The first report of a relic of lawsonite eclogite in the Sambagawa belt, eastern Shikoku, Japan

Abstract

We found lawsonite(Lws)-eclogite(Ecl) facies mineral assemblages in garnet(Grt) in a glaucophane(Gln)-epidote(Ep)-Ecl from the Kotsu area. The main mineral assemblage of the host rock is Grt–Gln–Ep–omphacite(Omp)–phengite–paragonite(Pg)–quartz (Tsuchiya et al., 2010). The Lws-Ecl facies assemblages are Lws inclusions (ca. 20μm), Pg-Ep polyphase inclusions (10-150μm) and Omp inclusions (5-100μm). The stability fields of these assemblages and Grt-Cpx geothermometer (Krogh, 2000) on pairs of Omp inclusions and nearby Grt suggest that Gln-Ep-Ecl of the Kotsu area formed at 590^oC/20kbar after experiencing PT conditions of Lws-Ecl facies at ca. 530^oC/17kbar.