| 榴辉岩造岩矿物的热状态方程研究 |
| 魏舒怡
|
| Thesis Advisor | 周文戈
|
| 2014
|
| Degree Grantor | 中国科学院研究生院
|
| Place of Conferral | 北京
|
| Degree Name | 博士
|
| Degree Discipline | 矿物学、岩石学、矿床学
|
| Keyword | 榴辉岩
高温高压
Pvt状态方程
同步辐射x射线衍射
金刚石压腔（dac）
|
| Abstract | 榴辉岩是一种高温高压变质岩，其中绿辉石和石榴子石的含量之和大于80%，常常含蓝闪石等矿物。本文研究的样品采自于著名的大别山高压变质带。作者通过模拟下地壳上地幔温度压力环境，对榴辉岩主要造岩矿物石榴子石和绿辉石进行高温高压实验，拟合矿物的PVT状态方程，推算出榴辉岩主要造岩矿物在一定温度压力条件下的晶胞体积、体弹模量与温度、压力之间的关系，进而了解矿物在高温高压下的密度、弹性、热膨胀等性质。建立模型演算不同温度压力条件下的榴辉岩+二辉橄榄岩密度，并与软流圈物质的密度进行对比，初步分析在什么温度压力条件下，可能会发生拆沉作用。作者利用外电阻加温金刚石压腔装置(DAC)结合同步辐射粉晶X射线衍射方法，对四种不同成分产地的榴辉岩样品中的石榴子石和辉石矿物进行了PV状态方程和PVT状态方程研究，结合前人研究成果，讨论了一系列镁铝-铁铝-钙铝榴石的成分变化对其晶胞体积、体弹模量等物性参数的影响。获得了研究结果如下：1. 分析四种不同成分的镁铝-铁铝-钙铝榴石在室温300K的PV状态方程，发现随着石榴石中镁铝榴石端元组分含量的增大，晶胞体积值随之变小，体弹模量值也同时减小。作者结合前人的研究结果，拟合了镁铝-铁铝-锰铝-钙铝榴石系列石榴石体弹模量与其铁铝榴石端元组分（XAlm）和镁铝榴石端元组分（XPyr）含量之间的定量关系，根据这个关系式，可以在知道石榴石的铁铝榴石端元组分或者镁铝榴石端元组分的情况下估算石榴石的体弹模量。2. 对MW01、SH962和SM969三种石榴子石样品进行高温高压PVT状态方程研究，得到零压晶胞体积、零压体弹模量、体弹模量的温度导数和热膨胀系数值，由于高温条件下的数据点较少，获得的石榴子石的体弹模量的温度导数和热膨胀系数值比前人的结果明显偏高。3. 拟合四种不同成分的辉石PV状态方程，得到室温300 K条件下的零压晶胞体积、零压体弹模量、体弹模量的温度导数等。本实验结果结合前人的研究成果，发现在透辉石-硬玉系列辉石和镁铁质辉石中，体弹模量与端元组分没有明显的相关性。4. 首次获得了成分为Di89Jd11的辉石的高温高压弹性数据。但由于高温条件下的数据点较少，获得的辉石的体弹模量的温度导数和热膨胀系数值是前人温度导数和热膨胀系数值的4-6倍。5. 利用前面拟合得到的石榴石、绿辉石、透辉石和顽火辉石的状态方程的数据，结合前人大量的有关这些矿物以及橄榄石和熔体的状态方程研究成果，以及岩石圈热状态的研究成果，建立岩石圈底部温压条件下（90-250 km，1250-1350°C）的温度压力模型，估算榴辉岩、pyrolite地幔岩模型二辉橄榄岩以及含一定量熔体的二辉橄榄岩的密度，初步分析得到在富含榴辉岩且软流圈顶部深度小于200km的情况下，拆沉作用得以发生。 |
| Other Abstract | Eclogite is a kind of metamorphic rock, which contents the omphctite and garnet more than 80%, and glaucophane some. The samples studied in this paper are collected from the high-pressure metamorphic belts of Dabie Mountains. The main rocks forming minerals of eclogite are researched on high-pressure and high-temperature which is simulating the lower mantle crust condition. The PVT equation of state (EOS) is fitted to calculate the cell volume and bulk modulus and the relation of them. Modeling the relationship between the density of eclogite+ lherzolite and the temperature and pressure. Comparing The density of eclogite+ lherzolite and asthenosphere is compared to get in what condition the delamination may occur. The author uses external resistance heating diamond anvil cell (DAC) combined with synchrotron radiation powder X -ray diffraction method, to study the PVT EOS and PV EOS of four eclogite samples of different components. Combined with previous studies, discussed a series composition change of Pyr-Alm-Grs with their cell volume , bulk modulus and other physical parameters. The results obtained are as follows:1. Analysising the PV EOS of four different components of Pyr-Alm-Grs at room temperature 300K, found that the cell volume decreasing with the content of Pyr increasing. Combined with the previous studies, fitting the relationship of Pyr content and bulk modulus at a series composition change of Pyr-Alm-Grs. According to the relationship , you can estimate the bulk modulus of garnet in the know Pyr-Alm end-member component.2. Researching for garnet samples MW01, SH962 and SM969 HPHT PVT EOS, get zero pressure cell volume , zero-pressure bulk modulus , bulk modulus temperature derivative and the thermal expansion coefficient values. Due to the high temperature conditions fewer data points , the temperature derivative of bulk modulus and the thermal expansion coefficient values are significantly higher than the previous results .3．Fitting four different omphacite samples PV EOS, get zero pressure cell volume, zero-pressure bulk modulus , bulk modulus and temperature conductivity at room temperature 300 K. Combined with results of previous studies , found that there’s no obviously correlationship between contents of pyroxene and the bulk modulus.4. The HTHP elastic data of the Di89Jd11 pyroxene is obtained first time. However, due to fewer data points under high temperature conditions , the temperature derivative of bulk modulus and the thermal expansion coefficient values are 4-6 times the previous research result.5. Combined the EOS data of garnet, omphacite, diopside and enstatite before, with previous research result to build the condition model of under-lithosphere(90-250km, 1250-1350°C). Using that model, you can estimate the density of eclogite , pyrolite mantle rocks and lherzolite. The delamination may occur at the top of the asthenosphere depth of less than 200km after preliminary analysis the model. |
| Subject Area | 地球深部物质与流体作用地球化学
|
| Language | 中文
|
| Document Type | 学位论文
|
| Identifier | http://ir.gyig.ac.cn/handle/352002/5885
|
| Collection | 研究生_研究生_学位论文
|
Recommended Citation
GB/T 7714 |
魏舒怡. 榴辉岩造岩矿物的热状态方程研究[D]. 北京. 中国科学院研究生院,2014.
|
Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.
Edit Comment