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。110深入了解无水和含水CaCO_3和MgCO_3体系的相关系和熔融行为对理解地幔中的碳循环至关重要，本研究所的项目8就是关于这一主题的。该项目分为三个部分：第一部分，我们将通过在多砧压力机上原位测量菱镁矿熔融时的电导率变化，确定菱镁矿在4 - 13 GPa压力范围内的无水条件下的熔融曲线。在第二部分中，我们将通过在无水条件下的淬火多砧实验，确定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相关系，然后建立水合CaCO_3和MgCO_3体系在超固相线P，T空间中的相关系。我们将使用一个旋转的多砧压力机来克服淬火问题，在以前的研究中观察到的。在第三部分中，我们将检查的压力依赖性的菱镁矿的熔化曲线在含水条件下，通过原位X射线衍射测量与新安装的多砧装置在同步加速器储存环PETRA III在汉堡。在这里，在高压和高温下的熔化将通过在X射线衍射图中发生漫散射来建立。这种不同的实验方法来确定含水系统中的熔化关系是必要的，因为水的存在会使电导率的结果变假。

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.