FLUID INCLUSION STUDIES IN THE CARTHAGE/COLTON MYLONITE ZONE

The Carthage/Colton Mylonite Zone (CCMZ) is a kilometer(s) wide shear zone that separates rocks of the Adirondack lowlands from those of the Adirondack highlands. Variously interpreted as a major strike slip fault, a low angle normal fault, or a major suture zone, it separates metamorphic rocks of primarily igneous affinity (highlands) from those of a primarily sedimentary protolith (lowlands). Samples were collected from well-exposed outcrops near Colton, NY for the purpose of examining the fluid inclusions to determine the nature of the fluids, the temperature of recrystallization, and the temperature of crystallization of quartz veins cutting the mylonite zone. The mineral assemblage of the gneiss consists of quartz, kspar, plagioclase, biotite, +/- hornblende, +/- orthopyroxene, +/- diopside, +/- garnet. Textures are recrystallized, exhibiting good 120^o angles, so most microstructures are obscured. In the gneisses, fluid inclusions enclosed within quartz grains (not along grain boundaries or linear fractures) yield freezing temperatures averaging -16.5^oC which corresponds to 19.8 equivalent wt% NaCl. In quartz veins, freezing temperatures average -20^oC, which is near the eutectic for the H₂O-NaCl system. The highest homogenization temperatures (Th) for inclusions in quartz grains in the gneiss, uncorrected for pressure, are around 360^oC. Another group of inclusions cluster at Th = 260-295^oC, while a third group clusters at 160-190^oC. This third group corresponds to the Th of inclusions in quartz veins that average about 170^oC.