Geochemical Characteristics and Tectonic Environment of Volcanic Rocks in Suhaitu Arear, Xinjiang

Native copper mineralization has been found in volcanic rocks of Suhaitu formation, with a feature of transition from tholeiite basalts to calc-alkaline basalts. Geochemistry shows that the volcanic rocks have lower TiO₂ content(less than 1%), fewer Rare Earth Elements and high Al₂O₃ content. In addition, their REE pattern is characterized by the weak enrichment of LREE. In the primitive mantle normalized trace element spider diagram, Suhaitu volcanic rocks are characterized by the enrichment of large ion lithophile elements, and deficit of the high field strength element. They have strongly negative anomalies in Nb and Ta, weakly negative anomalies in Ti, and weakly positive anomalies in P and Sm. Their Zr/Nb and Sm/Nd ratios are close to the range of MORB, the value of Th/Nb is larger than 0.11, while the Nb/Zr ratio is less than 0.04. All these characteristics mentioned above suggest that volcanic rocks of Suhaitu formation were typical volcanic arc rocks, their tectonic environment was continental island arc, and its magmas were generated by partial melting of the depleted mantle modified by fluids or sediments.