Stratabound Zinc Mineralization at the Salerno Lake and Calumet-Sud Occurrences hosted in the Proterozoic Central Metasedimentary Belt Marbles of the Grenville Province, Canada

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Lang, Hannah
Zinc , Economic Geology , Grenville Province , Metamorphism , Central Metasedimentary Belt , Grenville Supergroup , Skarn
High-grade marbles of the southeastern Central Metasedimentary Belt in the Grenville Province host several stratabound zinc deposits and occurrences, interpreted in previous work to have been formed from exhalative brines during carbonate sedimentation (SEDEX-type). However, the results from detailed mapping, paragenesis, mineral chemistry, and lithogeochemistry at the Salerno Lake (Ontario) and Calumet-Sud (Quebec) occurrences revealed that syenite, carbonatite, and felsic intrusions occur proximal and may have contributed to the zinc mineralization. At the Salerno Lake occurrence, yellow (Fe- and Mn-poor), intrusion-proximal sphalerite is associated with apatite displaying elevated concentrations of F, Na2O, and SO3, similar to apatite in the intrusive rocks. Moreover, both the proximal hydrothermally altered marble and meta-syenite contain elevated K2O, Al2O, TiO2, Ba, Sr, Rb, Ce and Nd. Red sphalerite (Fe- and Cd-rich) occurs as overgrowths on yellow sphalerite in the proximal zones and extends along bands in the distal zones and is associated with apatite and graphite. Calumet-Sud shares similar mineralogical relationships. I propose that the marble-hosted zinc mineralization is epigenetic and had input of fluids that exsolved from or interacted with the alkaline magmatic rocks particularly in the proximal zones. The stratabound controls on sphalerite mineralization is interpreted to be due to the interaction of magmatic and possible basinal mineralizing fluids with favorable reduced-carbonate layers rich in organic matter and phosphate. Amphibolite-facies metamorphism and deformation have caused changes in the textures of the ore, but the compositional signature of the mineralized zones is interpreted to represent that of the original hydrothermal system.
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