为探讨那拉提岩浆岩带的构造属性,对中天山南缘那拉提构造带中侵位于下元古界木扎尔特岩群的变质地层和中上志留统巴音布鲁克火山-沉积岩系中的达格特闪长岩进行了详细的地球化学和定年研究.研究结果显示,岩石中含角闪石、黑云母等富水暗色矿物,具有低SiO2(54.17％～56.38％),高MgO(4.00％～4.47％)和高Al2O3(17.24％～18.04％)的特征,富集Cr(50.40×10-6～79.00×10-6)、Ni(35.90×10-6～43.20×10-6)、Sr(397×10-6～454× 10-6)等元素,亏损重稀土元素Yb(1.89× 10-6～2.51×10-6)和Y(20.00×10-6～25.00×10-6)、发育弱的Eu负异常(δEu=0.76～0.98),具有低Zr/Nb值(15.62～29.72)、高Zr/Y值(5.37～8)的特征,同时表现出Nb、Ta等高场强元素的负异常.锆石LA-ICP-MS U-Pb年龄为355Ma±9Ma,即早石炭世早期.表明达格特岩体的源岩为壳幔混合的产物,结合区域地质特征认为,该岩体是大陆伸展作用的产物.%The Nalati magmatic belt is located along the southern margin of the Middle Tianshan faults, and Dagete diorite is one of the pluton in this belt, which intruded into the Early Proterozoic Muzhaerte metamorphic strata and Middle-Upper Silurian volcanic—sedimentary rocks. Geochemical and geochronological studies of Dagete diorite were conducted to investigate the tectonic attribute of the Nalati magmatic belt. Dagete diorite consists of such water—rich minerals as hornblendes and biotite, and is characterized by low content of SiO2 (54.17%-56.38%), and high content of MgO (4.00%-4.47%) and A12O3 (17.24%-18.04%). Geochemical data also display enrichment of Cr (50.40×10-6-79.00×10-6), Ni (35.90×l0-6-43.20×l0-6)and Sr (397×10-6-454×10-6), depletion of Yb (1.89×10-6-2.51×10-6) and Y (20.00×10-6-25.00×10-6, high values of Zr/Y (5.37-8), low ratios of Zr/Nb (15.62-29.72), and slight anomalies of Nb, Ta and Eu. The LA-ICP—MS zircon U-Pb ages reveal that Dagete diorite was formed at 355 Ma+9Ma. Combined with regional geology, the authors hold that Dagete diorite was probably derived from the mixed magma source of the crust and the mantle and resulted from continental extension.
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