华北北缘东段开原-夹皮沟韧性剪切带变形及时代特征

The Kaiyuan-Jiapigou ductile shear zone is located in the eastern part of the northern margin of the North China Bloc. And based on former researches and according to the Ar/Ar chronology data (161-165Ma) of the mica and hornblende of mylonite in the Kaiyuan-Jiapigou ductile shear zone, first, we will reveal the spatial feature of the shear zone and then analyze its geometry, kinematics, dynamics and chronology. And according to the features of deformed mineral assemblage, we will identify the temperature-pessure conditions of defromation about the sheat zone . And finally we will reveal the features of the deformation and chronology of the shear zone. And then we will relate this tetonic event (forming of the shear zone) with other tetonic activity formed during the Middle-Late Jurassicthe in eastern Asia, then analysis the forming mechanism and dynamis setting of the shear zone. We also will analysis how this shear zone control the deformation in the other the gological units beside it. We also will discuss if the Kaiyuan-Jiapigou ductile shear zone controlled the disply of ore along it.

开原-夹皮沟剪切带位于华北板块北缘东部，其变形和时代有待进一步确定。本项目将在以往研究基础上，根据开原-夹皮沟韧性剪切带内糜棱岩获得云母（Ar/Ar）年代学线索（161-165Ma），对该剪切带进行集中采样和构造解剖，对其几何学，运动学和年代学加以甄别，并通过分析同变形期矿物组合关系，确定剪切带形成的温压条件，最终厘定该韧性剪切的时空特征，在此基础上，与中国东部中-晚侏罗世广泛而强烈的构造活动相联系，探讨该剪切带的形成机制和动力学背景；同时，通过对比分析该剪切带两侧构造活动的差异，分析剪切带对两侧地质体构造活动的影响；再者，通过分析剪切带内矿产的分布特征，探讨剪切带与带内成矿过程的关系。

在参与完成深部探测专题项目Sinoprobe08-01-02过程中，新发现华北北缘东段发育一条大型韧性剪切带，即开原-夹皮沟剪切带，其变形和时代有待进一步确定。本项目在以往研究基础上，对该剪切带进行集中采样和构造解剖，对其几何学，运动学和构造年代学加以甄别，并通过分析石英EBSD特征和同变形期矿物组合关系，确定了剪切带形成的温压条件，最终厘定该韧性剪切的时空特征，在此基础上，与中国东部中-晚侏罗世广泛而强烈的构造活动相联系，探讨该剪切带的形成机制和动力学背景。开原-夹皮沟韧性剪切带变形分析，揭示该剪切带面理平均产状为18°/54°，线理平均产状为28°/39°，具有上盘由NNE往SSW的剪切性质；剪切带周边地区脆性变形分析，脆性变形表明中-晚侏罗世该区受NEN–SWS 挤压应力场作用，形成一系列逆冲和平移断层，该期古应力场作用的最新地层为中侏罗世砂岩，意味着这期应力场形成的时代最有可能为晚侏罗世。显微变形特征表明，开原-夹皮沟韧性剪切带内长石发生了韧性拉伸，具有波状消光，以及亚晶和核幔结构，同时剪切带内石英亚晶发生了重结晶， 石英EBSD测试揭示石英主体发生底面滑移和菱面滑移，由此推测该韧性剪切带的形成温度约为400℃-450℃，介于黑云母封闭温度和角闪石封闭温度之间。对采自开原-夹皮沟韧性剪切带的共计8件样品进行了黑云母及角闪石Ar-Ar定年工作，结合剪切带的形成温度，限定了该韧性剪切带的形成年龄约为165.19 ± 0.6Ma至161.44M± 0.39 Ma；对剪切带形成的动力学背景进行了详细探讨，结合区域上岩浆岩类型和时代特征，认为开原-夹皮沟韧性剪切带的形成与中-晚侏罗世蒙古-鄂霍次克洋板块向东亚陆块的俯冲/碰撞密切相关。