I.—Glaucophane-schist, Eclogite, and Associated Rocks from Knockormal in the Girvan-Ballantrae Complex, South Ayrshire

Abstract

SynopsisGlaucophane-Schists and eclogite are associated with ultrabasic rocks, basic intrusions and Ordovician spilitic lavas at Knockormal in the Girvan-Ballantrae complex, South Ayrshire. Detailed mineralogical and chemical data are presented which indicate that the various glaucophane and blue-amphibole rocks have been derived from spilitic lavas. In addition to glaucophane a blue-amphibole related to crossite is also described. While there is no evidence for an introduction of soda, the deformation attending the glaucophanitic metamorphism was accompanied by chemical changes which appear to have occurred at high water-vapour pressures. There is no evidence of any relationship between the eclogite and adjacent glaucophane-rocks. The eclogite, which is highly aluminous, is interbanded with wehrlite, pyroxenite and serpentinite, and represents a particular phase in the crystallization of these ultrabasic rocks.