橄榄石集合体部分熔融成带分布和压力影形成的实验研究

项目名称： 橄榄石集合体部分熔融成带分布和压力影形成的实验研究

项目编号： No.40874043

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 矿业工程

项目作者： 赵永红

作者单位： 北京大学

项目金额： 42万元

中文摘要： 流体的迁移和输运对于各种地球过程例如地壳变质、水文以及地幔动力学等过程起到关键的作用。而部分熔融岩石的力学行为对于地幔柱、洋中脊以及上地幔动力学则至关重要。野外观测还发现：部分熔融岩石产生变形时，熔融会聚集成带状分布，在单晶周围形成压力影。本项目通过高应变简单剪切和扭转变形实验，研究部分熔融岩石变形产生的熔融成带分布以及刚性球周围的压力影特征、其形成机制和在地球物球上的启示。试验材料为95%圣卡罗橄榄石+5%MORB+ZrO2刚性球和95%圣卡罗橄榄石+5%MORB+橄榄石单晶刚性球，试验温度为1200C，围压300MPa，加载方式有10%-20%应变的三维压缩，200%的简单剪切和〉200%的扭转变形。通过改变熔融含量、熔融组分、应力和加载方式，将试件的力学特性和微结构状态与外加应变、剪切应力以及压实特征长度进行相关性分析，将大应变简单剪切和扭转实验、小应变三轴实验结果结合起来定量确定其流变学性质，扭转和剪切变形试验结束后，用电子显微镜和扫描电镜分析变形后试件的分带富熔融层和压力影，包括方向、间距、宽度和熔融百分比，定量刻划了分带富熔融层和压力影的形成过程和机制。

中文关键词： 实验研究；变形；部分熔融成带分布；压力影；橄榄石集合体

英文摘要： The migration and transport of fluids is central to understanding a wide variety of Earth processes, including crustal metamorphism, hydrology, and mantle dynamics. In the mantle, the separation of a melt from a partially molten aggregate and its subsequent transport plays an important role in understanding the dynamics of mantle plumes and mid-ocean ridges. The mechanical behavior of partially molten rocks plays is central in understanding the geodynamical behavior of the upper mantle. Consequently, to investigate the ratio between the bulk and shear viscosity in partially molten aggregates, a series of high pressure, high temperature rock deformation experiments have been preformed on synthetic olivine+basalt aggregates containing small zirconia inclusions. This ratio measures the resistance a partially molten aggregate exerts to a volumetric change in melt fraction versus its resistance to shear deformation. The redistribution of the fluid phase around these inclusions has been quantified and compared to the theoretical results predicted by compaction theory. The samples were composed of either 95% San Carlos Olivine+5% MORB+ZrO2beads or 95% San Carlos Olivine+5% MORB+olivine single crystal beads. Samples were deformed to strains of 10-20% in triaxial compression， 200% strain in simple shear or >200% in torsion. These experiments were conducted at P=300 MPa and T=1200 C. The effect of strain, sample mechanical property and the way of loading on the melts distribution and pressure shadow microstructure were analysed to get a qualitative as well as quantitative discription of the process and mechanism of the formation of the compaction length as well as the formation of pressure shadows.

英文关键词： Experimental study; olivine aggregates; partial melt distrabution; pressure shadow; deformation