Abstract

The Tarcoola goldfield in central South Australia is hosted by the Paleoproterozoic Paxton Granite and Tarcoola Formation metasedimentary rocks. Both of these units are intruded by narrow dikes of the Lady Jane Diorite, which is considered to be part of the Gawler Range-Hiltaba volcano-plutonic event. Crosscutting relationships and 40Ar/39Ar dating of alteration sericite and primary hornblende have demonstrated that veining, alteration, and mineralization occurred synchronously with intrusion of the diorite dikes at ~1580 Ma. Mineralization at the Perseverance deposit in the Tarcoola goldfield is hosted by quartz veins in both granite and the lower parts of the Tarcoola Formation. Alteration intensity and mineralization are related to fracture density. Very high gold grades (up to 270 ppm) are recorded in carbonaceous siltstones of the Tarcoola Formation. Primary fluid inclusions from mineralized quartz veins at Perseverance are dominated by two-phase aqueous inclusions and three-phase H2O-CO2(l)-CO2(v) ± CH4 inclusions. Both inclusion types have salinities of <10 wt percent NaCl equiv, with evidence of other salts being present. Both types homogenize between 150° and ~340°C. They occur together in single quartz grains, which suggests the coexistence of aqueous and carbonic fluids. At the Perseverance deposit the maximum depth of fluid inclusion formation is estimated as 10 km. Processes resulting from pressure fluctuations during brittle fracturing causing phase separation are suggested to be the dominant gold precipitation mechanism, although definitive fluid inclusion evidence for either phase separation or fluid mixing is lacking. Wall-rock sulfidation may have also contributed to gold deposition. Pb isotope compositions of galena from gold-bearing mineralized veins at Perseverance are similar to K-feldspar and whole-rock samples of the Paxton Granite. This is consistent with a common source of Pb and possibly other ore components for both the granite and galena, but not all potential reservoirs were tested. Variably altered and gold mineralized samples that had Paxton Granite precursors show a loss of Nd and a trend from {varepsilon}Nd(1580Ma) values of about -6.2 in slightly altered samples toward more positive {varepsilon}Nd values of about -3.3 in high-grade gold samples. Of the local lithologic units, the Lady Jane Diorite has {varepsilon}Nd(1580Ma) values of about +0.1 and is the most probable source of the more primitive Nd isotope components in mineralized samples. Mineralization in the Tarcoola goldfield has similarities to both orogenic and intrusion-related gold styles. The demonstrated coeval timing of diorite dikes and mineralization at Tarcoola, together with the Nd isotope constraints on metal sources, and the presence of similar mafic dikes in several other known gold prospects in the central Gawler gold province, suggests that the diorite was an essential part of the gold mineralization event throughout this province.
Google map showing geographic bounding box with values North bound -28.0 East bound 138.0 West bound 132.0 South bound -32.0
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Product Type/Sub Type

dataset - External Publication - Scientific Journal Paper

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2007

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

External Publication
Scientific Journal Paper
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-28.0
East bound
138.0
West bound
132.0
South bound
-32.0

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Unknown

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onLine

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distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-f9df-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2010-10-11

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

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pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Related Links
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays