Mesoproterozoic (~1.32 Ga) modification of lithospheric mantle beneath the North China craton caused by break-up of the Columbia supercontinent
Mesoproterozoic (~1.32 Ga) modification of lithospheric mantle beneath the North China craton caused by break-up of the Columbia supercontinent
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DOI：
10.1016/j.precamres.2020.105674
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发表时间：
2020-06
影响因子：
3.8
通讯作者：
Yu‐Sheng Zhu;Jin-Hui Yang;Hao Y. C. Wang;Fu-Yuan Wu
中科院分区：
文献类型：
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作者：
Yu‐Sheng Zhu;Jin-Hui Yang;Hao Y. C. Wang;Fu-Yuan Wu
延辽中元古代辉绿岩床广泛分布于北中国克拉通东部北缘，为研究北中国克拉通岩石圈地幔从拼合到分裂、扩散的演化提供了手段。本文报道了不同岩基辉绿岩的新的斜石英U-Pb年龄、全岩地球化学和Sr-ND-Hf同位素数据，以及辉绿岩的Hf同位素，为进一步研究岩浆的来源、成因和北缘中元古代的演化提供了新的线索。斜晶石U-Pb定年结果表明，这些岩床的年龄一致，约为1320 Ma，表明同时代的侵位作用。辉绿岩样品均为拉斑玄武岩，二氧化钛和总氧化铁含量较高，碱含量较低。它们具有不同的Mg#值和主微量元素含量，但具有统一的原始地幔归一化的微量元素配分模式，轻稀土元素(LREE)和大离子亲石元素(LILEs)的富集较弱，高场强元素(HFSE)的亏损。辉绿岩样品的全岩和原位同位素含量均一，初始87Sr/86Sr比值为0.7032~0.7049，εNd(T)值为−0.70~+3.1，εHf(T)值为+0.8~+3.7，斜辉绿岩εHf(T)值为+1.9~+7.2。所有这些地球化学特征表明，这些岩石来自于在尖晶石稳定深处，富饶的岩石圈地幔来源的高度部分熔融，随后发生了橄榄石、单斜辉石和斜长石的分馏作用。该岩石圈地幔不同于上一次太古代-古元古代克拉通岩石圈地幔，反映了中元古代软流圈物质上涌的参考过程。这种上升流与克拉通边缘的其他中元古代岩浆活动一起，将在中元古代显著改变NCC东部的次大陆岩石圈地幔，从而增加克拉通对随后中生代去克拉通的敏感性。
The Mesoproterozoic Yanliao diabase sills are widespread at the northern margin of the eastern North China Craton (NCC) and provide a means to examine the evolution of the NCC lithospheric mantle from amalgamation to breakup and dispersal of the Columbia supercontinent. Here, we report new baddeleyite U–Pb ages, whole-rock geochemical and Sr–Nd–Hf isotopic data, and baddeleyite Hf isotopes for diabase rocks from different sills, which provide insights into the source and petrogenesis of the magmas and the Mesoproterozoic evolution of the NCC. In situ baddeleyite U–Pb dating yields consistent ages of ca. 1320 Ma for these sills, suggesting coeval emplacement. The diabase samples are all tholeiitic and have high TiO2and total Fe2O3, and low alkali contents. They have variable Mg#values and major- and trace-element contents but uniform primitive-mantle-normalized trace-element patterns, with weak enrichment in light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), and depletion in high-field-strength elements (HFSEs). The whole-rock and in situ isotopic contents of the diabase samples are homogeneous, with initial87Sr/86Sr ratios of 0.7032–0.7049, εNd(t) values of −0.7 to +3.1, εHf(t) values of +0.8 to +3.7, and baddeleyite εHf(t) values of +1.9 to +7.2. All of these geochemical features suggest that these rocks were derived from high-degree partial melting of a fertile lithospheric mantle source at the depth of spinel stability, with subsequent olivine, clinopyroxene, and plagioclase fractionation. This lithospheric mantle was distinct from the previous Archean to Paleoproterozoic cratonic lithospheric mantle beneath the NCC, indicating a refertilization process by upwelling asthenospheric materials during the Mesoproterozoic. This upwelling, together with other Mesoproterozoic magmatism at the craton margin, would have significantly modified the subcontinental lithospheric mantle of the eastern NCC during the Mesoproterozoic, thereby increasing the susceptibility of the craton to subsequent Mesozoic decratonization.