今天是2018年01月17日

长春东南劝农山地区早二叠世范家屯组 岩石变形组构及流变学特征

DOI:10.3799/dqkx.2017.139

作者:梁琛岳,刘永江,朱建江,李伟民,常瑞虹,张丽

联系地址:吉林大学地球科学学院,吉林长春 130061

摘要:劝农山地区位于长春市东南部,处于佳-伊断裂和西拉木伦河缝合带交汇处.详细野外调查发现,该区曾遭受强烈韧性剪切变形,剪切带内岩石普遍糜棱岩化,主要由下二叠统范家屯组(P1f)钙质糜棱岩与侵入其中的燕山期花岗质糜棱岩组成,变形程度处于初糜棱岩至糜棱岩之间,多具有糜棱结构.岩石应变类型主要为压扁型应变,偏一般压缩,为L=S型构造岩,指示其形成于挤压型剪切带的构造环境.多种宏微观韧性剪切变形标志,指示明显的左行剪切运动.电子探针方解石-白云石地质温度计、方解石和石英EBSD组构特征、方解石e双晶形态以及石英长石变形行为等均显示岩石具有低温塑性流变特点,变形环境不超过绿片岩相.剪切带内应变速率偏高,应变集中带应变速率最大,在10-6.95~10-8.89之间,远离强变形带应变速率在10-9.25~10-12.17之间,糜棱岩化作用过程中差异应力下限应大致为51.27~65.46MPa,代表剪切带糜棱岩化作用为低温中等强度应变,在稍快的应变速率条件下形成.压溶扩散和双晶滑移为劝农山韧性剪切带变形初期的主要变形机制,随着递进变形,逐渐以双晶滑移和晶内滑移为主,递进变形晚期,局部强变形域内发生了粒间滑移.劝农山韧性剪切带形成与早白垩世中晚期伊泽纳崎板块NNW向高斜度斜向俯冲于欧亚大陆之下有关,是佳-伊断裂带左旋走滑事件的局部表现.

关键字:构造变形;EBSD;变形温度;差异应力;应变速率;佳-依断裂带;构造.

Deformation Fabrics and Rheological Features of Early Permian Fanjiatun Formation from Quannongshan Area, Southeastern Changchun

Author:Liang Chenyue Liu Yongjiang, Zhu Jianjiang, Li Weimin, Chang Ruihong, Zhang Li

Author Address:College of Earth Sciences, Jilin University, Changchun 130061, China

Abstract:The Quannongshan area is located in the southeastern part of Changchun, at the junction of the Jiamusi-Yilan fault belt and Xar Moron suture zone. Detailed field observations indicate strong ductile deformation event which developed in these mylonites: Lower Permian Fanjiatun Formation (P1f) calcmylonites and the intrusive Yanshanian granitic mylonites. Most rocks were deformed to protomylonites and mylonites macroscopically in a gneissic-like structure. The major strain type is plan-strain and marked by much compression, which is general compression. And the deformed rocks are characterized by L=S type tectonites demonstrating a strong tectonic condition of a compressive ductile shear zone. A variety of macro/micro-ductile deformation kinematic marks indicate a significant sinistral shearing. Based on detailed macro/microstructural analysis, quartz c-axis EBSD fabrics, calcitedolomite geothermometer from electron probe, calcite twin morphology and quartz/feldspar deformation behaviors, a low-temperature plastic flow characteristics and greenschist metamorphic environment were estimated. The ductile shear zone has a relatively high strain rate, which is between 10-6.95 and 10-8.89 in a highly strained zone and 10-9.25-10-12.17 away from the strong deformation zone. The lower limit of the differential stress during the mylonization process should be approximately 51.27-65.46MPa, which represents that the mylonitization formed at a slightly faster strain rate with low deformation temperature and moderate strain strength. In the initial deformation period, the pressolution diffusion and the twin gliding are the main deformation mechanisms, then in the middle of the deformation they are dominated by the twin gliding and the grain boundary slip. In the late stage of the progressive deformation, the grain boundary sliding occurred in parts of strong stain zone. The formation of this ductile shear zone might be related to the Izanagi plate obliquely NNW subducting under the Eurasia plate during the middle and late Early Cretaceous, which is a local performance of the sinistral strike-slip Jia-Yi fault.

Keyword:structural deformation; EBSD; deformation temperature; paleostress; strain rate; JiaYi fault; tectonics.

 

【点击数:61【下载数:52】【PDF预览】


作者简介:梁琛岳(1986-),男,讲师,主要从事构造地质学与岩石流变学研究.ORCID:0000-0002-4269-5010.E-mail:chenyueliang@jlu.edu.cn

参考文献