Geology, Geochemistry and Evolution of the Esfordi Phosphate - Iron Deposit, Bafq Area, Central Iran
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Geology, Geochemistry and Evolution of the Esfordi Phosphate - Iron Deposit, Bafq Area, Central Iran by Morteza Jami BSc MSc A Thesis Submitted in Fulfillment of the Requirements for the Degree of Doctor of Philosophy THE UNIVERSITY OF NEW SOUTH WALES SCHOOL OF BIOLOGICAL, EARTH AND ENVIRONMENTAL SCIENCES, August, 2005 i Esfordi Choghart Bafq Satellite image of the Bafq region. ii ABSTRACT Esfordi is a Kiruna-type Fe–P oxide deposit in the Bafq district of Iran. It formed within a predominantly rhyolitic volcanic sequence that formed in a continental margin tectonic regime and is of Cambrian age. The gently dipping, stratabound ore body is lenticular and displays a well-developed mineralogical zonal pattern. The Fe-oxide rich core contains a central zone of massive magnetite and a more hematitic brecciated rim. The overlying P-rich ore body contains massive and brecciated, apatite-rich variants with accessory hematite and actinolite. A zone of apatite-bearing veins and disseminations envelopes the Fe-oxide and P-rich zones and extends into overlying volcaniclastics that contain detrital magnetite ± apatite clasts. The main ore zones are surrounded by Ca-rich alteration, dominated by actinolite, extending ~100 m into the more permeable overlying volcaniclastics. Beyond this envelope is widespread development of secondary K-feldspar. Mesoscopic and microscopic observations reveal a paragenetic sequence containing four generations of apatite. The early stage is a LREE-rich apatite 1 that occurs within the massive and brecciated magnetite core. The second generation is large and brecciated apatite 2, associated with hematite and actinolite. Both apatite 1 and 2 exhibit widespread dissolution and reprecipitation to form a LREE-poor granular apatite that is generally associated with quartz-carbonate±REE minerals. The final stage involved an overprint of LREE-poor apatite 3-carbonate-quartz-actinolite-chlorite-epidote±bastnaesite±synchesite extending into the host rocks. Fluid inclusions in apatite 1 have homogenisation temperatures of 375-425oC and indicate salinities of 14–18 wt. % NaCl. The magnetite displays low į18O of -0.1–1.7 ‰, suggesting precipitation from fluids with į18O of 7.8–9.6 ‰ at ~400oC, consistent with a magmatic source. Fluid inclusions in apatite 2 homogenise between 195–295oC with indicated salinities of 13–19 wt. % NaCl. The associated hematite displays į18O of -0.2–2.3 ‰ which would be in equilibrium with fluids having a į18O of 10.7–13.0 ‰ at ~250oC. Such enriched isotopic fluids suggest interaction of magmatic fluids with cooler saline fluids that were probably derived from the underlying carbonate-rich sequences. Fluid inclusions in apatite 3 and quartz homogenise at 145–155oC and, together with a quartz į18O of 16.0–17.1 ‰, suggests precipitation from a fluid with į18O of -0.7–2.1 ‰ that is likely to have resulted from the introduction of a cooler, less saline and isotopically depleted fluid (such as sea water). The results of this study clearly indicate a significant role for fluids in the evolution of the Esfordi deposit but do not preclude a role for immiscible Fe-oxide–P-rich melts in the initial stages of the mineralising process. iii ACKNOWLEDGEMENTS The author wishes to thank Dr Alistair Dunlop and Dr David Cohen for their close and untiring supervision of this project during the field and laboratory work, and for their constructive discussions during the writing of this thesis. I would like to thank staff of the School of Biological, Earth and Environmental Sciences (BEES) for their support and assistance. Mr Rad Flossman is especially thanked for making outstanding polished sections and advice on sample preparations; Mr John Owen and Mr Yanni Zakaria for IT support; Ms Dorothy Yu and Mrs Irene Wainwright for ICP-MS and XRF analyses; Simon Gatehouse, Professor Bas Henson, Dr Peter Rickwood and Dr Irvin Slansky for their useful advice on petrography, geochemistry and mineralogy, and Dr Colin Ward for assistance with XRD. Many thanks are extended to Mr Barry Searle of the UNSW electron microscope unit and Dr David Steele (University of Tasmania) for technical input concerning REE microprobe analysis. I also express my thanks to the staff of CSIRO Exploration and Mining, North Ryde, and particularly Dr Anita Andrew for access to instrumental facilities for stable isotope and fluid inclusion studies and also for discussions concerning interpretation of the isotopic data. The Esfordi mine personnel, particularly the mine manager Mr Hassan Farjood, are thanked for providing access, geological data, core samples and for logistical support during fieldwork at Esfordi. Dr Samad Alipour and Dr Hamid Amiri also assisted with the fieldwork at Esfordi. Mr