地核物质成分研究进展

Advances in Studying the Composition of the Earth′s Core

系统介绍了地核的形成时间、地核的物理特性、化学成分和物质存在相态。利用W-Hf同位素系测年方法厘定地核与地幔分异的年龄是在地球形成的最初30 Ma。但是,内核的结晶年龄还是未知的。地核声波速度的各向异性可能是六面体紧密堆积（hcp）相铁的c轴方向沿地球轴线优选定向排列引起的。利用地球物理资料估算的地核密度与响应温压条件下液态铁的密度差值是5%~10%,因此,判断主要是铁镍合金的地核应该含有一定量的比铁轻的元素,如碳、硫、磷、硅、氧、氢以及其他轻元素。这些轻元素对D″的形成、地幔柱的形成、演化以及地震、火山活动的影响应该是值得探索的新领域。

The age,physical properties and chemical compositions of the Earth＇s core are reviewed.The formation time of the core and mantle is determined by W-Hf isotope dating to be 30 Ma at the beginning of the earth formation.However,the time of the inner core crystallization from the liquid core remains an open question.The inner core is anisotropic in elastic wave velocity,which is considered as a result of the c axis of hcp-structure iron arranged predominantly along the Earth′s pole axis.The density difference of the core between the PREM model and liquid iron at the core temperature and pressure is about 10%,which indicates that the core contains light elements,such as C,S,P,Si,O,H,Mg,etc.The light elements in the core may play an important role in the formation of D″ layer between the core and mantle,formation and evolution of the plume and activities of volcano and earthquake,which is the new field for us to investigate.