彭松柏, 李昌年, Kusky Timothy M, 王璐, 张先进, 蒋幸福, 熊承仁. 2010: 鄂西黄陵背斜南部元古宙庙湾蛇绿岩的发现及其构造意义. 地质通报, 29(1): 8-20.
    引用本文: 彭松柏, 李昌年, Kusky Timothy M, 王璐, 张先进, 蒋幸福, 熊承仁. 2010: 鄂西黄陵背斜南部元古宙庙湾蛇绿岩的发现及其构造意义. 地质通报, 29(1): 8-20.
    PENG Song-bai, LI Chang-nian, KUSKY Timothy M, WANG Lu, ZHANG Xian-jin, JIANG Xing-fu, XIONG Cheng-ren. 2010: Discovery and its tectonic significance of the Proterozoic Miaowan ophiolites in the southern Huangling anticline, western Hubei, China.. Geological Bulletin of China, 29(1): 8-20.
    Citation: PENG Song-bai, LI Chang-nian, KUSKY Timothy M, WANG Lu, ZHANG Xian-jin, JIANG Xing-fu, XIONG Cheng-ren. 2010: Discovery and its tectonic significance of the Proterozoic Miaowan ophiolites in the southern Huangling anticline, western Hubei, China.. Geological Bulletin of China, 29(1): 8-20.

    鄂西黄陵背斜南部元古宙庙湾蛇绿岩的发现及其构造意义

    Discovery and its tectonic significance of the Proterozoic Miaowan ophiolites in the southern Huangling anticline, western Hubei, China.

    • 摘要: 对鄂西黄陵背斜南部宜昌太平溪、邓村一带崆岭岩群中的元古宙庙湾岩组强烈变形变质超镁铁—镁铁质岩的研究表明,镁铁质岩主要为似层状细粒斜长角闪岩,变辉长岩岩体、岩脉及辉绿岩岩脉,超镁铁质岩则主要为蛇纹石化纯橄榄岩、方辉橄榄岩,呈构造岩片、岩块分布于斜长角闪岩之中。细粒斜长角闪岩TiO2=1.14%~1.48%,稀土元素配分型式为略亏损—平坦型,无明显的Eu异常,(La/Yb)N=0.87~1.12, La/Nb、Ce/Zr、Zr/Nb、Zr/Y、Ti/Y平均值分别为1.04、0.15、18.78、2.53、290.51,Nb/Th平均为9.88,显示为大洋中脊构造环境形成的N-MORB型拉斑玄武岩;变辉长岩具典型的堆晶结构特征,稀土元素配分型式为平坦型,具明显的Eu正异常;蛇纹石化纯橄榄岩的稀土元素配分型式具中稀土元素略亏损的U形特征,显示为LREE略富集的地幔岩。上述特征表明,黄陵背斜南部崆岭岩群中的元古宙庙湾岩组实际上是一套混杂堆积的古大洋蛇绿岩残片。元古宙庙湾蛇绿岩的发现为华南扬子克拉通存在中元古代洋盆和哥伦比亚超大陆聚合、裂解构造事件提供了重要的证据。

       

      Abstract: Studies of strongly deformed and metamorphosed mafic- ultramafic rocks from the Proterozoic Miaowan Formation in the high-grade metamorphic Kongling Group in the southern Huangling anticline show that the mafic rocks are composed of layered fine-grained amphibolites, metagabbro rockbodies and dykes and diabase dykes, while the ultramafic rocks are mainly composed of serpentinized dunite and harzburgite, cropping out as tectonite slices and blocks within amphibolites. The geochemical features of the fine-grained layered amphibolite rocks including: TiO2=1.14%-1.48%, slightly depleted-flat type REE curve with no obvious Eu anomaly, (La/Yb)N= 0.87-1.12, average La/Nb, Ce/Zr, Zr/Nb, Zr/Y, Ti/Y are respectively 1.04,0.15,18.78,2.53,290.51, and the average of Nb / Th is 9.88. These features show that these amphibolites are N-MORB type tholeiites typical of those formed in mid-ocean ridge tectonic settings. The metagabbro have typical cumulate texture, flat REE distribution and obvious positive Eu anomaly; The REE characteristics of serpentinized dunite show a U-shape of slight loss of middle REE, representing cumulates metasomatized by LREE slightly enriched mantle. All these features indicate that the mafic-ultramafic rocks from the Proterozoic Miaowan Formation within Kongling Group in the southern part of Huangling anticline, are a structurally dismembered ophiolite resting above an ophiolitic mélange, sitting on top of the Proterozoic shelf sequence on the Yangtze Craton. The discovery of the Proterozoic Miaowan ophiolite supplies important evidence for the existence of an Mesoproterozoic oceanic basin, as well as tectonic events of Columbia supercontinent aggregation and break-up.

       

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