Keketuohai mafic–ultramafic complex in the Chinese Altai, NW China: Petrogenesis and geodynamic significance
Keketuohai mafic–ultramafic complex in the Chinese Altai, NW China: Petrogenesis and geodynamic significance
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DOI：
10.1016/j.chemgeo.2011.11.031
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发表时间：
2012-02
期刊：
影响因子：
3.9
通讯作者：
Keda Cai;M. Sun;C. Yuan;Guochun Zhao;W. Xiao;X. Long
中科院分区：
文献类型：
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作者：
Keda Cai;M. Sun;C. Yuan;Guochun Zhao;W. Xiao;X. Long
泥盆纪岩浆作用在中亚造山带重要组成部分中国阿尔泰山的构造演化史上非常强烈。中国阿尔泰山泥盆系可可托海镁铁质-超镁铁质杂岩体是由纯橄榄岩、橄榄辉长岩、角闪辉长岩和辉石闪长岩组成的分区侵入体。辉石闪长岩的锆石 U-Pb 年龄为 409±5Ma。矿物组合和化学成分的变化表明，可可托海杂岩的岩石成因主要受共同岩浆室的分异结晶控制。低 SiO2、K2O 和 Na2O 含量，P2O5、TiO2 和 Mg# 值之间的负协变表明地壳同化/污染不显着。因此，正的εNd(t)值（0至+2.7）和轻稀土元素的轻微富集（例如La/YbN=0.98-3.64）表明它们的母岩浆可能是由岩石圈地幔的部分熔融产生的。模型计算表明其母岩浆为高镁（Mg#=66）拉斑玄武岩熔体。可可托海岩体与多种岩浆作用、高温变质作用和热液成矿作用同时存在，这支持了先前提出的模型，即山脊俯冲很可能在中国阿尔泰山的构造演化中发挥了重要作用。
Devonian magmatism was very intensive in the tectonic evolutionary history of the Chinese Altai, a key part of the Central Asian Orogenic Belt (CAOB). The Devonian Keketuohai mafic–ultramafic complex in the Chinese Altai is a zoned intrusion consisting of dunite, olivine gabbro, hornblende gabbro and pyroxene diorite. The pyroxene diorite gives a zircon U–Pb age of 409±5Ma. Variations in mineral assemblage and chemical composition suggest that the petrogenesis of the Keketuohai Complex was chiefly governed by fractional crystallization from a common magma chamber. Low SiO2, K2O and Na2O contents, negative covariations between P2O5, TiO2and Mg# value suggest insignificant crustal assimilation/contamination. Thus the positive εNd(t) values (0 to +2.7) and slight enrichments in light rare earth elements (e.g., La/YbN=0.98–3.64) suggest that their parental magma was possibly produced by partial melting of the lithospheric mantle. Model calculation suggests that their parental magma was high-Mg (Mg#=66) tholeiitic basaltic melt. The Keketuohai intrusion was coeval with diverse magmatism, high temperature metamorphism and hydrothermal mineralization, which support a previously proposed model that ridge subduction most likely played an important role in the tectonic evolution of the Chinese Altai.