Geomagnetism and magnatic evolution from Iceladic Volcanics

1993年7月和1994年7月在冰岛进行了实地工作。主要的工作是收集上新世和更新世时期连续熔岩流的古地磁样本。还从历史和史前酸性熔岩流中收集样本进行地球化学研究。东京大学地球物理和行星物理系（DEPP）和地震研究所（ERI）、东京工业大学地球和行星科学系和地球内部研究所（ISEI）正在进行利用古地磁和地球化学样品的实验。以下是对各种研究活动的简要描述。连续熔岩流的古地磁。每年大约有250次熔岩流取样。钻了五个岩心，并根据太阳方向、参考方向或磁方向测量了方位。对少量样品，采用自旋磁强计和交变磁场退磁器在现场进行了自然剩余磁化强度的测量。K-Ar约会。用K-Ar法测定了Storutjarnir剖面约50个样品的年代。钾是ERI的测量入口火焰光度法，而氩的同位素比值是isei的质谱仪测量的。用Thellier的方法研究了冰岛样品的古地球磁场强度。冰岛西部的结果表明，极性反转时的低强度在极性反转完成后仍持续一段时间。长期变化数据。利用冰岛和世界其他地区的资料，研究了地磁场的古长期变化（PSV）。通过对已发表资料的整理，建立了古强度数据库，并根据随机变化的高斯系数建立了PSV模型。

Field works were performed in Iceland during July 1993 and July 1994. Major effort was directed to the collection of paleomagnetic samples from successive lava flows with ages of Pliocene and Pleistocene. Samples were also collected from historic and prehistoric acidic lava flows for geochemical studies. Experiments using paleomagnetic as well as geochemical samples are under progress in Department of Geophysics and Planetary Physics (DEPP) and Earthquake Research Institute (ERI), University of Tokyo, Department of Earth and Planetary Sciences, Tokyo Institute of Technology, and Institute for Study of Earth's Interior (ISEI). Following is a brief description of various research activities.1.Paleomagnetism of successive lava flows.About 250 lava flows were sampled in each year. Five cores were drilled and orientation was measured in terms of directions of sun, reference, or magnetic directions. For a small number of samples, measurement of natural remanent magnetization was carried out in the field using spinner magnetometer and alternating field demagnetizer.2.K-Ar dating.About 50 samples from Storutjarnir section are now dated by K-Ar method. Potassuim is measurementry flame photometry at ERI,while Argon isotope ratios are measured by mass spectrometer at ISEI.3.Paleointensities.Paleointensity of the earth's magnetic field was studied using Icelandic samples by Thellier's method. Result from Western Iceland indicates that the intensity low at the time of polarity reversal continues sometime after the reversal of direction was completed.4.Secular variation data.With the use of Icelandic data as well as data from other areas worldwide, paleosecular variation (PSV) of the geomagnetic field was studied. A paleointensity database was set up through the compilation of published data, and models of PSV were developed in terms of the randomly varying Gauss coefficients.