
Geochronology,geochemistry and Hf isotopic study of Early Carboniferous granodiorites in Taerqi region, central Daxing'anling and its tectonic implication
YUN Xiuyu, HE Zhonghua and YAN Weibing
Global Geology ›› 2015, Vol. 18 ›› Issue (2) : 98-108.
Geochronology,geochemistry and Hf isotopic study of Early Carboniferous granodiorites in Taerqi region, central Daxing'anling and its tectonic implication
Zircon U- Pb age, whole rock geochemical and zircon Hf isotopic data are presented for Late Paleozo- ic granodiorites from the Taerqi region,central Daxing'anling to constrain its petrogenesis and tectonic implica- tion. LA- ICP- MS zircon U- Pb age data indicates that the Late Paleozoic granodiorites were emplaced with age of 333.4 ± 2.2 Ma (Early Carboniferous). Geochemically,the granodiorite samples have SiO2 = 60.54%-71.40%,Na2O =4.04%- 4.66%, K2O = 1.65%- 4.27% and MgO =0.96%-3.53%, belonging to medium- K to high- K calc- alkaline I- type granites. They are slightly enriched in large ion lithophile elements (e.g. Rb,Th, U and K) and light rare earth elements,and depleted in high field strength elements (e.g. Nb,Ta and Ti), with ε Hf (t) values of 8.0- 11.8 and Hf two- stage model ages of 586- 829 Ma. All these geochemical features suggest that the primary magma was derived from partial melting of Neoproterozoic to Phanerozoic newly accreted lower crust. According to the geochemical data and regional geological investigations,the Early Carboniferous granodiorites formed in an island arc setting linked to the subduction of the Paleo- Asian Oceanic Plate beneath the Xing'an Terrane. This also implies that the Xing'an and Songliao terranes have not amalgamated before the Early Carboniferous.
Taerqi region / granodiorite / zircon U- Pb age / geochemistry / tectonic implication
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