Paleomagnetic intensity in a geomagnetic excursion.

地磁漂移的古强度研究十分匮乏，尤其是火山岩资料，其古强度测定方法具有坚实的理论基础。这是因为只有两个关于火山岩漂移的报道很少，只有两个，年轻到足以与普通的逆转区分开来。其中一幅来自澳大利亚芒果湖，由Barbetti和McElhinny(1976)创作。他们的结果显示，短途旅行的强度比平时更强。然而，这一结果被批评为闪电造成的人工制品。他们的样本来自考古壁炉，不能重新取样进行检查。另一种是拉尚之旅(Rperch等人，1988年)。结果表明，漂移时的古地磁强度(7.7muT)明显弱于现今的地磁场。为了将古强度数据添加到漂移中，我们进行了奥克兰漂移的较低方法实验，我们已经报告了一次小于50ka的…漂移More m奥克兰火山田新西兰(Shibuya等人，1992)。实验采用科版本的泰勒方法。在每个温度阶段，样品在空气中加热两次。在每次加热中，样品在室温下放置在炉中，然后在15min内将炉加热到安排的温度，并在该温度下停留15min。特别注意加热循环的重现性，使两次加热的温度重现性小于1ﾟC。第一次加热循环在零磁场中进行，以确定NRM的剩余部分，第二次加热循环在已知磁场中进行，以产生实验室部分TRM。来自18个位置的24个样品，11个中间位置和7个垂直方向的样品已提交给实验。5个正常部位的样品在4~50muT之间，14个中间部位的样品在3~14muT之间，另外5个样品的NRM与TRM没有直接的关系，这一结果与LasChamp偏移的结果以及一般的预期是一致的。较少

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