Mineralization of the Daolundaba Cu & ndash;Sn & ndash;W & ndash;Ag deposit in the southern Great Xing & rsquo;an Range, China: Constraints from geochronology, geochemistry, and Hf isotope

摘要

The Daolundaba deposit, located in the southern Great Xing?an Range, is a medium-sized Cu?Sn?W?Ag deposit dominated by Cu. The intrusive rocks in the ore district mainly include the Early Permian Qianjinchang mediumgrained biotite monzogranite and the Early Cretaceous Zhangjiayingzi fine-grained granite and porphyritic granite. Cassiterite U?Pb dating for two Cu?W?Sn ore samples yielded ages of 134.7 Ma and 136.8 Ma, respectively. Zircon U?Pb dating for fine-grained granite and porphyritic granite of the Zhangjiayingzi intrusion yielded ages of 134?136 Ma and 135 Ma, respectively. The Zhangjiayingzi intrusion is high-K calc-alkaline and featured by enrichment of Rb, Th, U, K, Nd, Zr, Hf, and Sm and steady depletion of Ba, Sr, P, Eu, and Ti, with extremely negative Eu anomalies and noticeable tetrad effect of rare earth elements, indicating the intrusion has a highly fractionated granite affinity. The Zhangjiayingzi intrusion has high zircon ?Hf(t) values (4.1?10.2) and relatively young zircon Hf two-stage model ages (541?929 Ma), suggesting that it dominated originated from the partial melting of a Neoproterozoic juvenile lower crust. The geochronology and geochemistry indicate that the mineralization of the Daolundaba deposit is closely related to Early Cretaceous highly fractionated granites. Fractional crystallization of granitic magmas is the important controlling factor for the formation of the Zhangjiayingzi highly fractionated granite and the Daolundaba Cu?W?Sn?Ag deposit.