Calculation of Rare Earth Element Patterns in Magmatic Fluids: Evidence for Origin of the Lake George Sb-Au-W-Mo Ore Deposit, New Brunswick, Canada

ABSTRACT

This contribution illustrates the procedures of calculating rare earth element (REE) patterns of magmatic fluids in equilibrium with granitic melts. These patterns can then be compared to those of altered and (or) mineralized rocks in order to investigate the source of the ore-fluids. This technique is applied to the Lake George Sb-Au-W-Mo mineral deposit, New Brunswick, Canada. The results suggest that ore-fluids are dominated by magmatic fluids, consistent with the origin of intrusion-related mineralization systems. The magmatic hydrothermal fluids emanating from progressively cooling, voluminous and volatile-saturated magma at depth may have reacted with earlier magmatic sulphide minerals formed by liquation in the Lake George granodiorite stock, scavenged ore components (e.g., Au, S) in the sulphides, which would have enhanced ore materials in the ore-fluids and precipitated ore minerals in hydrofractures and preexisting faults that crosscut graphitic country rocks (e.g., greywacke) within the metamorphic halos and resulted in intrusion-related gold-antimony mineralization associated with an earlier W-Mo-(Au) mineralization.

Keywords:

Rare earth element (REE) patterns, partition coefficients, granitoid, intrusion-related gold system, Lake George.