龙门山造山带中段茂县-汶川断裂中生代变形条件研究与构造启示  

Mesozoic deformation characteristics and tectonic implications for Maoxian-Wenchuan Fault:A aase from central Longmenshan Orogenic Belt

作　　者：陈玮 刘翔瑞 游劲 CHEN Wei;LIU Xiangrui;YOU Jin(College of earth and planetary sciences,chengdu university of technology,chengdu,sichuan 610059,china;Sinoprobe laboratory,chinese academy of geological sciences,beijing 100094,china;School of earth sciences and resources,china university of geosciences,beijing 100083,china;School of earth sciences,china university of geosciences,wuhan,hubei 430074,china)

机构地区：[1]成都理工大学地球与行星科学学院,四川成都610059 [2]自然资源部深地科学与探测技术实验室,北京100094 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《矿物岩石》2024年第4期111-124,共14页Mineralogy and Petrology

基　　金：自然资源部深地科学与探测技术实验室开放基金(编号:SinoProbe Lab 202226)。

摘　　要：位于青藏高原东缘的龙门山造山带深部构造与变形机制一直是广泛讨论的课题。目前针对该造山带的研究多集中于新生代剥露历程、动力学机制以及与四川盆地的耦合演化关系。现有的研究表明,在印支期随着华北地块、扬子地块与松潘-甘孜褶皱带的汇聚,龙门山造山过程已经开始,并在早白垩世发生一定隆升。以上针对龙门山造山带中生代的构造环境研究多建立在变质矿物温压计之上,而从构造解析与岩石变形组构特征研究中生代变形较少,缺乏来自构造岩变形的直接约束。因此,本研究以龙门山造山带中段茂县-汶川断裂两侧糜棱岩化改造的志留系变质岩与彭灌杂岩为研究对象,在野外露头观察和显微镜下分析基础之上,采用EBSD技术分析石英、斜长石晶格优选定向特征,以期限定龙门山造山带中段茂县-汶川断裂中生代不同阶段变形环境。研究表明,茂县-汶川断裂最初发生了类比温度为500~650℃的韧性变形,尔后发生了类比温度为300~400℃脆性-低温韧性变形叠加。后期的叠加变形反映出,随着龙门山造山带的抬升,茂县-汶川断裂由透入性变形带转变为应变局部化带。The deep structure and deformation mechanisms of the Longmenshan Orogenic Belt,located on the eastern edge of the Qinghai-Tibet Plateau,have long been a subject of extensive research and de-bate.Current studies primarily focus on the Cenozoic exhumation processes,dynamic mechanisms,and the coupled evolutionary relationship with the Sichuan basin.Previous studies suggest that orogenesis in the Longmenshan began during the Indosinian period,driven by the convergence of the north China block,Yangtze block,and the Songpan-Ganzi fold belt,with notable uplift occurring during the early Cretaceous.Mesozoic tectonic studies of the Longmenshan orogenic belt have largely relied on thermobarometers of metamorphic mineral,with relatively limited attention to structural analysis and rock deformation charac-teristics,This lack of focus on structural deformation analysis has resulted in insufficient direct constraints from the deformation of rocks themselves.This study investigates Silurian mylonitized metamorphic rocks and the Pengguan complex on both sides of the Maoxian-Wenchuan fault.Through field observations,mi-croscopic analyses,and Electron Backscatter Diffraction(EBSD)technology,the preferred crystallograph-ic orientation of quartz and feldspar is analyzed to elucidate the deformation environments during different Mesozoic stages along the Maoxian-Wenchuan fault in the central section of the Longmenshan orogenic belt.The findings reveal that the Maoxian-Wenchuan fault initially underwent ductile deformation at tem-peratures between 500 and 650℃,followed by superimposed brittle to low-temperature ductile deforma-tion at temperatures ranging from 300 to 400℃.This superimposed deformation reflects a transition of the Maoxian-Wenchuan fault from a pervasively deforming zone to a localized strain zone,coinciding with the uplift of the Longmenshan orogenic belt.

关 键 词：龙门山造山带 茂县-汶川断裂 晶格优选 EBSD技术 韧性变形特征 

分 类 号：P579[天文地球—矿物学]