Local Geology Geology In the project area the oldest (Ordovician) rocks of the Regional Geology Coombing Formation comprise tremolite schists, biotite Kempfield lies within the Lachlan Fold hornfels, a porphyritic andesite and black carbonaceous slate. Belt, straddling the boundary between Unconformably overlying these rocks are the Kangaloolah the Molong High to the west, and the Volcanics, a felsic volcanic-derived sequence of sediments and Hill End Trough to the east. The minor volcanics which can be sub-divided into three units; boundary between these two units is • a sequence of fine grained and quartz-phyric an imbricate thrust fault zone known tuffaceous rocks separated by a fault from; as the Copperhania Thrust. • volcanoclastic sedimentary rocks with high Mineralisation at Kempfield is hosted in felsic volcanic rocks background in lead, zinc and barium. In the upper known as the Kangaloolah Volcanics. These have been in- part of the sequence is minor allochthonous faulted and folded into Middle Ordovician meta-sediments of crinoidal limestone/dolomite and massive barite, the Coombing Formation, along the Copperhania Thrust. that grades up into; The Coombing Formation meta-sediments include mudstone, fine quartz sandstone, and actinolite schist. To the south the • barren siltstone with low background lead, zinc and Kangaloolah Volcanics are locally terminated by the intensely barium. foliated and marginally altered Kempfield Granodiorite of The mineralised barite-rich horizons occur near the Silurian age. boundary of the two latter units. Mineralisation The Kangaloolah Volcanics belong to the Late Silurian Mumbil Group, comprising sub-marine, carbonate-shale facies The geology and mineral assemblage is consistent with the interspersed with extensive felsic volcanic piles. These grade distal portion of a volcanic-hosted base metal sulphide conformably upwards into turbiditic sandstone and siltstone deposit or VHMS. sequences in a generally deepening depositional environment. The primary (sulphide) mineralogy comprises pyrite, These turbiditic rocks are known as the Campbells chalcopyrite, galena, sphalerite, argentite, tetrahedrite, native Formation and at Kempfield comprise siltstone, sandstone silver (in tetrahedrite) and pyrargyrite. Silver is present in and andesitic tuff. tetrahedrite, native silver, pyrargyrite and argentite. The All the above rocks near Kempfield are now metamorphosed gangue is primarily barite with lesser quartz and sericite. In to lower greenschist facies. the oxide zone chlorargyrite has been identified.