Early Jurassic high-K calc-alkaline and shoshonitic rocks from the Tongshi intrusive complex, eastern North China Craton: Implication for crust-mantle interaction and post-collisional magmatism

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• 作者：Ting-Guang Lan^a ; Hong-Rui Fan^a ; ^{fanhr@mail.igcas.ac.cn} ; M. Santosh^b ; Fang-Fang Hu^a ; Kui-Feng Yang^a ; Yue-Heng Yang^c ; Yongsheng Liu^d
• 关键词：High-K calc-alkaline series ; Shoshonitic series ; Crust&ndash ; mantle interaction ; Post-collisional magmatism ; North China Craton
• 刊名：Lithos
• 出版年：2012
• 期刊代码：54_00244937
• 类别：ear
• 出版时间：May, 2012
• 卷：140-141
• 期：Complete
• 页码：183-199
• 文件大小：4062 K

摘要

The Tongshi intrusive complex, located within the western Shandong Province (Luxi Block) in the eastern North China Craton, comprises high-K calc-alkaline series (fine-grained quartz monzonite and porphyritic quartz monzonite) and shoshonitic series (coarse- to fine-grained porphyritic syenites). Here we report comprehensive data on petrology, geochemistry, Sr-Nd-Pb isotopes and zircon U-Pb and Hf isotopic compositions from the intrusive complex. LA-ICPMS zircon U-Pb ages show that this complex was emplaced at 180.1-184.7 Ma. The fine-grained quartz monzonite and porphyritic quartz monzonite have similar major and trace elements features, implying a similar petrogenetic history. Coupled with the widespread Neoarchean inherited zircons in these rocks, the high SiO₂ and Na₂O as well as the low MgO contents and low Pb isotopic ratios ((²⁰⁶Pb/²⁰⁴Pb)_i = 15.850-16.881, (²⁰⁷Pb/²⁰⁴Pb)_i = 14.932-15.261, (²⁰⁸Pb/²⁰⁴Pb)_i = 35.564-36.562) of the quartz monzonites suggest an origin from ancient tonalite-trondhjemite-granodiorite (TTG) crust. However, their higher Nd and Hf isotopic ratios (蔚_Nd (t) = 鈭?#xA0;11.7 to 鈭?#xA0;7.0, 蔚_Hf (t) = 鈭?#xA0;25.0 to 鈭?#xA0;10.3) as compared to the basement rocks indicate input of enriched lithospheric mantle-derived materials. The coarse- to fine-grained porphyritic syenites were derived from similar sources as inferred from their comparable major and trace elements contents as well as the Nd, Hf and Pb isotopic compositions. The Neoarchean inherited zircons and depletion of Nb, Ta, P and Ti in these rocks indicate the involvement of ancient crust. However, the high Nd and Hf isotopic ratios (蔚_Nd (t) = 鈭?#xA0;0.8 to 1.5, 蔚_Hf (t) = 鈭?#xA0;4.4 to 4.8) coupled with high Pb isotopic compositions ((²⁰⁶Pb/²⁰⁴Pb)_i = 18.082-19.560, (²⁰⁷Pb/²⁰⁴Pb)_i = 15.510-15.730, (²⁰⁸Pb/²⁰⁴Pb)_i = 37.748-39.498) suggest that the porphyritic syenites were mainly derived from an asthenospheric mantle. Based on the geochemical and isotopic features, a magmatic process similar to MASH (melting, assimilation, storage and homogenization) is proposed for the fine-grained quartz monzonite and AFC (assimilation and fractional crystallization) is envisaged for the porphyritic quartz monzonite and porphyritic syenites. Our data suggest the interaction of various crustal and mantle sources including lower to upper crust, lithospheric mantle and asthenospheric mantle in the generation of the Tongshi intrusive complex. Sharing common characteristics with other post-collisional magmatic rocks, the high-K calc-alkaline and shoshonitic rocks from the Tongshi complex are considered to have originated in post-collisional setting, marking the beginning of lithospheric destruction in the inner domains of the NCC during Mesozoic.