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Geology of the Namosi Porphyry Cu-Au deposits, Fiji

Citation

Orovan, E and Cooke, DR and Harris, AC and Micko, J and Ackerman, B, Geology of the Namosi Porphyry Cu-Au deposits, Fiji, Society of Economic Geologists 2012: Integrated Exploration and Ore Deposits, 23-26 September, Lima, Peru, pp. 77. (2012) [Conference Extract]


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Abstract

The Namosi Cu-Au district in southeastern Viti Levu, Fiji, hosts several mineralized porphyry centers. Porphyry emplacement coincided with a time of major tectonic reorganization in the southwest Pacific that resulted in counterclockwise rotation and fragmentation of the Fiji platform, calc-alkaline magmatism, and hydrothermal activity. The principal resources in the district are the Waisoi deposits (Waisoi East and Waisoi West), which contain an estimated combined reserve of 1,791 million tonnes (Mt) at 0.37 % Cu and 0.12 grams per tonne (g/t) Au, ranking them among the largest undeveloped Cu resources in the world. The basement rocks of the Namosi district, the late Oligocene to late Miocene andesitic Wainimala Group, are unconformably overlain by gently dipping late Miocene andesitic volcaniclastic rocks of the Namosi Formation. These successions were intruded by many calc-alkaline diorite to quartz-diorite porphyries and altered to high-temperature mineral assemblages of albite biotite magnetite bornite chalcopyrite. Peripheral to the mineralized centers, medium- to low-temperature alteration assemblages are composed of chlorite albite epidote actinolite, and chlorite + magnetite. Chlorite + illite pyrite alteration assemblages have locally overprinted the cores and the peripheries of the porphyry deposits. These southwest Pacific Cu deposits, with a central core of dominantly ore bearing sodic-calcic alteration, contrast with the giant Cu-rich Andean calc-alkaline porphyry deposits.

Item Details

Item Type:Conference Extract
Keywords:Namosi, Cu-Au porphyry, Fiji
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:Orovan, E (Mr Evan Orovan)
Author:Cooke, DR (Professor David Cooke)
Author:Micko, J (Ms Janina Micko)
ID Code:123749
Year Published:2012
Deposited By:CODES ARC
Deposited On:2018-01-24
Last Modified:2018-01-25
Downloads:0

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