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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >An impact origin for the foliation of chondrites
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An impact origin for the foliation of chondrites

机译：球粒陨石冲击的起源

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The origin of the foliation of ordinary chondrites is addressed through the study of the anisotropy of magnetic susceptibility (AMS) of these meteofites, based on a database of 295 different meteorites, including 35 achondrites (HED and SNC). AMS is a reliable proxy for preferred orientation in ordinary chondrites. Moreover, the intensity of magnetic anisotropy is constant over a given chondrite. The intensity of L chondrite petrofabric, evaluated by means of AMS measurements, and shock stage, determined independently by microscopic observation of shock features in silicates, appear to be positively correlated. This suggests that the oblate petrofabric in L chondrites is shock-induced. The inverse correlation between porosity and AMS intensity suggests that hypervelocity impacts compacted and lithified an originally loose material, causing the deformation of metallic Fe, Ni grains. ILL and H ordinary chondrites cannot be studied as easily as L chondrites: tetrataenite in LL chondrites affects the AMS in an unpredictable way, and shape anisotropy due to the strong susceptibility of H chondrites imposes strong constraints on sample shape. Our limited dataset for carbonaceous chondrites is compatible with a shock-induced foliation model. The very low degrees of AMS in Rumuruti chondrites testify that, surprisingly, the easily deformable Fe-sulfides in these chondrites show almost no deformation, suggesting that sulfidation is a secondary phenomenon that occurred after the major impacts on the Rumuruti parent body. The weak magnetic anisotropy of Martian meteorites implies that no significant macroscopic deformation took place during the severe impacts suffered by these rocks, which is explained by the weak initial porosity and high compressive strength of these igneous products. (c) 2005 Elsevier B.V. All rights reserved.
机译：通过对这些陨石的磁化率各向异性（AMS）进行研究，可以解决普通球粒陨石的起源，该数据库基于295种不同陨石的数据库，其中包括35个陨石（HED和SNC）。 AMS是普通球粒陨石中首选取向的可靠代表。而且，磁各向异性的强度在给定的球粒陨石上是恒定的。通过AMS测量评估的L球粒岩岩棉的强度和通过显微镜观察硅酸盐中的冲击特征独立确定的冲击阶段似乎呈正相关。这表明L球粒陨石中的扁圆形石油织物是由激振引起的。孔隙率与AMS强度之间呈负相关关系，表明超高速撞击会压实并石化本来就松散的材料，从而导致金属Fe，Ni晶粒变形。 ILL和H普通球粒陨石很难像L球粒陨石一样容易研究：LL球粒陨石中的四方榴石以不可预测的方式影响AMS，并且由于H球粒陨石的强烈易感性而对形状各向异性造成了对样品形状的强力约束。我们关于碳质球粒陨石的有限数据集与激波诱发的叶面模型兼容。令人惊讶的是，Rumuruti球粒陨石中的AMS含量非常低，这证明这些球粒陨石中易变形的Fe-硫化物几乎没有变形，这表明硫化是对Rumuruti母体产生重大影响之后发生的第二现象。火星陨石的弱磁各向异性表明，在这些岩石遭受的严重撞击过程中，没有发生明显的宏观变形，这可以解释为这些火成岩的初始孔隙度弱和抗压强度高。 （c）2005 Elsevier B.V.保留所有权利。

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