Phase relations and melting in the system CaCO3 und MgCO3 at high pressures and temperatures

CaCO3 和 MgCO3 体系在高压和高温下的相关系和熔化

• 批准号: 390971151
• 负责人: Professorin Dr. Monika Koch-Müller
• 金额: --
• 依托单位: Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum (GFZ)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/390971151?language=en
• 关键词: Phase; relations; melting; system; CaCO3

Calcite and magnesite are among the most common carbonates of the Earth. A deeper insight into the phase relations and melting behavior of the anhydrous and hydrous CaCO3 and MgCO3 system is crucial to understand the carbon cycle in the Earth mantle and project 8 of the Research Unit is dealing with this topicThe project is devided in three parts:In part 1 we will determine of the melting curve of magnesite under anhydrous conditions in the pressure range of 4 to 13 GPa by in situ measurements of the electrical conductivity change in a multi anvil press when magnesite melts. In part 2 we will determine the sub and super solidus phase relations of the CaCO3 and MgCO3 system at 9 GPa and high temperature (starting from 900 C) by quenched multi anvil runs under anhydrous conditions and then establish the phase relations in the super solidus P, T space of the hydrous CaCO3 and MgCO3 system. We will use a rotating multi anvil press to overcome quenching problems as observed in previous studies.In part 3 we will examine the pressure dependence of the melting curve of magnesite under hydrous conditions by means of in situ X ray diffraction measurements with the newly installed multi anvil apparatus at the synchrotron storage ring PETRA III in Hamburg. Here melting at high pressures and temperatures will be established by the occurrence of diffuse scattering in the X ray diffraction pattern.This different experimental approach to determine the melting relation in the hydrous system is necessary as the presence of water would falsify the results on the electrical conductivity.

方解石和菱镁矿是地球上最常见的碳酸盐。深入了解无水和有水CaCO3和MgCO3体系的相关系和熔融行为对于了解地幔中的碳循环是至关重要的，该研究单位的项目8正在处理这一主题。该项目分为三个部分：在第一部分中，我们将通过原位测量在多个砧压机中镁矿熔化时电导率的变化来确定在无水条件下在4~13 Gpa的压力范围内菱镁矿的熔融曲线。在第二部分中，我们将在无水条件下用淬火多个顶锤测定CaCO_3和MgCO_3体系在9 Gpa和高温(从900℃开始)下的亚固相线和超固相线的相关系，然后在含水CaCO_3和MgCO_3体系的超固相线P、T空间建立相关系。我们将使用旋转多砧压机来克服先前研究中观察到的淬火问题。在第三部分中，我们将利用新安装在汉堡同步加速器存储环Petra III上的多砧压机进行原位X射线衍射测量，研究含水条件下菱镁矿熔化曲线的压力依赖性。在这里，高温高压下的熔化是通过X射线衍射谱中弥散散射的发生来建立的。这种不同的实验方法来确定含水体系中的熔融关系是必要的，因为水的存在会使电导率的结果失真。