ResearchOnline@JCU This file is part of the following reference: Hewson, Simon Andrew John (1996) A structural examination of the Telfer gold-copper deposit and surrounding region, northwest Western Australia: the role of polyphase orogenic deformation in ore-deposit development and implications for exploration. PhD thesis, James Cook University. Access to this file is available from: http://eprints.jcu.edu.au/27718/ If you believe that this work constitutes a copyright infringement, please contact [email protected] and quote http://eprints.jcu.edu.au/27718/ A Structural Examination of the Telfer Gold-Copper Deposit and Surrounding Region. northwest Western Australia: The Role of Polyphase Orogenic Deformation in Ore-deposit Development and Implications for Exploration. VOLUME 1 Thesis submitted by Simon Andrew John HEWSON BSc (Hans) (Curtin) in October, 1996 for the degree of Doctor of Philosophy in the Department of Earth Sciences at James Cook University of North Queensland. I, the undersigned, the author of this thesis, understand that the following restriction placed by me on access to this thesis will not extend beyond three years from the date on which the thesis is submitted to the University. I wish that access to this thesis not to be permitted for a period of three years. After this period has elapsed I understand that James Cook University of North Queensland will make it available for use within the University Library and, by microfilm or other photographic means, allow access to users in other approved libraries. All users consulting this thesis will have to sign the following statement: " In consulting this thesis I agree not to copy or closely para-phrase it in whole or in part without the written consent of the author; and to make proper written acknowledgement for any assistance which I have obtained from it. .?..q(:!.:.!Z'!t (signed) (date) DECLARATION I declare that this thesis is my own work and has not been submitted in any form for another degree or diploma at any university or other institution of tertiary education. Information derived from the published or unpublished work of others has been acknowledged in the text and a list of references is given. Simon A.J. Hewson 3rd October, 1996. I dedicate this thesis to my parents, John and Monica Hewson, without whose love, support and financial assistance over my life this would never have happened. I will remain forever indebted for their encouragement throughout my academic endeavours. "The heights by great men reached and kept Were not attained by sudden flight But they, while their companions slept Were toiling upward in the night". HENRY WORDSWORTII LONGFELLOW CONTENTS of VOLUME 1 PREAMBLE THESIS OVERVIEW ACKNOWLEDGEMENTS SECTION A - Multiple Orthogonal Overprinting Deformation Events in the Telfer Region, w.A.: Preservation of a Complex Tectonic History in Weakly Deformed Rocks. SECTION B - Structural Reconnaissance afthe Lower Yeneena Group, Paterson Province, W.A.; Overprinting of an Ensialic Intracratonic Basin by Migrating late­ Proterozoic Collisional Orogenesis and Resolution of Conflicting Tectonic Indicators. SECTION C - Late Structural Timing of Mineralisation in the Telfer Au-Cu deposit and the Role oj Orogenic Defannation in Regional Fluid Flow and Mineralisation. SECTION D - Progressive Structural Development a/the Telfer Dome and Controls on Gold-Copper Mineralisation. SECTION E - Exploration Modelsfor Fold-hosted and Other Epigenetic Mineralisation Styles in the NE Paterson Province. REFERENCES - all sections CONTENTS of VOLUME 2 SECTION A .................... Figures SECTION B .................... Figures SECTION C .................... Figures SECTION D ........ ......... ... Figures SECTION E .......... .......... Figures APPENDICES APPENDIX 1 - Stereographic data for Section A APPENDIX 2 - Location descriptions, field diagrams and stereographic data for Section B APPENDIX 3 - Sample catalogue (referred specimens). CONTENTS of MAP CASE MAPS MAP 1 -Structural Geology of the Telfer Mine (1:7,500) MAP 2 -Structural Geology of the Telfer region (1: 100,000) MAP 2B -Structural Geology of the O'Cailaghan, Corridor (1:50,000) ENCLOSURES: Laminated full A4 size versions of figures that are regularly referred to in the teltt (e.g . defonnation chronology tables, regional maps etc.) are also enclosed in the Map Case. A number of regularly referred to figures are also enclosed in the Map Case. These have been included for the reader to hold/place in front of themselves so as to negate the need to search backwards through the Figure volume for reference to these figures. ENCLOSURE 1 - Summary Table of the Defannation History in the Telfer Region ( For use with Sections A, C, D & E). EN CLOSURE 2 - Geology of the Rudall Metamorphic Complex and Lower Yeneena Group, Paterson Province, and field locations. (For use with Section B). ENCLOSURE 3 - Stratigraphic Distribution of Stratabound Mineralised Reefs in the Telfer Dome. (For use with Sections C & D). ENCLOSURE 4 - Structural Geology of the Telfer DomelMine. (For use with Section D). EN CLOSURE 5 - Regional Geological Map of the Telfer District (For use with Section E, and Section A). TWO GENERAL USE ENCLOSURES: 1. Orientation of Unoriented Drill Core Utilising Cleavage­ Bedding Relationships. 