MICROTHERMOMETRY OF FLUID INCLUSIONS FOUND IN METAMORPHIC ROCKS FROM THE UCHEE BELT, COLUMBUS, GEORGIA

We have studied the composition and homogenization temperature of fluid inclusions found in high grade metamorphic rocks from the Uchee Belt, which is part of the Appalachian Piedmont in Georgia.  The inclusions were found in quartz grains from a pegmatite within the Phenix City gneiss from Columbus, Georgia.  The pegmatites lie within the foliation of the gneiss and appear to be partial melt generated at peak metamorphic conditions.  The fluid inclusions studied contained three phases, CO₂ gas, CO₂ fluid and aqueous saline fluid.  Three of the inclusions produced isochores that were consistent with entrapment during the rock's return from retrograde metamorphic conditions at  ~524° C and 6 kbar (Chalokwu & Kuehner, Am. Min., 1992). These inclusions belonged to trails of inclusions, indicating that they were secondary in nature and formed from fluids trapped in healed cracks in the quartz.  One of the inclusions had an isochore that was consistent with estimates of peak metamorphic conditions (~750° C and 10 kbar) for the Uchee belt (Chalokwu & Kuehner, Am. Min., 1992).  This inclusion was isolated and decrepitated at a much higher internal pressure than the other inclusions; which is consistent with it being a primary inclusion.  These data can be used to place further constraints on the pressure-temperature path of the Uchee Belt.