冀北赤城退变榴辉岩的岩石地球化学及原岩恢复

Geochemistry and Protolith of the Retrograded Eclogite in Chicheng, North Hebei

冀北赤城退变榴辉岩主元素特征显示所有样品均属拉斑玄武岩系列,可分出三种不同的REE配分型式。在MORB标准化微量元素配分图中,LREE亏损型与REE平坦型样品的HFSE与MORB相似,而LREE富集型样品则具有较高的Zr、Hf和Y值,Nb和Ta明显富集,显示出陆壳物质混染的特征。这些特征表明,冀北赤城退变榴辉岩的原岩可能为兼具洋中脊和岛弧地球化学属性的洋壳拉斑玄武岩类,在后期俯冲消减过程中,发生榴辉岩相高压变质作用,并混入了部分陆壳物质。

The retrograded eclogite from Chicheng, north Hebei is associated with biotite plagiogneiss in the Paleoproterozoic Hongqiyingzi Group. The major element geochemistry for the eclogite is characterized by oceanic tholeiite. REE geochemistry of the eclogite is characterized by 3 REE distribution patterns. HSFE for the eclogite with depletion in LREE and normal REE are similar to those for MORB, while the eclogite with enrichment in LREE is characterized by rich in Zr, Hf, Y, Hb and Ta, indicating continental crust contamination. These suggest that the protolith of the eclogite might be oceanic tholeiite contaminated with continental crust.