Origin of hydrous cordierite and isotopically light oxygen in granulite-facies rocks, Strangways Range, Central Australia

Abstract

AbstractThe origin of hydrous cordierite from a granulite-facies terrain in the Strangways Range, Central Australia, reported by Wilson (1978) is reviewed. In the light of geochemical and microstructural evidence for a metasomatic episode which affected the terrain subsequent to the growth of the cordierites, it is contended that the hydrous character of the cordierites results from hydration of the cordierite at this time. Extraneous argon also recorded in these cordierites may either have been incorporated into the cordierites at this time or at a later stage in the history of the terrain due to partial loss of radiogenic argon from micas which grew during the metasomatic episode. Furthermore, in view of the history of these cordierites, oxygen isotope values for the cordierites reported by Wilson are likely to be anomalous, and the isotopically light oxygen in the host granulites recorded by Wilson and Baksi (1978) probably reflects exchange with the metasomatic fluids which permeated the terrain.