摘要
中生代川东褶皱带发育着两种不同的褶皱组合型式,以NE向齐岳山断裂为界,东侧为隔槽褶皱,西侧为隔档褶皱,二者在成因上均与不同埋深的滑脱带密切相关。本文利用FLAC6.0软件模拟了川东褶皱带的两阶段形成过程：隔槽褶皱区和隔档褶皱区依次形成。在断坡倾角为30°的情形下,当滑脱带在隔档褶皱区和隔槽褶皱区分别处于寒武系和角度不整合面向下3~4 km的基底深处时,模拟得到的结果能很好地再现该褶皱带的总体形态特征。只有当连接两个褶皱区滑脱带的断坡具有≤30°的低倾角时,它才能高效地将水平位移传递到隔档褶皱区,意味着地表出露的高倾角齐岳山断裂基本上没有参与整个褶皱带的形成过程,是晚期或后期形成突破地表的。断弯褶皱的出现会造成被卷入的早期褶皱发生共轴叠加的递进变形。这样机械加厚的地壳在重力均衡作用下发生抬升,并遭受风化剥蚀直至准平原化,似乎就可以形成两褶皱区之间近数千米的整体剥蚀厚度差。
The Mesozoic East Sichuan fold belt is divided by the northeast-trending Qiyueshan fault into two areas with different fold patterns, trough-like folds to the east and comb-like folds to the west. Both areas are genetically related to decollement at depth. This paper uses FLAC6.0 software to simulate the two-stage evolution of the East Sichuan Fold Belt, where the comb-like folds have a younger age than the trough-like folds. According to simulation results, the general characteristics of the fold belt is reproducible for a 30° dip angle of the thrust ramp connecting the decollement zones that occur at a depth of 3–4 km from the unconformity between the basement and the platform cover for the trough-like folds and in the Cambrian strata for the comb-like folds, respectively. If only the ramp has a dip angle of no more than 30°, it can efficiently transfer the horizontal displacement to the comb-like fold area. This suggests no involvement of the high-angle Qiyueshan fault and, hence, breaking through shallow strata later. The presence of the fault bend fold may cause progressive deformation. The crust mechanically thicken in the way is subsequently uplift and worn down toward a peneplane, which is probably responsible for the difference in denudation between the comb-like fold area and the trough-like fold area.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2015年第6期1022-1032,共11页
Geotectonica et Metallogenia
基金
国家自然科学基金项目(41272228和41476035)联合资助
关键词
川东褶皱带
总体形态
滑脱带
断坡
数值模拟
the East Sichuan fold belt
overall pattern
decollement zone
thrust ramp
numerical simulation
