarn mineralization in Batu Hijau porphyry is associated with porphyry which is ozonated mineralogically and metalogenically where the transition between one type of deposit to the next type of deposit is relatively very fast, as seen from the close development zone and formed together and the zone of quartz-pyrite alteration overprinting.
She added that the result of this study indicates that the range of porphyry-related deposits, skarn (calc-silicate rocks, magnetite) and porphyry (potassic alterated rocks) can be formed in a long hydrothermal event.
One member of the promoter team, Dr. Arifudin Idrus, said skarn mineralization in the gold and copper deposits rarely happens in Indonesia. "It's an interesting thing, skarn mineralization in Indonesia in gold and copper is rarely found," he said.