地质力学学报2026，Vol.32Issue(4)：771-785,15.DOI:10.12090/j.issn.1006-6616.2025052
云开地块西北缘十里韧性剪切带变形特征及40Ar/39Ar年龄
Deformation characteristics and 40Ar/39Ar geochronology of the Shili ductile shear zone at the northwestern margin of the Yunkai Block
摘要
Abstract
[Objective]The Yunkai Massif is one of the Precambrian metamorphic crystalline basements within the South China Block.To better understand the Indosinian deformation characteristics in the Yunkai area,the Shili ductile shear zone at the northwestern margin of the Yunkai Massif was selected for this study.[Methods]Through detailed field investigations,finite strain measurements,kinematic vorticity analyses,and 40Ar/39Ar geochronology,the structural char-acteristics and evolutionary process of the shear zone were constrained.[Results]The Shili ductile shear zone generally strikes WNW-ESE with NNE-directed thrusting.It has undergone four phases of deformation.Among which,the D2 to D4 deformations all indicate movement from SSW to NNE.D2 to D4 formed under a unified tectonic stress field,reflecting an evolution from ductile shear through brittle-ductile deformation to folding during the Late Triassic.Mylonites formed synchronously with the ductile shear deformation yield a muscovite 40Ar/39Ar plateau age of 232±2.3 Ma(MSWD=3.65).The Flinn index(K)is 0.06-0.77,the Lode parameter(ν)is 0.13-0.89,the Effective strain(Es)is 0.41-0.51,and the kinematic vorticity value(Wk)is 0.70-0.78.These parameters indicate a flattening-type strain regime dominated by general shear,with comparable contributions of pure shear and simple shear.The dynamic recrystallization of minerals suggests that the deformation environment reached the upper greenschist facies.[Conclusions]This study indicates that the mylonitization,crenulation cleavage development,and folding within the Shili ductile shear zone were dynamically driven by the propagation of far-field stress resulting from the NE-SW collision between the Indochina and South China blocks during the Indosinian period.[Significance]These findings provide critical constraints on the Indosinian tectono-thermal event and its geodynamic framework in South China.关键词
华南板块/云开地块/韧性剪切带/有限应变/运动学涡度/40Ar/39ArKey words
South China Block/Yunkai Block/ductile shear zone/finite strain/kinematic vorticity/40Ar/39Ar geochronology分类
天文与地球科学引用本文复制引用
郭尚宇,吴祥珂,赵兵,黎丹..云开地块西北缘十里韧性剪切带变形特征及40Ar/39Ar年龄[J].地质力学学报,2026,32(4):771-785,15.基金项目
深地国家科技重大专项(2024ZD10017700) （2024ZD10017700）
中国地质调查局地质调查项目(DD20160035) This research was financially supported by the National Science and Technology Major project for Deep-Earth Exploration(Grant No.2024ZD10017700)and the China Geological Survey Project of the China Geological Survey(Grant No.DD20160035). （DD20160035）
