南海新生代地壳减薄特征分析

Abstract

拉伸因子β是直接反映地壳减薄程度的参数。为了分析南海新生代以来地壳减薄特征，对比南、北部的差异性演化，利用网格密度为1˚ × 1˚全球地壳模型CRUST 1.0提供的南海地壳厚度数据，结合NGDC提供的水深数据，在假设南海拉伸前的地壳厚度为32 km的基础上，通过地壳减薄量计算了拉伸因子β，并绘制了南海拉伸因子分布图。拉伸因子计算结果介于1~4.2之间，其中最大值在南海南部的双子群礁附近取得，最小值分布在北部湾陆架。拉伸因子β的分布规律表明南海南部减薄程度靠近海盆突然增强，北部则是由陆架至海盆逐渐加强；总体而言，南海北部减薄程度大于南部减薄程度，西部减薄程度最低。 The stretching factor β is a parameter which directly reflects the extent of crustal thinning. In order to analyze the characteristics of crustal thinning in the South China Sea, β is calculated by the crustal thinning. Applying the continental crustal model of the global crustal model CRUST 1.0 with the grid of 1˚ × 1˚, combined with the water depth data from NGDC and on the assumption that the crustal thickness is 32 km, the distribution of β in the South China Sea is analyzed. The results of β are between 1 and 4.2; the maximum is obtained in the vicinity of the Gemini reefs in the southern South China Sea, and the minimum is distributed in the Beibu Gulf shelf. The distribution of β indicates that the degree of thinning in the southern part of the South China Sea is gradually enhanced near the basin, and the northern part is gradually strengthened from the shelf to the ba-sin. Overall, the degree of thinning in the northern part of the South China Sea is greater than that in the south.