东亚地幔流动速度研究
Mantle flow velocity of East Asia
-
摘要: 提要：用高分辨率地震体波速度成像以及相关的地球物理资料，计算地幔垂直和切向流动形式及流动速度，得到东亚及西太平洋大体分为3个区域物质流动大致方式：东亚边缘裂谷系和西太平洋边缘海为下部会聚上部扩散的地幔上升流，尤其对于南海来说，大致勾勒出南海地区构造特征——从上到下的大体结构可能是上部呈“工”字型结构、中间为圆柱型、底部呈发散形的地幔上升流；西伯利亚地幔物质上部会聚下部扩散的“人”字型下降流；青藏高原—缅甸—印度尼西亚特提斯俯冲带上部会聚下部扩散的“人”字型地幔下降流。东亚西太平洋分为3个区域地幔对流与地表的西太平洋构造域、古亚洲构造域和特提斯构造域相吻合。东亚中部的物质在地幔深部无明显流动趋势。地幔上升流起源于核幔边界，主要表现在下地幔和上地幔下部，到上地幔顶部和地表与现代热点位置符合。地幔垂直流动速度每年1～4 cm，切向速度为每年1～10 cm。Abstract: Abstract: Based on the high-resolution body wave tomographic images and relevant geophysical data the authors calculated the form and vertical and tangential velocities of mantle flow. Mantle flow in East Asia and the Western Pacific may fall into three patterns: (1) in the East-Asia marginal rift system and western Pacific marginal seas the mantle flow is marked by an upwelling mantle flow, characterized by flow convergence in the lower mantle and divergence in the upper mantle, especially for the South China Sea, where the structure of the upwelling mantle flow may be roughly outlined as a “工” shape in the upper mantle, a column shape in the middle and a divergent shape at the bottom; (2) in Siberia there is a “人”-shaped downwelling mantle flow, characterized by mantle material convergence in the upper mantle and divergence in the lower mantle; and (3) in the Qinghai-Tibet Plateau-Burma-Indonesia Tethys subduction zone, there is a “人”-shaped downwelling mantle flow, which is also characterized by flow convergence in the upper mantle and divergence in the lower mantle. The three regions of mantle convection beneath East Asia and the Western Pacific are in agreement with Western Pacific, Paleo-Asiatic and Tethyan tectonic domains. The material in the central part of East Asia shows no trend of flow in the deep interior of the mantle. The upwelling mantle flow originates from the core-mantle boundary and is mainly manifested in the lower mantle and lower part of the upper mantle. At the top of the upper mantle and at the surface, its location coincides with that of modern hot spots. The rate of vertical mantle flow is about 1 to 4 cm per year and the tangential rate is 1 to 10 cm per year.
-
计量
- 文章访问数: 3072
- HTML全文浏览量: 44
- PDF下载量: 3342
下载:
