X-ray computed tomography: Morphological and porosity characterization of giant Antarctic micrometeorites
X-ray computed tomography: Morphological and porosity characterization of giant Antarctic micrometeorites
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X 射线计算机断层扫描：巨型南极微陨石的形态和孔隙度特征
DOI：
10.1111/maps.13533
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发表时间：
2020
影响因子：
2.2
通讯作者：
Dionnet Z
中科院分区：
文献类型：
--
作者：
Dionnet Z
巨型微陨石（直径400-2000 µm）非常罕见，具有科学价值。通过X射线计算机断层扫描（X-CT）进行的三维非破坏性表征提供了有关岩石学和岩石成因的信息，并作为指导，以最大限度地提高后续对这些珍贵行星材料的多分析研究。在这里，我们讨论了通过X-CT对22个巨大MM获得的结果以及基于其3-D密度对比图像的分类。火山渣和未熔化的火山灰具有不同的孔隙度范围（分别为10-40体积%和0-25体积%）。我们观察到一个孔隙度的变化内scoriaceous火山灰，这使得他们的大气进入飞行历史得到解决。对于第一次，自旋进入明确证明了四个部分熔化的熔体。此外，我们能够解析单个颗粒中的热梯度，基于孔隙率变化（被视为随着峰值温度的升高，孔隙丰度和尺寸逐渐增加）。此外，我们通过孔隙分布的3D分析来探索母体的改变，表明在我们的数据集中，激波组构要么不存在，要么发展得很弱。最后，由于检测到假晶球粒，我们估计强烈的水蚀变的C1或C1-类物质可以代表该尺寸分数（400-1000 µm）的MM通量的18%。
Giant micrometeorites (MMs; 400–2000 µm) are exceedingly rare and scientifically valuable. Three‐dimensional nondestructive characterization by X‐ray computed tomography (X‐CT) provides information on the petrography and thus petrogenesis of MMs and serves as a guide to maximize subsequent multi‐analytical studies on such precious planetary materials. Here, we discuss the results obtained by X‐CT on 22 giant MMs and the classification based on their 3‐D density contrast images. Scoriaceous and unmelted MMs have distinct porosity ranges (10–40 vol% versus 0–25 vol%, respectively). We observe a porosity variation inside scoriaceous MMs, which allows their atmospheric entry flight history to be resolved. For the first time, spinning entry is explicitly demonstrated for four partially melted MMs. Furthermore, we are able to resolve the thermal gradient in a single particle, based on porosity variation (seen as a progressive increase in pore abundance and size with higher peak temperatures). Moreover, we explore parent body alteration through the 3‐D analysis of pores distribution, showing that shock fabrics are either absent or weakly developed in our data set. Finally, owing to the detection of pseudomorphic chondrules, we estimate that the intensively aqueously altered C1 or CI‐like material could represent 18% of the MM flux at this size fraction (400–1000 µm).