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...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.展开更多
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)+1 种基金the China Postdoctoral Science Foundation (No. 2019M652431)the National Basic Research Program of China (No. 2014CB440801)
文摘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.
