Mantle-Derived Peridotites in Southwestern Oregon: Relation to Plate Tectonics

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Science  04 Sep 1970:
Vol. 169, Issue 3949, pp. 971-974
DOI: 10.1126/science.169.3949.971


A group of peridotites in southwestern Oregon contains high-pressure mineral assemblages reflecting recrystallization at high temperatures (1100° to 1200°C) over a range of pressure decreasing from 19 to 5 kilobars. It is proposed that the peridotites represent upper-mantle material brought from depth along the ancestral Gorda-Juan de Fuca ridge system, transported eastward by the spreading Gorda lithosphere plate, and then emplaced by thrust-faulting in the western margin of the Cordillera during late Mesozoic time.

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