大兴安岭北段伸展构造

Extensional Detachment,Northern Great Xing'an Ranges,NE China

本文对大兴安岭北段额尔古纳七卡地区发育的大型区域伸展滑脱构造开展了详细的研究,并系统地总结讨论了大兴安岭地区伸展构造及其与大兴安岭隆升的成因联系。查明七卡伸展构造带总体走向NE,滑脱面倾向NW,变形为具有减薄特征的简单剪切应变,发育SL构造岩,运动指向标志J显示向NW的伸展滑脱。结合区域上嫩江科洛伸展构造、嘎啦山伸展构造和磋岗伸展构造的对比研究表明,大兴安岭地区的伸展构造应该是区域伸展作用的产物,形成时间为早白垩世。随着大规模区域伸展作用,大兴安岭地区发生强烈的岩浆底侵,导致大兴安岭快速隆升,从而使其形成东侧向SE和西侧向NW方向滑脱的伸展构造。

We carried out a detail study of the large-scale extensional detachment structure in Qika, Erguna, northern Great Xing＇an Ranges, NE China. The extensional detachment structures in the northern Great Xing＇an Ranges and their relation to the uplift of Great Xing＇an Ranges were also summarized and discussed. The extensional detachment structure in Qika dips northwest with NE strike. The shear deformation is a simple shearing with thinning strain and SL tectonites. The movement direction structures indicate a NW-directed sliding in the Qika extensional detachment. The comparing studies of the Nenjiang Keluo, Galashan, Cuogang extensional detachment structures indicate that the extensional detachment structures in Great Xing＇an Ranges were produced by regional extension in Early Cretaceous. With developing of the large-scale extensional detachment, strong magmatic underplating took place in Great Xing＇an Ranges, which resulted in the rapid uplift of Great Xing＇an Ranges and extensional detachment structures with SE-directed sliding in the east side and NW-directed sliding in the west side of the Great Xing＇an Ranges.