Origin of iron meteorites - the oldest materials in the Solar System

铁陨石的起源——太阳系中最古老的物质

• 批准号: 147256222
• 负责人: Dr. Jutta Zipfel
• 金额: --
• 依托单位: Abteilung Isotopengeologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/147256222?language=en
• 关键词: Origin; iron; meteorites; oldest; materials

Models of the formation of magmatic iron meteorites assume gravitational segregation of liquid metal from a silicate melt. The Hf-W dating method determines the timing of this event and shows that iron meteorites have about the same age as Ca,Al-rich inclusions (CAI), the oldest rocks in the solar system but are older than chondrules the major component of chondrites. This age relationship is in contrast to the general assumption that differentiated bodies are the product of melting of chondritic parent bodies. It emphasizes the importance of magmatic iron meteorites which represent the metal cores of the oldest planetesimals. Similarly old silicate-rich material does not exist. The former silicate-rich mantles of the iron meteorites may be reconstructed i) by studying non metal inclusions that could have formed by exsolution and ii) by direct analyses of lithophile elements, like Si, Al, Cr, and P in metal phases. The concentrations of these elements are inconsistent with metal/silicate melt equilibrium at high temperature but reflect low temperature processes. The process responsible for loosing lithophile elements from the metal was most efficient in IIIAB iron meteorites which have extremely low concentrations of such elements. Inclusions of silicates, oxides, phosphates, phosphides or sulfides in iron meteorites may have acted as sink for these elements. We will continue to analyze metal phases of group IC, IIC and especially IVA and IVB magmatic irons which have the highest concentrations of Si and Al in all studied iron meteorites. We will also continue to search for non-metal inclusions in these meteorites. In addition, oxygen isotopes of inclusions will be measured to provide information about the isotopic signature of the parent body, degree of homogenization and origin of the oxygen.

岩浆铁陨石的形成模型假设硅酸盐熔体的液态金属重力分离。 HF-W年期方法确定了此事件的时机，并表明铁陨石的年龄与CA，富含Al的夹杂物（CAI）大致相同，这是太阳系中最古老的岩石，但比软骨更古老，是软骨的主要组成部分。这种年龄关系与一般假设形成鲜明对比：分化体是软骨母体融化的产物。它强调了岩浆铁陨石的重要性，它代表了最古老的行星的金属岩心。同样，不存在旧硅酸盐的材料。以前的铁陨石的富含硅酸盐的地幔可以通过研究非金属夹杂物来重建i），这些非金属夹杂物可以通过exsolution和ii）通过直接分析金属阶段的岩石，Al，cr和p的直接分析来形成。这些元素的浓度与金属/硅酸盐熔体在高温下的平衡不一致，但反映了低温过程。负责从金属中丢失岩石元素的过程在IIIAB铁陨石中最有效，这些陨石的含量极低。铁陨石中的硅酸盐，氧化物，磷酸盐，磷酸盐或硫化物的夹杂物可能是这些元素的下沉。我们将继续分析IC组，IIC，尤其是IVA和IVB岩浆铁的金属阶段，在所有研究的铁陨石中，Si和Al浓度最高。我们还将继续在这些陨石中搜索非金属夹杂物。此外，还将测量夹杂物的氧同位素，以提供有关母体同位素特征，均匀化程度和氧气起源的信息。