Trace element composition of quartz from porphyry systems: a tracer of the mineralizing fluid evolution

Abstract

Trace element composition of hydrothermal quartz reflects the P-T-X conditions of the mineralizing fluids and can be a potential tracer of the fluid evolution. To explore this potential, quartz trace element data from 21 porphyry Cu-(Au-Mo) and epithermal polymetallic deposits were compiled. In addition, quartz trace element data from six granite-related systems (granite, pegmatite, greisen, Sn-W-Mo veins) and from a subset of calc-alkaline arc-related volcanic rocks were also compiled for comparison. For porphyry Cu-(Au-Mo) deposits, quartz compositions are from publications in which the sequence of quartz-bearing veins and their potential reopening were documented as well as their precipitation temperatures and pressures. The compiled dataset shows that trace element composition of quartz continuously evolved between the different porphyry veins and quartz generations (A, B, C, D, and E). The observed evolution reflects the cooling and/or compositional variations of the hydrothermal fluids. The quartz Al/Ti, Sb/Ti, Ge/Ti, and (Sb+Ge)/Ti ratios allow for the discrimination of quartz from different vein generations of porphyry Cu-(Au-Mo) deposits. This study shows that quartz composition preferentially combined with cathodoluminescence images is an efficient proxy for tracing the evolution of the hydrothermal fluids in porphyry systems and can be used as a vectoring tool to target the centers of porphyry systems.