Kempfi eld Silver, Barite and Base Metal (Pb-Zn) Deposit, Lachlan Orogen, Eastern Australia

摘要

The Kempfi eld deposit is located in the Hill End Trough, one of several intracratonic basinsrndeveloped during Silurian–Devonian time, in the eastern province of the Lachlan Orogen, EasternrnAustralia.rnThe deposit contains an oxide resource of 5.8 Mt @ 58 g/t Ag and a sulfi de resource of 14.4 Mtrn@ 45 g/t Ag, 1.7 per cent Zn and 0.6 per cent Pb, classifi ed and reported in compliance with thernJORC Code. The deposit has been previously explored by a number of companies, including INCO,rnShell, Jones Mining, Golden Cross Resources and recently Argent Minerals Ltd (Argent). Argent isrncurrently completing a defi nitive feasibility study with a view to mining the deposit.rnThe deposit is hosted at the boundary between the Molong High to the west, comprisingrnOrdovician sediments and volcanic rocks and the Hill End Trough to the east, interpreted as arnback-arc basin containing Silurian sediments and siliceous-feldspathic volcanic rocks. Thernboundary between these two strato tectonic units is an imbricate thrust fault zone known as thernCopperhannia Thrust.rnThe Kempfi eld deposit is hosted in felsic volcanic rocks known as the Kangaloolah Volcanics.rnThese have been in-faulted and folded into the Middle Ordovician meta-sediments of the CoombingrnFormation of metasediments along the Copperhannia Thrust. The Kangaloolah Volcanics belongrnto the Late Silurian Mumbil Group, comprising submarine carbonate-shale facies interspersedrnwith extensive felsic volcanic piles, which grade conformably upwards into turbiditic sandstonernand siltstone sequences (interpreted to represent a deeper depositional environment). Thesernturbiditic rocks are known as the Campbells Formation, comprising siltstone, sandstone andrnandesitic tuff. The rocks at Kempfi eld are metamorphosed to lower greenschist facies, refl ectedrnthrough the different type of schists.rnSilver, gold, lead, zinc mineralisation is hosted in barite-rich horizons, near the boundary tornquartz-phyric tuffaceous rocks in submarine, immature, reworked felsic ash tuffs. Barite appearsrnto be hosted in greatest concentrations by the coarser grained volcanoclastic sandstones and grits,rnwhilst intercalated siltstones are volumetrically minor and tend to return low barite and silver.rnMineralisation is hosted in stratiform and probably stratabound barite-rich horizons. A northeasttrending,rnsteeply dipping, metamorphic cleavage (S_1) occurs throughout the project area.