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The Middle Triassic Pingtai pluton, which occurs in the southeastern part of Wulonggou gold orefield, East Kunlun orogen, provides new insights into the subduction history of the Paleo-Tethyan ocean. The detailed petrology, whole-rock geochemistry, zircon U-Pb age and Hf isotopic data of granodiorite from Pingtai pluton were conducted. The results show that the granodiorite of Pingtai pluton mainly comprises plagioclase(the volume fraction is 45%-50%), quartz(20%-25%), K-feldspar(20%-25%), hornblende(5%), and biotite(5%), and it yields a zircon U-Pb weighted mean age of(247±1)Ma, suggesting an emplacement age of Middle Triassic; whole-rock geochemistry characteristics show that SiO2 content varies from 64.88% to 65.90%, average ratios of FeOT/MgO and Fe2O3/FeO are 3.70 and 1.48, respectively, and average saturation temperature for zircon is calculated to be 770 ℃. Therefore, it is suggested that the granodiorite belongs to strong peraluminous and high-potassium calcium alkaline series, which is similar to typical I-type granite. Chondrite-normalized REE pattern shows that the granodiorite is enriched in LREEs and depleted in HREEs with weak negative Eu anomaly. The εHf(t)values range from -4.51 to 0.64, and the Hf model age is 1.54-1.22 Ga. In combination with regional geological data, it is suggested that the granodiorite of Pingtai pluton is generated in a continental magmatic arc setting, which is related to the northward subduction of the Paleo-Tethyan ocean, and its parental magma is derived from meta-sandstone of continental crust. It is further indicated that the subduction of the Paleo-Tethyan ocean might have lasted until the late Middle Triassic. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Petrologica et Mineralogica / Yanshi Kuangwuxue Zazhi is the property of Acta Petrologica et Mineralogica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There are many Zn-Pb deposits in Tianshan of China and abroad, forming a giant Zn-Pb metallogenic belt. Why so many Zn-Pb deposits are located here? how geodynamic setting results in their formation? What is the regional ore-forming types and the key to the Zn-Pb metallogeny? Where is the future prospecting orientation? All these significant geological and exploration problems are attracted much more attentions. Based on investigating the regional geology and Zn-Pb deposits in Tianshan and consulting various references, the important metallogenic environments, geological characteristics of typical Zn-Pb deposits and their ore-forming types were demonstrated, and tectonic-metallogenic evolution of Tianshan orogen and prospecting direction of Zn-Pb mineral resources were then discussed. The results show that Tianshan orogen experiences four geodynamic processes, namely the formation of Precambrian continent, ocean-continent subduction accretion, continent-continent collision orogeny, and intraplate deformation, and four corresponding metallogenic environments, including Proterozoic paleo-continent margin rift basin, Paleozoic ocean-continent subduction accretion island arc, Late Paleozoic continent-continent collision orogeny and Meso-Cenozoic depression basin. Accordingly, four important metallogenic systems and ore-forming types are formed as follow. The SEDEX Zn-Pb deposits are formed in Proterozoic paleo-continent margin rift basin environment, and controlled by contemporaneous faults and reduced fine-grained clastic rocks or carbonate rocks. The skarn, magmatic hydrothermal vein and VMS Zn-Pb deposits are formed in island arc of Paleozoic ocean-continent subduction accretion environment, and controlled by arc-related magmatism, faults and favorable strata. The MVT Zn-Pb deposits are formed in Late Paleozoic continent-continent collision orogeny environment, and controlled by marine carbonate in passive margin, extensional faults and thrust nappe structures. The sandstone-hosted Zn-Pb deposits are formed in Meso-Cenozoic depression basin environment, and controlled by basinal structure, infilling of oil and gas, bleaching of red beds, and sulfate. The Paleozoic subduction accretion island arc Zn-Pb system and skarn, magmatic hydrothermal vein and VMS types play a more important role in Zn-Pb mineral resources of Tianshan orogen compared to other parts of the world, which should be paid more attentions. North Tianshan island arc belt, the northern and southern margins of Kazakhstan-Yili block and central Tianshan block are all favorable for Paleozoic subduction accretion island arc Zn-Pb system, and show promising potential for ore prospecting of more large-scale Zn-Pb deposits. Meanwhile, the northern margin of Kazakhstan-Yili block and central Tianshan massif of East Tianshan for Proterozoic paleo-continent margin rift basin Zn-Pb system and SEDEX type, the northern margin of foreign central Tianshan and South Tianshan orogen for Late Paleozoic continent-continent collision orogenic Zn-Pb system and MVT, and the piedmont/intermontane basins along South Tianshan orogen for Meso-Cenozoic depression basin Zn-Pb system and sandstone-hosted type are all favorable, which should continue to be concerned about. These results may provide reference and indication for regional Zn-Pb metallogenic understanding and future Zn-Pb ore exploration. [ABSTRACT FROM AUTHOR]