Host: The Japanese Association of Mineralogists, Petrologists and Economic Geologists
To reveal exhumation history of UHPM rocks, isochron ages in K-Ar system are examined with phengite and paragonite in the eclogitic rocks from the Tso Morari complex (TMC), western Himalaya, India. TMC is composed of pelitic gneisses and schists including mafic rock lenses (eclogites and basic schists). Eclogite has coesite pseudomorph in garnet and/or quartz rods in omphacite, suggesting UHPM. Pelitic schist gives an isochron age of 91±13 Ma using K-Ar analyses of paragonite and phengite. Phengite and paragonite in eclogite were analyzed by Ar/Ar method. Step-heating analyses using single phengite crystal showed 132 Ma plateau ages. The inverse isochron age by spot analyses of paragonite and phengite is 130±39 Ma.