High-pressure K-feldspar - Vesuvianite-bearing assemblage in the central metasedimentary belt of the Grenville Province, Saint Jovite Area, Quebec

A lens consisting largely of calcite, microcline, vesuvianite, quartz, diopside, calcic plagioclase, and wollastonite occurs within calcite marble of the Central Metasedimentary Belt (CMB) of the Grenville Province, in the Saint Jovite area of Quebec. This unusual assemblage exhibits a polygonal granoblastic texture and reflects high-grade phase equilibrium during a Grenvillian metamorphic event. The coarse grain-size of the calcite, microcline, vesuvianite and quartz in patchy zones within the lens is attributed to grain growth in macro-pressure shadows during shearing. There is no evidence for fluid infiltration, but water may have concentrated by solution-transfer into the patches. A T-X(CO₂) phase diagram constructed for ≥6 kbar total pressure suggests temperatures in the order of ≥750°C and X(CO₂) at ∼0.2.