Geochemical and isotopic evidence bearing on the origin of large, igneous-textured inclusions in ordinary chondrites

スポンサーリンク

概要

• 論文の詳細を見る

• Geochemical and isotopic data for large, igneous-textured inclusions in ordinary chondrites suggest that the inclusions formed by the melting of diverse precursors, and that various inclusions had different origins. Some inclusions were metasomatized (chemically altered) and metamorphosed, and many appear to have degassed argon in late shock events. The inclusions can be subdivided into two chemical groups, Na-rich (Na/Al>0.35 at.) and Na-poor (≤0.35), which may have originated in different ways. The major-and trace-element abundances of Na-rich inclusions are best explained by these inclusions having formed by the shock-melting of ordinary chondrites, often accompanied by loss of FeNi-metal and sulfide and by preferential melting and accumulation of an albitic feldspar component. In contrast, there is no evidence that shock-melting was involved in the formation of Na-poor inclusions, which have compositions that were largely controlled by vapor-fractionation processes. It is suggested that the precursors to Na-poor inclusions consisted of mixtures of vapor-fractionated materials in a system of condensed phases that chemically resembled CI-chondrites, except for being depleted in volatile-lithophile elements and in metal and sulfide. Sodium-poor inclusions can be subdivided into two types, Trend A and Trend B, which differ in their trace-element characteristics, in the nature of their compositional variations, and in their inferred precursors. Trend A Na-poor inclusions are enriched in refractory elements, and could have formed by the melting of mixtures containing a chondritic (CI-like) component and a refractory (Al-rich, CAI-like) component. Trend B Na-poor inclusions are enriched in elements of intermediate volatility (Si) and appear to have formed from precursors that lost both a refractory (Mg-rich, olivine-rich) and a volatile component. The precursors to these inclusions could have been produced by the removal of an olivine-rich condensate during fractional condensation, or by the condensation of Si-rich gases during fractional vaporization.

著者

• Snyder Gregory

  Planetary Geosciences Institute Department Of Geological Sciences University Of Tennessee

• Taylor Lawrence

  Planetary Geosciences Institute Department Of Geological Sciences University Of Tennessee

• Ruzicka Alex

  Planetary Geosciences Institute, Department of Geological Sciences, University of Tennessee

関連論文

• Geochemical and isotopic evidence bearing on the origin of large, igneous-textured inclusions in ordinary chondrites
• Constraints on the genesis and evolution of the Moon's magma ocean and derivative cumulate sources as supported by lunar meteorites

スポンサーリンク