Genesis and tectonic setting of the Bulage Pb–Zn deposit, Inner Mongolia, China: Evidence from geology, fluid inclusions, EMPA, H–O isotope systematics, zircon U–Pb geochronology, and geochemistry

Abstract

The recently discovered Bulage Pb-Zn deposit is located in the central part of the Erlianhot-Dongwuqi Metallogenic Belt (eastern Central Asian Orogenic Belt) in Inner Mongolia, China. The ore bodies of the deposit are hosted in alkali feldspar granite and in dacitic crystal tuff within Unit 2 of the Carboniferous Baoligaomiao Formation.The Bulage deposit is a low to moderate temperature hydrothermal vein-type deposit and is controlled by fractures. The hydrothermal mineralization can be divided into three stages: early (quartz + specularite ± magnetite), middle (quartz + sphalerite + galena ± chalcopyrite ± pyrite), and late (calcite ± quartz + sphalerite + galena). The deposit contains liquid-rich two-phase (VL-type) and pure-liquid (L-type) fluid inclusions. The initial ore-forming fluids are attributed to the low to moderate temperature and low salinity of a NaCl-H 2 O system. Hydrogen and oxygen isotopic compositions of quartz and calcite indicate that the ore-forming fluids were dominated by meteoric water with minor contributions of magmatic water. The quartz diorite, monzonite porphyry, and alkali feldspar granite in the deposit yield LA-ICP-MS zircon U-Pb ages of 305-300 Ma. These high-K calc-alkaline I-type granitoids are enriched in large-ion lithophile elements (LILEs; e.g., Rb, Cs, and K) and light rare earth elements (LREEs) and are depleted in high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs). The primary magma of these granitoids was derived from the partial melting of lower crust. The parental magma of the quartz diorite may have provided part of the ore-forming material and acted as a heat source for mineralization. Therefore, we infer that the Bulage Pb-Zn deposit was formed as a result of the southward subduction of the Paleo-Asian Ocean beneath the North China Craton during the Late Carboniferous.

Paleoproterozoic Adakitic Rocks in Qingchengzi District, Northeastern Jiao-Liao-Ji Belt: Implications for Petrogenesis and Tectonism

“…In summary, the whole-rock geochemical composition reported in this study shows that the Paleoproterozoic adakitic rocks in the Qingchengzi district are characterized by high Al 2 O 3 and SiO 2 contents and Sr/Y ratios, LREEs and LILEs enrichment, and HREEs and HFSEs depletion ( Supplementary Table S2). Combining the Hf isotopic characteristics, these granitoids are derived from the partial melting of the Meso-Neoarchean thickened lower crust material, consistent with the magmatic rocks formed in the tectonic setting of an active continental margin or island arc (e.g., [83][84][85][86]). In addition, previous studies have shown that the JLJB Paleoproterozoic volcanic rocks (e.g., Liaohe Group) are calc-alkaline series and show the characteristics of I-type granites, and they were formed in an volcanic arc environment [34].…”

Initial decratonization of the eastern North China Craton: New constraints from geochronology, geochemistry, and Hf isotopic compositions of Mesozoic igneous rocks in the Qingchengzi district

“…As mentioned in the previous section, the continent–continent collision between the YZC and NCC during the Triassic represents the initial cratonic destruction in the eastern NCC. However, the subduction and closure of the Carboniferous–Permian Paleo‐Asian Ocean introduced the initial cratonic destruction of the northern margin of the NCC (e.g., Xiao et al, ; Windley, Alexeiev, Xiao, Kröner, & Badarch, ; Safonova et al, ; Pei et al, , Pei et al, ; J. Li et al, ). This denotes that the cratonic destruction of the NCC is heterogeneous (Y. G. Xu, Li, et al, ), and this heterogeneity is related to different dynamic mechanisms.…”

“…The NCC is an Archean to Paleoproterozoic cratonic block, which has been overprinted by the deformational, thermal, and magmatic effects of several Proterozoic orogenies, unlike true Precambrian cratons; in addition, it has been subjected to Phanerozoic accretion, collision, and subduction along its northern, southern, and eastern margins, respectively (Hart et al, ). To the north, the closure of the Paleo‐Asian Ocean occurred during the Late Permian to the Middle Triassic (Xiao, Windley, Hao, & Zhai, ; Li, ; Wu, Li, Yang, & Zheng, ; Wu et al, ; Cao et al, ; J. Li et al, ). In the south, the NCC was affected by the subduction and collision of the continental crust of the Yangtze Craton (YZC) during the Triassic (Dong et al, ).…”