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Geochronology of the tumpangpitu porphyry Au-Cu-Mo and high-sulfidation epithermal Au-Ag-Cu deposit: evidence for pre- and postmineralization diatremes in the Tujuh Bukit District, Southeast Java, Indonesia

Citation

Harrison, RL and Maryono, A and Norris, MS and Rohrlach, BD and Cooke, DR and Thompson, JM and Creaser, RA and Thiede, DS, Geochronology of the tumpangpitu porphyry Au-Cu-Mo and high-sulfidation epithermal Au-Ag-Cu deposit: evidence for pre- and postmineralization diatremes in the Tujuh Bukit District, Southeast Java, Indonesia, Economic Geology, 113, (1) pp. 163-192. ISSN 0361-0128 (2018) [Refereed Article]

Copyright Statement

Copyright 2018 Society of Economic Geologists, Inc.

DOI: doi:10.5382/econgeo.2018.4547

Abstract

The Tumpangpitu porphyry and high-intermediate-sulfidation epithermal deposit is the largest deposit in the Tujuh Bukit district, southeast Java, Indonesia. The porphyry resource contains 1.9 billion tonnes @ 0.45% Cu and 0.45 g/t Au, for 28.1 Moz Au and 19 billion lbs of Cu. There are an additional 2.1 Moz Au and 72.9 Moz of Ag in oxidized high-sulfidation epithermal mineralization.

Tumpangpitu is located along a NW-striking structural corridor covering an area of 12 5 km that hosts several Cu-Au-Mo mineralized tonalitic porphyries, each with varying degrees of metal enrichment. At least eight discrete intrusions spanning the alteration-mineralization sequence have been identified at Tumpangpitu. What is unusual, however, is the presence of both a premineralization, relatively dry volcanic breccia pipe (Tanjung Jahe) and a late-mineralization diatreme complex associated with a significant, large magmatic-hydrothermal system (Tumpangpitu) in the same district.

Magmatism, mineralization, and alteration at Tumpangpitu occurred in response to north-directed subduction of the Indo-Australian plate beneath the Asian continental plate margin. The Tujuh Bukit district is floored by early to late Miocene sedimentary and andesitic volcanic rocks. Volcanic-hydrothermal activity at Tujuh Bukit began with the formation of the weakly altered Tanjung Jahe diatreme complex (U-Pbzircon ages of 8.78 0.228.52 0.21 Ma). Mineralization at Tumpangpitu was preceded by the intrusion of a large, equigranular, dioritic batholith (5.81 0.205.18 0.27 Ma). Hydrothermal activity associated with mineralization has been constrained by U-Pb age determinations from syn- to late-mineralization porphyries that were emplaced in the early Pliocene from 5.40 0.46 to 3.94 0.69 Ma.

High- and intermediate-sulfidation Au-Ag Cu mineralization and associated advanced argillic alteration (part of a district-scale lithocap) has overprinted and significantly upgraded the top of the porphyry orebody. 40Ar/39Ar dating of alunite (4.385 0.049 Ma) and Re-Os dating of molybdenite (4.303 0.018 Ma) have defined a short time period between the high-sulfidation epithermal and porphyry mineralization events. This suggests extreme rates of uplift, exhumation, and erosion in the vicinity of the Sunda-Banda magmatic arc.

Volcanic-hydrothermal activity associated with the Tumpangpitu diatreme occurred during epithermal mineralization (breccia matrix zircon age of 2.7 1.0 Ma with systematic errors). Clasts of high-sulfidation state mineralized rocks are a minor but significant component of the diatreme, and late-stage epithermal veins cutting the diatreme demonstrate an intermineralization timing with respect to epithermal activity in the district, implying that epithermal mineralization continued intermittently for 1 to 1.5 m.y. after porphyry mineralization ceased at Tumpangpitu.

Item Details

Item Type:Refereed Article
Keywords:porphyry copper gold, Indonesia epithermal, Tujuh Bukit tumpangpitu
Research Division:Earth Sciences
Research Group:Geology
Research Field:Ore Deposit Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Precious (Noble) Metal Ore Exploration
UTAS Author:Harrison, RL (Miss Rachel Harrison)
UTAS Author:Cooke, DR (Professor David Cooke)
UTAS Author:Thompson, JM (Mr Jay Thompson)
ID Code:124585
Year Published:2018
Funding Support:Australian Research Council (IH130200004)
Web of Science® Times Cited:6
Deposited By:CODES ARC
Deposited On:2018-02-28
Last Modified:2019-03-12
Downloads:0

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