Genesis of the gold-bearing breccia bodies at the Lebong Tandai mine, Sumatra
Genesis of the gold-bearing breccia bodies at the Lebong Tandai mine, Sumatra
The Lebong Tandai mine, located in the foothills of the Barisan mountains on the Indonesian island of Sumatra, is a volcanic-hosted, low-sulphidation epithermal gold deposit of Neogene age. The mineralization occurs as a series of moderately- to steeply-dipping, tabular quartz-cemented breccia bodies which are highly transgressive to the bedding in the host rocks. Vertical and horizontal dimensions of the breccia bodies are 100-700m and widths average 2m. The contact between the breccias and the host rocks is commonly planar, displaying striations which indicate either dip-slip or strike-slip movement, although some surfaces provide evidence for both senses of movement. In places, the hangingwall contact comprises a zone of quartz stockwork, which may be up to 1m in width, where the intensity of the quartz veining decreases away from the mineralisation. The breccias comprise sub-angular to sub-rounded clasts, up to 1m in diameter, of the wallrocks and earlier quartz-cemented breccias, although the average clast size is 20cm. The quartz cement of the breccias in places is massive and structureless, although more commonly it displays cockade or colloform banding of quartz and chlorite.
Ore minerals are confined to the quartz cement of the breccias, occurring either as disseminated polymineralic aggregates or cockade or colloform bands concentric around the breccias clasts. The ore minerals commonly form 1-2% of the breccias, although sulphide-rich breccias, in which virtually the entire cement is composed of ore-minerals, occur at the west end of the mine. The ore-minerals are predominantly base-metal sulphides, mainly pyrite, chalcopyrite, galena and sphalerite, with precious metals occurring primarily as electrum and acanthite. Additional silver-bearing phases include hessite, cervelleite and pearceite-polybasite. Although at least three brecciation and quartz cementation events have occurred, sulphide and precious metal mineralisation was confined to the final event.
University of Southampton
1993
Jobson, David Hamilton
(1993)
Genesis of the gold-bearing breccia bodies at the Lebong Tandai mine, Sumatra.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The Lebong Tandai mine, located in the foothills of the Barisan mountains on the Indonesian island of Sumatra, is a volcanic-hosted, low-sulphidation epithermal gold deposit of Neogene age. The mineralization occurs as a series of moderately- to steeply-dipping, tabular quartz-cemented breccia bodies which are highly transgressive to the bedding in the host rocks. Vertical and horizontal dimensions of the breccia bodies are 100-700m and widths average 2m. The contact between the breccias and the host rocks is commonly planar, displaying striations which indicate either dip-slip or strike-slip movement, although some surfaces provide evidence for both senses of movement. In places, the hangingwall contact comprises a zone of quartz stockwork, which may be up to 1m in width, where the intensity of the quartz veining decreases away from the mineralisation. The breccias comprise sub-angular to sub-rounded clasts, up to 1m in diameter, of the wallrocks and earlier quartz-cemented breccias, although the average clast size is 20cm. The quartz cement of the breccias in places is massive and structureless, although more commonly it displays cockade or colloform banding of quartz and chlorite.
Ore minerals are confined to the quartz cement of the breccias, occurring either as disseminated polymineralic aggregates or cockade or colloform bands concentric around the breccias clasts. The ore minerals commonly form 1-2% of the breccias, although sulphide-rich breccias, in which virtually the entire cement is composed of ore-minerals, occur at the west end of the mine. The ore-minerals are predominantly base-metal sulphides, mainly pyrite, chalcopyrite, galena and sphalerite, with precious metals occurring primarily as electrum and acanthite. Additional silver-bearing phases include hessite, cervelleite and pearceite-polybasite. Although at least three brecciation and quartz cementation events have occurred, sulphide and precious metal mineralisation was confined to the final event.
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Published date: 1993
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Local EPrints ID: 462488
URI: http://eprints.soton.ac.uk/id/eprint/462488
PURE UUID: 8e005b57-dbcd-45d1-8fac-95c15016e6b9
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Date deposited: 04 Jul 2022 19:09
Last modified: 04 Jul 2022 19:09
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Author:
David Hamilton Jobson
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