Cenozoic Island Arc Magmatism in Java Island (Sunda Arc, Indonesia): Clues on Relationships between Geodynamics of Volcanic Centers and Ore Mineralization

Abstract

. Java island, regarded as a classic example of island arcs, is built through multi events of Cenozoic arc magmatism produced by the subduction of Indian‐Australian oceanic crusts along the southern margin of Eurasian plate. Regional crustal compositions, subducted slabs, and tectonics determined the spatial‐geochemical evolution of arc magmatism and regional metallogeny. Tertiary geodynamics of island arc was dominated by backarc‐ward migrations of volcanic centers. Only after the Miocene‐Pliocene roll‐back effects of retreating slab, slab detachment, and backarc magmatism took place in central Java. The source of arc magmas is mainly partial melting of mantle wedge, triggered by fluids released from dehydrated slabs. Increasing potassium contents of arc magmas towards the backarc‐side and younger magmas is typical for all magmas, while alkali and incompatible trace elements ratios are characteristics for different settings of volcanic centers. The oceanic nature of crust and the likely presence of hot slab subducted beneath the eastern Java determine the occurrences of adakitic magmas. Backarc magmatism has a deeper mantle source with or without contributions from subduction‐related materials. The domination of magnetite‐series magmatism determines the sulfide mineralization for the whole island. District geology, geodynamics, and magma compositions in turn control particular styles and scales of precious metals concentrations. Deep‐seated crustal faults have focused the locations of overlapping volcanic centers and metalliferous fluids into few major gold districts. Porphyry deposits are mostly concentrated within Lower Tertiary (early stage) volcanic centers in eastern Java which are not covered by younger volcanic centers, and whose sulfides are derived from partial melting of basaltic parental materials. On the other hand, high‐grade low‐sulfidation epithermal gold deposits formed in later stages of arc development and are spatially located within younger volcanic centers (Upper Miocene‐Pliocene) that overlap the older ones. Gold in low‐sulfidation epithermal system is likely to be derived from crustal materials. The overall interacting factors resulting in the petrochemical systematics that are applicable for exploration: 1) early‐stage volcanic centers with high Sr/Y and Na2O/K2O ratios are more prospective for porphyry mineralization, while 2) later‐stage volcanic centers with high K2O, total alkali, and K2O/Na2O ratios are more prospective for low‐sulfidation epithermal mineralization.

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

“…5a) in the east of Selogiri was reported to be 11.9 ± 0.7 Ma (location 21‐10, Fig. 3[link]; Setijadji et al , 2005, 2006).…”

“…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).…”

40Ar/39Ar Geochronology of Volcanic and Intrusive Rocks in the Papandayan Metallic Prospect Area, West Java, Indonesia

“…The distinct ages of the Jampang Formation basalt and andesite samples suggest at least two volcanic episodes. In addition, the age of the Jampang Formation basalt is broadly consistent with the previously reported K–Ar ages for Jampang Formation basalts of 17.6 ± 0.6 and 17.9 ± 0.9 Ma (Soeria‐Atmadja et al, ) and with Lower Miocene volcanic activity reported in West Java (Setijadji et al, ).…”

Characteristics of the Cibaliung Gold Deposit: Miocene Low‐Sulfidation‐Type Epithermal Gold Deposit in Western Java, Indonesia

“…The volcanic arc was formed along the northern margin of the active convergence plate, that is, the subduction of the Indian -Australian plate beneath the Eurasian plate during Cenozoic time and has been active since at least Eocene time ( Katili, 1975;Hamilton, 1979 ). This subduction resulted in a volcanic chain along Java ( Van Bemmelen, 1949;Katili, 1975;Whitford et al , 1979;Setidjaji et al , 2006 ). The volcanic front has migrated from south to north with time and has remained calcalkaline in composition throughout its history (Nicholls et al , 1980;Soeria-Atmadja et al , 1994 ).…”