New finding of paragonite–clinozoisite association in garnet from the type locality of Sanbagawa belt (Kanto Mountains, Japan)

Abstract

Paragonite-clinozoisite associated within garnets (pyrope 2-7 almandine 60-64 grossular 10-28 spesartine 1-10 ) was newly found in the type locality of the Sanbagawa schist in the Kanto Mountains, Japan. The composite inclusions were confirmed in prograde-zoned garnet porphyroblasts in garnet-zone metapelites that have a typical pelitic whole-rock composition (Mn/Fe = 0.019, Mg/Fe = 0.381). The garnets also contain mineral inclusions of quartz, albite, phengite, chlorite, rutile, calcite, apatite, and zircon. Phengite in the metapelite yielded a K-Ar age of 67.3 ± 1.6 Ma as the younger part of the Sanbagawa schist in this region. This paragonite-clinozoisite association provides a mineralogical index of high pressure (P)-temperature (T ) metamorphism of the type locality of the Sanbagawa schist. Moreover, the clinozoisite-paragonite composite inclusions within progradezoned garnets suggest a prograde P-T path from the stability of lawsonite and albite.