FLUID INCLUSION INVESTIGATIONS OF THE BURKESVILLE, KY SULFIDE DEPOSITS

The studied deposits are carbonate-hosted sulfide ore bodies near Burkesville in south-central Kentucky. Dominant minerals are dolomite, calcite, sphalerite, barite, pyrite, quartz, galena, and fluorite. Highest concentrations of ore are found in the Knox Dolomite, which is also the primary oil and gas producing unit in the region. The deposits lie near the crest of the Cincinnati Arch in the Cumberland Saddle, which influences fluid migration throughout the area. The southernmost extent of the Grenville Front also lies below the deposits.

This study is investigating the sources of the ore-forming fluids which precipitated the Burkesville deposits by comparing these with MVT Pb-Zn locales to the northwest in the KY-IL fluorspar district. Samples from the Burkesville deposits contain numerous primary and pseudosecondary fluid inclusions with vapor bubbles. Inclusions range from spheres <1 micron in diameter to an irregularly shaped zoned scallop feature several hundred microns in size. Most observed inclusions are equant or slightly elongated, and are found within zoned intergrowth planes in sphalerite crystals with smaller primary inclusions forming disseminated planar oval clusters. This contrasts with ores from the KY-IL MVT fluorspar district, which generally contain smaller inclusions and larger abundances of secondary and pseudosecondary inclusions. The Burkesville deposits also contain less relative Pb abundance than the MVT deposits to the northwest.

Differing mineralogies and inclusion properties between the Burkesville and KY-IL MVT ores indicate differing paragenetic and diagenetic conditions, suggesting that fluids of different origins than the KY-IL MVT ores are responsible for the formation of the Burkesville deposits. LA-ICP-MS, SEM, and microthermometry analyses of inclusion and matrix material from Burkesville and other MVT sites are being obtained to quantify chemical compositions. Results will be used to determine temperatures of formation and identify trace elements present in both regions to narrow the possible sources of primary mineralizing fluids. Current models suggest interaction of base metal brines from the Appalachian Basin and sulfur brines from the Ozarks during two or more of the Appalachian orogenies.