Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material
Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material
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DOI：
10.1016/j.pepi.2014.12.007
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发表时间：
2015-04-01
影响因子：
2.3
通讯作者：
Ron, H.
中科院分区：
文献类型：
--
作者：
Cromwell, G.;Tauxe, L.;Ron, H.
已发表的古强度估计来自已知领域的熔岩挤出是高度可变的，很少恢复预期的磁场强度的准确度超过10%。对现代火山岩的不一致的结果甚至给在地磁场强度未知的时期对熔岩流进行的强度实验带来了更大的不确定性。大多数已发表的古强度数据都是从缓慢冷却的熔岩流中心收集的，那里的磁性颗粒更可能是多畴的，并产生不理想的实验结果。然而，玻璃状火山物质（在陆上熔岩流顶部和水下及冰下环境中发现）会迅速冷却，因此最有可能表现为尼尔理论所要求的单域颗粒。我们提出了一个新的古强度研究的历史和现代夏威夷熔岩和测试的可行性subaerially侵位玻璃玄武岩材料作为一个准确的记录磁场强度。在夏威夷大岛（1843年、1859年、1935年、1950年、1960年、1990年）采集的8个熔岩流样本中，产生表现良好的Arai图，并将平均强度恢复到预期场强的2.7 μ T以内或精度高于8%。我们采用非常严格的选择标准，包括每个地点至少三个标本，以防止无关的字段估计影响最终结果。1960年的火山玻璃。熔岩流的变化比同一火山单元公布的数据要小得多。因此，应尽可能收集玻璃质材料，因为它们能够以前所未有的准确度恢复地磁场强度。(C)2015爱思唯尔B.V.保留所有权利。
Published paleointensity estimates derived from lavas extruded in known fields are highly variable and rarely recover the expected field strength within an accuracy of better than 10%. Inconsistent results on modern volcanic rocks lend even greater uncertainty to intensity experiments performed on lava flows emplaced during periods of unknown geomagnetic field strength. The majority of published paleointensity data are collected from the slowly cooled, massive centers of lava flows, where the magnetic grains are more likely to be multi-domain and produce non-ideal experimental results. Glassy volcanic material (found on subaerial lava flow tops and in sub-aqueous and subglacial environments), however is rapidly cooled, and therefore most likely of all volcanic materials to behave as single-domain particles demanded by Neel theory. We present a new paleointensity study of historic and modern Hawaiian lavas and test the viability of subaerially emplaced glassy basaltic material as an accurate recorder of magnetic field intensity. Six of eight lava flows sampled on the Big Island of Hawaii (1843, 1859, 1935, 1950, 1960, 1990 C.E.) produce well behaved Arai plots and recover an average intensity to within 2.7 mu T of the expected field strength or better than 8% accuracy. We apply very strict selection criteria, including a minimum of three specimens per site, to prevent extraneous field estimates from affecting the final results. Individual volcanic glass results from the 1960 C.E. lava flow have a much lower variance than published data from the same volcanic unit. Glassy materials should therefore be collected wherever possible as they allow recovery of geomagnetic field strength with unprecedented accuracy. (C) 2015 Elsevier B.V. All rights reserved.