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月球岩浆洋演化与岩浆挥发分含量的制约
许英奎
导师刘耘
2014
学位授予单位中国科学院研究生院
学位授予地点北京
学位名称博士
学位专业地球化学
关键词嫦娥计划 月球 岩浆洋 温度梯度 挥发分
摘要我国深空探测的发展和嫦娥一号、二号、三号(玉兔号)探测器的成功发射,标志着我国已经步入全球深空探测强国之列。我国嫦娥工程总体分为“探月”、“登月”、“驻月”三大步骤,目前正在实施的“中国探月工程”就是嫦娥工程的第一步,又分为“绕”、“落”、“回”三小步骤,嫦娥一号、二号及玉兔号已经成功实现绕月和落月计划,接下来我国将在2017年前后实现探测器采样返回地球。我们相信在深空探测科学技术发展和全球太空竞争中,我们国家一定会抢先一步,取得举世瞩目的成绩! 尽管人类已经登上月球,并且能够利用现代精密望远镜观察遥远的星际,但是对自己生存的地球内部却了解非常有限。人类迫切地想了解我们所居住的星球的起源,想知道地球生命究竟是来自地球本身的演化过程还是来自外星移民。地质学家们通过对古老克拉通中零星保存的太古宙岩石和矿物,对25亿年前地球的地壳和地幔特征有了初步了解,但是对38亿前年冥古宙的地球演化知之甚少。获得这些信息的一个主要途径是比较行星学的研究成果,其中的一个重要研究对象就是月球。随着人类采集到的月球表层信息量的增加,我们对月球有了进一步的认识。但是月球起源及早期演化历史,仍然停留在理论假说的层面,需要进一步发展和探讨。本论文围绕月球前沿领域的两个热点问题展开工作:岩浆洋演化及月球内部含水量的制约。 月球和地球的年龄相近,但是月球由于体积小,散热快,早在30亿年前月球已经停止演化,进入所谓行星演化“死亡阶段”,也保存下来许多30亿年前的演化信息。研究当前的月球,就是研究30亿年前的地球。月球岩浆洋概念,是研究早期月球演化工作的一个重要成果,虽然岩浆洋演化还存在诸多猜测性和不确定性,但是行星早期岩浆洋阶段已经广为地学界和天文学界的学者接受。另外,月球内部挥发分的含量,尤其是水的含量,是当前月球研究热点问题之一。月球水的含量及来源,不但对地月系统起源具有重要意义,对生命的起源和演化起着指示作用,也关系到人类将来驻月并建立月球基地的可能性。 本论文使用大腔体铰链式六面顶压机,对玄武岩熔融体及部分熔融体在温度梯度下的热扩散效应进行实验模拟,并对样品薄片的主量元素沿温度梯度方向的含量变化进行电子探针打点分析。结果显示玄武岩熔体在温度梯度下,主量元素发生分异:Fe,Ca,Mg, Ti, P等元素倾向低温端富集,而Si, Na, K等元素倾向高温端富集,Al元素的分异不明显;玄武岩部分熔融体中由于不同温度下熔体的矿物饱和溶解度不同,结晶矿物成分及含量的不同造成熔体部分的不均一,在这种不均一的熔体之间也会发生浓度迁移,最终的平衡状态受热扩散和化学扩散共同控制。将高温高压实验结果应用到月球岩浆洋在温度梯度下的演化,得出岩浆洋不均一分异模型,并在此基础上进一步讨论月球斜长岩月壳的成因及古老年龄等问题。 月幔水含量的多少直接决定着月幔部分熔融过程形成岩浆的密度。因为月球表面的一级地质事实表明,斜长岩高地基本无岩浆事件,即岩浆密度高于斜长岩高地的密度。本论文通过收集月球探测Lunar计划,Apollo计划返回地球的月海玄武岩数据,添加可变的水含量至其中,辅以MELTS及MATLAB编程计算得出含水月海玄武岩密度,并对比高地斜长岩密度,根据月海玄武岩未喷发至地表的观察事实,制约月球内部含水量的最大值。计算结果表明,月海玄武岩岩浆含水量越高密度越小,当岩浆中水含量超过1000ppm,月海玄武岩岩浆就会因为密度低于斜长岩高地的密度而喷发至月表。由此,我们认为月球玄武岩岩浆中水含量小于1000ppm,并得出月球相对地球亏损挥发分的基本结论。
其他摘要With development of deep space exploration and successfully launch of China’s Chang’e spacecrafts, our country has stepped to the top list in this field in the world. China’s Chang'e project is divided into three large steps, which are “exploration”, “landing” and “stationing”. The first step, “China’s lunar exploration project” being implemented currently is divided into three steps “surrounding the moon”, “landing on the moon” and “backing to the Earth”. Chang’e I, II and the third spacecraft named “Rabbit” have successfully achieved the plans of surrounding and landing. Sample collecting and return to the Earth would be achieved in 2017. We believe that our country will make outstanding achievements in the space competition. Although the mankind have landed on the moon and watch the remote outer space using Modern precision telescope, they know little about the planetary interior that they live. We eagerly want to know the origin of the Earth and the life in this planet. The geologists analyzed the tine rocks and minerals that preserved in the ancient cratons and have preliminarily understood some of the character of Earth’s crust and mantle in 2.5Ga, but they know little about the Earth evolution before 3.8 Ga. A important access to know the Earth before that time is comparative