岩石磁场测量得出的热不稳定性证实了圣罗莎地磁偏移期间绝对古强度记录被低估的情况

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Junxiang Miao , Huapei Wang
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引用次数: 0

摘要

地磁偏移事件是了解地球磁场演变的一个关键过程,近年来已被广泛研究。在全球范围内,沉积序列和熔岩流中都记录了松山纪期间的圣罗莎地磁偏移(SRE)事件。分布在近赤道地区的加拉帕戈斯熔岩的 40Ar/39Ar 年龄为 925.7 ± 4.6 ka,其绝对古磁场强度值约为现代磁场的 14%,这是对 SRE 事件期间地球磁场强度的宝贵记录。然而,上述对SRE期间古磁强度的极低估计值是根据以往古磁强度实验中温度较高的区段(400 ℃-575 ℃)拟合的,这与加拉帕戈斯熔岩样本在高温加热处理过程中的热不稳定性有偏差。从本研究的综合岩石磁性实验来看,加拉帕戈斯熔岩样本在经过高于 400 °C 的加热处理后表现出了热不稳定性。加热温度达到 500 °C后发生了严重的热变异,主要表现为剩磁携带能力的增加,例如古强度试样记录部分热永磁的能力增强,导致在 SRE 期间古强度被低估。深入的岩石磁性实验和磁滞参数分析为检测熔岩样本的热不稳定性提供了有力的方法,可以帮助我们确认这一短时偏移期的地磁场强度偏差,防止因错误的低古强度记录而误读地球磁场演化。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Thermal instability from rock magnetic measurements confirms the underestimates of absolute paleointensity records during the Santa Rosa geomagnetic excursion

Thermal instability from rock magnetic measurements confirms the underestimates of absolute paleointensity records during the Santa Rosa geomagnetic excursion

Geomagnetic excursion events have been widely studied in recent years as a key process for understanding the evolution of the Earth's magnetic field. The Santa Rosa geomagnetic excursion (SRE) event during the Matuyama chron has been globally recorded in sediment sequences and lava flows. Galapagos lavas distributed in near-equatorial with an 40Ar/39Ar age of 925.7 ± 4.6 ka display absolute paleointensity values of about 14% of the modern magnetic field, which is a valuable record of the Earth's magnetic field strength during the SRE event. However, the above extremely low estimates of paleointensities during the SRE were fitting from higher temperature segments (400 °C–575 °C) from previous paleointensity experiments, which is biased by the thermal instability of Galapagos lava samples during high-temperature heating treatments. From our comprehensive rock magnetic experiments in this study, Galapagos lava samples exhibit thermal instability after heating treatments higher than 400 °C. The severe thermal alteration occurred after the heating temperature reached 500 °C, mainly manifested as an increase in remanence-carrying capacities, such as the enhanced ability of paleointensity specimens to record partial thermoremanent magnetization, resulting in underestimated paleointensities during the SRE. In-depth experiments on rock magnetism and hysteresis parameters analysis provide a powerful method to detect the thermal instability of lava samples, which can help us confirm the biased geomagnetic field strength during this short-lived excursion period and prevent misinterpretations of the Earth's magnetic field evolution through erroneous low paleointensity records.

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来源期刊
Physics of the Earth and Planetary Interiors
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
78
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.
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