Changes in thermomagnetic and X-ray diffraction properties of Asby dolerite with distance from the Lockne impact structure, Sweden

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors Pub Date : 2024-01-30 DOI:10.1016/j.pepi.2024.107145

Pradyut Phukon , Amar Agarwal , Bruno Daniel Leite Mendes , Agnes Kontny , Gaurav Joshi

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Abstract

The Lockne impact structure in Sweden formed due to a meteorite impact into the Proterozoic basement rocks in the Ordovician. The dykes of Asby dolerite are part of the target basement and are located outside the crater rim. We investigated the variation in thermomagnetic properties and X-ray diffraction (XRD) spectra of Asby dolerite with distance from the crater centre to find evidence of a potential low shock overprint. Ti-poor, (Ti)-magnetite with dominantly pseudo-single domain behaviour is the main magnetic carrier in the studied samples. Towards the centre of the crater, the Verwey transition temperature (T_v) and Curie temperature (T_c) decrease, whereas alteration indices increase systematically. Higher alteration indices and lower T_v near the crater centre may be owed to more intense fracturing of the silicate minerals which facilitated low-temperature oxidation of (Ti)-magnetite and alteration of mafic dykes by improving fluid circulation in a network of fractures in the silicate minerals. Higher deformation near the crater centre is supported by our XRD results, as the peak position (2θ value) of plagioclase (040), pyroxene $(\bar{3} 11$ ) and magnetite (311) peaks decrease, while the width of the plagioclase (040) and pyroxene $(\bar{3} 11$ ) peaks increase towards the centre. This study shows that changes in thermomagnetic properties and lattice parameters of magnetite are a powerful tool to characterise low shock pressure deformation in impacted target rocks.

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阿斯比辉绿岩的热磁和 X 射线衍射特性随与瑞典洛克内撞击结构的距离变化而变化

瑞典的洛克内撞击结构是由于奥陶纪陨石撞击新生代基底岩石而形成的。阿斯比辉绿岩堤坝是目标基底的一部分，位于陨石坑边缘之外。我们研究了阿斯比辉绿岩的热磁性能和 X 射线衍射（XRD）光谱随与陨石坑中心的距离变化而变化的情况，以寻找潜在低冲击叠印的证据。所研究样品中的主要磁性载体是贫钛（Ti）磁铁矿，主要表现为伪单畴。在陨石坑中心，维氏转变温度（Tv）和居里温度（Tc）降低，而蚀变指数则系统地增加。陨石坑中心附近的蚀变指数较高，Tv较低，这可能是由于硅酸盐矿物的断裂更为剧烈，通过改善硅酸盐矿物断裂网络中的流体循环，促进了（钛）磁铁矿的低温氧化和岩浆岩堤的蚀变。陨石坑中心附近较高的形变得到了 XRD 结果的支持，因为斜长石（040）、辉石（3¯11）和磁铁矿（311）峰的峰值位置（2θ 值）减小，而斜长石（040）和辉石（3¯11）峰的宽度向中心增大。这项研究表明，磁铁矿的热磁性能和晶格参数的变化是描述冲击靶岩低冲击压力变形特征的有力工具。

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来源期刊

Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理

CiteScore

5.00

自引率

4.30%

发文量

审稿时长

18.5 weeks

期刊介绍： Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.