Abstract Primitive chondrites have bulk compositions close to that of the solar photosphere, with however significant variations of elemental ratio relative to the solar composition, depending on the volatility of the elements considered. This is classically understood as indicating a primary geochemical signature due to the formation of the components of chondrites (refractory inclusions, chondrules and matrix), or of their precursors, through condensation of a gas of near solar composition, plus secondary variations due to processes such as (i) incomplete volatilization of presolar components, (ii) complex high-temperature exchanges between condensed phases and the nebular gas, and (iii) sorting and transport of grains in the accretion disk before accretion of chondrite parent bodies. Because most of the mass of chondrites is made by elements which condense at high temperatures, equilibrium condensation produces in general little isotopic fractionation for these elements. Silicon is however an exception with per mil level equilibrium isotopic fractionation at high temperature between the SiO gas and condensed silicates, allowing to use silicon isotopes in chondrites to constrain the origin of their components and to put at test scenarios of condensation. Individual components (chondrule fragments, isolated olivines in the matrix, and matrix fragments) of the carbonaceous chondrite Allende were separated and analysed at high-precision for their silicon isotopic composition. Large variations have been found among chondrules ( δ 30 Si from -0.86 ± 0.16‰ 2 s.e. to +0.04 ± 0.03‰ for 11 chondrules), isolated olivines ( δ 30 Si from -0.51 ± 0.12‰ 2 s.e. to +0.20 ± 0.10 ‰ for 12 olivines), and matrix ( δ 30 Si from -0.95 ± 0.08‰ 2 s.e. to -0.41 ± 0.01 ‰ for 17 matrix fragments). These variations distribute on both sides of the bulk δ 30 Si value of Allende (-0.43 ± 0.03‰ 2 s.e., Armytage et al., 2011 ; Pringle et al., 2013 , Pringle et al., 2014 ; Savage and Moynier, 2013 ). There is a global positive trend between δ 30 Si values and Mg/Fe ratio for chondrules and isolated olivines. This systematics appears in agreement with what can be modeled for producing Allende components, or their precursors, from fractionated condensation of a single gaseous reservoir having initially the silicon isotopic composition of bulk Allende. Mass balance taking into account the mean abundances and δ 30 Si values of Allende components is consistent with their accretion in the Allende parent body in the proportions produced by the condensation of the parent parcel of nebular gas. This supports complementarity between chondrules, olivines and matrix as being a primary feature. However, this conclusion cannot be definitive because of the uncertainties in defining mean δ 30 Si values for Allende components.

中文翻译：

---

阿连德组分中与质量相关的硅同位素变化的凝聚起源：对互补性的影响

摘要 原始球粒陨石具有接近于太阳光球层的整体成分，但元素比例相对于太阳成分的显着变化，取决于所考虑元素的挥发性。这在经典上被理解为表明由于球粒陨石（耐火包裹体、球粒和基质）或其前体成分的形成而产生的主要地球化学特征，通过接近太阳成分的气体的冷凝，加上由于诸如此类的过程而产生的次生变化作为（i）太阳前成分的不完全挥发，（ii）凝聚相和星云气体之间复杂的高温交换，以及（iii）在球粒陨石母体吸积之前吸积盘中颗粒的分选和运输。因为大部分球粒陨石是由在高温下凝聚的元素制成的，平衡凝聚通常对这些元素产生很少的同位素分馏。然而，硅是一个例外，在高温下 SiO 气体和冷凝硅酸盐之间的每密耳级平衡同位素分馏，允许在球粒陨石中使用硅同位素来限制其成分的来源，并进行冷凝测试。对碳质球粒陨石阿连德的单个组分（球粒碎片、基质中分离的橄榄石和基质碎片）进行了分离，并高精度地分析了它们的硅同位素组成。在球粒中发现了很大的变化（对于 11 个球粒，δ 30 Si 从 -0.86 ± 0.16‰ 2 se 到 +0.04 ± 0.03‰），分离的橄榄石（δ 30 Si 从 -0.51 ± 0.12‰ 2 se 到 +0.20 ± 0.10 ‰，12 种橄榄石）和基质（δ 30 Si 从 -0.95 ± 0.08‰ 2 se 到 -0.41 ± 0.01 ‰），用于 17 个基质碎片. 这些变化分布在阿连德块体 δ 30 Si 值的两侧 (-0.43 ± 0.03‰ 2 se, Armytage et al., 2011 ; Pringle et al., 2013 , Pringle et al., 2014 ; Savage and Moynier, 2013 ）。球粒和孤立橄榄石的 δ 30 Si 值和 Mg/Fe 比值之间存在全球正趋势。该系统学似乎与从最初具有块体阿连德的硅同位素组成的单个气态储层的分馏冷凝中生产阿连德组分或其前体的模型相一致。考虑到阿连德组分的平均丰度和 δ 30 Si 值的质量平衡与它们在阿连德母体中以星云气体母体凝聚产生的比例相一致。这支持球粒、橄榄石和基质之间的互补性作为主要特征。然而，由于在定义阿连德组件的平均 δ 30 Si 值时存在不确定性，因此该结论无法确定。