Geochronology, geochemistry, and Hf isotopes of the Jiudinggou molybdenum deposit, Central China, and their geological significance

Abstract

The Jiudinggou molybdenum deposit is situated along the southern margin of the North China Block and belongs to the East Qinling molybdenum belt. Molybdenum mineralization in the deposit is primarily takes place in a skarn zone where the Yanshanian granitoid pluton (Daping pluton) is in contact with older carbonate strata. We obtained an isochron Re-Os age of 141.1 ± 2.5 Ma for molybdenite from the Jiudinggou molybdenum deposit, which correlates well with the zircon U-Pb age of the Daping pluton of 141.2 ± 0.5 Ma, the host rock of the molybdenum deposit. The Daping pluton is a high-K, Si-rich, calc-alkaline granite with metaluminous to weakly peraluminous characteristics. Its chondrite-normalized REE patterns show moderately negative Eu anomalies and no Ce anomaly. Its primitive mantle-normalized elemental patterns indicate enrichment in LREEs (Light Rare Earth Elements) and LILEs (Large Ion Lithophile Elements), and depletion in HFSEs (High Field Strength Elements). These geochemical features are similar to those of highly fractionated I-type granites. Its zircon ϵHf(t) values and two-stage model ages (TDM2) range from -28.0 to -10.5 and 1857 to 2949 Ma, respectively, which indicate that the source material for the Daping granitoid pluton was derived from the remelting of subducted continental crust of the Yangtze Block. The geochronologic and geochemical analyses of the Jiudinggou molybdenum deposit and the molybdenum-related granite (Daping pluton) indicate that the observed molybdenum mineralization is closely related to a magmatic evolution under a transition in the tectonic regime from compression to extension during the Late Jurassic to Early Cretaceous.