Gholamhossein Dehghani, Choghart Mine exploration and development division, provided access to the Choghart Mine, core store, geological data, field excursions and very useful discussions. This study was supported by an Australian Postgraduate Award (APA) and UNSW FRS grants to ACD and DRC. I greatly thank my fellow postgraduate students in the BEES - Ramin Nikrouz, Patrick Tyrrell, Ahmad Reza Mokhtari and Rushdy Ottman. Finally, I would like to express my thanks to my wife and family for their support, encouragement and patience during my study program. iv CONTENTS CHAPTER 1 INTRODUCTION 1 1.1 Introduction 1 1.2 Literature review: an initial perspective 2 1.3 Iron oxide–Cu(–Au) deposits 4 1.3.1 Olympic Dam 5 1.3.2 Cloncurry District, Australia 9 1.3.3 Chilean Fe-oxide-Cu-Au (Zn-Ag) deposits 10 1.4 Kiruna-type magnetite–apatite deposits 10 1.4.1 Kiruna District, Sweden 15 1.4.2 Chilean magnetite–apatite deposits 18 1.4.3 Southeast Missouri iron metallogenic province 20 1.4.4 Pea Ridge deposit 21 1.5 Apatite rich rocks associated with massif anorthosites 23 1.6 The Proterozoic Fe-oxide Deposits of the NE United States 23 1.7 Iranian iron ores 24 1.7.1 Gol-e-Gohar 25 1.7.2 Baba Ali and Jalali 26 1.7.3 Sangan 26 1.7.4 The Bafq District 27 1.8 Study area environment 29 1.9 Aims and Objectives 30 1.10 Thesis Structure 33 CHAPTER 2 GEOLOGICAL SETTING 34 2.1 Introduction 34 2.2 Zagros Fold Belt and Thrust Zone 34 2.3 Alborz Range and Kopeh-Dagh Fold Belt 39 2.4 Makran Ranges 40 2.5 Central Iran 40 2.6 Geology of The Bafq District 44 2.6.1 The Boneh-Shurow Complex 54 2.6.2 The Tashk Formation 55 2.6.3 Cambrian Volcano-Sedimentary Unit (CVSU) 56 2.6.4 Zarigan and Narigan Granites 59 2.6.5 Overlying sedimentary units 69 CHAPTER 3 GEOLOGY OF THE ESFORDI AREA 71 3.1 Introduction 71 3.2 Footwall sequence of Esfordi 77 3.3 Hanging wall sequence 92 CHAPTER 4 IRON-OXIDE – APATITE MINERALISATION AT ESFORDI 109 4.1 Introduction 109 4.2 Fe-oxide core 110 4.2.1 Massive magnetite 117 4.2.2 Brecciated hematite-rich marginal zone 120 4.2.3 Apatite mineralisation associated with Fe-oxide rich core 125 4.3 Apatite-rich mineralisation zone 135 4.3.1 Massive apatite ore 135 4.3.2 Brecciated apatite zone 138 4.4 Low grade apatite ore 142 4.5 Apatite chemistry 150 4.6 Magnetite-hematite horizons 151 4.6.1 Fe-oxide – jaspilite -carbonate horizons 153 4.7 Fe oxide Chemistry and comparison with other Fe oxide ores worldwide 154 v CHAPTER 5 ALTERATION ZONES AND THEIR CHARACTERISTICS 163 5.1 Introduction 163 5.2 Devitrification and diagenetic imprints 164 5.3 K-feldspar alteration 168 5.4 Amphibole alteration 175 5.4.1 Exotic alteration 194 5.5 Carbonate-quartz-(epidote-chlorite-sericite) alteration 195 CHAPTER 6 RARE EARTH ELEMENT MINERALOGY AND GEOCHEMISTRY 201 6.1 Introduction 201 6.2 REE phosphate and carbonate minerals 202 6.2.1 Monazite 202 6.2.2 Xenotime 207 6.2.3 Synchysite and Bastnaesite 210 6.3 Rare earth element silicates 211 6.3.1 Allanite 211 6.3.2 Britholite 223 6.4 REE content of apatite 225 6.5 Whole rock rare earth element distributions 227 CHAPTER 7 FLUID INCLUSION AND STABLE ISOTOPE STUDIES 242 7.1 Introduction 242 7.2 Fluid inclusion studies 242 7.2.1 Apatite 1 243 7.2.2 Apatite 2 246 7.2.3 Apatite 3 247 7.2.4 Quartz inclusions 247 7.3 Oxygen stable isotope studies 251 7.3.1 The hydrothermal waters oxygen isotope composition 257 7.4 Sulphur isotope studies 260 CHAPTER 8 DISCUSSION AND CONCLUSIONS 262 8.1 Thesis objectives 262 8.2 Esfordi zonation and mineral paragenesis 262 8.3 REE mineralogy and geochemistry 270 8.4 Fluid characteristics and sources 277 8.5 Potential Fe–P sources 282 8.6 Association between Esfordi and related Bafq district deposits 287 8.7 Evolution of the Esfordi Fe–P oxide deposit 290 8.8 Conclusion 294 8.9 Future studies 297 REFERENCES 281 APPENDICES Appendix 1: Sample listing 297 Appendix 2: Mineral analyses and electron microprobe data 300 Appendix 3: Geological cross-sections of the Esfordi P-Fe deposit. 323 Appendix 4: Drillhole logs and geochemical analyses 328 vi LIST OF FIGURES Satellite image of the Bafq region.ABSTRACT.............................................................................ii Figure 1. 1 Schematic model of igneous-driven circulation of fluids causing alteration zoning in mafic and felsic systems......................................................................3 Figure 1. 2 Location map of the Bafq–Robat-e-Posht-e-Badam magnetic targets and the Esfordi deposit...................................................................................................32 Figure 2. 1 Relief map of the Alpine-Himalayan mountain ranges. ...................................35 Figure 2. 2 Simplified tectonic map of Iran and adjacent areas..........................................37 Figure 2. 3 Tectonic map of Iran with major structural units..............................................38 Figure 2.