H漫画

2001 - David Barlow Memorial Award

Fluid inclusions in garnet have recently been discovered in migmatitic paragneisses in the polycyclic Algonquin domain (McClintock subdomain), Central Gneiss Belt, Grenville Province, Ontario. The host rocks are metapelitic migmatitic garnet bearing gneisses; the fluid inclusions occur in garnet. Two kinds of fluid inclusions are recognized: GSI a, monophase negative crystal shaped inclusions of pure or near pure CO₂; and GSI b, two phase (liquid vapour), aqueous carbonic inclusions. Inclusions may represent end members of an evolving fluid. GSI a inclusions have densities ranging ca. 0.9 1.05 g/cm³. Isochores plotted from GSI a inclusions give P T estimates of approximately 6 kbars at 700^oC. An independent P T estimates from local metapelites gives 726^oC and 7.6 kbars. Monazite age constraints on garnet growth limit the age of the inclusions to sometime after ca. 1474 Ma. The fluid inclusions represent the evolution of fluid in the Algonquin domain trapped at various stages during high-T decompression, ca. 1080 Ma. Other evidence of low aH₂O Grenvillian fluids in the region can be found in the migmatites and granulites of the Muskoka domain.

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Pages: 171
Supervisor: Rebecca A. Jamieson