The St. Lawrence prospect, Seeley’s Bay, SE Ontario: a potentially economic high-P wollastonite skarn in the Frontenac Terrane.

CIM Vancouver 2002
Alan H Clark, Robert A Vasily,
Abstract Tassos A. Grammatikopoulos, Lakefield Research Limited, 185 Concession St., Lakefield, ON, Canada, K0L 2H0
Alan, H. Clark, Dept. of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON, K7L 3N6
Robert Vasily, St. Lawrence Wollastonite, 6675 Hwy 15, Seeley’s Bay, Ontario Canada K0H 2N0

The St. Lawrence prospect is a large wollastonite skarn (ca. 9 Mt @ ar. 41.3% wollastonite) adjoining the gabbroic-to-syenitic Leo Lake pluton in the granulite facies of the Frontenac Terrane of the Grenvillian Central Metasedimentary Belt. It occurs within a horseshoe-shaped horizon of quartzite, open to the east. The skarn is limited to a 1.2 km2 area, and comprises wollastonite-dominant, wollastonite-clinopyroxene, and diverse quartz-feldspar-sulphide
(-titanite) layers interbanded with, and strongly folded within, the quartzite.

As in the world-class wollastonite deposits of the Willsboro district, New York State, no carbonate protolith is preserved and calcite is a negligible constituent of the mineralized zones. Wollastonite development is nonetheless ascribed to metasomatism of a metacarbonate unit by magmatogene, silica-rich, CO2-poor (XCO2 < 0.05) fluids, at P = 350 MPa and ca. 560C, or, alternatively, 550 MPa and ca. 630C.

Several potentially-economic zones, averaging 40 %, but locally exceeding 70%, of translucent, white, tabular wollastonite grains, with lengths of 0.2 - 2 cm, have been delimited by drilling. Preliminary beneficiation studies yield high aspect-ratio and high-purity (low Fe and Mn) concentrates.

Canada currently has no commercial wollastonite production, but the St. Lawrence prospect is positioned to become a successful entrant. It exhibits satisfactory mineral characteristics and tonnages, and a favourable location with respect to shipment, labour and power, and would benefit from a low Canadian dollar.

Keywords: St. Lawrence wollastonite, Processing, Geology, Mineralogy
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