Copper and gold in skarn at Brown's Creek, Blayney, N.S.W.

Abstract

Abstract Mineralisation at Brown's Creek, Blayney, N.S.W., occurs in calcsilicate skarns at the contact between the Carcoar Granite and Ordovician limestones within the Angullong Tuff. Stratabound skarns have formed at the contact between limestone and several interbedded tuffaceous mudstone units. Vein‐skarns in the limestone emanate from several sub‐vertical fractures, and are possibly derived from underlying stratabound skarn. Within the calcsilicate skarns, several discrete mineral assemblages represent increasing degrees of carbonate replacement. Stratabound skarns, consisting of fine‐grained bands of quartz, calcite and idocrase alternating with bands of epi‐dote and sulphides, indicate a period during which diffusion processes were effective. Coarse‐grained stratabound skarn is comprised of wollastonite, garnet, diopside, sulphides (pyrrhotite, chalcopyrite, arsenopyrite, tennantite) and gold. Vein‐skarns are also composed of wollastonite, garnet and diopside, but are accompanied by bornite, chalco...