Zhang X.,Gansu Institute of Geological Survey |
Zhang L.-L.,Lanzhou University |
Wang L.-B.,Lanzhou University |
Liu B.,Lanzhou University |
And 4 more authors.
Journal of Chengdu University of Technology (Science and Technology Edition) | Year: 2015
This paper reports the zircon U-Pb dating and the lithogeochemistry of the small-scale neutral-acidic intrusions in the Wuligou gold deposit in the east of Danghenanshan, South Qilian Mt., and interprets their tectonic settings and the linkage to gold mineralization. Our data show that the emplacement age of the amphibole diorite is 457 ±6.3 Ma. The mass fraction of SiO2 is 48.98% - 59.16%, that of A12O3 is 14.51%-16.77%, that of (K2O + Na2O) is 8.24%-9.47% and that of DI is 58-79, indicating that the amphibole diorite belongs to the ultra-alkaline to alkaline, subaluminous rock series and I-type granitoid rocks. The amphibole diorite is poor in Cr and has low value of Mg#, suggesting that its source rock has many crust materials. The total REE is moderate and LREE is rich, with slightly negative Eu abnormity. The large ion lithophile elements of Rb, Ba, Th, K, U are relatively rich and Nb, Ta, P, Ti are poor. The monzonitic granite belongs to the alkaline rock series, and its total REE is lower than that of the amphibole diorite and its Nb and Ta are more poor. These two types of rocks are originated from the same magma source. The differentiation of the monzonitic granite is higher than that of the amphibole diorite. They have geochemical characteristics of the island arc magmatic rock, and formed in the island arc when the north margin of Qaidam subducted beneath South Qilian during middle-late Ordovician. The Wuligou gold deposit is temporally and genetically related to the intrusions, because the alternation and the mineralization occur in the intrusion's contact zones, and the Au content is extremely higher than that in the crust. All these show that the intrusions provide both the met allogenic materials and the thermal fluids for the formation of the gold deposit.