中国大陆科学钻探井区深部构造地震波反射特征
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摘要
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。
Chinese continental scientific drilling (CCSD) well is located in Donghai County which lies in the southern part of Sulu ultra-high pressure metamorphic zone. The seismic survey is one of the multi-scientific integrated research projects. The well has been surveyed by world advanced digital seismic instrument (HF300) and three component digital geophone (geochain). Combining the achievement of seismic survey and the information of rock core 5 000 m-CCSD, and through detailed analyses of deep structure reflection characteristics of seismic profile, we found that there is a three-unit-layer structure in the deep area. Six strong reflection bands appeared within 11 km in the first-unit-layer with the basically consistent attitudes, the trend is SE and the dip angle is 28 degree. The rock core sample and the VSP exploration data confirmed that the front four reflection bands are mainly the reflections from the eclogite and the ductile shear zone. The eclogite zone and the gneiss are distributed as irregularly alternative layers. Four quite clear reflection bands appeared between approximate 11 km to 30 km in the second-unit-layer, whose energy is weak, and the reflection continuity is poor. There are some weak anomalous reflections among the four bands. Their attitudes are also consistent basically, however, the dip angle is very small and the trend changes gradually to NW from shallow area to deep area. The interaction relation between the first-unit-layer and the second-unite-layer is angular unconformity. Only one quite strong reflection band appeared below approximate 30 km in the third-unit-layer, whose continuity is good; the attitude is gentle and the trend is still NW. However, the reflections are even and there isn't any anomalous reflection below the reflection band. According to the reflection characteristics and the geologic background mentioned above, we speculate that the first-unit-layer is the turned back terrane from the subduction zone of the Yangzi and Sino-Korean plate; the second-unit -layer is the Yangzi Craton; the third-unit-layer is the upper mantle, and the reflection of its top is from the Moho interface.
Chinese continental scientific drilling (CCSD) well is located in Donghai County which lies in the southern part of Sulu ultra-high pressure metamorphic zone. The seismic survey is one of the multi-scientific integrated research projects. The well has been surveyed by world advanced digital seismic instrument (HF300) and three component digital geophone (geochain). Combining the achievement of seismic survey and the information of rock core 5 000 m-CCSD, and through detailed analyses of deep structure reflection characteristics of seismic profile, we found that there is a three-unit-layer structure in the deep area. Six strong reflection bands appeared within 11 km in the first-unit-layer with the basically consistent attitudes, the trend is SE and the dip angle is 28 degree. The rock core sample and the VSP exploration data confirmed that the front four reflection bands are mainly the reflections from the eclogite and the ductile shear zone. The eclogite zone and the gneiss are distributed as irregularly alternative layers. Four quite clear reflection bands appeared between approximate 11 km to 30 km in the second-unit-layer, whose energy is weak, and the reflection continuity is poor. There are some weak anomalous reflections among the four bands. Their attitudes are also consistent basically, however, the dip angle is very small and the trend changes gradually to NW from shallow area to deep area. The interaction relation between the first-unit-layer and the second-unite-layer is angular unconformity. Only one quite strong reflection band appeared below approximate 30 km in the third-unit-layer, whose continuity is good; the attitude is gentle and the trend is still NW. However, the reflections are even and there isn't any anomalous reflection below the reflection band. According to the reflection characteristics and the geologic background mentioned above, we speculate that the first-unit-layer is the turned back terrane from the subduction zone of the Yangzi and Sino-Korean plate; the second-unit -layer is the Yangzi Craton; the third-unit-layer is the upper mantle, and the reflection of its top is from the Moho interface.
引文
[1]杨文采,程振炎,张春贺.中国大陆钻探选址地球物理调查与大别—苏鲁岩石圈[J].地球学报,2003,24(5):391-404.
[2]杨文采,朱光明,杨正华,等.中国大陆科学钻井孔区数字三分量反射地震调查[J].地球物理学报,2007,50(3):780-790.
[3]Xu Z Q,Zhang Z M,Liu F L,et al.The structure profile of0—1 200 min the main borehole,Chinese Continental Scien-tific Drilling and its Preli minary deformation analysis[J].Acta Petrologica Sinica,2004,20(1):53-72.
[4]杨正华,朱光明,周小伟.中国大陆科学探井岩性的VSP地震特征分析[J].现代地质,2009,23(6):1153-1159.
[5]陈意,金振民,欧新功,等.韧性剪切带中片麻岩和超高压榴辉岩变形特征及其与地震波速各向异性的关系[J].岩石学报,2004,20(1):97-108.
[6]朱光明,杨文采,杨正华,等.中国大陆科学钻探孔区的垂直地震剖面调查[J].地球物理学报,2008,51(2):479-490.
[7]杨文采,余长青.根据地球物理资料分析大别—苏鲁超高压变质带演化的运动学与动力学[J].地球物理学报,2001,44(3):346-359.
[8]杨文采,杨午阳,程振炎.中国大陆科学钻探区三维地震资料的初步解释[J].岩石学报,2004,20(1):127-138.
[9]杨文采,杨午阳,陈振炎.中国大陆科学钻探孔区的地震波速度模型[J].地球物理学报,2006,49(2):477-489.
[2]杨文采,朱光明,杨正华,等.中国大陆科学钻井孔区数字三分量反射地震调查[J].地球物理学报,2007,50(3):780-790.
[3]Xu Z Q,Zhang Z M,Liu F L,et al.The structure profile of0—1 200 min the main borehole,Chinese Continental Scien-tific Drilling and its Preli minary deformation analysis[J].Acta Petrologica Sinica,2004,20(1):53-72.
[4]杨正华,朱光明,周小伟.中国大陆科学探井岩性的VSP地震特征分析[J].现代地质,2009,23(6):1153-1159.
[5]陈意,金振民,欧新功,等.韧性剪切带中片麻岩和超高压榴辉岩变形特征及其与地震波速各向异性的关系[J].岩石学报,2004,20(1):97-108.
[6]朱光明,杨文采,杨正华,等.中国大陆科学钻探孔区的垂直地震剖面调查[J].地球物理学报,2008,51(2):479-490.
[7]杨文采,余长青.根据地球物理资料分析大别—苏鲁超高压变质带演化的运动学与动力学[J].地球物理学报,2001,44(3):346-359.
[8]杨文采,杨午阳,程振炎.中国大陆科学钻探区三维地震资料的初步解释[J].岩石学报,2004,20(1):127-138.
[9]杨文采,杨午阳,陈振炎.中国大陆科学钻探孔区的地震波速度模型[J].地球物理学报,2006,49(2):477-489.
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