Metamorphic studies: research in progress

Abstract

A Metamorphic Studies Group meeting on ‘Metamorphic Studies: Research in Progress’ and the eighth Annual General Meeting of the Group were held on 8 March 1989. It was attended by 81 delegates and 13 papers were presented on a range of topics, including an invited contribution from C. Chopin (Ecole Normale Supérieure, Park). Two poster contributions were also presented. The meeting was organized by G. T. R. Droop. The morning session was concerned mainly with high-grade metamorphism and fluid-rock interactions. The first talk was given by R. L. Oliver who gave an account of some hitherto undescribed high- T , high- P Al-rich ferruginous granulites from the western margin of the Gawler Craton, South Australia. Extreme metamorphic conditions of c. 10 kbar and 900–1000°C were inferred from the presence of the assemblage hypersthene + sillimanite + quartz. The coexistence of magnetite and Ti-hematite was taken as evidence for a relatively high oxygen fugacity. The rocks are apparently of much higher grade than those in the interior of the Gawler craton, but show similarities with granulites at the edge of the Yilgarn Block further west. D. J. Waters (with J. M. Moore) described an unusual granulite-facies assemblage of boron-rich aluminosilicate minerals (kornerupine + werdingite + grandidierite + sillimanite) from the highest grade part of the Namaqualand metamorphic complex (the spine1 + quartz zone). They noted that the mobility or otherwise of boron in high-grade metasediments could have important implications for partial melting in view of the effect of this element on the temperature