Xue-Ming Yang

Evidence for evolution of fluorine-chlorine activity in intrusion-related gold systems, southwestern New Brunswick, Canada

Chemical composition of biotite in two groups of Appalachian granitoid intrusions, i.e., Late Silurian to Early Devonian granodioritic to monzogranitic series (GMS), and Late Devonian granitic series (GS), southwestern New Brunswick, was used to constrain volatile exsolution and fluorine-chlorine activity of fluids associated with these gold-related intrusions. Oxidized to reduced I-type GMS rocks appear to have higher magmatic temperatures, variable levels of emplacement, a range of f(O2), and relatively low fHF/fHCl ratios in exsolved fluids, compared to fractionated I-type GS rocks. Reduced GMS intrusions bear higher gold potential, thus may be prospective targets for intrusion-related gold systems in the region.