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Diatreme Breccias at the Kelian Gold Mine, Kalimantan, Indonesia: Precursors to Epithermal Gold Mineralization


Davies, AGS and Cooke, DR and Gemmell, JB and Simpson, K, Diatreme Breccias at the Kelian Gold Mine, Kalimantan, Indonesia: Precursors to Epithermal Gold Mineralization, Economic Geology, 103, (4) pp. 689-716. ISSN 0361-0128 (2008) [Refereed Article]

DOI: doi:10.2113/gsecongeo.103.4.689


Early Miocene volcanism associated with a maar-diatreme breccia complex preceded main-stage epithermal gold mineralization at the Kelian gold mine, Kalimantan, Indonesia. Prior to brecciation, andesite intrusions (19.7 ± 0.06 Ma) were emplaced into a package of felsic volcaniclastic rocks and overlying carbonaceous sand-stones and mudstones, and a weakly mineralized geothermal system was established. Intrusion of quartz-phyric, (19.8 ± 0.1 Ma) and quartz-feldspar-phyric rhyolite (19.5 ± 0.1 Ma) into the active geothermal system triggered widespread fragmentation and formation of the maar-diatreme complex. Subsurface phreatomagmatic, and phreatic explosions disrupted the preexisting hydrothermal system, producing three composite diatreme breccia, bodies (the Tepu, Runcing, and Burung Breccias). The diatremes consist of polymict breccias and sandstones that contain abundant carbonaceous matrix. A distinctive facies association comprising coherent rhyohte, jigsaw-fit rhyolite breccia, and matrix-rich breccias that contain wispy to blocky juvenile rhyolite clasts define the root zones of the diatremes. The surficial products of maar-diatreme volcanic activity at Kelian are preserved as large blocks of well-stratified breccias. They contain accretionary lapilli and were deposited by a combination of wet, pyroclastic basesurge, fallout, and cosurge fallout processes. Evidence for syneruptive resedimentation of the pyroclastic: deposits is preserved in poorly stratified breccia beds. Megablocks of phreatomagmatic base-surge deposits were dropped down several hundred meters from the maar environment into the underlying diatremes. Volcanism in the Kelian maar-diatreme complex was dominated by a combination of phreatomagmatic and phreatic processes, with subordinate hydraulic, tectonic, and dry magmatic fragmentation. The carbonaceous -matrix-rich diatreme breccias acted as aquicludes during subsequent hydrothermal activity, focusing fluid flow into the wall rocks adjacent to the diatremes, where epithermal gold mineralization and hydrothermal brecciation occurred. © 2008 Society of Economic Geologists, Inc.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Resource geoscience
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Mineral exploration
Objective Field:Precious (noble) metal ore exploration
UTAS Author:Davies, AGS (Mr Andrew Davies)
UTAS Author:Cooke, DR (Professor David Cooke)
UTAS Author:Gemmell, JB (Professor Bruce Gemmell)
UTAS Author:Simpson, K (Miss Kirsten Simpson)
ID Code:53059
Year Published:2008
Web of Science® Times Cited:29
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2008-10-23
Last Modified:2009-05-21

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