Dneiper Granite Prospect - evaluation of the copper potential

Abstract

The Dneiper Granite forms the central part cf a regionally metamorphosed complex. True granite rocks form only about 20 percent of area mapped as Dneiper Granite. The remainder of the Dneiper complex is composed of a series of gneisses schists quartzites granulites and gneissic granite and granodiorite rocks. The two gneissic rocks are thought to be injection gneisses. Many of the schists granulite and quartzite are highly metamorphosed mudstones shales and siltstones. The granite phase rocks are microcline granites possessing at least two generations of microcline. They are thought to be alkali metasomatised sediments. Intermediate rocks have been found in close proximity to these granites. There is no textural evidence to suggest that these granite rocks crystallized in a volatile rich environment. Graphic textures perthites and micas are noticeably absent. Rock types common in many pophyry copper deposit viz: quartz orthoclase porphyries, quartz porphyries, felsites and quartzose breccia bodies are noticeably absent. Little volcanic or hypabysaal. material is found in the area. Pegmatites show no evidence of pneumatolytic or hydrothermal disposition (injection). The heavy mineral samples collected contained little mineral of economic value The heavy mineral composition was typical of that found in a regional metamorphic complex with limited hydrothermal pneumatolytic activity. Beryl tantalite, fluorite and pyrite including pseudomorphs were absent. The only sulphides seen were found in a pyroxene granulite, and are thought to he an original constituent of the metamorphosed sediment. It is recommended that no further consideration be given to the Dneiper Granite as a source of copper mineralisation.