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Petrofabric and Geochemical Analysis of the Great Smoky -- Snowbird Group Contact, Western Blue Ridge, North Carolina and Tennessee

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Petrofabric and Geochemical Analysis of the Great Smoky -- Snowbird Group Contact, Western Blue Ridge, North Carolina and Tennessee University of Kentucky UKnowledge University of Kentucky Master's Theses Graduate School 2006 PETROFABRIC AND GEOCHEMICAL ANALYSIS OF THE GREAT SMOKY -- SNOWBIRD GROUP CONTACT, WESTERN BLUE RIDGE, NORTH CAROLINA AND TENNESSEE Kristopher M. Clemons University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Clemons, Kristopher M., "PETROFABRIC AND GEOCHEMICAL ANALYSIS OF THE GREAT SMOKY -- SNOWBIRD GROUP CONTACT, WESTERN BLUE RIDGE, NORTH CAROLINA AND TENNESSEE" (2006). University of Kentucky Master's Theses. 297. https://uknowledge.uky.edu/gradschool_theses/297 This Thesis is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Master's Theses by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF THESIS PETROFABRIC AND GEOCHEMICAL ANALYSIS OF THE GREAT SMOKY – SNOWBIRD GROUP CONTACT, WESTERN BLUE RIDGE, NORTH CAROLINA AND TENNESSEE Detailed structural and petrographic analysis of the Greenbrier Fault (GBF) reveal different fold and fabric styles and generations preserved in the Great Smoky Group (GSG) hanging wall and Snowbird Group (SG) footwall. Four planar fabrics (S0, S1, S2, and S3) are completely overprinted within meters of the contact by shear zone-related fabrics. Bedding (S0) is defined by planar laminations in the SG siltstones. S1 is weak, not associated with folding of S0, and defined locally by sub-parallel alignment of biotite. S2 (slaty cleavage) is deflected into a disjunctive planar (in GSG) or continuous planar (in SG) S3 foliation characterized by mica formation and dynamic recrystallization of quartz. Metamorphic microstructures indicate lower greenschist to upper amphibolite facies Taconian metamorphism is syn- to post-S2, and pre-S3. Local lower greenschist facies retrograde metamorphism precedes S3 formation. A meter scale, ductile mesoscopic shear zone in SG at the GSG-SG contact is characterized by S/C fabric; this is the youngest deformational event and postdates retrograde mineral assemblages indicating postmetamorphic motion along the contact. Premetamorphic fault fabrics indicative of GSG thrusting onto the SG were absent or completely reconstituted during metamorphism and deformation. The Metcalf phyllite and Pigeon siltstone were also compared to test the hypothesis that the Metcalf phyllite is tectonized Pigeon siltstone. Major and trace element abundances are similar between the lithologies, with the exception of depletion of Ca, Na and Zr in the Metcalf. The system appears to have been open with respect to these elements. It is concluded that the Metcalf phyllite is the tectonized equivalent of the Pigeon siltstone based on lateral continuity, the strong macroscopic and microscopic resemblance of weakly deformed Metcalf to the Pigeon, similar mean values and ranges in major, minor, and trace elements, and identical rock densities. KEYWORDS: Great Smoky Mountains, Greenbrier Fault, Metamorphism, Structure, Tectonics Kristopher M. Clemons August 16, 2006 PETROFABRIC AND GEOCHEMICAL ANALYSIS OF THE GREAT SMOKY – SNOWBIRD GROUP CONTACT, WESTERN BLUE RIDGE, NORTH CAROLINA AND TENNESSEE By Kristopher M. Clemons David P. Moecher Director of Thesis Susan Rimmer Director of Graduate Studies August 16, 2006 iv THESIS Kristopher M. Clemons The Graduate School University of Kentucky 2006 Copyright © Kristopher M. Clemons 2006 v PETROFABRIC AND GEOCHEMICAL ANALYSIS OF THE GREAT SMOKY – SNOWBIRD GROUP CONTACT, WESTERN BLUE RIDGE, NORTH CAROLINA AND TENNESSEE ___________________________________ THESIS ____________________________________ A thesis submitted in partial fulfillment of the Requirements for the degree of Master of Science in the College of Arts and Sciences at the University of Kentucky By Kristopher M. Clemons Lexington, Kentucky Director: David P. Moecher, Associate Professor of Geology Lexington, Kentucky 2006 Copyright © Kristopher M. Clemons 2006 vi MASTER’S THESIS RELEASE I authorize the University of Kentucky Libraries to reproduce this thesis in whole or in part for purposes of research. Kristopher M. Clemons August 16, 2006 vii ACKNOWLEDGMENTS First and foremost, I would like to thank my Thesis Advisor, Prof. David P. Moecher, who believed in me and who has challenged and inspired me to become a better scientist. I owe him a huge debt of gratitude providing me a great opportunity to learn and develop my analytical skills while working on a truly challenging and enjoyable project. I would also like to thank my Thesis Committee members, Prof. Kieran O’Hara, who kept me on my toes by questioning my interpretations, offered new points of view, and who provided assistance in interpreting microstructures and isochon analysis and Prof. Michael Handke, whose office I visited often for advice and instruction. In addition, I would like to thank my loving wife Amy without whose support and encouragement, none of this would have been possible, Jeremy Burns and Mary Ann Hollingshead for their outstanding field assistance, David and Helen Brumfield, Danny and Anna Lee Albertson, Dan and Melissa Hillis, Sarabeth Burns, Tom Compton, Jason Heck, and my family for their support and encouragement. Last but not least, Phoebe and Gretchen for the comic relief. iii TABLE OF CONTENTS Acknowledgments……………………………………………………………….