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Trace and Rare Earth Element Chemistry of Fluorite from the Illinois-Kentucky Fluorspar District and its Implications for the Origins of Mineralizing Fluids

Bergbower, Joshua N

Abstract Details

2018, MS, University of Cincinnati, Arts and Sciences: Geology.
The Illinois-Kentucky Fluorspar District (IKFD) is a fluoritic sub-type of a Mississippi Valley Type (MVT) deposit characterized by the District’s abundance of fluorite compared to minor Pb-Zn mineralization. Found along the axis of the District are a host of Permian ultramafic dikes, pipes, and diatremes, and Hicks Dome, a crypto-explosive structure formed by the release of magmatic volatiles from a carbonatite complex intruded into Precambrian basement. Below the center of Hicks Dome is a large breccia deposit enriched in fluorite and REEs that are principally contained in secondary REE-bearing phosphate and fluorocarbonate minerals. Decreasing fluid inclusion temperatures and changes in fluorite chemistry from Hicks Dome to the fringes of the District indicate heating of the regional MVT system from magmatic activity at Hicks Dome. Previous studies support a model for magmatic gases lowering fluid pH, supplying fluorine, and brecciating country rocks. Fluid inclusion studies in fluorite show the presence of two distinct mineralizing fluids: a lower temperature-higher salinity fluid in paragenetically early fluorite, and a higher temperature-lower salinity fluid in later fluorite. The REE and other selected trace element chemistry of over 530 fluorite samples from 32 locations across the District was analyzed in this study using LA-ICP-MS. Chondrite normalized REE patterns of early F1 fluorite are depleted in LREEs, have nearly flat to gently negative sloping HREEs, and can have a small positive Gd anomaly. REE patterns of late F2 fluorite are similarly depleted in LREEs, show small MREE enrichment, similar to more steeply negative HREEs, and a positive Eu anomaly. REE concentrations are similar between the two patterns, typically 10x chondrite or less. With a few exceptions there is an overall decrease in REE concentration with increasing distance from Hicks Dome. Neither early nor later fluorite has REE patterns similar to fluorite from a mineralized fracture within the ultramafic Sparks Hill diatreme, characterized by LREE enrichment and a pattern sloping from La to Lu. This pattern is similar to whole rock REE patterns of the Sparks Hill diatreme and other intrusive rocks within the IKFD. Data obtained in this study suggest little REE input from magmatic fluids into the regional MVT system.
Craig Dietsch, Ph.D. (Committee Chair)
Andrew Czaja, Ph.D. (Committee Member)
Lewis Owen, Ph.D. (Committee Member)
John Rakovan, Ph.D. (Committee Member)
Jared Singer, Ph.D. (Committee Member)
90 p.

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Citations

  • Bergbower, J. N. (2018). Trace and Rare Earth Element Chemistry of Fluorite from the Illinois-Kentucky Fluorspar District and its Implications for the Origins of Mineralizing Fluids [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269153862162

    APA Style (7th edition)

  • Bergbower, Joshua. Trace and Rare Earth Element Chemistry of Fluorite from the Illinois-Kentucky Fluorspar District and its Implications for the Origins of Mineralizing Fluids. 2018. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269153862162.

    MLA Style (8th edition)

  • Bergbower, Joshua. "Trace and Rare Earth Element Chemistry of Fluorite from the Illinois-Kentucky Fluorspar District and its Implications for the Origins of Mineralizing Fluids." Master's thesis, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269153862162

    Chicago Manual of Style (17th edition)