Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Baker, D. E. L. Articles by Collins, W. J. Search for Related Content GeoRef GeoRef Citation

Structural History and Timing of Gold Mineralization in the Northern East Strelley Belt, Pilbara Craton, Western Australia

D. E. L. Baker, P. K. Seccombe and W. J. Collins

School of Geosciences, University of Newcastle, Callaghan, New South Wales 2308, Australia

Corresponding author: e-mail, dbaker{at}geology.newcastle.edu.au

The McPhees and Iron Stirrup deposits, recent gold producers in the Pilbara Craton, Western Australia, are located within a succession of Early to Middle Archean metavolcanic rocks of the northern part of the East Strelley belt. Deformation occurred during five stages (D₁-D₅), with mineralization late in the tectonic cycle (D₄). D₁ structures only affected rocks below a regional, Early Archean unconformity. D₂ deformation produced a ubiquitous, variably developed S₂ foliation, defined by peak metamorphic minerals. Mineralization is hosted within, but postdates a 100- to 400 m-wide, D₂ high-strain zone of talc-chlorite-carbonate schist (ultramafic protolith) that contains competent boudins of actinolite-chlorite schist (mafic protolith). D₃ deformation produced localized open folds, outlined by lithological layering and S₂ foliation. Regional, open folding, and sinistral shearing of reactivated D₂ structures occurred during D₄ deformation, which controlled synkinematic intrusion of granitic pegmatite at ca. 2880 Ma. At the McPhees deposit, narrow, sinistral, north-northeast–trending D₄ shear zones were conduits for mineralizing fluids, which reacted with, and preferentially mineralized, mafic rocks. Gold occurs in altered schistose wall rock and within veins composed of actinolite, quartz, and pyrrhotite, and minor tourmaline, albite, talc, and magnesite; vein selvages consist of albite and tourmaline. Mineralization at Iron Stirrup was also controlled by north-trending D₄ structures that reactivated D₂ fabrics, and was concentrated at a sheared contact between serpentinite and talc-chlorite ± carbonate schist. Similar north-trending D₄ shear zones overprint earlier structures and control ca. 2890 Ma gold mineralization nearby in the Mount York gold district, suggesting a single mineralizing event for the entire belt, which is the same age (within analytical error) as granitic pegmatite intrusions. Gold was deposited under amphibolite metamorphic conditions at Mount York and greenschist conditions at Iron Stirrup and McPhees, indicating a decrease in metamorphic conditions away from the western granite-greenstone contact, where granitic pegmatite dikes are abundant. Therefore, mobilization and transport of gold occurred in response to thermal perturbations related to granitic pegmatite dike emplacement during D₄ deformation.

This article has been cited by other articles:

				D. E.L. Baker and P. K. Seccombe PHYSICAL CONDITIONS OF GOLD DEPOSITION AT THE McPHEES DEPOSIT, PILBARA CRATON, WESTERN AUSTRALIA: FLUID INCLUSION AND STABLE ISOTOPE CONSTRAINTS Can Mineral, October 1, 2004; 42(5): 1405 - 1424. [Abstract] [Full Text] [PDF]

				D. L. Houston, D. L. Huston, R. S. Blewett, B. Keillor, J. Standing, R. H. Smithies, A. Marshall, T. P. Mernagh, and J. Kamprad Lode Gold and Epithermal Deposits of the Mallina Basin, North Pilbara Terrain, Western Australia Economic Geology, July 1, 2002; 97(4): 801 - 818. [Abstract] [Full Text] [PDF]