The geology and genesis of massive sulphide, barite-gold deposits on Wetar Island, Indonesia
The geology and genesis of massive sulphide, barite-gold deposits on Wetar Island, Indonesia
Volcanic hosted massive sulphide mounds are preserved at Wetar Island, Indonesia with flanking Au-Ag-Hg bearing baritic ore bodies. Wetar Island measures 100 km x 40 km and is part of the Inner Banda Arc, formed during the arc-continent collision of the NNE moving Indian-Australian plate beneath the Eurasian plate. The island is composed entirely of Oligocene to Recent volcanics and minor oceanic sediments with centres of mineralisation at Kali Kuning (KK3) and Lerokis that are located approximately 3 km inland at an elevation of 400-500 m. The orebodies occur marginal to rhyodacite domes within hydrothermally altered calc-alkaline volcanics which overly ocean floor basaltic - andesites. 40Ar/39Ar dating of biotite grains from a syeno-granite intrusion from the Meron area yielded a Zanclian age of 4.72 ± 0.22 Ma, biotites from a post-mineralisation overlying dacitic flow yielded a Piacenzian age of 2.4 ± 0.28 Ma.
The massive sulphides are dominantly pyrite with minor chalcopyrite in upper parts, the pyrite is arsenian (up to 6.7 wt% As) and cut by late fractures infilled with covellite, chalcocite, tennantite-tetrahedrite, enargite, bornite and Fe-poor sphalerite. Mining removed the associated Au-Ag-bearing barite sands (2.17 Mt at 3.98 g/t Au at Lerokis; 1.9 Mt at 4.63 g/t Au at Kali Kuning), with the sulphide mounds at each deposit remaining unexploited. The barite ores are generally friable and are cemented by a series of complex arsenates, sulphates with gold present as < 10μm free grains. Anhedral < 20μm inclusions of sulphides and sulphosalts are present within the barite. The morphology of the barite within the deposits ranges from euhedral rectangular, rhombohedral and polyhedral crystals up to 6 mm in diameter to finer subhedral to anhedral crystals towards the footwall and hanging wall of deposits. Linear and pipe-like barite- Fe-oxide structures are evident and are fluid feeders for the barite ore bodies.
University of Southampton
Scotney, Philip M
de324b91-8087-48a9-8e47-b926b5bd1bf6
2002
Scotney, Philip M
de324b91-8087-48a9-8e47-b926b5bd1bf6
Scotney, Philip M
(2002)
The geology and genesis of massive sulphide, barite-gold deposits on Wetar Island, Indonesia.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Volcanic hosted massive sulphide mounds are preserved at Wetar Island, Indonesia with flanking Au-Ag-Hg bearing baritic ore bodies. Wetar Island measures 100 km x 40 km and is part of the Inner Banda Arc, formed during the arc-continent collision of the NNE moving Indian-Australian plate beneath the Eurasian plate. The island is composed entirely of Oligocene to Recent volcanics and minor oceanic sediments with centres of mineralisation at Kali Kuning (KK3) and Lerokis that are located approximately 3 km inland at an elevation of 400-500 m. The orebodies occur marginal to rhyodacite domes within hydrothermally altered calc-alkaline volcanics which overly ocean floor basaltic - andesites. 40Ar/39Ar dating of biotite grains from a syeno-granite intrusion from the Meron area yielded a Zanclian age of 4.72 ± 0.22 Ma, biotites from a post-mineralisation overlying dacitic flow yielded a Piacenzian age of 2.4 ± 0.28 Ma.
The massive sulphides are dominantly pyrite with minor chalcopyrite in upper parts, the pyrite is arsenian (up to 6.7 wt% As) and cut by late fractures infilled with covellite, chalcocite, tennantite-tetrahedrite, enargite, bornite and Fe-poor sphalerite. Mining removed the associated Au-Ag-bearing barite sands (2.17 Mt at 3.98 g/t Au at Lerokis; 1.9 Mt at 4.63 g/t Au at Kali Kuning), with the sulphide mounds at each deposit remaining unexploited. The barite ores are generally friable and are cemented by a series of complex arsenates, sulphates with gold present as < 10μm free grains. Anhedral < 20μm inclusions of sulphides and sulphosalts are present within the barite. The morphology of the barite within the deposits ranges from euhedral rectangular, rhombohedral and polyhedral crystals up to 6 mm in diameter to finer subhedral to anhedral crystals towards the footwall and hanging wall of deposits. Linear and pipe-like barite- Fe-oxide structures are evident and are fluid feeders for the barite ore bodies.
Text
895100.pdf
- Version of Record
More information
Published date: 2002
Identifiers
Local EPrints ID: 464943
URI: http://eprints.soton.ac.uk/id/eprint/464943
PURE UUID: 680d48fb-6ffa-42c1-8593-46d7cf41a7b0
Catalogue record
Date deposited: 05 Jul 2022 00:13
Last modified: 16 Mar 2024 19:50
Export record
Contributors
Author:
Philip M Scotney
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics