Combined Petrologic, 40Ar/39Ar, and Fluid Inclusion Study ofan Inverted Metamorphic Sequence, Maclaren Metamorphic Belt,Alaska

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Continued field and lab studies of the Maclaren metamorphic belt are proposed to determine the thermal and tectonic history of these rocks, which occur in a suture zone between accreted terranes in South-central Alaska. The belt is an example of inverted metamorphic rocks which grade upward in temperature. Syntectonic tonalite sills are associated with the higher grade rocks but the thermal gradient is interpreted as being caused by thrusting of hot, deeper crust rocks over a thick sediment package during continent - continent collision. They are exposed by subsequent uplift and erosion. The aim of the research is to determine P-T history from which magnitude of uplift can be estimated. Ar-Ar geochronology will be used to estimate uplift rates. These results will be used to interpret the tectonic history and causes for heating.