论文部分内容阅读
松树沟纯橄岩体是东秦岭造山带规模最大的超镁铁岩体, 出露面积达20 km2, 纯橄糜棱岩、粗粒纯橄岩占岩体出露面积的95%以上. 岩石组合、结构构造、矿物成分、全岩主元素和微量元素组成、原生岩浆包裹体等方面研究揭示该岩体是熔体多孔隙流动渗滤成因纯橄岩块体. 与Oman等蛇绿岩剖面底部熔体渗滤成因纯橄岩席和方辉橄榄岩中纯橄岩脉的对比研究显示, 该岩体具有低的Al2O3, CaO和HREE丰度, 高的强不相容元素以及Zr和Hf含量. LREE富集的稀土模式和原始地幔标准化微量元素蛛网图都显示与Oman纯橄岩有明显不同. 结合橄榄石中原生熔体包裹体的发现, 认为该岩体是地幔柱源高镁熔体大尺度渗滤流动改造其顶部高度亏损地幔橄榄岩形成的纯橄岩块体. 岩体产出的地质背景支持其与新元古代超级地幔柱在扬子板块的物质活动相关.
The pines of the Songshugou pluton are the largest ultramafic intrusions in the East Qinling orogenic belt with an exposed area of 20 km2 and pure olivine and coarse-grained monolith accounting for more than 95% of the exposed area of the rock. The study on the assemblage, structure, mineral composition, whole-lithofacies and trace elements and primary magmatic inclusions reveal that this rock mass is a pure peridotite block with multi-porosity flow diafiltration, The bottom melt infiltration results from the comparison of pure dug veins in the pure olivine majolites and the harzburgites show that the pluton has low abundances of Al2O3, CaO and HREE, high strong incompatible elements, and Zr and Hf Content.LREE-enriched REE patterns and standard trace element cobweb maps of the original mantle show a significant difference from Oman dunite.According to the discovery of the primary melt inclusions in olivine, the rock mass is considered to be a mantle plume source with high Mg melt Large-scale infiltration flow transforms the monoliths formed by the highly depleted mantle peridotite at the top, and the geological background of the rock mass supports its correlation with the material activity of the Neoproterozoic super mantle plume in the Yangtze Plate.