Geochemical characteristics of hydrothermal sedimentary cherts in the Erlangping Group, East Qinling Range, China

A suite of cherts closely related to Cu-Pb-Zn mineralization is widespread in the Erlangping Group in the East Qinling Range.The silica content of the cherts is generally low.SiO2 is negatively correlated with Al2O3 and Fe2O3/FeO is less than 1.Their characteristics are similar to those of hydrothermal sedimentary cherts.MnO/TiO2 of cherts west of the Nanyang basin is lower than 0.5 and Al/(Al+Fe)is close to that of the Northern Pacific,whereas MnO/TiO2 east of the basin is higher than 0.5 and Al/(Al+Fe)is similar to that of Triassic laminated cherts on continental margins of central Japan.In the cherts,the total REE is low,the heavy REE tends to be enriched,Ce is obviously depleted,and Eu shows positive anomalies,which shows that the cherts in this area is the product of hydrothermal sedimentation.The trace elements such as V,Ni and Cu have the double characteristics of mid-oceanic ridge(or pelagic basin)cherts and continental-margin cherts.