Katsura Tomoo
Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, Germany.
Commun Chem. 2025 Feb 1;8(1):28. doi: 10.1038/s42004-024-01389-8.
The knowledge of phase relations of constitutive minerals is essential to investigate the structure, dynamics and evolution of the Earth and planetary interiors. This paper reviews the phase relations of bridgmanite, the most abundant mineral in the Earth's lower mantle, with an ideal composition of MgSiO. Bridgmanite has an orthorhombic structure with larger dodecahedral A and smaller octahedral B cation sites. The A-sites can incorporate Mg, Fe, Fe, and Al, while the B-sites accommodate Si, Al and Fe. The incorporation of hydrogen and large cations like Ca is likely limited, although these issues are still debated. Al and Fe, respectively, can form the charge-coupled components, AlAlO and FeFeO occupying both A- and B-sites. When both Al and Fe are present, Al occupies B-sites, and Fe occupies A-sites, forming FeAlO. In systems with excess MgO, Al and Fe also form the oxygen vacancy components MgAlO□ and MgFeO□. The phase relationships of bridgmanite with coexisting phases are discussed as a function of pressure, temperature, and oxygen fugacity from the simple MgSiO system to the complex MgO-FeO-FeO-AlO-SiO system.
了解组成矿物的相关系对于研究地球和行星内部的结构、动力学及演化至关重要。本文综述了下地幔中最丰富的矿物——布里奇曼石（理想组成为MgSiO）的相关系。布里奇曼石具有正交结构，有较大的十二面体A阳离子位和较小的八面体B阳离子位。A位可容纳Mg、Fe、Fe和Al，而B位容纳Si、Al和Fe。氢和Ca等大阳离子的掺入可能有限，尽管这些问题仍存在争议。Al和Fe分别可形成占据A位和B位的电荷耦合组分AlAlO和FeFeO。当Al和Fe都存在时，Al占据B位，Fe占据A位，形成FeAlO。在MgO过量的体系中，Al和Fe还会形成氧空位组分MgAlO□和MgFeO□。本文讨论了从简单的MgSiO体系到复杂的MgO-FeO-FeO-AlO-SiO体系中，布里奇曼石与共存相的相关系随压力、温度和氧逸度的变化情况。
