FLUID AND SOLID INCLUSIONS IN THE MOSHEIM ANTICLINE OCCURRENCE OF EAST TENNESSEE FIELD DIAMONDS (QUARTZ CRYSTALS)

Doubly terminated euhedral quartz crystals occur within cavities and vugs in deformed rocks associated with orogenic belts globally. East Tennessee Field Diamonds are those found in areas of the southern Appalachians in eastern Tennessee and western Virginia. Here we investigate fluid inclusions in quartz crystals of the Mosheim Anticline locality, to aid in our understanding of Alleghenian orogenesis. The paleo-fluids which formed these crystals may have been related to migrating brines associated with regional Mississippi Valley-type zinc and barite deposits. Hydrocarbon-bearing fluid inclusions can inform us about paleo petroleum maturation and migration in the region. The quartz crystals are found in residual clays overlying Knox group dolomites, which formed in the Upper Cambrian and Lower Ordovician, within the northwest limb of the Mosheim anticline. Quartz crystal morphologies seen in the locality range from elongate-prismatic to bipyramidal. Methods used for conducting this research include petrographic microscopy (plane and fluorescent light), microthermometry and laser Raman spectroscopy on doubly polished thick sections. Fluid inclusions are mostly observed as secondary inclusions, with cross-cutting relationships available to distinguish timing between individual assemblages. Initial microthermometry for methane bearing aqueous (H₂O-CH₄) inclusions show a large range in salinity between individual assemblages with Tm_ice from -3 to -15 °C. Methane-rich assemblages are also observed, with some homogenizing to liquid and others homogenizing to vapor. Late fluids are consistent with a high order of petroleum maturation.