Variations in the Magnetic Properties of Meteoritic Cloudy Zone
Variations in the Magnetic Properties of Meteoritic Cloudy Zone
复制标题
陨石云带磁性的变化
DOI：
--
复制
发表时间：
2020
影响因子：
3.5
通讯作者：
R. Harrison
中科院分区：
文献类型：
--
作者：
C. Nichols;J. Bryson;R. Blukis;J. Herrero‐Albillos;F. Kronast;R. Rüffer;A. Chumakov;R. Harrison
铁和石铁陨石在缓慢冷却过程中形成魏德曼图案。该图案由多个微观结构组成，其长度尺度、成分和磁性能取决于冷却速率。在这里，我们重点关注多云区：该区域包含具有特殊古磁记录特性的纳米级辉长岩岛。我们系统地回顾了浑浊区特性如何随冷却速率和邻近的辉铜矿边缘的接近程度而变化。 X 射线光发射电子显微镜用于比较中菱铁矿（缓慢冷却速率）、IAB 铁陨石和橄榄石（中等冷却速率）以及 IVA 铁陨石（快速冷却速率）中云层的成分和磁化强度图。多云区域内磁相的比例也可以使用穆斯堡尔光谱来表征。我们首次对中菱铁矿中浑浊带的磁性状态进行了观察，结果表明，对于如此缓慢的冷却速率，四菱铁矿岛的生长大于多域阈值，从而在整个浑浊带上形成了大范围的均匀磁化区域，使其不适合进行古地磁分析。对于冷却速度最快的 IVA 陨石，Fe-Ni 有序化的时间不足以形成辉长岩，再次导致不适合古地磁分析的行为。最可靠的古地磁剩磁是由中等冷却速率（约 2–500 °C Myr -1 ）的陨石记录的，这些陨石产生的岛屿在尺寸和 Fe-Ni 有序度方面都“恰到好处”。
Iron and stony‐iron meteorites form the Widmanstätten pattern during slow cooling. This pattern is composed of several microstructures whose length‐scale, composition and magnetic properties are dependent upon cooling rate. Here we focus on the cloudy zone: a region containing nanoscale tetrataenite islands with exceptional paleomagnetic recording properties. We present a systematic review of how cloudy zone properties vary with cooling rate and proximity to the adjacent tetrataenite rim. X‐ray photoemission electron microscopy is used to compare compositional and magnetization maps of the cloudy zone in the mesosiderites (slow cooling rates), the IAB iron meteorites and the pallasites (intermediate cooling rates), and the IVA iron meteorites (fast cooling rates). The proportions of magnetic phases within the cloudy zone are also characterized using Mössbauer spectroscopy. We present the first observations of the magnetic state of the cloudy zone in the mesosiderites, showing that, for such slow cooling rates, tetrataenite islands grow larger than the multidomain threshold, creating large‐scale regions of uniform magnetization across the cloudy zone that render it unsuitable for paleomagnetic analysis. For the most rapidly cooled IVA meteorites, the time available for Fe‐Ni ordering is insufficient to allow tetrataenite formation, again leading to behavior that is unsuitable for paleomagnetic analysis. The most reliable paleomagnetic remanence is recorded by meteorites with intermediate cooling rates ( ∼ 2–500 °C Myr −1 ) which produces islands that are “just right” in both size and degree of Fe‐Ni order.
非岩浆铁陨石和winonaites的形成和暴露历史：来自Sm和W同位素的线索
影响因子：
5
作者：
Schulz;Upadhyay;Münker;C. Mezger
通讯作者：
C. Mezger