【摘要】 野外构造解析和地震遗址的构造应力分析显示,龙门山断裂带在新生代早期对应于当时的南东—北西主压应力场,发育了北北东向的左旋走滑构造体系;其后才被具有右旋兼具逆冲的龙门山断裂带叠加改造,对应的近东西向构造主压应力场一直延续至今,是区内地震构造的应力场机制。龙门山断裂带河流岩屑磷灰石裂变径迹分析显示,龙门山断裂带在走向上位移量有显著的差别,呈现正态分布的整体趋势。依照龙门山隆起剥蚀单调冷却的热史特征,判定前述两期变形的转换时限是40 Ma前后。结合龙门山断裂带地层厚度和变形时的深度模型,认为现今龙门山断裂带是一个宽达数十千米的大型走滑断裂带,剖面上呈现花状构造特征。近地表的逆冲构造是薄皮构造,并由此建立了龙门山断裂带走滑变形的深度变形样式模型。更多还原

【Abstract】 Field structure and stress field analyses indicate that the Longmenshan fault zone was in NW-SE compressive stress field in early Cenozoic,developing the NNE-trending sinistral strike-slip structural system,which was superimposed and reformed by the late Longmenshan fault zone characterized by dextral transpressional deformation.Since the superimposition and reformation,the Longmenshan fault zone has been in the E-W compressive stress field,contributing to the seismic structure.Detrital apatite fission track analysis of the fluvial sands shows remarkable discrepancy in the displacement along the trend direction in the Longmenshan fault zone,with a trend of normal distribution.According to the monotonic thermal history responding to the uplift and cooling,we speculate the transformation time of the two stages of deformation to be around 40 Ma.Based on the stratigraphic thickness and the deformation-depth model,the Longmenshan fault zone is considered to be a large strike-slip fault zone,extending tens of kilometers wide,which shows flower-structural feature on the cross section.The near-surface thrust structure is thin-skinned structure,and we establish a depth-deformation model in Longmenshan fault zone.更多还原