Discussion on metallogenesis of Zhaojinggou Ta-Nb deposit in Inner Mongolia: Evidence from amazonitization and albitization granite geochronology and geochemistry

The petrogenesis and mineralization of Zhaojinggou Nb–Ta deposit, Inner Mongolia: Evidence from geochronology, rock, and mineral geochemistry

“…The reason why Nie's et al (2013) ages are inconsistent with most scholars may be that his study objects are the Hercynian and Indosinian ore‐bearing intrusive complexes replaced by the Yanshanian ore‐forming fluids. The author's previous study reported magmatic and hydrothermal zircon U–Pb ages of 116 ± 2 Ma and 112.8 ± 2.2 Ma from the amazonitization granite, and hydrothermal ziron U–Pb age of 118.9 ± 1.8 Ma from the AG (X. Li et al, 2021). CGMs is the main Ta–Nb‐rich mineral in the deposit, 18 analyses of CGMs from the AGP yielded a weighted mean 206 Pb/ 238 U age of 116.9 ± 1.4 Ma, Which is nearly coeval with those ages reported by L. Zhang and Jiang (2021) and X. Li et al (2021).…”

“…The author's previous study reported magmatic and hydrothermal zircon U–Pb ages of 116 ± 2 Ma and 112.8 ± 2.2 Ma from the amazonitization granite, and hydrothermal ziron U–Pb age of 118.9 ± 1.8 Ma from the AG (X. Li et al, 2021). CGMs is the main Ta–Nb‐rich mineral in the deposit, 18 analyses of CGMs from the AGP yielded a weighted mean 206 Pb/ 238 U age of 116.9 ± 1.4 Ma, Which is nearly coeval with those ages reported by L. Zhang and Jiang (2021) and X. Li et al (2021). Different minerals in Zhaojinggou Nb–Ta deposit record the time of different magma‐hydrothermal stages.…”

“…The diagenetic and metallogenic process of Zhaojinggou deposit is as follows (Figure 15): in the late Early Cretaceous, the crust in the study area changed from the north–south compression deformation system to the north–south extension deformation system under the action of gravity, and the mantle upwelling caused the high position underplating of basaltic magma, which made the Nb–Ta‐rich Zhaertaishan Group and Baiyun Obo Group partially melt, and the incompatible elements Nb and Ta preferentially entered the melt and were pre‐enriched. Marine strata such as limestone in Zhaertaishan Group are enriched in F, Cl, and H 2 O, so the contents of volatile fraction in magma are high (X. Li et al, 2021). In the process of the primary magma rising, the contents of Nb and Ta in the melt are constantly enriched because of the strong incompatibility of Nb and Ta, and the high volatile fraction in magma.…”

“…The Zhaojinggou Nb–Ta deposit, located in Wuchuan County, Hohhot City, Inner Mongolia Autonomous Region, is one of the granite‐type rare metal deposits discovered in recent years, with controlled oxide reserves close to 9000 t and associated components such as Rb, Li, Zr, Hf, Cs, and Ce (Chai & Wu, 2013). Previous studies on the geochronology of Zhaojinggou Nb–Ta deposit based on field observations, and dating methods for U–Pb of zircon, cassiterite, monazite, and columbite‐group minerals (CGMs), as well as 40 Ar‐ 39 Ar isotope of muscovite and biotite (Gao et al, 2017; X. Li et al, 2021; Z. D. Li, Li, Cui, et al, 2019; Nie et al, 2013; Y. Sun, 2013; Wei et al, 2020; Wu et al, 2020; C. Zhang et al, 2019; L. Zhang & Jiang, 2021), however, different dating methods have different results in a single deposit.…”

“…Sun, 2013; Wei et al, 2020; Wu et al, 2020; C. Zhang et al, 2019; L. Zhang & Jiang, 2021), however, different dating methods have different results in a single deposit. In addition, there are great bifurcations on the genesis and Nb–Ta enrichment mechanism of Zhaojinggou Nb–Ta deposit; some scholars believed that the metallogenic mechanism is that Na‐rich calc‐alkalic magma evolved by multi‐stage and high differentiation (Chai & Wu, 2013; Z. D. Li, Li, Cui, et al, 2019; J. K. Li, Li, Wang, & Li, 2019; Nie et al, 2013), while most scholars believed that is the result of magma crystallization and hydrothermal metasomatism (X. Li et al, 2021; Wei et al, 2020; Wu et al, 2020; C. Zhang et al, 2019; L. Zhang & Jiang, 2021). Previous studies mostly focused on the metallogenic stage, but lacked the understanding of the whole mineralization.…”