Silicon-lead-sulfur isotopic constitution of Shijuli copper deposits of North Qilian Mountains

Shijuli copper deposits are typical Cyprus-type ones in the western part of North Qilian Mountains.On the basis of the silicon-lead-sulfur isotope constitution of the ores and wall rocks in Shijuli ore area, the author thinks that it is volcanic genesis.The δ³⁰Si(-0.9‰～-0.2‰) from jaspilite and quartz of ores show that they are consistent with ones of basaltic rocks.Lead isotope compositions of pyrites and chlcopy rites are similar to those of basalts in the area.Thus, it is considered that the lead from ores comes mainly from altered basalts.However, sulfur in the deposits may be the results of reactions to different degrees between sea-water and basaltic rocks, because δ³⁴S in pyrites and chlcopyrites varies between 1.5‰～8.88‰