Porphyry‐Type Mineralization at Selogiri Area, Wonogiri Regency, Central Java, Indonesia

Abstract

The Selogiri area, situated in Wonogiri regency, Central Java, is one of several gold prospecting areas in the Southern areas Mountain Range in Java, Indonesia. Three types of dioritic -andesitic intrusive rocks occur in the Selogiri area, namely, hornblende andesite porphyry, hornblende diorite porphyry and hornblende diorite, exposed in a half-circular depression where volcanic breccia and tuff are widely distributed. The occurrence of stockwork quartz veinlets and associated with magnetite and malachite coating along the cracks in the diorite porphyry suggests porphyry type mineralization. This is also supported by the occurrence of polyphase hypersaline fl uid inclusions in the stockwork veinlet quartz. Small-scale miners are mining NS-trending quartz veins for gold associated with base metal sulfi des. These veins are probably epithermal-type mineralization that overprinted porphyry-type mineralization. The Neogene intermediate to silicic hydrous magmatism in Java could have formed the porphyry-type mineralization in Selogiri, as in the rest of the Sunda -Banda arc. Keywords : fl uid inclusion , Indonesia , Java , metallogeny , porphyry copper deposit , stockwork , Sunda-Banda arc . Geologic outline of the Southern Mountain Range of JavaThe Selogiri area is part of the Southern Mountain Range in Central Java. The Southern Mountain Range is situated in the present-day fore-arc region between the Quaternary volcanic chain and the Java trench. The Indo-Australian plate is subducting northwards at the Java trench ( Katili, 1975;Hamilton, 1979;Setijadji et al. , 2006 ) ( Figs 1, 2).The geology of the Southern Mountain Range consists of a series of volcanic rocks and fl ysch-like deposits ( Rahardjo et al. , 1995 ) MethodsWhole-rock compositions of intrusive and volcanic rocks were determined by X-ray fl uorescence spectrometer Rigaku RINT-3100 at the

Mineralogy, Lithogeochemistry and Elemental Mass Balance of the Hydrothermal Alteration Associated with the Gold‐rich Batu Hijau Porphyry Copper Deposit, Sumbawa Island, Indonesia

“…The mineralisation style changes to the east (e.g. Central‐East Java and Sumbawa Island), marked by the porphyry‐type mineralisation at the Selogiri area, Central Java and the Batu Hijau deposit in south‐western Sumbawa Island (Maula & Levet, 1996; Imai et al. , 2007).…”

About the Special Issue: Collection of Achievements on Earth Resources from AUN/SEED‐Net, Part II

“…They demonstrate that bornite solid solution and intermediate solid solution ( iss ) were deposited as primary phases. Imai et al (2007) discuss the occurrence of porphyry-type mineralization at Selogiri area, central Java, Indonesia. This is the fi rst paper in an international journal that reports the presence of porphyry-type mineralization in the Java island.…”

“…Most papers were presented at the AUN/SEED-Net eighth Fieldwise Seminar on Geological Engineering Field and the third International Symposium and Exhibition entitled "Contribution of Science and Engineering for Geo-Hazard and Geo-Resources Management Toward Sustainable Development" held on 3 -4 August 2006 at Yogyakarta, Indonesia. Three papers describe magmatic and hydrothermal systems of porphyry-type mineralization ( Idrus et al , 2007;Imai et al , 2007;Suerte et al , 2007 ), while seven papers including one short communication report on hydrothermal systems associated with gold mineralization ( Ariffi n & Hewson, 2007;Crisostomo et al , 2007;Harijoko et al , 2007;Jimenez et al , 2007;Syafrizal et al, 2007;Warmada et al , 2007 ). In addition, one paper discusses temporal evolution of island arc magmatism ( Polve et al , 2007 ).…”

Chemical Composition of Rock‐Forming Minerals in Copper–Gold‐Bearing Tonalite Porphyries at the Batu Hijau Deposit, Sumbawa Island, Indonesia: Implications for Crystallization Conditions and Fluorine–Chlorine Fugacity

“…Central–East Java and Sumbawa Island). The change of the mineralization style is marked by discovery of the Porphyry‐type mineralization at Selogiri area (Central Java) (Imai et al , 2007) as well as the discovery of the Batu Hijau porphyry copper–gold deposit in southwestern Sumbawa Island (Maula & Levet, 1996).…”