A FLUID INCLUSION AND STABLE-ISOTOPE STUDY OF THE PROTEROZOIC BIDJOVAGGE AU-CU DEPOSIT, FINNMARK, NORTHERN NORWAY

The Bidjovagge Au-Cu deposit, northern Norway, hosted within a shear z one in the Early Proterozoic Kautokeino greenstone belt, is more base metal-rich than Archaean mesothermal gold deposits. An early phase of gold and copper mineralization is hosted by sheared albitic felsites, within an alteration and oxidation zone to graphitic schists, along wi th a series of syenodiorite dikes. Fluid inclusions related to gold mi neralization comprise varying amounts of H2O, CO2, CH4, and salt, havi ng salinities between 30 to 45 wt % NaCl equivalent. Zonation of the f luid inclusions exists with CH4 predominantly in the ore zone. Microth ermometric data indicate that fluid trapping occurred between 300 to 3 75-degrees-C and 2 to 4 kbars. Carbon-isotope data display a trend fro m - 0.7 parts per thousand in the footwall to - 4.6 parts per thousand within the ore zone. Fluid inclusion and carbon-isotope data suggest that redox reactions between the fluid and the graphitic schists resul ted in gold precipitation from chloride complexes.