ResearchOnline@JCU This file is part of the following reference: Hammerli, Johannes (2014) Using microanalysis of minerals to track geochemical processes during metamorphism: examples from the Mary Kathleen fold belt, Queensland, and the Eastern Mt. Lofty Ranges, South Australia. PhD thesis, James Cook University. Access to this file is available from: http://researchonline.jcu.edu.au/39966/ The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please contact [email protected] and quote http://researchonline.jcu.edu.au/39966/ Using microanalysis of minerals to track geochemical processes during metamorphism: Examples from the Mary Kathleen Fold Belt, Queensland, and the Eastern Mt. Lofty Ranges, South Australia Thesis submitted by Johannes Hammerli February 2014 For the Degree of Doctor of Philosophy in the School of Earth and Environmental Sciences of James Cook University Statement of Access I, the undersigned author of this thesis, understand that James Cook University will make this thesis available for use within the university library and allow access in other approved libraries after its submission. All users consulting this thesis will have to sign the following statement: In consulting this thesis I agree not to copy or closely paraphrase it in whole or in part without the written consent of the author; and to make proper public written acknowledgement for any assisstance which I have obtained from it. Beyond this, I do not wish to place any restrictions on access to this thesis. Johannes Hammerli February 2014 I 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 institute or 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 Information derived from the published or unpublished work of others has been acknowledged in the text and a list of references is given. Johannes Hammerli February 2014 II Statement of Contribution by Others Nature of Assistance Contribution Names and Affiliations of Co-Contributors Intellectual Support Proposal writing Carl Spandler, JCU Data Analysis Carl Spandler, JCU Nick Oliver, JCU Tony Kemp, UWA Brian Rusk, WWU Poul Emsbo, USGS Editorial Assistance Carl Spandler, JCU Nick Oliver, JCU Tony Kemp, UWA Brian Rusk, WWU Poul Emsbo, USGS Financial Support Stipend IPRS Research funding ARC Grant (DP 1095280) to C. Spandler, N. Oliver and T. Kemp Statement of Contribution by Others Chapter # Details of publication(s) Nature and extent of the intellectual on which chapter is based input of each author 1 Chemical Geology I contributed to primary idea discussion Journal of Metamorphic I contributed to primary idea discussion 2 Geology and sample collection Earth and Planetary I contributed to primary idea discussion 3 Science Letters and sample collection I confirm the candidate’s contribution to this paper and consent to the inclusion of the paper in this thesis. Name: Carl Spandler Signature: Date: III Statement of Contribution by Others Chapter # Details of publication(s) Nature and extent of the intellectual on which chapter is based input of each author 1 Chemical Geology I contributed to primary idea discussion I confirm the candidate’s contribution to this paper and consent to the inclusion of the paper in this thesis. Name: Poul Emsbo Signature: Date: Chapter # Details of publication(s) Nature and extent of the intellectual on which chapter is based input of each author 1 Chemical Geology I contributed to primary idea discussion Journal of Metamorphic I contributed to primary idea discussion 2 Geology and sample collection I confirm the candidate’s contribution to this paper and consent to the inclusion of the paper in this thesis. Name: Nick Oliver Signature: Date: IV Statement of Contribution by Others Chapter # Details of publication(s) Nature and extent of the intellectual on which chapter is based input of each author 1 Chemical Geology I contributed to primary idea discussion Journal of Metamorphic 2 I contributed to primary idea discussion Geology I confirm the candidate’s contribution to this paper and consent to the inclusion of the paper in this thesis. Name: Brian Rusk Signature: Date: Chapter # Details of publication(s) Nature and extent of the intellectual on which chapter is based input of each author Earth and Planetary I contributed to development of con- 3 Science Letters cepts and idea discussion. I confirm the candidate’s contribution to this paper and consent to the inclusion of the paper in this thesis. Name: Tony Kemp Signature: Date: V Acknowledgments There are many people who were involved or contributed in some way to my thesis work over the last four years. Although they cannot all be thanked here individually, their help is greatly appreciated. I owe the greatest debt of thanks to my supervisors, Carl Spandler, Nick Oliver, Tony Kemp, and Brian Rusk. Firstly, a huge thanks to my primary supervisor Carl for all his support during the last 4 years. His wisdom on a wide range of subjects is