川西北磁组构演化及其揭示的应变特征  

Magnetic fabric evolution in the northwestern Sichuan basin,China and its strain characteristics

作　　者：罗良[1] 贾东[1] 陈竹新[1] 胡潜伟[1] 贾秋鹏[1] 李一泉[1] 张元元[1] 

机构地区：[1]南京大学地球科学系,江苏南京210093

出　　处：《地质通报》2006年第11期1342-1348,共7页Geological Bulletin of China

基　　金：国家自然科学基金项目(编号40372091);中国石油天然气集团公司创新基金;国家"十五"重点科技攻关项目(2001BA605A-06-01);南京大学地质学研究生创新基金联合资助。

摘　　要：对龙门山褶皱冲断带北段前锋带至四川盆地边缘的川西北地区进行了磁组构研究。在江油和广元之间,沿着垂直于龙门山构造走向的4条采样路线,在18个采样点钻取了173个定向样品,样品采自侏罗纪和白垩纪砂岩及粉砂质泥岩。综合分析表明川西北磁组构反映的是新生代的变形,并在研究区域内总结出了3类磁组构:沉积磁组构、初始变形磁组构和铅笔状磁组构。除沉积磁组构之外的所有采样点样品的K1优势方向都是NE—SW向,说明研究区域的最大主压应力方向为NW—SE向,主要来源于龙门山褶皱冲断带。在垂直于龙门山褶皱冲断带构造走向上,从四川盆地到龙门山前锋,磁组构由沉积磁组构逐渐变为初始变形磁组构,直至铅笔状磁组构,说明盆地内部应变十分微弱,靠近造山带应变逐渐增强,且侏罗纪、白垩纪以来研究区的构造变形主要集中在造山带边缘或者还未传递到盆地内部。An investigation of magnetic fabrics has been carried out in northwestern Sichuan from the front zone in the north- ern segment of the Longmen fold-thrust belt to the margin of the Sichuan basin. Between Jiangyou and Guangyuan, 173 oriented specimens were obtained from 18 well sites along four sampling routes perpendicular to the strike of the Longmen belt. All the specimens were taken from Jurassic and Cretaceous sandstones and silty mudstones. Integrated analysis indicates that the magnetic fabrics in northwestern Sichuan reflect Cenozoic deformation. There are three types of magnetic fabrics in the study area： sedimentary magnetic fabric, initial deformation magnetic fabric and pencil-shaped magnetic fabric. Except the sites showing sedimentary magnetic fabrics, the preferred orientation of K1 at all the specimen sites is NE-SW, which indicates that the maximum principal compressional stress in the study area is oriented in a NW-SE direction, which shows that the stress mainly came from the Longmen fold-thrust belt. Along four sampling routes perpendicular to the strike of the Longrnen belt, the sedimentary magnetic fabric changes to initial deformation magnetic fabric and finally to pencil-shaped magnetic fabric from the Sichuan basin to the front of the Longmen Mountains. This suggests that the strain in the Sichuan basin is feeble and becomes strong progressively near the orogen, and that since the Jurassic and Cretaceous, the tectonic deformation in the study area mainly took place at the edge of the orogen or has not been transferred to the Sichuan basin.

关 键 词：川西北 磁组构 龙门山北段 米仓山 应变 

分 类 号：P54[天文地球—构造地质学] P318.44[天文地球—地质学]