Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2015 Geological, mineralogical, and geochemical studies of the Paleoproterozoic base metal Stollberg ore field, Bergslagen, Sweden Katherine Suzanne Frank Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Geochemistry Commons, and the Geology Commons Recommended Citation Frank, Katherine Suzanne, "Geological, mineralogical, and geochemical studies of the Paleoproterozoic base metal Stollberg ore field, Bergslagen, Sweden" (2015). Graduate Theses and Dissertations. 15911. https://lib.dr.iastate.edu/etd/15911 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Geological, mineralogical, and geochemical studies of the Paleoproterozoic base metal Stollberg ore field, Bergslagen, Sweden by Katherine Suzanne Frank A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Geology Program of Study Committee: Paul G. Spry, Major Professor Carl E. Jacobson Halil Ceylan Iowa State University Ames, Iowa 2015 Copyright © Katherine Suzanne Frank, 2015. All rights reserved. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ......................................................................................... v CHAPTER 1. GENERAL INTRODUCTION .......................................................... 1 Introduction ......................................................................................................... 1 Thesis Organization ............................................................................................ 2 References ......................................................................................................... 2 CHAPTER 2. VARIABILITY IN GEOLOGICAL, MINERALOGICAL, AND GEOCHEMICAL CHARACTERISTICS OF BASE METAL SULFIDE DEPOSITS IN THE STOLLBERG ORE FIELD, BERGSLAGEN, SWEDEN ...... 4 Abstract ......................................................................................................... 4 Introduction ......................................................................................................... 6 Regional Geology ............................................................................................... 10 Sampling and Analytical Methods ...................................................................... 12 Local Geology ..................................................................................................... 14 Mineral Deposits ................................................................................................. 17 Mineralogy of Metamorphosed Altered Rocks ................................................... 21 Quartz-garnet-pyroxene ................................................................................. 21 Skarn ......................................................................................................... 22 Garnet-biotite ................................................................................................. 24 Gedrite-albite ................................................................................................. 25 Cordierite-biotite ............................................................................................ 25 Silicified rock ................................................................................................. 25 Sericitized rock .............................................................................................. 26 Quartz-fluorite ................................................................................................ 26 Geochemistry of Altered Rocks .......................................................................... 27 Alteration geochemistry of metamorphosed felsic igneous rocks ................. 28 Quartz-garnet-pyroxene ............................................................................ 29 Skarn ......................................................................................................... 29 Garnet-biotite ............................................................................................ 30 Gedrite-albite ............................................................................................ 30 Cordierite-biotite ....................................................................................... 30 Silicified rock ............................................................................................ 30 iii Sericitized rock ......................................................................................... 31 Hanging wall rhyolitic ash-siltstone ......................................................... 31 Footwall rhyolitic ash-siltstone ................................................................. 31 Alteration geochemistry of metamorphosed mafic rocks at Gränsgruvan ..... 31 Rare earth element patterns of altered rocks .................................................. 32 Alteration indices ........................................................................................... 33 Discussion ......................................................................................................... 36 Comparison of sulfide mineralization and alteration styles within the Stollberg ore field .......................................................................................... 36 Element ratios, element concentrations, mineral compositions, and alteration indices as potential exploration guides to ore ................................ 39 Alteration indices ...................................................................................... 39 Mineralogical vectors ................................................................................ 40 Elemental vectors ...................................................................................... 43 Comparisons between the Stollberg and Garpenberg districts ...................... 44 Conclusions ......................................................................................................... 47 Acknowledgements ............................................................................................. 50 References ......................................................................................................... 50 Figure Captions ................................................................................................... 62 Figures ......................................................................................................... 68 Tables ......................................................................................................... 91 CHAPTER 3. AN IN-SITU LA-ICP-MS STUDY OF MAGNETITE ASSOCIATED WITH METAMORPHOSED BASE METAL SULFIDE DEPOSITS IN THE STOLLBERG ORE FIELD, BERGSLAGEN, SWEDEN: PROVENANCE AND EXPLORATION POTENTIAL ........................................... 100 Abstract ......................................................................................................... 100 Introduction ......................................................................................................... 101 Regional Geology ............................................................................................... 104 Local Geology ..................................................................................................... 105 Mineralogy of magnetite-bearing rocks ....................................................... 107 Sampling and Analytical Methods ..................................................................... 111 Magnetite Chemistry ........................................................................................... 112 Trace element compositions ......................................................................... 112 Principal component analysis ....................................................................... 114 iv Discussion .........................................................................................................117 Composition of magnetite in the Stollberg ore field ..................................... 117 Conditions of formation of magnetite ........................................................... 122 Implications for exploration .......................................................................... 125 Conclusions ......................................................................................................... 126 Acknowledgements ............................................................................................. 128 References ......................................................................................................... 128 Figure Captions ................................................................................................... 135 Figures ......................................................................................................... 139 Tables ......................................................................................................... 151 CHAPTER 4. GENERAL CONCLUSIONS ............................................................ 156 General Discussion ............................................................................................