Abstract

Well-preserved eclogitic rocks near Faro (Yukon-Tanana terrane, Canada) underwent a prograde evolution from ∼510 °C and ≥ 1.1 GPa to 690 °C and ≥ 1.5 Gpa followed by near-isobaric cooling to ∼540 °C. A remarkable feature of the garnet porphyroblast cores is the presence of minute garnet “inclusions” of distinctly different composition. Preservation of a sharp compositional gradient at the interface between the host and the inclusion garnets and results of diffusion modeling indicate that the counterclockwise pressure-time evolution took place on a very short time scale of about 0.2 m.y. Minimum rates of heating (950 °C/m.y.) and burial (7 cm/yr) calculated along the prograde part of the path are in good agreement with values extracted from thermal models of newly initiated subduction zones.

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