Grenville Marble-Hosted Zinc Mineralization at the Salerno Lake Deposit, Canada: Stratigraphic, Mineralogical, and Lithogeochemical Constraints

Abstract

Previous studies in the zinc mineralization hosted in the high-grade metamorphosed marbles of the Grenville Supergroup suggest that the zinc mineralization formed syngenetically with the sedimentation of the carbonate sequence (SEDEX-type). However, observation of drill cores, mineralogical composition of rock types, texture of mineralized samples, paragenesis, and lithogeochemistry data reveal that magmatic- hydrothermal fluids may have contributed to the formation and/or transformation of the zinc mineralization. The main ore mineral, yellow and red sphalerite occurring as disseminated, banded, and semi-massive, is hosted mainly in the dolomitic marble units containing up to 25 % silicate minerals (dominantly phlogopite, tremolite +/- diopside), which are intercalated with siliciclastic, calcitic marble, diopside-tremolite dolomitic marble, pyritic dolomitic marble, and quartz-diopside rich marble. The sedimentary sequence is cut by syenite and calciocarbonatite intrusions exhibiting contact metasomatic zones with endoskarn and exoskarn alteration. Most of the intrusive rocks were found in close proximity (1-10 m) to the zones with higher grade zinc, and sphalerite was found included in calcite in a sample of calciocarbonatite. Significantly, enrichment of Ag, As, Co, K2O, Rb, and REE in both intrusions and mineralized zones proximal to the intrusions compared to the distal dolomite marbles may suggest magmatic fluid-rock interaction. Furthermore, zinc enrichment in the siliciclastic rock, which does not typically contain high concentrations of zinc, was found in proximity to the calciocarbonatite intrusion. Nevertheless, we cannot exclude the possibility that zinc mineralization has occurred during sedimentation and was transformed or enriched during a subsequent magmatic event. In this case, the permeable zones that acted as conduits for the early mineralizing fluids could have been exploited by the magma. This could explain the early occurrence of pyrite and yellow sphalerite during an early event (exhalative?) and red sphalerite in higher- grade zinc zones found in close proximity to intrusions. However, further research is required to verify this hypothesis.