Extensive normal faulting during exhumation revealed by the spatial variation of phengite K-Ar ages in the Sambagawa metamorphic rocks, central Shikoku, SW Japan

Metamorphic rocks experience change in the mode of deformation from ductile flow to brittle failure during their exhumation. We investigated the spatial variation of phengite K – A r ages of pelitic schist of the S ambagawa metamorphic rocks (sensu lato) from the S aruta R iver area, central S hikoku, to evaluate if those ages are disturbed by faults or not. As a result, we found that these ages change by ca 5 my across the two boundaries...