Relationship between Shear Zones and Sr Isotope Compositions of Granitic Rocks in the Hida Belt, Japan

Abstract

The dextral shear zones in the Hida belt, central Japan, show close temporal and spatial relationships with some of the Late Triassic to Early Jurassic Funatsu granitic intrusions. The Sr isotopic compositions of intrusions associated with the shear zones suggest large crustal contributions to the magma chemistries. In contrast, granitic intrusions not accompanied by shear zones show less crustal signatures. Various models could possibly explain the genetic relationship between shear zones and granitic magmas with crustal isotope characteristics, though it is not clear which model is most applicable. It is suggested that contrasting characteristics in the two types of intrusions reflect different stress conditions. The granitic rocks without large crustal contributions are likely to be the products of extensional stress conditions. Those with a larger amount of crustal contamination seem to be generated in compressional stress situations that accompanied the development of ductile shear zones along the co...