Geochronology and geochemistry of the palaeoproterozoic mafic dikes in the Jiaobei terrane: implications for tectonic evolution of the Jiao-Liao-Ji Belt, eastern North China Craton
Geochronology and geochemistry of the palaeoproterozoic mafic dikes in the Jiaobei terrane: implications for tectonic evolution of the Jiao-Liao-Ji Belt, eastern North China Craton
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DOI：
10.1080/00206814.2020.1746932
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发表时间：
2020-04
影响因子：
2.6
通讯作者：
Yayun Liang;Jun Deng;Xuefei Liu;Qingfei Wang;Yao Ma;Tianxiang Gao;Enquan Zhao;Zhihui Zhou
中科院分区：
文献类型：
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作者：
Yayun Liang;Jun Deng;Xuefei Liu;Qingfei Wang;Yao Ma;Tianxiang Gao;Enquan Zhao;Zhihui Zhou
摘要胶辽冀带是中国克拉通北部三个具有代表性的古元古代构造单元之一，其古元古代构造/地球动力学演化仍存在争议。位于JLJB南段的胶北地体中的古元古代镁铁质岩脉可以为JLJB的演化提供重要的证据。其LA-ICPMS锆石U-Pb定年数据表明，这些岩脉的侵位时代约为2175 Ma。它们的SiO_2含量相对较低，而Al_2O_3、镁、铬、镍的含量相对较高。此外，它们还表现出高场强元素(HFSE)(如Nb和Ta)的亏损和弱的Eu异常。此外，它们的初始87Sr/86Sr比值(0.700478-0.705069)和低的ɛND(T)值(−2.07-−0.09)也有限，模式年龄(TdM1)为2722-2967 Ma。岩浆晶体锆石的ɛHf(T)值较低，−为9.22~−3.82，而相应的Hf模式年龄为2627~2870 Ma。这些岩脉的地球化学特征表明，它们起源于北中国克拉通富集型岩石圈地幔在尖晶石稳定场内5-10%的部分熔融。古元古代胶北基性岩脉与同时代A型花岗岩、基性岩等变质火山岩组合形成于弧后伸展构造环境。这进一步表明，JLJB在~2175 Ma以前经历了俯冲洋板回退触发的弧后伸展。本文报道了中国克拉通北部前寒武纪构造演化的新证据。
ABSTRACT The palaeoproterozoic tectonic/geodynamic evolution of the Jiao-Liao-Ji Belt (JLJB), one of the three representative palaeoproterozoic tectonic units in the North China Craton (NCC), remains controversial. The palaeoproterozoic mafic dikes sampled in the Jiaobei terrane, situated in the southern segment of the JLJB, could provide significant evidence for the JLJB’s evolution. Their LA-ICP-MS zircon U-Pb dating data show that these dikes were emplaced at the period of ~2175 Ma. They have relatively low SiO2 contents and relatively high contents of Al2O3, MgO, Cr, and Ni. Further, they exhibit high field strength elements (HFSE) (e.g. Nb and Ta) depletion and weak Eu anomalies. Also, they show limited initial 87Sr/86Sr ratios (0.700478–0.705069) and low ɛNd(t) values (−2.07 to −0.09) with model ages (TDM1) of 2722–2967 Ma. The magmatic crystal zircons yielded low ɛHf(t) values of −9.22 ~ −3.82 relative to the corresponding Hf model ages of 2627–2870 Ma. These geochemical characteristics of the dikes indicate that they originated via 5–10% partial melting of the North China Craton’s enriched lithospheric mantle within the spinel stability field. In combination with contemporaneous A-type granites, mafic rocks, and other meta-volcanic associations, palaeoproterozoic Jiaobei mafic dikes formed in a back-arc extensional tectonic setting. This further indicates that the JLJB experienced back-arc extending triggered by slab rollback of subducted oceanic plate at ~2175 Ma ago. This study reports new evidence regarding the evolution of Precambrian tectonics of the North China Craton.