Geochronology, petrogenesis and isotopic characteristics of the palaeoproterozoic Gladkop Suite, north-western portion of the Namaqua sector, Namaqua-Natal Metamorphic complex, South Africa
Nke, Ansahmbom Yong
MetadataShow full item record
The Gladkop Suite (GS) granitic gneisses in the Bushmanland Domain (BD) represent one of the oldest rock units in the Namaqua-Natal Metamorphic Province (NNMP), and are located adjacent to the northern Richtersveld Magmatic Arc (RMA). This study represents results of a series of studies on the granitic gneisses which make up the GS, aiming to characterize them, explain their petrogenesis and understand their role in the development of the NNMP. The GS rocks preserved evidence of the 1.0 Ga Namaqua Orogeny, with evidence of an older tectonic event preserved only in metasedimentary xenoliths. The GS is made up of three distinct gneisses, namely: the Steinkopf (STK) Gneiss, the Brandewynsbank (BWB) Gneiss and the Noenoemaasberg (NNM) Gneiss. Petrographically, these rocks range from granites to granodiorites. Quartz, plagioclase and K-feldspar are the principal phases, accompanied by minor amounts of biotite, hornblende, sericite, chlorite ± clinopyroxene and accessory minerals. Geochemically, the granitoids are silica-rich, magnesian, metaluminous to weakly peraluminous with a calcic to calc-alkalic characteristic and were generated in a high-K calc-alkaline series. These rocks invariably show enrichment in light rare earth elements (LREE) and significant negative Eu anomalies. All the granitic gneisses show characteristic negative anomalies in Ba, Ti, Nb, P, Sr and Eu, and a positive anomaly in Pb in the multi-element trace element plot (spider-diagram).