Petrogenesis and Geodynamic Implications of the Carboniferous Granitoids in the Dananhu Belt,Eastern Tianshan Orogenic Belt  

作　　者：Long Du Chao Yuan Xu-Ping Li Yunying Zhang Zongying Huang Xiaoping Long 

机构地区：[1]Shandong Key Laboratory of Depositional Mineralization and Sedimentary Minerals,Shandong University of Science and Technology,Qingdao 266590,China [2]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China [3]State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China [4]Department of Earth Sciences,The University of Hong Kong,Hong Kong,China

出　　处：《Journal of Earth Science》2019年第6期1243-1252,共10页地球科学学刊（英文版）

基　　金：supported by the National Key Research and Development Program of China (No. 2016YFC0601003);the National Natural Science Foundation of China (Nos. 41903031,41421002);the China Postdoctoral Science Foundation (No. 2019M652431);the National Basic Research Program of China (No. 2014CB440801)

摘　　要：This paper presents new LA-ICP-MS zircon U-Pb geochronology,whole-rock major and trace element geochemistry,and Sr-Nd isotopes systematically on porphyritic granitic and K-feldspar granitic intrusions from the Dananhu belt,eastern Tianshan orogenic belt(ETOB).Zircon U-Pb dating indicates that the porphyritic granitic and K-feldspar granitic plutons were formed at 357±3 and 311±3 Ma,respectively.The porphyritic granites show geochemical and isotopic characteristics(high Si O2,low Mg O and Mg^#,depleted Sr-Nd isotopic values(about 0.7034 and 6.13,respectively),with Nb/Ta(13.3–14.7)and Zr/Hf(31.0–33.9)ratios)similar to those of the crustal-derived magmas.The above characteristics suggest they were probably originated from juvenile lower crustal materials.The K-feldspar granites also have high Si O2,low Mg O and Mg^#,depleted Sr-Nd isotopic values(0.7033–0.7046 and 4.41–5.67,respectively).But some trace elements contents vary widely,with variable Nb/Ta(12.7–22.7),Zr/Hf(21.3–36.1)and Nb/La(0.38–1.07)ratios,indicating that the K-feldspar granites were formed by partial melting of juvenile lower crustal materials with old crustal materials.Combined with previous data on Carboniferous granitoids in the Dananhu belt,we infer that all the Carboniferous granitic plutons in the Dananhu belt were most likely emplaced in an island arc environment(Dananhu arc).Subsequently,a tectonic transition from oceanic subduction to post-collisional extension probably occurred in the ETOB.This paper presents new LA-ICP-MS zircon U-Pb geochronology,whole-rock major and trace element geochemistry,and Sr-Nd isotopes systematically on porphyritic granitic and K-feldspar granitic intrusions from the Dananhu belt,eastern Tianshan orogenic belt(ETOB). Zircon U-Pb dating indicates that the porphyritic granitic and K-feldspar granitic plutons were formed at 357±3 and 311±3 Ma,respectively. The porphyritic granites show geochemical and isotopic characteristics(high Si O2,low Mg O and Mg#,depleted Sr-Nd isotopic values(about 0.703 4 and 6.13,respectively),with Nb/Ta(13.3–14.7) and Zr/Hf(31.0–33.9) ratios) similar to those of the crustal-derived magmas. The above characteristics suggest they were probably originated from juvenile lower crustal materials. The K-feldspar granites also have high Si O2,low Mg O and Mg#,depleted Sr-Nd isotopic values(0.703 3–0.704 6 and 4.41–5.67,respectively). But some trace elements contents vary widely,with variable Nb/Ta(12.7–22.7),Zr/Hf(21.3–36.1) and Nb/La(0.38–1.07) ratios,indicating that the K-feldspar granites were formed by partial melting of juvenile lower crustal materials with old crustal materials. Combined with previous data on Carboniferous granitoids in the Dananhu belt,we infer that all the Carboniferous granitic plutons in the Dananhu belt were most likely emplaced in an island arc environment(Dananhu arc). Subsequently,a tectonic transition from oceanic subduction to post-collisional extension probably occurred in the ETOB.

关 键 词：eastern Tianshan OROGENIC belt(ETOB) Dananhu BELT GRANITOID CARBONIFEROUS 

分 类 号：P59[天文地球—地球化学]