Carbonate is an important component of gold-bearing quartz veins in the Klondike district, and also makes up an under-recognized proportion of the Klondike schist host rocks. The predominantly metavolcanic Klondike schist contains carbonate as disseminated porphyroblasts and as coarse quartz-carbonate segregations, and contains rare layers of marble. Chemical staining and LA-ICP-MS analyses reveal that, irrespective of paragenesis, carbonate is dominated by Mg-Fe-Mn calcite. Laser spectroscopic analyses of C and O isotopes reveal that marble is a 13C-enriched isotopic reservoir compared to carbonate in micaceous schist. Carbonate in gold-stage veins has a similar isotopic signature to carbonate in metamorphic segregations and porphyroblasts in the host rocks. We tentatively interpret these results to indicate that the CO2 component of vein carbonate has been remobilized from local sources during brittle deformation. The results of this study may bear on interpreting the scale of rock-fluid interaction during orogenic gold mineralization in the area.
