基于电导率模型的月幔水含量估算研究

发布时间：2018-01-14 03:02

本文关键词：基于电导率模型的月幔水含量估算研究　出处：《中国地质大学》2014年硕士论文　论文类型：学位论文

【摘要】：月球蕴藏着丰富的能源和矿产资源,能源和资源能否被充分利用与月球存在的水环境密切相关。月球上水资源的存在和被利用在月球探测计划中具有非常重要的科学研究价值和应用前景。最新研究采用新的化学分析技术重新分析阿波罗月球样品中的火山玻璃珠、橄榄石熔融包裹体,磷灰石和高地斜长岩,均检测到大量水的存在,暗示月球内部某些区域可能包含和地球地幔相同的水含量。由于矿物岩石的电导率对于水含量非常敏感,理论和实验研究都已经证实水能够极大增加矿物岩石的电导率。最近六年,在实验室高温高压条件下测量矿物岩石的电导率已经成为深部地质-地球物理领域的一个研究热点,而将实验室高温高压条件下获得矿物岩石的电导率和大地电磁探测和地磁测深的结果相结合,已经成为推断地球内部水含量的一种有效途径。目前月球内部含水的有关证据主要来自地球化学方法,而仅仅利用阿波罗时期月球表面采集的样品推断月球内部水含量将具有较大不确定性。本文尝试将实验室高温高压条件下获得下地壳、上地幔主要矿物组成橄榄石、辉石和石榴子石的电导率与月而磁力仪获得的典型月球电导率-深度剖面结合用于推断月幔的水含量。论文的主要内容包括以下几个方面： (1)回顾月球含水研究现状和概述实验室高温高压条件下矿物岩石电导率的研究现状。 (2)将影响实验室高温高压条件下矿物岩石电导率的因素划分为外部因素和内部因素,综述这些因素对地幔矿物岩石电导率的影响程度。地幔矿物岩石的电导率分别随着温度,铁含量,水含量和熔融熔体体积分数的增加而增加；不含水条件下,电导率随着氧逸度和压力的增加而分别增加和减小,含水条件下则恰恰相反；忽略颗粒边界对电导率的影响；测量频率和结晶方向对电导率的影响尚存在一定争议；在进行电导率测量时有必要考虑系统平衡时间和样品中的铁损失。 (3)回顾月幔内部结构、物质成分和实验室高温高压条件下地壳、上地幔主要矿物组成橄榄石、斜方辉石、单斜辉石和石榴子石在含水和不含水条件下的电导率数据。 (4)推导适用月幔温度、压力、氧逸度条件具有相似整体化学成分和矿物组成含水和不含水电导率模型,采用有效介质平均方法计算月幔矿物组成平均电导率与温度、水含量的函数关系,联合月面磁力仪获得的典型月球电导率-深度剖面计算具不同总水含量的月幔温度-深度曲线,与来自月球重力和月震数据推断的温度范围进行对比,推断月幔的总水含量小于10ppm,这和关于月球起源的“大撞击说”假说,近期对于月球岩浆海岩石学建模和月球样品氯同位素分析结果符合。 (5)总结和归纳全文主要研究成果,指出本文研究工作不足之处以及未来改进方向。
[Abstract]:The moon is rich in energy and mineral resources. Whether energy and resources can be fully utilized is closely related to the water environment of the Moon. The existence and utilization of water resources on the Moon has very important scientific research value and application prospect in the lunar exploration program. A new chemical analysis technique was used to reanalyze the volcanic glass beads in Apollo lunar samples. A large amount of water was detected in olivine melt inclusions, apatite and highland plagioclase. It suggests that some areas of the moon may contain the same amount of water as the Earth's mantle. The conductivity of mineral rocks is very sensitive to water content. Both theoretical and experimental studies have shown that water can greatly increase the electrical conductivity of mineral rocks. Measuring the conductivity of mineral rocks under high temperature and high pressure in laboratory has become a research hotspot in the field of deep geology and geophysics. Combining the conductivity of mineral rocks with magnetotelluric sounding and geomagnetic sounding under the conditions of high temperature and high pressure in laboratory has become an effective way to infer the water content in the earth's interior. At present, the evidence of water content in the interior of the moon mainly comes from geochemical methods. However, it is uncertain to infer the water content of the lunar interior only from the samples collected from the lunar surface during the Apollo period. In this paper, we try to obtain the lower crust under the conditions of high temperature and high pressure in the laboratory. The main minerals in the upper mantle are olivine. The conductivity of pyroxene and pomegranate is combined with the typical lunar conductivity depth profile obtained by the lunar magnetometer to infer the water content of the lunar mantle. The main contents of this paper are as follows: 1) the present situation of research on water content in the moon and the electrical conductivity of mineral rocks under high temperature and high pressure in laboratory are reviewed. 2) the factors affecting the conductivity of mineral rocks under high temperature and high pressure in laboratory are divided into external factors and internal factors. The influence of these factors on the conductivity of mantle mineral rocks is summarized. The conductivity of mantle mineral rocks increases with the increase of temperature, iron content, water content and melt volume fraction, respectively. The conductivity increases and decreases with the increase of oxygen fugacity and pressure under the condition of no water content, but the opposite is true under the condition of water content. The influence of particle boundary on conductivity is ignored. The influence of measuring frequency and crystallization direction on conductivity is still controversial. It is necessary to consider the equilibrium time of the system and the iron loss in the sample when conducting the conductivity measurement. The main minerals in the upper mantle consist of olivine and clinopyroxene. Conductivity data of clinopyroxene and pomegranate in and without water. 4) the model is applicable to the temperature, pressure and oxygen fugacity of the moon mantle with similar chemical composition and mineral composition of water and no water conductivity model. The effective medium average method is used to calculate the functional relationship between the average conductivity of the mineral composition of the lunar mantle and the temperature and water content. The typical lunar conductivity depth profile obtained by the lunar magnetometer is used to calculate the temperature depth curves of the mantle with different total water contents, which is compared with the temperature range inferred from the lunar gravity and lunar earthquake data. It is inferred that the total water content of the lunar mantle is less than 10 ppm, which is consistent with the "big impact theory" hypothesis about the origin of the moon, and the recent petrological modeling of the lunar magmatic sea and the chlorine isotope analysis of the lunar sample. 5) summarizing and summarizing the main research results, pointing out the shortcomings of the research work and the direction of improvement in the future.
【学位授予单位】：中国地质大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P184

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