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Paleomagnetic intensity in a geomagnetic excursion.

地磁偏移中的古磁强度。

基本信息

批准号：
06640550
负责人：
SHIBUYA Hidetoshi
金额：
$ 1.34万
依托单位：
College of Integrated Arts & Sciences, Osaka Prefecture University.
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640550/
关键词：
Geomagnetic excursion Paleointensity Thellier method New Zealand Auckland volcanic field Basalt Paleomagnetism

项目摘要

Paleointensity study of geomagnetic excursion is very scarce, especially for the data from volcanic rocks, which have methods of paleointensity determination with firm theoretical basis. It is because there were very few, only two, reports of excursions from volcanic rocks young enough to distinguish from ordinary reversals. One is from lake Mungo, Australia, by Barbetti and McElhinny (1976). Their results showed that the intensity is stronger in excursion than usual. This result is, however, critisized to be an artifact due to lightning. Their samples were from archeological fireplace and can not be re-sampled for examination. The other is from the Laschamp excursion (Roperch et al., 1988). It shows that the paleointensity at the excursion is significantly weaker (7.7muT) than the present geomagnetic field. In order to add paleointensity data in excursion, we carried out Thellier method experiments of the Auckland excursion, which we have reported as an excursion younger than 50ka fro … More m Auckland volcanic field New Zealand (Shibuya et al., 1992).The experiments were carried out Coe's version of Thellier method. At each temperature stage, the samples were heated twice in air. In each heating, samples were situated in the furnace in room temperature then the furnace was heated to the arranged temperature within 15min.and stayd at the temperature for 15min. Special care was taken for the reproducibility of the heating cycle, so that the reproducibility of the temperature of the two heatings is less than 1ﾟC.The first heating cycle was done in null magnetic field to determine the residual portion of the NRM and the second was done in a known magnetic field to produce a laboratory partial TRM.Twenty four samples from 18 sites, 11 sites of intermediate and 7 of normal direction, have been submitted to the experiments. Five samples from the normal sites ranged from 4 to 50muT,while 14 samples from the intermediate sites ranged from 3 to 14muT,and other 5 samples did not show straight relation between NRM and TRM.This result is concordant to the result from Laschamp excursion as well as general expectation. Less

地磁漂移的古强度研究非常缺乏，特别是火山岩资料，其古强度测定方法有坚实的理论基础。这是因为只有很少的报告，只有两个，从年轻的火山岩的漂移足以区分普通的逆转。一个是来自澳大利亚芒戈湖的Barbetti和McElhinny（1976）。他们的结果表明，在漂移中强度比平时更强。然而，这一结果被批评为是由于闪电的伪像。他们的样本来自考古壁炉，不能重新取样进行检查。另一个是来自Laschamp偏移（Roperch等人，1988年）。结果表明，该偏移处的古地磁强度（7.7 μ T）明显弱于现今地磁场。为了补充漂移中的古强度数据，我们对奥克兰漂移进行了Thellier方法实验，我们已经报道了一个小于50 ka的漂移， ...更多信息 m新西兰奥克兰火山区（涩谷等人，1992).实验采用Coe的Thellier方法。在每个温度阶段，样品在空气中加热两次。在每次加热中，将样品置于室温下的炉中，然后在15 min内将炉加热到预定温度，并在该温度下保持15 min。特别注意加热循环的再现性，使得两次加热的温度再现性小于1 ° C。第一次加热循环在零磁场中进行以确定NRM的残留部分，第二次在已知磁场中进行以产生实验室部分TRM。来自18个地点的24个样品，11个中间点和7个法线方向点已提交实验。5个正常位点的NRM与TRM之间的关系在4 ~ 50 μ T之间，14个中间位点的NRM与TRM之间的关系在3 ~ 14 μ T之间，另外5个NRM与TRM之间的关系不存在直线关系，这一结果与Laschamp偏移的结果以及一般的预期是一致的。少