【摘要】 在对大背坞地区双桥山群变质岩中“斑点构造”研究的基础上发现了同生碎屑—一种发育于沉积岩中反映动荡沉积环境的典型沉积构造 ,为进一步证实双桥山群属于半深海—深海的浊流相沉积环境特点提供重要依据。通过详细的构造变形分析 ,确认双桥山群主要经历了区域紧闭褶皱和韧性剪切两期构造变形 ;运用平衡剖面方法和应变测量估算双桥山群褶皱变形的地壳缩短量为 71.6 % ,双桥山群地层层内压扁变形压缩率为 2 3.1%～ 4 5 .3%。在对大背坞韧性剪切带进行系统研究后 ,建立了一套浅变质碎屑岩中进变质韧性剪切带的识别标志 ,进而对该区韧性剪切带进行划分和厘定 ;同时依据韧性剪切带中同生碎屑和同构造变斑晶的应变测量结果 (Kxz值 ) ,估算出大背坞韧性剪切带剪应变 (γ)为 1.0 1～ 2 .13、最大剪位移量为 0 .6～ 0 .8km。结合区域构造演化分析 ,认为双桥山群褶皱变形形成于晋宁期 ,韧性剪切变形发生于燕山期 ,前者是扬子地块基底岩系形成时期 ,后者是鹅湖花岗岩侵位和隆升过程中引发的花岗岩外围地区变质岩的以垂向剪切运动为特征的韧性剪切变形作用。更多还原

【Abstract】 Based on the study of the "mottled structure" of the Shuangqiaoshan Group metamorphic rock in Dabeiwu area, Jiangxi province, the authors discover the syngenetic clast for the fisrt time in the area. As a structural phenomenon representing a turbulent sedimentary environment, syngenetic clast in sedimentary rock provides a strong support to the view that the Shuangqiaoshan Group is a turbidite. There mainly occur two type deformations in the area. One is an appressed fold and the other is a ductile shear zone. By equilibrium diagram, it is calculated that the shorting ratio caused by appressed fold in the area is about 71.6%. The Dabeiwu ductile shear zone, formed in the epimetamorphic clastic rocks, has typical features and particular discerning signs. According to the strain measurements of syngenetic clast and syntectonic porphyroclast, the shear strain(γ) of Dabeiwu ductile shear zone is about 1.01～2.13 and the shear displacement is about 0.6～0.8km, while the intrastratal compressed ratio of Shuangqiaoshan Group is about 23.1～45.3%. Combining to the analysis of the evolution history of regional structure, the authors believe that the Shuangqiaoshan Group in the area has undergone two phases of deformation. The former is the appressed fold formed in Jinning epoch with the forming and deforming of the basement rock system of Yangzi platform. The latter is the ductile shear deformation occurred in the Yanshan epoch and related to the emplacement and upwelling of Ehu granitic intrusive, which caused the vertical ductile shear deformation in the metamorphic rock of the northwest side.更多还原