Geochemical Characteristics of Hydrothermal Cherts of Erlangping Group in East Qinling and Their Geologic Significance

Key words: 
• East Qinling Mountain

Abstract: The genetic study of the cherts in Erlangping Group is the key to reveal copper polymetallic deposits genesis and tectonic setting of Erlangping Group.By studying the geological and geochemical characters of the three types of cherts in Erlangping Group in the east Qinling orogenic belt, it is believed that the cherts in Erlangping Group are hydrothermal sedimentogenic rocks. The major elements characteristic value (N(Al)/N（Al+Fe+Mn）) indicates that the cherts were formed in different marine environments .The cherts formed at the west of Nanyang basin were deposited in continental margin basin environment, but those formed at the east of Nanyang basin were deposited in pelagic environment and had a little of material from the continental margin. Comprehensive analysis of rare earth elements geochemistry(negative Eu ,Ce anomaly) and geologycharacteristics of the cherts show sthat the cherts of Erlangping Group are formed by the mixing of backarc basin type hydrothermal solutions of low temperature and seawater, so a new evidence is provided to determine the backarc basin tectonic setting of Erlangpin Group.The paragenetic relationship of hydrothermal sedimentogenic cherts and copper polymetallic deposits manifest that the copper polymetallic deposits are formed by the submarine hydrothermal exhalative lithogenesis and mineralization.