Skarn mineral characteristics of the Tiantang Cu-Pb-Zn polymetallic deposit in Guangdong Province and their geological significance

The large Tiantang Cu-Pb-Zn polymetallic skarn deposit in Yuexi area is hosted in limestone of Devonian Tianziling Formation,and the ore bodies occur in the skarn and skarnized marble in stratoid,lamellar,lenticular and irregular forms.Metallic minerals consist mainly of chalcopyrite,galena,sphalerite and pyrite,whereas gangue minerals are composed of garnet,diopside,epidote,wollastonite,chlorite etc.With skarn minerals as the study object and by using electron microprobe technology,the authors investigated the mineralogical characteristics.Electron microprobe analyses show that the skarns in the Tiantang Cu-Pb-Zn polymetallic deposit belong to typical calcic skarns.Garnets in the ore deposit are mainly andradite-grossularite and varied with time from grossular to andradite,suggesting that the ore-forming fluid had a evolutionary trend from acidic to basic.Augites are mainly diopside.Components of garnet and proxene are Adr4.60~96.47Grs2.10~94.28(Prp+Sps)0.41~3.88 and Di88.51~95.09 Hd3.31~9.76 Jo0.28~3.98,respectively,and their wide compositional variation range suggests that skarns were not formed under a totally enclosed equilibrium condition.The end member of the epidote group is dominated by epidote,and contains a little zoisite.The Mn/Fe ratio of pyroxene may be related to mineral metals.Characteristics of skarn in the Tiantang Cu-Pb-Zn polymetallic deposit shows that it is a typical skarn deposit resulting from the replacement of the marble by granitoid magma.