摘要
青藏高原东北部小峡背斜是一个新生代发展起来的基底卷入型背斜。研究表明背斜的形成经历了三次重要变形,新生代早期由于印度板块与欧亚板块的碰撞(约49～29Ma),造成了西宁盆地顺时针旋转,在此变形中,背斜基底早期发育的北西向断层以及新生断层开始右行斜滑,造成了小峡地区盖层轴向北西向褶皱的形成,基底与盖层的变形类似Trishear型褶皱机制。新生代中期由于构造体制发生重大变革,在基底中形成一系列左行斜冲断层,在新生代晚期(14～5Ma),由于西宁盆地南北缘强烈的左行走滑运动致使盆地基底早期北北东向断层和新生的R’断层活动,导致了目前的小峡背斜主体的形成,构造研究表明,这些透入性北东向断层的活动使得基底变形宏观上表现出一定的"韧性",背斜基底变形以断层活动为主,而盖层属于以横弯作用控制的被动褶皱变形。小峡背斜的形成表明,基底早期断层是控制背斜形成的重要因素之一,而高原下地壳的增厚可能与该类型的褶皱形成有关。
The Xiaoxia anticline of the northeastern Qinghai-Tibetan Plateau is one basement-involved fold forming during the Cenozoic. This study shows that the formation of the anticline underwent at least three deformation events. Due to the Indo-Eurasian collision in the Early Cenozoic （~49Ma）,the Xining basin rotated clockwise. And the early northwest-southeast trending faults developed within the basement and new-born faults started to move right-laterally,which resulted in the development of the northwest-southeast trending folding of cover layers. The deformation of the basement and sedimentary layers is similar to that of Trishear model. During the Middle-Late Cenozoic （49～5Ma）,the intensive left-lateral strike-slipping of the north and south margins of the Xining basin resulted in NNE-trending faulting of the basin basement and new-born R＇ fault activity,which gave rise to the formation of current Xiaoxia anticline. Structural analysis shows that these NNE-trending penetrative faults made the basement show some characteristics of ductile deformation macroscopically,with faulting mainly in the basement and passive folding deformation in the cap rock. The formation of the Xiaoxia anticline shows that the development of early faults in the basement is one of the important factors controlling the basement-cored folds,and the thickening of the lower crust of the plateau may be related to the development of the basement-involved fold.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2011年第1期34-55,共22页
Acta Geologica Sinica
基金
中国地震局地质研究所中央级公益性科研院所基本科研业务专项(JB-07-20)资助的成果
关键词
小峡
基底卷入型褶皱
厚皮构造
青藏高原
斜冲断层
Xiaoxia Gouge
basement-involved fold
thick-skinned structure
Qinghai-Tibetan Plateau
oblique thrust fault
