地球早期地幔不均一的Hf-W同位素制约

早期地幔性质及其演化的研究对全面理解地球演化历史至关重要。地球早期地幔不均一性及形成不均一性的动力学过程是近年来地球化学研究的热点。短寿命Hf-W放射性衰变体系几乎不受后期改造作用的影响，早期分异形成的地球化学储库的W同位素组成差异明显，因而W同位素能够很好地揭示地球早期物质分异、混合、交换等过程，从而确定形成早期地幔不均一的动力学过程。本项目以太古宙科马提岩为研究目标（包括华北克拉通、加拿大Slave克拉通、南非Kaapvaal克拉通和印度Dharwar克拉通的科马提岩样品），通过分析样品的W同位素组成，结合样品的Nd同位素组成以及铂族元素含量，建立起地幔W同位素组成与早期地幔演化的内在联系，揭示地球早期各圈层间物质分异、混合以及交换等过程，确定形成地球早期地幔不均一的主要动力学机制，并为地球早期构造样式提供制约。

The nature and evolution of early Earth's mantle are critical for a comprehensive understanding of the Earth’s evolution. The dynamic process causing mantle heterogeneity in the early Earth is highly debated in recent years. The short-lived Hf-W radioactive decay system is hardly affected by the later geological processes. The geochemical reservoirs formed by early differentiation have different W isotope compositions. Tungsten isotopes, therefore, could reveal the differentiation, mixing, and exchange processes of the material as well as the dynamic process for the formation of the mantle heterogeneity of early Earth. Tungsten isotope compositions of the Archean komatiites (i.e., komatiites from the North China Craton, the Slave Craton, the Kaapvaal Craton, and the Dharwar Craton) will be measured in this study. Combined with the Nd isotope and Platinum Group Elements (PGEs) concentrations, our W isotope data will provide clues for the links between W isotopes and evolution of the early mantle, reveal the differentiation, mixing, and exchange processes of the material of early Earth, determine the dynamic process causing the mantle heterogeneity of early Earth, and constrain the tectonic style of early Earth.