GRANITOIDS FROM THE MARGATE TERRANE AND THEIR IMPLICATIONS FOR TECTONO-MAGMATIC MODELS OF THE NATAL METAMORPHIC PROVINCE (SOUTH AFRICA)

摘要

Accepted models suggest that the c. 1.21 to 1.02 Ga Margate Terrane is one of three volcanic arc-like terranes that form the Natal Metamorphic Province in South Africa. Integration of new and compiled geological mapping and whole rock geochemical data, however, shows that -83% of bedrock exposure of the Margate Terrane is formed of ferroan to magnesian alkali-calcic granites that are more typical of petrogenesis within thick continental-like crust. Prominent negative Nb and Ti anomalies, as well as relatively low Sr furthermore suggest petrogenesis above a subduction zone and/or derivation from juvenile volcanic arc-related rocks. Exposures of volcanic arc-like lithologies, on the other hand, comprise just -9 of all bedrock in the Margate Terrane and only -2 the granitoids. An alternative interpretation is therefore presented that suggests most of the "Margate Terrane" is in fact a -1.09 to 1.02 Ga granitic batholith.