月球物质的Re-Os同位素组成研究:对月球后期增生历史的指示

发布时间：2019-02-15 14:49

【摘要】：Re-Os同位素体系是理解月球强亲铁元素的分布规律和示踪月球的后期增生历史的重要手段。目前人们对月球物质Re-Os同位素成分的了解还是十分有限的,已有的Re-Os同位素数据显示一些能代表月幔成分特征的月海玄武岩具有很低的Re和Os的浓度,以及类似于球粒陨石的187Os/188Os成分特征,而月球火山玻璃和月壤等表现出相对高的Re、Os丰度和相对富放射成因Re-Os同位素成分。一般认为月球月幔的Re、Os和其他强亲铁元素相对球粒陨石是非常亏损的,而地球地幔则具有相对较高的强亲铁元素丰度(0.008倍CI球粒陨石的丰度)。新的Re-Os同位素结果证明月幔确实是亏损的,但是月球和地球在太阳系演化的较晚时期都有外来的球粒陨石物质的大量加入,即后期增生(late accretion)过程,导致了月球和地球上部物质(如月球火山玻璃、月壤等)相对地富集Os同位素和强亲铁元素,这些外来物质的后期增生可能是长期和持续的,增生过程主要发生在3.9～4.4Ga。但目前仍不清楚后期增生的陨石物质是被逐渐加入的,还是在一个相对较短的时期大量加入的,因此尚需对更多的月球物质做进一步的Re-Os同位素和强亲铁元素成分的研究。
[Abstract]:The Re-Os isotopic system is an important means to understand the distribution of the strong ferriphilic elements and trace the late proliferative history of the moon. At present, people's understanding of the Re-Os isotopic composition of lunar material is still very limited. The available Re-Os isotopic data show that some lunar basalts, which can represent the characteristics of the lunar mantle composition, have very low Re and Os concentrations. The characteristics of 187Os/188Os compositions are similar to chondrites, while the lunar volcanic glass and lunar soil show relatively high Re,Os abundance and relatively rich radiogenic Re-Os isotopic compositions. It is generally considered that the Re,Os and other strong iron elements in the lunar mantle are very depleted relative to chondrites, while the mantle of the earth has a relatively high abundance of strong ferriphilic elements (0.008 times the abundance of CI chondrites). The new Re-Os isotope results prove that the mantle is indeed depleted, but both the moon and the earth have a large addition of chondrites in the late solar system, that is, the late accretive (late accretion) process. This has led to the relative enrichment of Os isotopes and strong iron elements in the lunar and upper parts of the Earth (such as lunar volcanic glass, lunar soil, etc.), and the late accumulation of these foreign substances may be long-term and persistent. The proliferative process mainly occurred in 3.9L 4.4Ga. However, it is still unclear whether the late accretionary meteorites were gradually added or were added in large quantities in a relatively short period of time, so further studies on Re-Os isotopes and strong iron-friendly elements are needed for more lunar matter.
【作者单位】：中国科学院广州地球化学研究所;
【基金】：国家自然科学基金(40873054,40930316)
【分类号】：P184

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