滇东南马关木厂新生代玄武岩中橄榄岩包体的含水性和元素地球化学特征

发布时间：2017-12-28 02:02

本文关键词：滇东南马关木厂新生代玄武岩中橄榄岩包体的含水性和元素地球化学特征　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文对采自滇东南马关木厂新生代玄武岩及其中的橄榄岩包体进行详细研究。运用EPM对包体主要组成矿物的主量元素进行测试,采用熔融法对玄武岩全岩的主量元素进行分析,利用LA-ICPMS分析了玄武岩和包体中单斜辉石的微量元素以及玄武岩的Sr-Nd同位素组成,对橄榄岩包体的主要组成矿物单斜辉石、斜方辉石和橄榄石进行了详细的FTIR分析。初步获得了以下几点认识:木厂玄武岩具有相对较高的Mg#和全碱含量。样品的Sr-Nd同位素组成具有高143Nd/144Nd和低87Sr/86Sr的特征,ε Nd值均大于0,暗示样品来自于亏损的地幔源区。玄武岩微量元素表现出富集HFSE和LILE的特征,表明岩浆源区可能经历了由软流圈上涌的小体积熔/流体的交代富集作用。玄武岩在上升过程中没有经历明显的结晶分异作用,其化学成分可能与原生岩浆比较接近。玄武岩中的橄榄岩包体是岩浆上升过程中捕获的偶然包体,与寄主玄武岩之间不存在成因联系。橄榄石的Mg#在88.87-90.77之间,表现出饱满型地幔的特点。主要元素之间的相关性表明,橄榄岩包体是岩石圈地幔经历不同程度部分熔融的残余,可能经历了以硅酸盐熔体为介质的微弱的地幔交代作用。包体表现出与MORB相似的微量元素组成特征。木厂橄榄岩很可能代表了软流圈地幔经历减压上升和热扩散后新增生的岩石圈地幔。红外光谱分析显示,木厂橄榄岩包体的主要组成矿物单斜辉石、斜方辉石和橄榄石都含有一定量以羟基形式存在的结构水。不同样品之间的水含量变化范围并不大,同一样品中同种矿物之间的水含量也不存在明显差异。与华北克拉通岩石圈地幔相比,滇东南所代表的华南地区岩石圈地幔具有明显富水的特征,可能与该区自中生代以来遭受的新特提斯洋壳大规模俯冲流体交代作用有关。华南地区与华北克拉通水含量的明显差异有可能反映的是两地岩石圈地幔正处于不同的演化阶段。
[Abstract]:This paper collected from basalt and peridotite in Southeast Yunnan Maguan mill Cenozoic inclusions were studied in detail. The main elements of the main components of EPM mineral inclusions were tested, analyzed by melting method of major elements of basalt rock, using LA-ICPMS analysis of trace elements and inclusions in monoclinic pyroxene basalt and basaltic Sr-Nd isotopic compositions of peridotite xenoliths consisting mainly of clinopyroxene, orthopyroxene olivine and carried out a detailed analysis of the FTIR. The following points have been obtained: the basalt of wood plant has relatively high Mg# and total alkali content. The Sr-Nd isotopic composition of the sample has the characteristics of high 143Nd/144Nd and low 87Sr/86Sr, and the epsilon Nd values are all greater than 0, suggesting that the samples come from the depleted mantle source. The trace elements of basalt show enrichment characteristics of HFSE and LILE, indicating that magma source area may have undergone metasomatic enrichment of small volume molten / fluid upwelling through asthenosphere. The basalt did not undergo obvious crystallization differentiation during the process of rising. The chemical composition of the basalt may be close to the primary magma. The peridotite xenoliths in basalt are accidental inclusions captured during the process of magma rising, and there is no genetic link between the host basalt and the host basalt. The Mg# of olivine is between 88.87-90.77, showing the characteristics of full mantle. The correlation between main elements shows that the peridotite xenoliths are remnants of different degrees of partial melting of the lithospheric mantle, and may have undergone a shallow mantle metasomatism with silicate melt as the medium. The inclusions are characterized by the composition of trace elements similar to MORB. The peridotite of the wood plant is likely to represent the mantle of the lithospheric mantle that has undergone a new proliferation of the asthenosphere mantle after its decompression and thermal diffusion. FTIR analysis shows that the main components of the peridotite xenoliths in the wood factory include clinopyroxene, orthopyroxene and olivine, which contain a certain amount of structural water existing in the form of hydroxyl groups. The variation of water content between different samples is not significant, and there is no significant difference in the water content between the same minerals in the same sample. Compared with the lithospheric mantle in the North China Craton, the lithospheric mantle in Southern China area, Southeast Yunnan, has obvious water rich characteristics, which may be related to the metasomatism of the new Tethys oceanic crust due to large-scale subduction fluid since the Mesozoic era. The obvious difference between the water content of Southern China and North China Craton may reflect that the lithosphere mantle is in different stages of evolution.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.1

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