2. Conceptual Exploration Models for the Telfer Region/Paterson Province - schematic flow chart. PREAMBLE The Telfer Au (+Cu) deposit is one of Australia's premier gold-producers, currently accounting for approximately 4OO,OOOoz. per year. It's discovery in 1972 heralded the recognition of the Proterozoic Paterson Province, in wtllch it is located, as a polymetallic terrane with the potential for significant gold and base-metal mineralisation. The Paterson Province represents a small exposure ('" 36 OOOkm2) of the large NW -SE rrending Paterson Orogen, a continental-scale orogenic belt that passes across northern Western Australia and into central Australia. Rocks in the Paterson Province have recorded a protracted Proterozoic history for this orogenic belt, which includes continent-continent collision at '" 1250Ma (Watrara Orogeny) and late-Proterozoic collisional tectonism (the Paterson Orogeny) between 700 and 6OOMa. The latter generated considerable mineralisation in middle- to late-Proterozoic metasedimentary rocks of the Paterson Province. Late-Proterozoic mineralisation in the Paterson Province is well developed in the NE region where numerous syn- and post-tectonic granitoids, gabbros and dolerites intruded the metasedimentary sequence. However, mineral exploration in this region is commonly hindered by extensive Phanerozoic and Tertiary cover that precludes observation of much of the Proterozoic sequence. Additionally, the province lies within the Great Sandy Desert, and is thus covered by extensive aeolian sand deposits. The large amount of younger cover has resulted in relatively small scattered "windows" that expose the mineralised Proterozoic rock sequence. The NE region of the Paterson Province provides one of the best exposures of this sequence and hosts the Telfer deposit. Sampling of gossanous and stratabound quartz veining in the Telfer Dome (a regional antiformal fold) in 1972 by geologists from both Day Dawn Minerals and Newmont Pty Ltd identified gold enriched horizons within the pelitic sedimentary sequence (felfer Formation) exposed in the dome. Subsequent drilling of these horizons confirmed an initial resource of I Million ounces of gold and mining activity commenced in 1975. During the early 19805 mining concentrated on one particular reef that outcropped in Main Dome, a sub-dome of the Telfer Dome. This reef, the Middle Vale Reef (MVR) exhibited strong secondary enrichment of gold and has historically comprised a significant resource in the Telfer deposit (Dimo, 1990). During the middle to late 1980s a shift to high-volume low-grade mining was facilitated by the ongoing success of dump leach extraction of gold from rocks previously too low-grade to be milled. TIlls inereased throughput caused production to expand to the second sub­ dome (West Dome) as the E-Reefs were mined, and helped to make Telfer one of the top four gold producers in Australia during the late 1980s. More recently, deep diamond drilling in Main Dome (commenced in 1992) has led to the discovery of approximately ten to twelve new reefs at depth in the dome. Underground mining, which had commenced in 1990, has been extended through an exploration decline 10 the upper of these newly discovered reefs (MIO and M30). This decline is currently being extended to reach !he deepest reef, the 130, at approximately 1 100m below !he present ground surface. This should occur by the end of 1997. Another consequence of the deep drilling has been the further confirmation of an epigenetic genesis for !he Telfer deposit. and panicularly the identification of mineralisation in units other !han the Telfer Formation. Initial research on !he stratabound reefs in !he Telfer deposit suggested thai !hey had formed through syngenetic eJdJalative processes (Tyrwhitt, 1979; Turner, 1982). A variation on this, whereby the MVR was considered to have formed as an evaporite horizon !hat was subsequently replaced by quartz­ sulphide assemblages, was proposed by Royle (1985). However, the expansion of mining and deep drilling within the deposit provided increasing evidence for an epigenetic origin. This came both through structural observations and geochemicaUfluid-inclusion studies that indicated the reefs were locally discordant,