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Fluid inclusion constraints on the uplift history of the metamorphosed massive sulphide deposits at Ducktown, Tennessee.
Hall-DL; Bodnar-RJ; Craig-JR
J Met 1991 Jan; 9:551-565
Standard petrographic, microthermometric, and raman spectroscopic analyses of fluid inclusions from the metamorphosed massive sulphide deposits at Ducktown, TN, indicate that fluids with a wide range of compositions in the c-o-h-n-s-salt system were involved in the syn- to post-metamorphic history of these deposits. Primary fluid inclusions from peak metamorphic clinopyroxene contain low-salinity, h2o-ch4 fluids and calcite, quartz, and pyrrhotite daughter crystals. Secondary inclusions in metamorphic quartz from veins, pods, and host matrix record a complex uplift history involving a variety of fluids in the c-o-h-n-salt system. Early fluids were generated by local devolatilization reactions, while later fluids were derived externally. Isochores calculated for secondary inclusions in addition to the chronology of trapping and morphological features of primary and secondary fluid inclusions suggest an uplift path that was concave toward the temperature axis over the pressure-temperature range of 6 to 3 kbar and 550 to 225 deg. C. Immiscible h2o-ch4-n2-nacl fluids were trapped under lithostatic to hydrostatic pressure conditions at 3 to 0.5 Kbar and 215 +/- 20 deg. C, and the fluids may have been derived by tectonically driven expulsion of pore fluids and thermal maturation of organic material in lower-plate sedimentary rocks. Episodic fracturing and concomitant pressure decreases in upper-plate rocks, which host the ore bodies, would have allowed these fluids to move upward and become immiscible. Post-alleghanian uplift appears to have been temperature-convex.
IH; Final Contract Report; Journal Article
Journal of Metals
TN; VA; DC
Virginia Poly Institute & State U.
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