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首页> 外文期刊>Journal of Asian earth sciences >Petrogenesis and tectonic implications of Early Cretaceous shoshonitic syenites in the northern Wuyi Mt Range, Southeast China
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Petrogenesis and tectonic implications of Early Cretaceous shoshonitic syenites in the northern Wuyi Mt Range, Southeast China

机译：中国东南部武夷山山脉北部早白垩世的蛇纹岩正长岩的岩石成因及其构造意义

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Potassic igneous rocks, such as shoshonitic rocks, are an important constituent of young volcanic-intrusive suites in varied tectonic settings. The genesis of these rocks is related to tectonic environments and is thus important for tectonic reconstruction of ancient terranes. Here we report zircon U-Pb and Hf isotopes and whole-rock geochemical compositions for shoshonitic quartz syenites from Madi and Chashan in the northern Wuyi Mt Range, southeast China. LA-ICP-MS zircon U-Pb dating shows that both the Madi and Chashan quartz syenites were formed at 134.8 Ma and 135.0 Ma, respectively. They also have similar geochemical compositions and are characterized by high K2O contents and enriched in LILEs and LREEs but depleted in HFSEs, suggesting a shoshonitic affinity. Elemental and isotopic compositions indicate that they were likely formed by partial melting of metasomatised lithospheric mantle with the presence of phlogopite and potassic amphibole. It is also suggested that silicate melts derived from subducted sediments played a dominant role in mantle metasomatism. An integration of our new results with previous ones allows us to propose a modified tectonic model about the evolution of SE China in which a continental arc related to the subduction of the Palaeo-Pacific plate during the Middle Jurassic was gradually changed to southeastward-migrating, extension-related magmatic arc and backarc basins formed in a continental arc-rifting setting as a consequence of slab rollback since the Early Cretaceous.
机译：在不同的构造环境中，钾质火成岩，例如肖肖尼时代的岩石，是年轻的火山侵入套件的重要组成部分。这些岩石的成因与构造环境有关，因此对于古代地层的构造重建非常重要。在这里，我们报告了中国东南部武夷山北部马迪和茶山的钾镁辉石石英正长岩的锆石U-Pb和Hf同位素以及全岩石地球化学组成。 LA-ICP-MS锆石U-Pb测年表明，Madi和Chashan石英正长岩分别形成于134.8 Ma和135.0 Ma。它们也具有相似的地球化学组成，并具有较高的K2O含量，富含LILE和LREE，但HFSE贫乏，这表明其具有亲铁矿性。元素和同位素组成表明，它们很可能是由交代的岩石圈地幔在金云母和钾闪石的存在下部分熔融而形成的。也有人认为，来自俯冲沉积物的硅酸盐熔体在地幔交代作用中起主要作用。将我们的新结果与以前的结果相结合，使我们能够提出一个关于东南中国演化的改良构造模型，其中与中侏罗纪古太平洋板块俯冲有关的大陆弧逐渐改变为向东南方向迁移，由于早白垩世以来板块的回滚，在大陆弧裂陷环境中形成了与伸展有关的岩浆弧和后弧盆地。

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