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定液态金属从硅酸盐熔体中重力分离。HF-W测年方法确定了这一事件的时间，并表明铁陨石与富钙铝包裹体(CaI)的年龄大致相同，CaI是太阳系最古老的岩石，但比球粒陨石的主要成分球粒陨石更古老。这种年龄关系与一般的假设相反，即分化的身体是软骨症母体融化的产物。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核心。同样，古老的富含硅酸盐的物质也不存在。通过研究出溶形成的非金属包裹体和直接分析金属相中的亲石元素，如Si、Al、Cr和P，可以重建铁陨石以前的富硅酸盐地幔。这些元素的浓度在高温下不符合金属/硅酸盐熔体平衡，但反映了低温过程。负责从金属中释放亲石元素的过程在IIIAB铁陨石中最有效，因为这些元素的浓度极低。铁陨石中硅酸盐、氧化物、磷酸盐、磷化物或硫化物的包裹体可能是这些元素的汇。我们将继续分析IC、IIC组的金属相，特别是IVA和IVB组的岩浆铁，它们的硅和铝在所有研究的铁陨石中都是最高的。我们还将继续在这些陨石中寻找非金属包裹体。此外，还将测量包裹体的氧同位素，以提供有关母体的同位素特征、均一化程度和氧的来源的信息。