东天山恰特卡尔一带镁铁质-超镁铁质杂岩体地球化学特征及构造意义

Geochemical Characteristics and Tectonic Significance of Maficultramafic Rocks from Qiatekaer Area,in Eastern Tianshan

恰特卡尔地区位于康古尔-黄山镁铁质-超镁铁质岩带西段,沿康古尔韧性剪切带NE向断续分布着以路北、条形山、黄羊沟、乱石岭和白梁山为代表的多个镁铁质-超镁铁质杂岩体。主量元素化学组成为铁质基性-超基性岩,部分属拉斑玄武岩系列,也有部分属钙碱性系列。稀土分布模式上,路北-白梁山杂岩体为平坦的E-MORB型,条形山-黄羊沟-乱石岭杂岩体兼具OIB和N-MORB型特征;富集Ba,U,亏损Nb,Ta,Ti;路北-白梁山杂岩体与条形山-黄羊沟-乱石岭杂岩体具不同岩浆源区,同一岩浆源区岩石内部之间的局部差异,是岩石不同程度部分熔融的结果。原始岩浆起源于主碰撞期受俯冲流体交代地幔楔的部分熔融,岩浆在上升过程中遭地壳物质混染,构造环境为碰撞后板内伸展环境。

Controlled by the Kangur ductile shear,many NE-trending mafic-ultramafic complex,represented by Lubei complex,Tiaoxingshan complex,Huangyangou complex,Luanshiling complex and Bailiangshan complex,distributed discretely in the Qiatekaer area located in western section of Kangur-Huangshan mafic-ultramafic rock belt.Mafic-ultramafic rocks from Qiatekaer are characterized by being of ferruginous basic-ultrabasic rocks,calc-alkalic and tholeiitic series.In the REE pattern,Lubei complex and Bailiangshan complex showes the features of flat E-MORB,while Tiaoxingshan complex,Huangyangou complex and Luanshiling complex have the characteristics of both OIB and N-MORB.Rocks are enriched Ba,U,and depleted Nb,Ta,Ti.Lubei-Bailiangshan complex and Tiaoxingshan-Huangyangou-Luanshiling complex have the differerent magma source.Little difference between rocks form same magma source is the result of partial melting of different level.The primary magma of mafic-ultramafic complex were derived from partial melting of mantle wedge which had been metasomatized by subduction fluids during the main collisional phase,besides subject to crust assimilation contamination.resulted from the lithospheric delamination at the root and the upwelling of asthenosphere in the partial melting of lithospheric mantle,corresponding to post-collision intermittent extension setting.