10Be-10B systematics of chondrules and refractory objects in primitive chondrites

原始球粒陨石中球粒和难熔物体的 10Be-10B 系统学

• 批准号: 211675105
• 负责人: Professor Dr. Mario Trieloff
• 金额: --
• 依托单位: Max-Planck-Institut für Chemie (Otto-Hahn-Institut)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/211675105?language=en
• 关键词: 10Be; 10B; systematics; chondrules; refractory

The short-lived isotope 10Be was present in the early solar system and produced by energetic particle irradiation, either from the early sun by solar cosmic rays or during collapse of the giant molecular cloud by interaction with galactic cosmic rays. Refractory inclusions with canonical 26Al/27Al ratio have a slightly higher initial 10Be/9Be ratio than hibonites from Murchison with 26Al deficit. As both types of refractory materials are commonly considered as earliest solar nebula material, the decoupling of initial 10Be/9Be and 26Al/27Al is interpreted as evidence for a different initial distribution in the solar nebula, 26Al being derived from a nucleosynthetic and 10Be from a solar irradiation source. However, it is unclear to what extent different irradiation settings of the precursor material (irradiation time and location, shielding effects and production rates) could lead to differences, as precursor material of refractory CAIs and hibonites may have principally very similar exposure histories. Chondrules are a type of material that formed 1-4 Ma after CAIs, by different energetic processes in a different environment. However, the low degree of Be/B fractionation mostly precludes evaluation of the initial 10Be/9Be ratio. Nevertheless, two promising—though not compelling—case studies exist on Al-rich chondrules, where it was shown that fractionation seems to be sufficiently large to constrain the initial 10Be/9Be with modern SIMS (IMS 1280-HR) techniques. Hence a new attempt on Al-rich chondrules of primitive carbonaceous and enstatite chondrites, as well as refractory materials from enstatite chondrites (CAIs and oldhamites) seems promising, particular if preparation and measuring techniques avoiding boron contamination are used.

短寿命同位素10 Be存在于早期太阳系中，由高能粒子辐射产生，要么来自早期太阳的太阳宇宙射线，要么在巨大分子云坍缩期间与银河宇宙射线相互作用。典型的26 Al/27 Al比的耐火夹杂物有一个稍高的初始10 Be/9 Be比从Murchison与26 Al赤字的黑云母。由于这两种类型的耐火材料通常被认为是最早的太阳星云材料，初始10 Be/9 Be和26 Al/27 Al的退耦被解释为太阳星云中不同初始分布的证据，26 Al来自核合成，10 Be来自太阳辐射源。然而，目前尚不清楚前体材料的不同辐照设置（辐照时间和位置、屏蔽效应和生产率）在多大程度上会导致差异，因为耐火CAI和灰岩的前体材料可能具有基本上非常相似的暴露历史。球粒是一类在CAIs后1-4 Ma，在不同环境中通过不同能量过程形成的物质。然而，低程度的Be/B分馏主要排除了初始10 Be/9 Be比的评价。然而，两个有前途的，但不是强制性的案例研究存在于富铝陨石球粒，在那里它被证明，分馏似乎是足够大，以限制与现代西姆斯（IMS 1280-HR）技术的初始10 Be/9 Be。因此，对原始碳质和顽火辉石的富铝球粒以及顽火辉石的耐火材料（CAIs和oldhamites）的新尝试似乎是有希望的，特别是如果使用避免硼污染的制备和测量技术。