Intracontinental extension and geodynamic evolution of the Paleoproterozoic Jiao-Liao-Ji belt, North China craton: Insights from coeval A-type granitic and mafic magmatism in eastern Liaoning Province
Intracontinental extension and geodynamic evolution of the Paleoproterozoic Jiao-Liao-Ji belt, North China craton: Insights from coeval A-type granitic and mafic magmatism in eastern Liaoning Province
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华北克拉通古元古代焦辽吉带陆内伸展及地球动力学演化——来自辽东同期A型花岗岩和基性岩浆作用的启示
DOI：
10.1130/gsab.s.13244231.v1
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发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Chen Hui
中科院分区：
文献类型：
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作者：
Liu Jianhui;Wang Xiangjian;Chen Hui
为了更好地认识华北克拉通古元古代胶辽吉带的成因和构造演化，对辽东地区古元古代二长（正长）花岗质片麻岩和变镁铁质岩进行了全岩地球化学和锆石U-Pb、Hf同位素分析。结果表明，这些二长（正长）花岗质片麻岩与变镁铁质岩石同时形成于约。2.2 - 2.1 Ga。二长（正长）花岗质片麻岩具有A型花岗岩的地球化学特征，是在伸展环境下由太古代英云闪长岩-奥长花岗岩-花岗闪长岩（TTG）脱水熔融形成的，并有少量同时代幔源岩浆的参与。变质镁铁质岩的地球化学特征类似于大洋中脊玄武岩，它们是在陆内伸展环境中由同位素亏损的软流圈地幔部分熔融而成，并经历了地壳和大陆岩石圈地幔混染和分离结晶作用。在此基础上，结合已发表的地质证据，提出胶辽吉带的成因和动力学演化的构造模式：（1）东部陆块高密度榴辉岩化下地壳的形成伴随着大量太古代TTG的形成：（2）2.20 - 2.0Ga期间，软流圈热点沿着胶辽吉带上涌驱动陆内伸展;（3）龙岗地块与楠林地块之间的会聚造山作用，由高密度榴辉岩化下地壳的重力驱动俯冲作用控制。（4）造山后伸展作用，由造山根的拆沉和随后的热软流圈上涌引起。该构造模式能较好地解释胶辽吉带的成因和动力学演化。
To better understand the origin and tectonic evolution of the Paleoproterozoic Jiao-Liao-Ji belt, North China craton, which have long been debated, we have conducted whole-rock geochemical and zircon U-Pb and Hf isotope analyses on Paleoproterozoic monzo(syeno)granitic gneisses and metamafic rocks from eastern Liaoning Province. The results indicate that these monzo(syeno)granitic gneisses and metamafic rocks formed concurrently at ca. 2.2−2.1 Ga. The monzo(syeno)granitic gneisses show geochemical features of A-type granites and were derived from dehydration melting of Archean tonalite-trondhjemite-granodiorite (TTG) with minor involvement of coeval mantle-derived magma in an extensional setting. The metamafic rocks are geochemically similar to mid-ocean-ridge basalt; they were generated by partial melting of isotope-depleted asthenospheric mantle in an intracontinental extensional setting and experienced crustal and continental lithospheric mantle contamination and fractional crystallization. Based on this study and published geological evidence, we propose the following tectonic model for the origin and geodynamic evolution of the Jiao-Liao-Ji belt: (1) Generation of high-density eclogitized lower crust accompanied by formation of voluminous Archean TTGs in the Eastern block; (2) intracontinental extension driven by upwelling of an asthenospheric hotspot along the Jiao-Liao-Ji belt in period of 2.20−2.0 Ga; (3) convergent orogenic processes between the Longgang block and Nangrim block governed by gravity-driven subduction of high-density eclogitized lower crust at ca. 1.95−1.85 Ga; and (4) postorogenic extension caused by delamination of the orogenic root and subsequent hot asthenospheric upwelling. This tectonic model can well explain the origin and geodynamic evolution of the Paleoproterozoic Jiao-Liao-Ji belt.