Geochemistry and Genetic Significance of the Yin'aocao Marine Facies Volcanic Type Zn-Cu Deposits in Qilian Mountains, Qinghai Province

The Yin'aocao Zn-Cu deposits are an important polymetallogenic area in Qilian Mountains, Qinghai Province. The previous work in this area is less. Combined with basic geological characteristics,the geochemical characteristics of the volcanic rocks and the S-Pb isotope of this deposit have been studied in this paper. The volcanic rocks from this deposit have high SiO₂(6.96%~53.85%) and TiO₂(0.90%~2.02%) contents,enriching large ion lithophile elements (Rb,Ba and K), with relatively loss of high field strength elements(Nb, Ta and Ti), positive Eu anomaly and negative Ce anomaly characteistics. These geochemical characteristics show the characteristics of and-arc tholeiite and N-MORB.The volcanic rock magma was derived from the depleted mantle and formed in the extension setting of arc back basin. The zinc and copper mineralization was caused by many geological factors related with volcanic rock, including material source, ore-bearing wall rocks and fluid channel. The zinc ore was mainly occurred in silicified maeble, while the copper mineralization was main; y occurred in the contact zone between marble and schistositized basalt.