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Proterozoic Gold-Copper Project: Tennant Creek and Starra Districts. Workshop Manual No. 4 (CODES publication 26)

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Large, RR and Davidson, GJ and Rattenbury, MS and McPhie, J and Huston, DL and Stoltz, J (1990) Proterozoic Gold-Copper Project: Tennant Creek and Starra Districts. Workshop Manual No. 4 (CODES publication 26). Technical Report. University of Tasmania, Hobart, Tasmania. (Unpublished)

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Abstract

INTRODUCTION RESTATEMENT OF AIMS To investigate the geological and geochemical controls on Proterozoic gold-eopper mineralisation in iron oxide dominated hydrothermal systems. Major emphasis is to be placed on the gold-copper deposits at Tennant Creek (NT) and in the Selwyn basin (Queensland). BACKGROUND This research project is sponsored by eleven mining companies and the Northern Territory Survey and commenced in 1988 to follow-on from the successful joint University-CSIRO project on the Tennant Creek district (1984-87). This fourth workshop manual is a progress report on our research carried out from July 1989 through to May 1990. Field trips to the Selwyn mineral district and Tennant Creek district will be conducted in conjunction with the workshop. PROGRESS IN THE PERIOD JULY 1989-MAY 1990 * Garry Davidson has completed his PhD research on the Starra and Trough Tank Au-Cu deposits and has included detailed papers on the geochemistry and genesis of the Starra ore deposits in this manual. Garry's work has shown that the ironstones and mineralisation have features which strongly suggest an initial stage of syngenetic volcanic related mineralisation which has been complexly deformed and partially remobilised by later metamorphism. This work has led to the identification of an oxidised style of volcanogenic exhalative ores (VCO deposits) which typically develop in shallow continental rift-settings filled with oxidised (low sulphide) sediments. * Mark Rattenbury has completed his structural mapping of the central-southern Tennant Creek goldfield, and has undertaken a detailed analysis of the Mary Lane Shear Zone - a major structural and magnetic lineament wbich extends through the gold field. In this report, Mark presents an integrated model for folding and thrusting within the district and their relationship to mineralisation. * Jocelyn McPhie, who has considerable experience in volcanology and volcanic-facies analysis has joined the project to study the porphyries and related volcanics at Tennant Creek. In a preliminary report presented here, Jocelyn demonstrates that the major quartz feldspar porphyries are sills intruded into wet unlithified sediments. This work has major implications for ironstone formation and hydrothermal solution flow in the Warramunga Group. * David Huston has continued his research on the paragenesis and fluid inclusion history of the Gecko K44 deposit and has extended this work to a similar study at White Devil. In his two papers presented here David demonstrates that the Gecko K44 and White Devil deposits have similar paragenetic and fluid inclusion characteristics. The major differences of the Gecko deposit are the higher proportion of pyrite and haematite in the ores, and these differences may account for the unusual metal concentrations and zonation of the Gecko K44 ores. Tennant Creek ores are thought to have been produced by the interaction of hot (350 degrees C, saline (15-25 eq. wt% NaCl), oxidized (hematite stable) fluids with reduced, pre-existing ironstones. The presence of certain types of fluid inclusions and chlorites are considered to be favourable signs of mineralization in the weakly mineralized portions of ironstones with economic mineralization. * Joe Stolz who has considerable experience in volcanic geochemistry joined the project this year to study the geochemistry of the Tennant Creek ironstones and related porphyries, granites and sediments, utilising a combination of the BMR database and University of Tasmania analyses. The geochemical data suggest that the porphyries and older granites are comagmatic and unrelated to the Au-Cu-Bi mineralization. The younger Warrego Granite has a distinctive trace element signature that compares closely with A-type granites from other regions which are often associated with mineralization.

Item Type: Report (Technical Report)
Publisher: University of Tasmania
Date Deposited: 12 Aug 2009 05:08
Last Modified: 18 Nov 2014 04:04
URI: http://eprints.utas.edu.au/id/eprint/9047
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