truly remarkable. Carl was definitely one of the main reasons why my PhD was a very enjoyable and worthwhile experience. Thanks Nick for the fun time in the field and especially for all the accident-free dirt road racing and all your crucial advice throughout my PhD. Tony introduced me to the mysteries of radiogenic isotopes and he had to fly across the island to help me with isotope work, which is greatly appreciated and Brian introduced me to the world of porphyry systems which was interesting indeed. I also want to thank Christa Placzek to be my official secondary surpervisor when everyone else left JCU. I look forward to working with all you guys in the future. Thanks to all the staff at SEES, especially Melissa, Beth, Bec, Jo and Judy, for all your time and help. And thanks to my fellow PhD, honours and master students over the years, particularly Rob who provided plenty of advice and many fruitful and endless discussions including tectonics in PNG. Hannah thank you for being so awesome! Also thanks to the staff of the Advanced Analytical Centre (Kevin, Shane, Yi, Gordon and Brendan) for assistance with analytical work. And finally, my father for his support during my early years at university. VI Abstract Understanding the behaviour of major and trace elements during metamorphism is fundamental for our understanding of the geochemical evolution of the Earth’s crust and the formation of orogenic orebodies. Furthermore, it is essential to know how key elements and radiogenic isotopes behave in metamorphic/hydrothermal systems in order to apply them meaningfully to solve important questions in geosciences. Metamorphic/hydrothermal reactions are most evidently preserved at the mineral scale, so in situ microanalytical techniques are best suited for tracing the record of metamorphism or hydrothermal alteration. In this thesis, I outline new analytical developments for in situ analysis of halogens in minerals and fluid samples, and of Sm-Nd isotopes in REE-rich minerals. These techniques, in conjunction with comprehensive bulk rock and mineral geochemistry and element distribution analysis, are then applied to well- characterised metamorphic rocks from the Adelaide Fold Belt and Mt Isa Inlier. Although fluid is an essential ingredient for mass transport during metamorphism, it is often difficult to identify the source of metamorphic/hydrothermal fluids. Traditionally, fluid inclusions have been used to gain insights into the source and composition of fluids. Until very recently, quantification of key elements such as bromine and chlorine in fluid inclusions relied almost solely on bulk rock analyses techniques (i.e., crush-leach). These methods do not allow distinction between different fluid inclusion generations that might hold crucial information on the evolution of a hydrothermal system and associated mineralization. The development of in situ LA-ICP-MS analysis of chlorine and bromine in fluid inclusions now allows for the targeting of individual fluid inclusions of a specific fluid type in a mineral. In this thesis these techniques were further tested and refined, and applied for the first time to a range of natural scapolite group minerals, minerals assumed to reflect the Cl/Br content of the coexisting hydrothermal fluids. The results show that fluid sources can be identified with a ~ 25 μm resolution in Cl and Br bearing minerals. This technique was applied on scapolite minerals from skarns, regional metamorphic rocks and a mineralized shear-zone of the Mary Kathleen Fold Belt in the Mt. Isa inlier. While scapolite minerals in skarns contain Cl/Br ratios typically associated with granitic fluids, metamorphic scapolite indicates that fluids were dominantly derived from basinal brines formed from sub- aerial evaporation of seawater beyond the point of halite saturation. This bittern fluid infiltrated the underlying sedimentary sequences prior to regional metamorphism. Zoned scapolite in the mineralized shear-zone records three discrete pulses of magmatic and metamorphic fluid, and it is suggested that fluid mixing may have assisted mineralization along and around this shear-zone. To investigate element mobility during metamorphism, I studied the Eastern Mt. Lofty Ranges in South Australia. Metamorphic rocks of the Mt. Lofty Ranges have a relatively simple VII metamorphic history, and metamorphic gradients and widespread up-temperature fluid flow has been documented previously. This allows monitoring of mineral and bulk rock compositional changes (or lack thereof) during metamorphism across a regional metamorphic gradient from ~350–400 ˚C to migmatite grade (~ 650–700 ˚C) at ~0.3–0.5 GPa, in a confined framework. The results show that, despite widespread up-temperature fluid flow, major elements and most trace elements are isochemical during metamorphism. These elements are effectively redistributed into newly formed major minerals or accessory phases.