planetology, especially the moon research. As we obtained more information of the lunar crust, we get further cognition of the moon than before. However, the origin of the moon and the preliminary evolution of it still stay on the level of hypothesis, and this issue needs to be discussed and develop. This thesis focus on two hot issues about the moon: the evolution of lunar magma ocean and the volatile concentration of the pre-eruptive magma of the moon. The moon has nearly the same age of the Earth, but much smaller volume than the latter. Duo to its fast heat dissipation, the moon has stopped evolving and stepped to the “dead stage” of planetary evolution. As a consequence, the information of this satellite before 3 billion years has been preserved. We are studying the primordial Earth to some degree when we do research of the moon. Lunar magma ocean, a concept deriving from early study about the moon, is now widely accepted by geologists and astronomers, though there is some uncertainty and speculative. Additionally, research about the volatile concentration in the lunar mantle, especially the water concentration, is one of the hottest issues. The concentration and origin of the lunar water has something to do with the Earth-moon system, the life coming and evolution, and the possibility that the mankind reside on the moon in the future. We use six sides press machine to take experiment aiming at the Thermal diffusion of basaltic melt and partial melt. And then we analyzed the major elements concentrations along the Thermal gradient using electronic probe. The results show that during Soret diffusion, elements such as Fe,Ca,Mg, Ti, P tend to migrate to low temperature, while Si, Na, K tend to migrate to high temperature. Thermal migration derives from crystal solubility with temperature. Spatial Thermal variation in a cumulus crystal pile sets up a gradient in interstitial melt composition, which in turn provides a diffusion potential for mass migration. And the last result of partially molten area is controlled by Thermal diffusion and chemical diffusion. We introduced Thermal diffusion concept to the lunar magma ocean evolving process, preliminarily established the differential magma ocean model, and based on this basis, discussed the genesis of lunar anorthositic crust. The Moon had long been thought to be depleted in volatiles such as H2O, S, COx and Cl2. Recently, researchers have measured volatile concentrations in minerals, glasses and inclusions of some lunar samples; results show that lunar rocks contain volatiles that are similar to terrestrial materials, much higher than previously thought. As we know, most mare basalts are located on
学科领域月球与行星科学
语种中文
文献类型学位论文
条目标识符http://ir.gyig.ac.cn/handle/352002/5890
专题研究生_研究生_学位论文
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许英奎. 月球岩浆洋演化与岩浆挥发分含量的制约[D]. 北京. 中国科学院研究生院,2014.
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