Study of the Evolutional History of the Earth based on the Paleomagnetic Observations of the Archean Geomagnetic variations

基于太古代地磁变化的古地磁观测研究地球演化史

基本信息

批准号：
06452076
负责人：
HAMANO Yozo
金额：
$ 4.67万
依托单位：
the University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
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-06452076/
关键词：
Paleomagnetism Archean Geomagnetic Variation Western Austraria Earth's Core growth of the inner core Geomagneti Reversal Paleointensity 地球史古地磁気学 BIF 地球進化

项目摘要

Observational and theoretical investigations were made, aiming for the evolutional history of the Earth. Observational study includes the paleomagnetic study of Archean rocks sampled from Pilbara district, Western Australia. Rock sampling was made during July-August, 1995, and sedimentary rocks (Banded lron Formation, chert, etc) and igneous rocks (pillow basalts, bastlt flows, komatiite, dacite, etc) with the Archean ages (3.3-2.5 by) were sampled from 4 areas (Cleaverville, Marble Bar, North Pole, and Beaseley River) at the Western Australia. Paleomagnetic study of the banded iron formation (BIF) revealed a reversal sequence of the geomagnetic field during the Archean period, although the frequency of the reversals are not clear yet. Paleointensity study of the igneous rocks indicates that the strength of the geomagnetic field during ca. 33 by ago is much higher than the present field, and the filed strength decreases around the archean-Proterozoic boundary (-2.5 by ago). Results of the simulation study on the growth of the inner core due to secular cooling of the earth, indicate some relations between the physical properties of the inner core (heterogeneity and anisotorpy of the seimic P wave, radial distribution of the density, etc) and the cooling rate of the core, which can be used to infer the evolution of the earth's core from the seismic observations.

进行了观察和理论研究，旨在旨在地球的进化史。观察性研究包括对西澳大利亚州皮尔巴拉区采样的大古岩的古磁研究。岩石采样是在1995年7月至8月的岩石上进行的，以及与天堂年龄（3.3-2.5 by）的岩石（枕头玄武岩，basalts，bastlt流量，bastlt流量，komatiite，dacite等）的沉积岩石（带子玄武岩，basalts，bastlt流量，komatiite，dacite等）。带状铁形成（BIF）的古磁研究表明，在数量磁场时期的逆转序列，尽管逆转的频率尚不清楚。对火成岩的古显着研究表明，大约期间的地磁场的强度。 33 By AGO远高于目前的田地，而所归档的强度降低了Archean-Proterozoic边界（-2.5 by Ago）。模拟研究的仿真研究结果是由于地球的世俗冷却而导致的内核生长的结果表明，内核的物理特性（异质性和隔离P波的异质性和各向异性，密度的径向分布等）与核心的冷却速率之间的关系，可用于推断地球核心从抗震中的核心的发展。