Radiogenic isotopes and geochemistry of mafic dykes and plutons in the Bakhuis belt, Western Suriname and their relationship to UHT metamorphism

Abstract

Within the Guiana shield, the Bakhuis belt forms a ~30 x 100 km horst-shaped geologic anomaly of UHT granulites and plutonic rocks oblique to the older TTG-greenstone in the north and the younger arc-related CSID-belt to the south. Consequently, the belt has the potential to provide important information on the history of the Guiana shield. The belt consists of a ~2.07 Ga metamorphic suite, which was intruded by ~1.97 – 1.99 Ga charnockitic and mafic bodies (de Roever et al., 2003b; Klaver et al., 2015; Klaver et al., in press; Nanne, 2013; Thijssen, 2015). Together with Thijssen (2015), this thesis forms a comprehensive study of the possible relationship between these mafic bodies and UHT metamorphism. Specifically, this thesis investigates: 1) the petrogenesis of cm-sized hornblende in metagabbroic bodies, 2) the petrography and geochemistry of a 3 x 4 km sized anorthosite body 3) the geochemistry and age of metadolerite dykes and xenoliths in plutonic bodies and 4) strontium, neodymium and hafnium isotope compositions of all presently discovered mafic magmatic bodies in the Bakhuis belt. The age and geochemistry of two types of gabbroic bodies (the Moi-Moi metagabbro and the Charlie gabbro) is described in Thijssen (2015).