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Hydrothermal fluid sources in the development of shallow potassic-sodic alteration at the Cadia East alkalic porphyry Au-Cu deposit, NSW

Citation

Fox, N and Harris, AC and Cooke, DR and Collett, D and Faure, K, Hydrothermal fluid sources in the development of shallow potassic-sodic alteration at the Cadia East alkalic porphyry Au-Cu deposit, NSW, Proceedings of 10th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 17-20 August, Townsville, Australia, pp. 222-224. ISBN 978-0-9805-5868-5 (2009) [Refereed Conference Paper]

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Copyright 209 Society for Geology Applied to Mineral Deposit

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Abstract

The Cadia East deposit occupies a mineralized zone 2 km in strike length, 600m in width and >1500m in vertical extent. Resource estimates indicate that >28 million ounces of gold and >5.5 million tonnes of copper may be contained in the deposit. Alkalic monzonite and monzodiorite dikes intrude a 2000m thick sequence of submarine basalt and basaltic-andesite volcanic and volcaniclastic rocks that are the principal host to mineralisation. Sheeted quartz-sulphide veins are spatially and temporally associated with these dikes, defining a high grade resource at depth. High-level, broadly stratabound, disseminated Cu–Au mineralisation is overprinted by a pervasive quartz–orthoclase–albite– muscovite–calcite alteration assemblage (upper potassicsodic) which may be >200m thick and extends laterally over the majority of the deposit. Stable isotope (O, D and S) data suggests that magmatic hydrothermal fluids were implicit in the development of both the upper potassicsodic alteration zone, and the deeper vein related alteration-mineralisation. There is limited evidence for the incursion of external waters into the hydrothermal system. The contrasting mineralisation and alteration styles imply that fracture permeability controlled the movement of mineralising fluids from source intrusions at depth whereas the development of the broadly stratabound mineralisation and subsequent alteration in the upper parts of the deposit was strongly influenced by host rock permeability.

Item Details

Item Type:Refereed Conference Paper
Keywords:alkalic porphyry, porphyry Cu-Au, stable isotopes, Macquarie Arc, Lachlan Orogen
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
Author:Fox, N (Dr Nathan Fox)
Author:Harris, AC (Dr Anthony Harris)
Author:Cooke, DR (Professor David Cooke)
ID Code:100607
Year Published:2009
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2015-05-22
Last Modified:2015-09-24
Downloads:0

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