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中国大陆科学钻探(CCSD)井位于苏鲁超高压变质带南部的东海县境内。井区地震勘探是钻探综合研究项目之一,该项目采用世界先进的数字地震仪和三分量数字检波器,对line 1线剖面进行了测量。依据地震勘探成果和CCSD岩心资料,通过对该地震剖面深部构造反射特征的详细分析,发现该区深部反射构造具有明显的三单元层结构。第一单元层,约在11 km内,出现6个强反射带,产状基本一致,倾向SE,倾角28°。岩心资料和VSP勘探资料证实前4个反射带主要是榴辉岩带和韧性剪切带的反射,榴辉岩带与片麻岩成不规则层状相间分布。第二单元层,约在11~30 km,有4个比较清楚的反射带,反射弱,连续性差,带内分布有不规则的弱反射。其产状也基本一致,倾角很小,比较平缓,由浅到深,倾向逐渐变为NW,它与第一单元层为角度不整合接触关系。第三单元层,约在30 km以下深度,其顶部出现了比较强的反射带,连续性较好,产状较平缓,倾向NW;而在顶部反射带以下,则反射均匀,没有不规则反射带。据上述反射特征,结合该区地质背景,推测第一单元层为中朝与扬子板块俯冲带的折返地壳层,第二单元层为扬子克拉通层,主要为变质岩层,第三单元层为上地幔层,其顶部的反射为莫霍面的反射。
The China Continental Scientific Drilling (CCSD) well is located in Donghai County, south of the Sulu UHP metamorphic belt. Wellbore seismic exploration is one of the comprehensive drilling research projects, the project uses the world’s most advanced digital seismometer and three-component digital geophone, line 1 line profile was measured. Based on the results of the seismic exploration and the CCSD core data, a detailed analysis of the deep structural reflection features of the seismic section shows that the deep reflection structure in this area has a distinct three-unit layer structure. In the first unit layer, within about 11 km, there are six strong reflection bands with the same shape and tendency of SE and dip angle of 28 °. Core data and VSP data confirm that the first four reflection bands are mainly eclogite and ductile shear bands, and the eclogite belt and gneiss are irregularly layered. The second unit layer, at about 11 ~ 30 km, has four clear reflection bands, weak reflection, poor continuity and irregular weak reflection in the band. Its occurrence is also basically the same, the inclination is small, relatively gentle, from shallow to deep, tend to gradually become NW, it is the first unit layer of the angle of the non-integrated contact relationship. The third unit layer, about 30 km below the depth of the top there is a relatively strong reflection zone, the continuity is better, the shape is more gentle, prone to NW; and below the top reflection, the reflection is uniform, there is no irregular reflection band. According to the above reflection features and the geological background of the area, it is presumed that the first unit layer is the re-crust crust of the subduction zone between China and the DPR and the Yangtze plate, the second unit layer is the Yangtze craton, mainly metamorphic rocks, and the third unit layer is The mantle layer, whose top reflection is the reflection of the Moho.