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

方解石和菱镁矿是地球上最常见的碳酸盐。更深入洞察相位关系和无水的融化行为和含水的碳酸钙和氧化物系统是至关重要的理解地球地幔和项目8中的碳循环的研究单位是处理这种topicThe项目分为三个部分:第1部分中我们将决定在无水条件下镁的熔化曲线的压力范围4 - 13 GPa的原位测量电导率变化多砧出版社当菱镁矿融化。在第二部分中，我们将在无水条件下，通过淬火多砧运行，确定CaCO3和MgCO3体系在9gpa和高温下（从900℃开始）的亚固相关系和超固相关系，然后建立含水CaCO3和MgCO3体系超固相P， T空间的相关系。我们将使用旋转多砧压力机来克服在以前的研究中观察到的淬火问题。在第三部分中，我们将通过在汉堡同步加速器储存环PETRA III上新安装的多砧装置进行现场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。这里，在高压和高温下的熔化将通过X射线衍射图中漫射散射的出现来确定。这种不同的实验方法来确定在含水体系中的熔化关系是必要的，因为水的存在会伪造电导率的结果。

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.