University of Wollongong Research Online Faculty of Science, Medicine & Health - Honours Theses University of Wollongong Thesis Collections 2014 Sulfide inclusions in zircon and their significance ot understanding the evolution of copper porphyries in the Macquarie Arc, New South Wales Ruslan Simpson University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/thsci University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. 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Recommended Citation Simpson, Ruslan, Sulfide inclusions in zircon and their significance ot understanding the evolution of copper porphyries in the Macquarie Arc, New South Wales, Bachelor of Science (Hons.), School of Earth and Environmental Sciences, University of Wollongong, 2014. https://ro.uow.edu.au/thsci/119 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Sulfide inclusions in zircon and their significance ot understanding the evolution of copper porphyries in the Macquarie Arc, New South Wales Abstract Zircons are best known as effective U-Pb geochronometers and more recently for their application to igneous and metamorphic inclusion suite petrology. A wide range of phosphate, oxide and silicate mineral inclusions in zircon have been studied but for reasons unknown, sulfide inclusions have been scarcely documented. This thesis explores the capacity of sulfide inclusions in zircon to preserve the metallogenic evolution of copper porphyry deposits, applied to porphyries in the Macquarie Arc, New South Wales. Zircons were extracted from the copper porphyries of Cadia Hill (Cadia), Endeavour 26 (Northparkes) and Copper Hill and observed by optical and electron microscopy techniques.. Globular inclusions predominantly of chalcopyrite-like compositions were found in zircon from both Cadia and Northparkes. These are interpreted to have been magmatic sulfide melts which became attached ot zircon via surface tension and encapsulated as zircon continued to grow. U-Pb zircon age determinations of analysis sites interior and exterior to magmatic sulfide inclusions were within error of the mean ages of their respective zircon populations. A history of subsequent hydrothermal fluid evolution is preserved in zircon as a sequence of sulfides and sulfates, hydrothermally precipitated along fractures. No sulfide inclusions were identified in zircon from Copper Hill and it may be that sulfide saturation did not occur, or did so to a lesser degree than at Cadia and Northparkes. Sulfide saturation is interpreted to have occurred as one or more temporally discrete events at Cadia and Northparkes. The observed magmatic sulfides are associated with copper, gold, silver and cadmium which is considered evidence of the strong chalcophile partitioning behaviour of sulfide melt phases. Magmatic sulfide melt globules may have heightened the availability of copper and other metals to hydrothermal fluids. A lack of sulfide saturation at Copper Hill may have limited the metal-budget and ore- forming potential of hydrothermal fluids. Detrital sulfides are readily oxidised and destroyed yet may be preserved when included within stable minerals such as zircon. High temperature sulfide inclusions were found in detrital zircons downstream of Cadia Hill. These are interpreted to have been eroded from intra-plate volcanic rocks unrelated to any porphyry system. Sulfide inclusions in detrital zircon may be a useful greenfields exploration proxy of copper porphyry deposits, however further research is required to define discriminating eaturf es which reveal their geological setting of origin. Degree Type Thesis Degree Name Bachelor of Science (Hons.) Department School of Earth and Environmental Sciences This thesis is available at Research Online: https://ro.uow.edu.au/thsci/119 SULFIDE INCLUSIONS IN ZIRCON AND THEIR SIGNIFICANCE TO UNDERSTANDING THE EVOLUTION OF COPPER PORPHYRIES IN THE MACQUARIE ARC, NEW SOUTH WALES By Ruslan Simpson A thesis submitted in part fulfilment of the requirements of the Honours degree of Bachelor of Science in the School of Earth and Environmental Sciences University of Wollongong, 2014 The information in this thesis is entirely the result of investigations conducted by the author unless otherwise acknowledged, and has not been submitted in part, or otherwise, for any other degree or qualification. Ruslan Simpson 14th October 2014 ii ABSTRACT Zircons are best known as effective U-Pb geochronometers and more recently for their application to igneous and metamorphic inclusion suite petrology. A wide range of phosphate, oxide and silicate mineral inclusions in zircon have been studied but for reasons unknown, sulfide inclusions have been scarcely documented. This thesis explores the capacity of sulfide inclusions in zircon to preserve the metallogenic evolution of copper porphyry deposits, applied to porphyries in the Macquarie Arc, New South Wales. Zircons were extracted from the copper porphyries of Cadia Hill (Cadia), Endeavour 26 (Northparkes) and Copper Hill and observed by optical and electron microscopy techniques. Globular inclusions predominantly of chalcopyrite-like compositions were found in zircon from both Cadia and Northparkes. These are interpreted to have been magmatic sulfide melts which became attached to zircon via surface tension and encapsulated as zircon continued to grow. U-Pb zircon age determinations of analysis sites interior and exterior to magmatic sulfide inclusions were within error of the mean ages of their respective zircon populations. A history of subsequent hydrothermal fluid evolution is preserved in zircon as a sequence of sulfides and sulfates, hydrothermally precipitated along fractures. No sulfide inclusions were identified in zircon from Copper Hill and it may be that sulfide saturation did not occur, or did so to a lesser degree than at Cadia and Northparkes. Sulfide saturation is interpreted to have occurred as one or more temporally discrete events at Cadia and Northparkes. The observed magmatic sulfides are associated with copper, gold, silver and cadmium which is considered evidence of the strong chalcophile partitioning behaviour of sulfide melt phases. Magmatic sulfide melt globules may have heightened the availability of copper and other metals to hydrothermal fluids. A lack of sulfide saturation at Copper Hill may have limited the metal-budget and ore-forming potential of hydrothermal fluids. Detrital sulfides are readily oxidised and destroyed yet may be preserved when included within stable minerals such as zircon. High temperature sulfide inclusions were found in detrital zircons downstream of Cadia Hill. These are interpreted to have been eroded from intra-plate volcanic rocks unrelated to any porphyry system. Sulfide inclusions in detrital zircon may be a useful greenfields exploration proxy of copper porphyry deposits, however further research is required to define discriminating features which reveal their geological setting of origin. iii CONTENTS INTRODUCTION ............................................................................................... - 1 - 1.1. Background ........................................................................................... - 1 - 1.2. Aims ...................................................................................................... - 2 - 1.3. Method .................................................................................................. - 3 - REGIONAL GEOLOGY ...................................................................................... - 8 - 2.1. The Macquarie Arc ................................................................................ - 8 - 2.2. Porphyries of the Macquarie Arc ......................................................... - 10 - PORPHYRY SYSTEMS: STRUCTURE AND GENESIS ................................. - 15 - 3.1. Introduction ......................................................................................... - 15 - 3.2. Primary Melt Production in Copper Porphyry Development ................ - 16 - 3.3. Crustal Ascent of Magmas in Copper Porphyry Deposits ................... - 18 - 3.4. Magma Freezing and Release of Hydrothermal Fluids ....................... - 21 - PORPHYRY SYSTEMS: METALLOGENIC EVOLUTION ............................... - 25 - 4.1. Introduction ........................................................................................