Hydrothermal scheelite precipitated in fault-veins at Paradise, Bonnie
Jean, Davidson's and Glenorchy mines display chemical variability involving REE
patterns that are transitional between two end-member types. Type I is a
MREE-enriched pattern with no or a small positive Eu anomaly. Type II is a flat
to MREE-depleted pattern with a strong positive Eu anomaly. The chemical
inhomogeneity of these scheelites can be explained by a model of fractional
precipitation of REE, with preferential removal of MREE from the fluid during
precipitation of scheelite. Irrespective of the mechanism responsible for
scheelite precipitation, the source of dissolved constituents is different for
scheelites from the Paradise Mine. Bonnie Jean, Davidson's and Glenorchy
scheelites formed from LREE-enriched fluids whereas Paradise scheelites
precipitated from fluids that were lower in LREE. These inferred fluid
characteristics cannot be linked unambiguously to specific source rocks in the
region, but could suggest that scheelite deposited in the Paradise fault-vein
reflects a more mafic source of REE possibly greenschists, whereas the REE in
scheelite from the other mines suggest a more felsic source.