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为研究东乌旗北部罕乌拉韧性剪切带的运动学性质及其时代,通过野外宏观调查和定向标本显微分析来研究花岗质糜棱岩的宏观-微观变形构造特征,并对经韧性剪切作用的花岗质糜棱岩进行LA-MC-ICPMS锆石U-Pb定年.研究表明花岗质糜棱岩的长石、石英等主要造岩矿物具塑性变形和动态生长的特征,发育典型的“σ”、“δ”和“S-C”组构,对研究区34组糜棱面理和线理数据进行赤平投影,剪切面(C面)平均面理产状为338°∠24°,线理产状为303°∠17°,显示出左行滑脱型韧性剪切带的特征;锆石U-Pb测年结果表明韧性剪切作用之前就位的花岗质岩石成岩年龄为135.9±1.2Ma~130.0±0.5Ma,属早白垩世,且该剪切带被下白垩统大磨拐河组(相当于凡兰吟期-欧特里沃期)砂砾岩覆盖.综上所述,结合最新区域研究成果认为,早白垩世(135.9±1.2Ma~130.0±0.5Ma)东乌旗地区经历了大规模左行伸展构造活动,这一成果深化了对该区早白垩世地壳构造演化的认识.
In order to study the kinematic characteristics and age of the Hanwula ductile shear zone in the northern part of Dongwu County, macroscopic and microscopic structural features of the granitic mylonites were studied through field investigation and microscopic analysis of directional specimens. Shear granitic mylonites are characterized by LA-MC-ICPMS zircon U-Pb dating.The results show that the major rock-forming minerals such as feldspar and quartz in granitic mylonites have plastic deformation and dynamic growth characteristics, The typical “σ ”, “δ ” and “SC ” structures were developed. The mylonitial and linear data of 34 groups were stereoscopically projected, and the mean plane of shear plane (C plane) The shape is 338 ° ∠24 ° and the lineal shape is 303 ° ∠17 °, which shows the features of the left-slip ductile shear zone. The zircon U-Pb dating results show that the The diagenetic age of granitic rocks is 135.9 ± 1.2Ma ~ 130.0 ± 0.5Ma and belongs to the Early Cretaceous. The shear zone is dominated by the Lower Cretaceous Damoguai Formation (corresponding to the Vanraninian period - Autotel Valley) Sandstone and conglomerate.According to the latest regional research results, the East Wuqi area of Early Cretaceous (135.9 ± 1.2Ma ~ 130.0 ± 0.5Ma) experienced large-scale left-lateral extensional tectonics activities, The results of a deepened awareness of the area early Cretaceous tectonic evolution.