Geochronology and zircon Hf isotope geochemistry of granites in the giant Chalukou Mo deposit, NE China: Implications for tectonic setting

Abstract

In this contribution, the largest porphyry Mo deposit in NE China, Chalukou, is selected to provide insights into the tectonic evolution of NE China. The deposit was considered to be rift-related (or Climax-type) porphyry Mo deposit developed in an extensional setting, while other researchers attributed its formation to the subduction of the Paleo-Pacific Ocean. In view of different granite petrogenesis between rift-type and subduction-type porphyry Mo deposits, geochronological and zircon Lu-Hf isotope studies have been carried out on granitic rocks associated with the Chalukou deposit. Zircon grains from the ore-host monzogranite and ore-causative granite porphyry yield weighted mean 206 Pb/ 238 U ages of 166 ± 2 Ma and 152 ± 2 Ma, with molybdenite samples yielding a Re-Os isochron age of 150 ± 2 Ma, indicating a Jurassic age for both granitic intrusion and Mo mineralization. Zircon εHf(t) values of monzogranite and granite porphyry range from 0.9 to 3.0 and from-1.4 to 0.5, respectively. When integrated with published zircon Lu-Hf isotopic data, our data suggest that the barren granites (both pre-and post-ore) were mainly derived from mantle-derived juvenile rocks, whereas the syn-ore granite requires additional involvement of old continental crust. Thus, a contribution of continental crust to Mo mineralization is suggested. The petrogenesis and geochemical data reveal that the Chalukou deposit is a subduction-related porphyry Mo deposits and not rift-related. Integrated evidence links its formation to the southeastward subduction of the Mongol-Okhotsk Ocean, instead of the westward subduction of the Paleo-Pacific Ocean.

Deformation patterns and timing of the thrust‐nappe structures in the Mohe Formation in Mohe Basin, Northeast China: Implication of the closure timing of Mongol–Okhotsk Ocean

“…The Erguna Block, overriding a southward subducting Mongol–Okhotsk oceanic plate in the Early Mesozoic (Li et al, ; Zhang & Li, ; Donskaya et al, , ; Tang et al, , ; Tang, Xu, Wang, Zhao, & Li, ; Chen, Zhang, Li, Yang, & Deng, ), contains a significant amount of Mesozoic magmatic rocks (~246, 225, 205, and 185 Ma; Zhang et al, ; Wu et al, ; Xu, Bian, & Wang, ; Jahn et al, ; Orolmaa et al, ; Li et al, ; Tang et al, , , ; Ouyang et al, ; Wang et al, ), which could also be an important source of immature, lithic‐rich sediments characteristic to a “dissected arc” provenance in the Early Mesozoic.…”

Genesis of the Xishadegai Mo deposit in Inner Mongolia, North China: Constraints from geology, geochronology, fluid inclusion, and isotopic compositions

“…In general, the porphyry Mo deposits can be further subdivided into three subtypes (Chen et al, , ; and references therein) according to tectonic setting, deposit geology, as well as features of ore‐forming fluid and ore‐related intrusions, that is, the Endako‐ or subduction‐type (Deng, Chen, Santosh, & Yao, ; Lawley, Richard, Anderson, Creaser, & Heaman, ; Selby, Nesbitt, Muehlenbachs, & Prochaska, ; Wang, Chen, et al, ; Zhang & Li, ), the Climax‐ or rift‐type (Chen, Zhang, et al, ; Klemm, Pettke, & Heinrich, ; Seedorff & Einaudi, , ; Wallace, ), and the Dabie‐ or collision‐type (Chen et al, , ; Li et al, , ; Mi et al, ; Wang et al, ; Wu et al, ; Yang et al, , , ). In the Xishadegai Mo deposit, the main ore‐stage quartz contains abundant CO 2 ‐ and daughter minerals‐bearing inclusions, which is considered as a diagnostic marker of intracontinental/collisional magmatic hydrothermal systems (Chen & Li, ; Pirajno & Zhou, ; Zarasvandi et al, ).…”

Geochronology of Magmatism and Mineralization in the Dongbulage Mo-Polymetallic Deposit, Northeast China: Implications for the Timing of Mineralization and Ore Genesis

“…These dates indicate that the Middle-Late Jurassic is an important Mo metallogenic stage in the region, although the peak of metallogenesis actually took place during Late Jurassic-Early Cretaceous periods (Figure 17). These ore-related granites are typically characterized by high degrees of fractionation, high silica content, and formations that were enriched by volatile elements such as F and Li [84][85][86].…”