中国东部海域居里面深度特征

Depth characteristics of Curie surface in the Eastern seas of China

通过对中国东部海域高精度的船测磁力数据的二阶小波逼近结果采用功率谱法,计算得到该区域的居里面深度特征。中国东部海域居里面深度16.8~36.6km,在构造环境稳定、地壳厚度正常的区域,如苏北—南黄海盆地、东海陆架盆地,居里面深度在28km以上且起伏变化平缓,可能与相对较弱的中、新生代构造活动有关;在构造活动区边缘或者中、新生代造山系,如渤海盆地、千里岩隆起区及冲绳海槽,居里面则以上隆为特征。其中南黄海中部隆起居里面深度西部下凹而东部相对上隆,可能是古陆核与岩浆侵入的综合反映;而东海的居里面深度则呈现与构造区划相一致的“东西分带”特征。另外,区内居里面深度与热流、地温梯度的自相关系数(Pearson相关系数)分别为-0.3896与-0.5160,显示出居里点深度与热流值间的弱负相关性及其与地温梯度间的中等程度负相关性特征。

The depth of this region’s Curie surface was calculated using the power spectrum method based on the second-order wavelet approximation of the high-precision ship-measured magnetic data in the Eastern seas of China.The results show that the depth of Curie surface in the Eastern seas of China is between 16.8~36.6 km.In the regions where the tectonic environment is stable and the crust thickness is normal,such as the Northern Jiangsu and South Yellow Sea basin and the continental shelf basin in the East China Sea,the depth is all above 28 km and the fluctuation is gentle,which may be related to the relatively weak Mesozoic and Cenozoic tectonic activities.At the edge of the tectonic activity area or the Mesozoic and Cenozoic orogenic systems,such as the Bohai Basin,the Qianliyan uplift,and the Okinawa Trough,the depth of Curie surface is characterized by the uplift.The Curie surface in the central South Yellow Sea is concave-down and uplift in west and east respectively,which may be a comprehensive reflection of existence of an ancient land and magma intrusion.The depth of Curie surface in the East China Sea shows an“East-West zoning”feature,which is consistent with the structural tectonic division.The results also show that the self-correlation coefficient of the depth of Curie surface with heat flow and geothermal gradient in this region is-0.389 6 and-0.516 0 respectively,which indicates that there is a weak negative correlation between Curie depth and heat flow value,and a moderate negative correlation with geothermal gradient.