…iii List of Tables……………………………………………………………………….vi List of Figures………………………………………………………………………vi Chapter 1 1 Chapter 2 2.1 Introduction…………………………………………………………….. 3 2.2 Geologic Setting……………………………………………………….. 4 2.3 Previous Work………………………………………………………..... 6 2.4 Outstanding Questions and Problems…….……………………………. 11 2.5 Data Collection and Methods…...………………………………………14 2.6 Results Fabric Relationships at Greenbrier Pinnacle…….………................ 15 Fabric Relationships at Big Creek…………………………..............27 Fabric Relationships at Mount Sterling………….……………….... 36 Fabric Relationships at Cove Creek……………….………..............41 2.7 Summary of fabrics…………………………………………………… 49 S0 Bedding…………..…………………………….……….. 49 S1 Foliation……………………………………….……….. 51 S2 Foliation …………….………………………….………. 51 S3 Foliation …………………...………………….……… 51 S/C Fabric………………..………...……………….……… 52 2.8 Interpretations…………………………………………………………. 54 Structural Evolution ……………………………………….………. 54 Discussion………………………………………………………….. 54 Additional work……………………………………………………. 56 2.9 Conclusions…………………………………………………………… 58 Chapter 3 3.1 Introduction…………………………………….………………………. 60 3.2 Geologic Setting……………………………….………………………..64 3.3 Lithologic Descriptions…………………………………………………67 Pigeon Siltstone……………………………………………………. 67 Metcalf Phyllite…………………………….……………………….70 3.4 X-Ray Fluorescence Geochemistry……..…….……………………….. 73 Methods…………………………………….……………………… 73 3.5 Results………………………………………….………………………. 77 Whole Rock Geochemistry………………………………………… 77 Discussion………………………………….………………………. 79 3.6 Conclusions…………………………………….………………………. 81 iv Appendices Appendix 1. Geochemical and Petrographic Analyses…………………… 82 Table 1a Estimated modal composition of the Pigeon siltstone…... 82 Table 1b Estimated modal composition of the Metcalf phyllite….. 83 Appendix 2. Geochemical Analyses……………………………………….. 84 Table 2 Chemical analysis of the Metcalf Phyllite and Pigeon siltstone (King, 1964)………….……………...… 84 Table 3 Major and minor element analysis…………………….... 85 Table 4a Trace element analysis – Metcalf phyllite………………. 86 Table 4b Trace element analysis – Pigeon siltstone…………….… 87 Table 5 Density values - Metcalf phyllite and Pigeon siltstone.....88 Table 6a Mean values and percent difference for major and minor element chemical analyses – Metcalf phyllite and Pigeon siltstone………………………………………..… 89 Table 6b Mean chemical analyses standard deviations for major and minor elements - Metcalf phyllite and Pigeon siltstone…………………………………………………. 89 Table 6c Mean values and percent difference of trace element chemical analyses – Metcalf phyllite and Pigeon siltstone……………………………………..…… 89 Table 6d Mean chemical analyses standard deviations of trace elements - Metcalf phyllite and Pigeon siltstone…. ……..89 Table 7 Zircon abundance estimate.…………………………...… 90 References………………………………………………………………………….. 91 Figure References…………………………………………………………………...94 Vita………………………………………………………………………………….95 v LIST OF TABLES Table 2.1 Summary of fold style, foliations/fabrics and faulting by location…...... 53 LIST OF FIGURES Figure 2.1 Regional geologic map…………………………………………………. 7 Figure 2.2 Ocoee Supergroup stratigraphy………………………………………… 8 Figure 2.3 Location of study area……………….…………………………………. 10 Figure 2.4 Cross section across Greenbrier Pinnacle (after Hadley and Goldsmith, 1963)…………………………………………….……………………... 12 Figure 2.5 Greenbrier Pinnacle area geologic and sample location map…………...16 Figure 2.6 Greenbrier Pinnacle S0 and S2 relations …………………………….......17 Figure 2.7 Equal area net of poles to S0, Greenbrier Pinnacle area…………………18 Figure 2.8 Equal area net of poles to S2, Greenbrier Pinnacle area………………... 18 Figure 2.9 M1 biotite in the Roaring Fork sandstone. ……………………………... 20 Figure 2.10 S0 and S2 in the Pigeon siltstone….. …..……………………………... 21 Figure 2.11 Weak S2 disjunctive cleavage in the Elkmont sandstone ...…………... 22 Figure 2.12 Shear band cleavage (S3) …………….……………………….……..... 23 Figure 2.13 Greenbrier Cove shear zone….. ……………………………………… 24 Figure 2.14 Greenbrier Cove shear zone S/C fabric ………………………………. 24 Figure 2.15 S/C microstructures in the Roaring Fork sandstone …..………..........
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