Abstract
The Wulandele molybdenum deposit is a porphyry-type Mo deposit in the Dalaimiao area of northern Inner Mongolia, China. Molybdenite Re-Os dating yields a model age of 134.8 ± 1.9 Ma, with the fine-grained monzogranite most closely related to the mineralization. The lithogeochemical data show that the monzogranite is weakly peraluminous, high-K calc-alkaline series, with reduced to slightly oxidized, highly fractionated I-type granite characteristics. The relatively low initial 87Sr/86Sr (range from 0.705347 to 0.705771), weakly negative εNd(t) (range from −2.0 to −1.3), and crust-mantle mixing of Pb isotopes suggest that the monzogranite originated from the partial melting of mafic juvenile lower continental crust derived from the depleted mantle, with a minor component of ancient continental crust. Combined with the regional tectonic evolution, we argue that the partial melting, then injection, of the monzogranite melt was probably triggered by collapse or delamination of the thickened lithosphere, which was mainly in response to the post-orogenic extensional setting of the Mongol–Okhotsk belt; this is possibly coupled with a back-arc extension related to Paleo-Pacific plate subduction. The extensively fractional crystallization of the monzogranite melt is the crucial enrichment process, resulting in magmatic hydrothermal Mo mineralization in the Wulandele deposit, and the Cretaceous granitoids are generally favorable to form Mo mineralization in the Dalaimiao area.
Highlights
The Mo mineralization age of the Wulandele Mo deposit can be considered as early Cretaceous
We suggested that the Mo mineralization age of the Wulandele Mo deposit can be considered as early Cretaceous
The geological investigations show that the disseminated Mo mineralization mainly occurs inner to the MG or along the contact zones between the MG and its wall rocks (QD and GD), which implies that the MG has a closer spatial relationship with Mo mineralization
Summary
In the past two decades, several molybdenum deposits, such as the Wulandele, Wurnitu, Zhunsujihua, Wuhua’aobao, and Dalaiaobao molybdenum deposits, have been found in the Dalaimiao area, which is located in the southwest of Xing’an-Mongolia Orogenic Belt (XMOB) [1,2,3,4,5,6] (Figure 1) These molybdenum deposits have close temporal-spatial relationships with intermediate-felsic intrusive rocks, and most of them formed in late Jurassic to early Cretaceous, except the Zhunsujihua Mo deposit, which formed during the late Carboniferous to early Permian [1,2,3,4,5,6]. Tao et al [1,7] reported a molybdenite Re-Os isochron age of 134.1 ± 3.3 Ma and zircon SHRIMP U-Pb dating of 131.3 ± 1.6 Ma for the MG, and suggested that
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