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Lithocaps characteristics, origins and significance for porphyry and epithermal exploration

Citation

Cooke, DR and White, NC and Zhang, L and Chang, Z and Chen, H, Lithocaps - characteristics, origins and significance for porphyry and epithermal exploration, Proceedings of the 14th SGA Biennial Meeting: Mineral Resources to Discover, 20-23 August 2017, Quebec City, Canada, pp. 291-294. ISBN 9782981689801 (2017) [Refereed Conference Paper]


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Abstract

Lithocaps are subsurface, broadly stratabound alteration domains that are laterally and vertically extensive. They form when acidic magmatic-hydrothermal fluids react with wallrocks during ascent towards the paleosurface. Although lithocaps typically have steeplydipping structural roots, there is a significant component of lateral fluid flow involved in lithocap formation, either through permeable aquifers and/or a well-developed fracture mesh. Lithocaps can have lateral dimensions greater than 10 km and thicknesses of more than 1 km. In ancient settings, partially eroded lithocaps are typically exposed as silicified ridges and cliffs. These features do not mark the original paleosurface instead they are erosional remnants of what was once an extensive subsurface alteration domain that may have been capped by low temperature argillic- and/or propylitic-altered rocks. High sulfidation state mineralisation typically occurs in silicicaltered rocks within lithocaps, either as stratabound replacements, veins and/or breccia cement. The quartz-rich mineralized domains can produce a resistivity high. Pyrite is ubiquitous in lithocaps prior to weathering, and can yield complicated chargeability responses, some of which may be associated with mineralization. The alteration assemblages are invariably magnetite-destructive, and can obscure the magnetic signature of an underlying porphyry deposit. Combining SWIR and whole rock geochemistry can provide effective vectoring tools within lithocaps.

Item Details

Item Type:Refereed Conference Paper
Keywords:porphyry, copper, gold, lithocap, exploration, geochemistry, mineralogy
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:Cooke, DR (Professor David Cooke)
Author:White, NC (Dr Noel White)
Author:Zhang, L (Mr Lejun Zhang)
ID Code:122936
Year Published:2017
Funding Support:Australian Research Council (IH130200004)
Deposited By:CODES ARC
Deposited On:2017-12-06
Last Modified:2017-12-07
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