Louisiana State University LSU Digital Commons LSU Master's Theses Graduate School 2013 Metamorphic and geochemical signatures of calc- silicate gneisses from the Sawtooth Metamorphic Complex, Idaho, USA : implications for crustal evolution in western North America Isis Fukai Louisiana State University and Agricultural and Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_theses Part of the Earth Sciences Commons Recommended Citation Fukai, Isis, "Metamorphic and geochemical signatures of calc-silicate gneisses from the Sawtooth Metamorphic Complex, Idaho, USA : implications for crustal evolution in western North America" (2013). LSU Master's Theses. 1931. https://digitalcommons.lsu.edu/gradschool_theses/1931 This Thesis is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Master's Theses by an authorized graduate school editor of LSU Digital Commons. For more information, please contact [email protected]. METAMORPHIC AND GEOCHEMICAL SIGNATURES OF CALC-SILICATE GNEISSES FROM THE SAWTOOTH METAMORPHIC COMPLEX, IDAHO, USA: IMPLICATIONS FOR CRUSTAL EVOLUTION IN WESTERN NORTH AMERICA A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science In The Department of Geology and Geophysics By Isis Fukai B.S., Oberlin College, 2009 May 2013 ACKNOWLEGMENTS Thanks to my committee members Dr. Barbara Dutrow, Dr. Darrell Henry, and Dr. Alexander Webb who helped me not only with the conceptual aspects of my research, but also spent a significant amount of their time, attention, and patience pushing me along, responding to my last-minute crises, and providing me with the encouragement I needed to complete this project. I would like to expecially thank my committee chair, Dr. Dutrow, for her constant support, insight, and motivation. The accomplishments and successes I’ve experienced throughout my graduate career would not have been possible without her excellent guidance as an advisor. I would also like to thank Dr. Paul Mueller, Dr. David Foster, and Dr. George Kamenov for their insight into the temporal evolution of The Sawtooth Mountains, ID, and for access to and help with the LA-ICP-MS at the University of Florida. Thanks to Dr. Dennis Norton and Charlie for helping with sample transport. Special thanks to Tessa Hermes for accompanying and assisting me in the field. Sample collection was made possible through the National Forest Service by David Fluetsch and Lieze Dean of the Sawtooth National Recreation Area. Thanks to Rick Young and Celina will for their assistance with the analytical equipment at Louisiana State University. Financial support for this project was provided by: NSF Grant-Tectonics #1145073 (Dutrow, Foster, and Mueller, 2012), GSA Student Research Grant, New Orleans Geological Society, and the Southeast Geophysical Society. I would also like to thank the Dept. of Geology and Geophysics at Louisiana State University for awarding me a TA assistantship that supported my graduate studies. ii TABLE OF CONTENTS ACKNOWLEGMENTS ................................................................................................................. ii ABSTRACT.................................................................................................................................... v INTRODUCTION .......................................................................................................................... 1 Geologic Background of the SMC.............................................................................................. 4 The Paleoproterozoic Selway Terrane ...................................................................................... 10 The Mesoproterozoic Belt Supergroup ..................................................................................... 11 The Winderemere Supergroup and Associated Neoproterozoic Terranes................................ 14 The Archean-Neoproterozoic Pioneer Mountains..................................................................... 15 Petrogenetic Significance of Calc-silicates............................................................................... 16 U-Pb Titanite Geochronology ................................................................................................... 17 Purpose...................................................................................................................................... 17 METHODS ................................................................................................................................... 20 Field Work................................................................................................................................. 20 Petrography ............................................................................................................................... 20 Electron Microprobe Analysis .................................................................................................. 22 X-Ray Fluorescence (XRF) Whole-Rock Analysis .................................................................. 24 Geothermometry........................................................................................................................ 27 Hornblende-Plagioclase Thermometry.................................................................................. 27 Titanium-in-Biotite Thermometry......................................................................................... 30 Phase-Diagram Sections (Pseudosections)............................................................................ 30 Laser Ablation-Inductively Coupled Plasma-Mass Spectometry (LA-ICP-MS)...................... 33 RESULTS ..................................................................................................................................... 35 Field Work................................................................................................................................. 35 Petrography ............................................................................................................................... 42 Petrography of NW Calc-silicates ......................................................................................... 50 Petrography of NE Calc-silicates .......................................................................................... 58 Petrography of SE Calc-silicates ........................................................................................... 65 U-Pb Titanite Geochronology ................................................................................................... 71 Mineral Chemistry..................................................................................................................... 72 NW Calc-silicate Mineral Chemistry .................................................................................... 72 NE Calc-silicate Mineral Chemistry...................................................................................... 77 SE Calc-silicate Mineral Chemistry ...................................................................................... 84 Whole-Rock Geochemistry....................................................................................................... 86 Major Element Compositions................................................................................................ 86 Trace Element Compositions................................................................................................. 91 Whole-Rock Compositional Trends with Distance............................................................... 96 iii Metamorphic Temperatures and Fluids..................................................................................... 98 Hornblende-Plagioclase Thermometry (Holland and Blundy, 1994).................................... 98 Titanium-in Biotite Thermometry (Henry et al., 2005)....................................................... 100 Pseudosections..................................................................................................................... 101 DISCUSSION............................................................................................................................. 116 Protolith of SMC Calc-silicates............................................................................................... 116 Depositional Environment and Tectonic Setting .................................................................... 124 Calc-silicate Metamorphism, Deformation, and Mineral Paragenesis.................................... 127 Geochronology........................................................................................................................ 134 Similarities between SMC Calc-silicates and nearby Precambrian Terranes ......................... 134 Future Work ............................................................................................................................ 136 CONCLUSIONS......................................................................................................................... 138 REFERENCES ........................................................................................................................... 140 APPENDIX A: OUTCROP PHOTOGRAPHS.......................................................................... 158 APPENDIX