摘要
龙首山韧性剪切带运动学及动力学特征在加里东运动早期以自下而上的张应力作用为主,加里东运动中期为北西南东向的右行纯剪切作用,加里东运动后期以北东南西向的正压力作用伴有局部的压扭作用。其中,右行剪切变形最大主应力方向为北西南东向,后期压应力的主应力方向为北东南西向。研究区韧性剪切带主要分布在蓟县系、震旦系中,在其后地层中未发现,可以确定剪切带的形成应在震旦纪之后。并认为发生于震旦纪末至志留纪末的加里东造山运动导致了研究区韧性剪切带的形成,并在加里东造山运动的不同阶段有所叠加。结合金川超基性岩体的形成年龄,认为该韧性剪切带对成矿没有贡献。但是,对深部超基性岩体向浅部带动可能会有帮助。根据石英亚颗粒的直径估算,其古差应力值为282.9MPa。
The kinematic and dynamic characteristics of Longshoushan ductile shear zone in the early period of Caledonian orogeny was mainly the bottom-up tensile stress. In the middle period, it was largely dextral pure shearing action which was NW-SE trend. In the last period, it was the positive pressure of NE-SW trend accompanied by local press twist action. At the same time, the maximum principal stress of the dextral pure shearing action is NW-SE trend. The principal stress in the last period was NE-SW trend. According to the distribution of the ductile shear zone in the strata, namely only in Jixianian System and Sinian System, we can conclude that the ductile shear zone should be formed after Sinian Period. As we all know, the Caledonian orogeny was from the end of Sinian Period to the end of Silurian Period, so it was the tectonic movement that resulted in the formation of the ductile shear zone in the studied area. In addition, it added layer upon layer at different stages. Combined with the age of Jinchuan ultrabasic complex, we can conclude that the ductile shear zone has no contribution to Jinchuan deposit, but maybe it can help the ultrabasic complex move to shallow zone. With the diameter of the subgrain of quartz, we can estimate that its paleostress D-value was 282. 9MPa.
出处
《西北地质》
CAS
CSCD
2013年第2期44-53,共10页
Northwestern Geology
基金
国家自然基金项目(40872070)
长安大学科技创新基础研究支持计划项目(CHD2009JC032)
关键词
龙首山
韧性剪切带
构造层次
运动学
动力学
石英亚颗粒
古差应力值
Longshoushan
ductile shear zone
tectonic level
kinematics
dynamics
subgrain of quartz
paleostress D-value
