Research from the Chinese Academy of Sciences: The strength of the ancient geomagnetic field 260 million years ago was about 51% of modern times

China News Service, Beijing, September 10 (Reporter Sun Zifa) The reporter learned from the Continental Collision Uplift and Impact Team of the Tibetan Plateau Institute of the Chinese Academy of Sciences on the 10th that the team, leading Chinese and foreign collaborators, conducted a series of studies on the layered gabbro in the Baima mining area of ​​Panzhihua that was about 260 million years old. The latest discovery was that the intensity of the ancient geomagnetic field at that time was about 51% of the modern geomagnetic field.

This important progress paper on the study of the intensity of ancient geomagnetic field and the impact of changes was recently published in an international academic journal.

Huang Wentao, the first author and corresponding author of the paper and researcher at the Tibetan Plateau Institute of the Chinese Academy of Sciences, said that during the Late Permian period about 260 million to 252 million years ago, two major biological extinction events occurred. Both events were highly consistent in time with the large-scale magmatic activity in Mount Emei and the Siberian Large Igneous Province. Was the earth's magnetic field severely weakened at that time, and was it even the driving force behind these two ancient mass extinctions? This issue has attracted much attention.

The research team conducted in-depth research using the layered gabbro in the Baima mining area of ​​Panzhihua in the Emeishan Large Ileogenous Province as a breakthrough point. They innovatively used advanced technical means and methods to finally obtain 22 high-quality paleomagnetic field intensity data from 134 plagioclase single minerals.

Data research and analysis show that 260 million years ago, the intensity of the ancient geomagnetic field in the Panzhihua area was about 51% of the intensity of the modern geomagnetic field. According to estimates of the geomagnetic field strength, the magnetopause at that time was about 7.9 Earth radii from the center of the Earth, while the modern distance is about 10.7 Earth radii. This means that although the earth's "magnetic protective shield" has shrunk at that time, it still has strong protective capabilities.

Huang Wentao said that the results of this study do not support the hypothesis that "the extremely weak geomagnetic field caused the magnetosphere to nearly collapse, and thus became the main driving force for environmental deterioration and biological extinction in the Late Permian."