气候变化领域集成服务门户(CCPortal): Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying Non-Ideal Behavior in Thellier-Style Paleointensity Experiments

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DOI	10.1029/2020JB019802
	Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying Non-Ideal Behavior in Thellier-Style Paleointensity Experiments
	Grappone J.M.; Biggin A.J.; Barrett T.J.; Hill M.J.; Sprain C.J.
发表日期	2020
ISSN	21699313
卷号	125 期号:8
英文摘要	Determining the strength of the ancient geomagnetic field is vital to our understanding of the core and geodynamo, but obtaining reliable measurements of the paleointensity is fraught with difficulties. Over a quarter of magnetic field strength estimates within the global paleointensity database from 0 to 5 Ma come from Hawaii. Two previous studies on the SOH1 drill core gave inconsistent, apparently method-dependent paleointensity estimates, with an average difference of 30%. The paleointensity methods employed in the two studies differed both in demagnetization mechanism (thermal or microwave radiation) and Thellier-style protocol (perpendicular and original Thellier protocols)—both variables that could cause the strong differences in the estimates obtained. Paleointensity experiments have therefore been conducted on 79 specimens using the previously untested combinations of thermal-perpendicular and microwave-original Thellier methods to analyze the effects of demagnetization mechanism and protocol in isolation. We find that, individually, neither demagnetization mechanism nor protocol entirely explains the differences in paleointensity estimates. Specifically, we found that non-ideal multidomain-like effects are enhanced using the original Thellier protocol (independent of demagnetization mechanism), often resulting in paleointensity overestimation. However, we also find evidence, supporting recent findings from the 1960 Kilauea lava flow, that microwave-perpendicular experiments performed without partial thermal remanent magnetization checks can produce underestimates of the paleointensity due to unaccounted-for sample alteration at higher microwave powers. Together, these findings support that the true paleointensities fall between the estimates previously published and emphasize the need for future studies (thermal or microwave) to use protocols with both partial thermal remanent magnetization checks and a means of detecting non-ideal grain effects. ©2020. The Authors.
英文关键词	Hawaiian lava; microwave method; SOH borehole; Thellier-style paleointensity
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187678
作者单位	Geomagnetism Laboratory, School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom; School of Physical Sciences, The Open University, Milton Keynes, United Kingdom; Department of Geological Sciences, The University of Florida, Gainesville, FL, United States
推荐引用方式 GB/T 7714	Grappone J.M.,Biggin A.J.,Barrett T.J.,et al. Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying Non-Ideal Behavior in Thellier-Style Paleointensity Experiments[J],2020,125(8).
APA	Grappone J.M.,Biggin A.J.,Barrett T.J.,Hill M.J.,&Sprain C.J..(2020).Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying Non-Ideal Behavior in Thellier-Style Paleointensity Experiments.Journal of Geophysical Research: Solid Earth,125(8).
MLA	Grappone J.M.,et al."Comparison of Thermal and Microwave Paleointensity Estimates in Specimens Displaying Non-Ideal Behavior in Thellier-Style Paleointensity Experiments".Journal of Geophysical Research: Solid Earth 125.8(2020).