南秦岭随州地区正长花岗岩锆石SHRIMP U-Pb年代学与地球化学特征

发布时间：2019-03-07 17:22

【摘要】：随州北部正长花岗岩体呈岩脉出露,年代学研究表明,正长花岗岩中岩浆锆石SHRIMP U-Pb加权平均年龄为648.8±1.9Ma(MSWD=0.86),属新元古代。岩石地球化学成分显示其属于高钾钙碱性、准铝质系列花岗岩。岩体高硅(SiO_2=70.67%～75.75%)、富碱(K_2O+Na_2O=7.28%～8.53%)、铁镁比(FeO~T/MgO=26.37～35.50)较高、钙镁含量较低(CaO=0.60%～1.53%,MgO=0.07%～0.12%);稀土元素配分曲线呈右倾斜型,显示Eu负异常(δEu=0.33～0.56);1000Ga/Al值介于2.60～3.41,Zr+Nb+Ce+Y=552.48×10~(-6)～648.87×10~(-6);微量元素原始地幔标准化蛛网图显示,Rb、K和Th等大离子亲石元素明显富集,相对富集Zr、Hf、Nb、Ta等高场强元素,相对亏损Sr、P和Ti,以上特征表明随州北部正长花岗岩为A1型花岗岩。结合区域构造演化,认为随州北部正长花岗岩形成于板内伸展的构造环境,新元古代晚期,秦岭-桐柏-大别地区构造体制经历了重要的转变,在南秦岭东段由古秦岭洋的俯冲导致的挤压作用转换为弧后拉伸减薄作用。在伸展体制下,岩浆上涌形成本区A1型正长花岗岩。
[Abstract]:The syenite granites in the northern part of Suizhou are dike-exposed. Chronological studies show that the SHRIMP U-Pb weighted average age of magmatic zircons in syenite granites is 648.8 卤1.9Ma (MSWD=0.86), which belongs to Neoproterozoic. The geochemical composition of the rocks indicates that they belong to the high potassium calc-alkaline, quasialuminous granite series. High silicon (SiO_2=70.67%~75.75%), alkali rich (K) 2O Na_2O=7.28%~8.53%, high Fe / mg ratio (FeO~T/MgO=26.37~35.50) and low Ca and mg content (CaO=0.60%~1.53%,) are found in rock mass. MgO=0.07%~0.12%); The distribution curves of rare earth elements are inclined to the right, showing a negative anomaly of Eu (未 EU = 0.33 脳 0.56), a 1000Ga/ Al value of 2.60 脳 3.41, a Zr Nb Ce of 552.48 脳 10 ~ (- 6) ~ 648.87 脳 10 ~ (- 6), and a negative anomaly of REE (未 EU = 0.33 脳 0.56). The trace element original mantle standardized cobweb map shows that the large ion lithophile elements, such as Rb,K and Th, are enriched obviously, and the high field strength elements such as Zr,Hf,Nb,Ta are relatively enriched, and the Sr,P and Ti, are relatively deficient. The above characteristics indicate that the syenite granite in the north of Suizhou is a type A _ 1 granite. Combined with the regional tectonic evolution, it is believed that the syenite granite in the northern part of Suizhou was formed in the tectonic environment of intraplate extension. In the late Neoproterozoic, the tectonic system of Qinling-Tongbai-Dabie region underwent an important transformation. In the eastern part of the South Qinling Mountains, the compression caused by the subduction of the Palaeo-Qinling Ocean is transformed into the post-arc stretching and thinning. Under the extensional system, magmatic upwelling formed a type A _ 1 syenite in this area.
【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;
【基金】：国家自然科学基金项目(编号41402180) 国土资源部中国地质调查局项目(编号12120113069000)资助成果
【分类号】：P588.12;P597.3

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