| 不同含Fe量硅酸盐玻璃的制备及其物理性质的研究 |
| 张新
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| 导师 | 刘永刚
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| 2014
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| 学位授予单位 | 中国科学院研究生院
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| 学位授予地点 | 北京
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| 学位名称 | 硕士
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| 学位专业 | 矿物学、岩石学、矿床学
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| 关键词 | 超低速带
硅酸盐玻璃
熔体
静高压
动高压
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| 摘要 | 地球形成至今已有46亿年的历史，形成了目前的岩石圈、地幔和地核三大层圈结构。在地幔的底部，有一个特殊圈层，其波速、密度、温度以及化学组分等多个方面，均表现出强烈的不均一性，这个特殊圈层被称之为地幔底层。地幔底层由具有高地震波速和高密度的D’’区和超低速带（ULVZ）组成。ULVZ纵向尺度达5~60 km，横向尺度达200~300 km，横波波速（Vs）最大下降了30%，纵波波速（Vp）最大下降了10%，密度异常达10%。对这样一个特殊的地带，其形成机制、成分和状态有不同推测。 一方面在地球深部极端高温高压条件下，地球深部物质有可能发生部分熔融作用，使地球内部固态物质部分转变为液态的硅酸盐熔体。因而推测这种岩浆熔体有可能与核幔底层ULVZ的形成有关。另一方面核幔边界是地幔底层和液态含Fe外核发生反应的场所，因而推测ULVZ极有可能含Fe，且有不少数据证明Fe可以导致地震波速下降。那么ULVZ是否由含Fe硅酸盐岩浆熔体组成，还有待证明。虽然可以直接观察和研究地表附近喷出的岩浆，但要深入了解核幔边界处的温度和压力对岩浆性质的影响，还必需借助于实验室的手段来进行测量和约束。 受一般实验条件限制，直接的熔体测量实验仍有一定难度。由于玻璃与熔体在结构及物理化学性质上的相似，使得硅酸盐玻璃被广泛用来代替岩浆熔体进行研究。另外，近几十年来，随着动高压技术在地学上的应用，能在实验室中模拟出地表至地核各层圈的压力和温度，再配合其它各类测试仪器，使得原位测量和观察岩石熔体也成为可能。 本论文工作首先在实验室制成一批不同含Fe量的玻璃样品，然后在常压下测量了样品的弹性波速和密度，获得其弹性性质，并讨论了Fe在硅酸盐玻璃结构中的重要作用。接着利用六面顶压机在静水压环境中，对硅酸盐玻璃的高温高压条件下的声速进行了测量，并据声速和常压下密度数据推导了高压下的密度和泊松比，进一步讨论了Fe在硅酸盐玻璃结构中的特殊作用和对玻璃性质的影响。最后为动高压实验准备了样品，计划日后进行动态高压物性测量实验，最终获取一条完整温度压力（常压至135 GPa）线上含Fe硅酸盐玻璃（熔体）的热力学参数，建立相应的非晶态物质状态方程。以此为依据，对地幔条件下熔体的物性与现有地球物理探测到ULVZ的弹性波速变化关系，热力学状态以及ULVZ与超级地幔柱物质上涌的重力分异关系等重大的地球科学问题做出探讨。 |
| 其他摘要 | Earth has a 4.6 billion years history of evolution, and at present it evolves lithosphere, mantle and earth core. At the bottom of the mantle, there exists a special circle named as core mantle boundary. Its wave velocity, density, temperature, chemical composition and other aspects show strong heterogeneity. The bottom of mantle is composed of the D’’ section with relatively high seismic velocity and high density and the ULVZ(Ultra Low Velocity Zone). The vertical and horizontal scale of the ULVZ reaches up to 5~60 km and 200~300 km, respectively. The maximum value of Vs and Vp of the ULVZ are decreased by 30%, and its density anomaly goes up to 10%. For such a special region, there are different speculation about its formation mechanism, components and status. On the one hand, partial melting in the earth’s interior materials may occur, which make the earth’s interior solid materials turning into liquid silicate melt. Therefore, it is supposed that this magmatic melt may relate with the formation of the ULVZ in the lowermost mantle. On the other hand, core-mantle boundary is reaction place of the lowermost mantle and the liquid iron outer core, and evidences suggest that iron can lead to the decrease of the seismic wave velocity. Whether the ULVZ is composed of silicate magma melt with iron or not remains to be proven. The magma erupted from the earth surface is observed and studied directly, but to have a thorough understanding of the influence of the temperature and pressure on magmatic property in the core-mantle boundary, laboratory methods are required to measure and restrain it. The experiment conditions are limited so that it is quite hard to measure the melt directly. Silicate glass is widely used in place of magmatic melt for research，because of the structure, physical and chemical properties of glass are similar to melt. Moreover, with the application of the high pressure technology, the pressure and temperature from the earth surface to earth core are simulated in labs, which make it possible for in situ measurement and observation of melt combining with other kinds of testing instruments in recent decades. In this thesis, a number of glass samples with different iron concentration are fabricated firstly. After that the elastic wave velocity and density are tested at normal pressure, and the important role of iron in silicate glass structure is discussed. Then the sound velocity of the silicate glass is measured by cubic press at hydrostatic high pressure environment, and the density and Poisson’s ratio of samples under high pressure are also calculated according to the sound velocity and normal pressure density.The special effect of iron in the structure and properties of the silicate glass are also discussed. Finally the glass samples for shock wave experiments with different Fe content are prepared. It is expected to obtain the thermodynamic parameters of the silicate glass (melt) with iron at a complete range of temperature of pressure (from normal pressure to 135 GPa), and construct the equation of state of amorphous material. On these basis，major earth science problems such as the relationship between the physical properties of the melt and the elastic wave velocity of the ULVZ measured by the existing geophysical survey technology，the thermodynamic state and the gravity anomaly relationship between the ULVZ and the upwelling of superplume material will be discussed in near future. |
| 学科领域 | 地球深部物质与流体作用地球化学
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/5910
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
张新. 不同含Fe量硅酸盐玻璃的制备及其物理性质的研究[D]. 北京. 中国科学院研究生院,2014.
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