FLUID DRIVEN METAMORPHISM ALONG THE CARTHAGE-COLTON MYLONITE ZONE: THE ROLE OF LATE GRANITE INTRUSION, AND REGIONAL FLUID FLOW DURING THE WANING STAGES OF THE OTTAWAN OROGENY: ADIRONDACK MOUNTIANS, NYS

Granulite facies cpx-plag-k-spar-qtz (+/- vesuvianite) calc silicate gneisses (Irish Hill Type: IHG) exposed in the footwall of the Carthage Colton Shear Zone (CCSZ) show evidence for multiple metamorphic/contact metamorphic and metasomatic events occurring during the waning stages of the Ottawan Orogeny (1090-1000Ma). Metasomatic alteration of the Irish Hill Gniess associated with the intrusion and solidification of late Ottawan-aged (Lyon Mountain Series) granite bodies resulted in widespread potassium metasomatism in the surrounding IHG, and produced magnetite+vonsenite (Fe²⁺₂Fe³⁺BO₅)+biotite (minor cassiterite) ore bodies hosted in IHG xenotliths within the granite (Jayville Mine). The transformation from IHG to hornblendite to magnetite/vonsenite biotite ore can be traced in samples taken at the Jayville Mine. Bulk and trace element chemistries show simple lines of descent between the IHG, hornblendite and ore indicating progressive replacement via incongruent dissolution of feldspar, diopside (vesuvianite) and hornblende during fluid infiltration. Fluorine and chlorine contents of biotite coupled with the presence of vonsenite, fluorite, and scapolite (absence of tourmaline) in various ore samples indicate a complex and evolving (HF,HCl, BO₃ CO₂-H₂O) fluid(s) accompanied ore deposition. The source for this fluid is thought to be (in part) derived from the granite intrusive. Temperature and pressure of ore formation is bracketed to 750-630^oC and 3.8-5.0 kbar. CO₂ and chloride rich fluid infiltration is common along and across the CCSZ marked by the widespread replacement of plagioclase by scapolite and appears to mark a separate and more regional movement of fluid along/across the CCSZ. Complex amphibole+quartz +calcite symplectites after cpx in the IHG are believed to have formed via rapid cooling in the presence of or infiltration of a CO₂ (and H₂O) fluid at temperatures ranging from 550-610^oC. This fluid infiltration event may be responsible for post ore scapolite formation in the Jayville deposit. Regional cooling along the CCSZ (Streepey et al. 2001) brackets this event between 1020-980 Ma indicating a complex and fluid-rich late Ottawan history in this region.