Grasmere 1:100 000 Sheet, Home to a Few Surprises

摘要

Mapping of the Grasmere sheet near Broken Hill was undertaken as part of the Koonenberry Mapping Project, part of the Exploration New South Wales program. This sheet joins Bunda and Kayrunnera as the third, first edition 1:100 000 scale map completed to date. A further two maps, Nuchea and Wonnaminta, are currently in progress and the remainder of the outcropping block is scheduled to be mapped at 1:100 000 scale. The Grasmere map area is within the southern portion of the outcropping Koonenberry Belt which defines the eastern margin of the Curnamona Craton in Western NSW. The belt is separated from the outcropping Broken Hill Block by the northwest striking Bancannia Trough, containing up to 6 km of Devonian and Mesozoic section. The Koonenberry Belt consists of multiply deformed Late Proterozoic and Cambrian sedimentary and volcanic rocks with less deformed, post Delamerian cover sequences that range from Late Cambrian to Cretaceous.The recent mapping has considerably extended the strike length of the horizon prospective for Cu, Zn, Ag and Au bearing massive sulphide mineralisation at Grasmere. The mapping has also located previously undocumented shafts sunk into carbonate altered mafic volcanic rocks, and an undocumented shaft sunk into gold bearing Devonian basal conglomerate. The delineation of the structural framework of the area also offers new exploration possibilities.