长江中下游地区中生代“蝴蝶结”形态的构造成因研究:来自殷店—马垅剪切带的证据  

Tectonic genesis of Mesozoic“bowknot”formation in the middle and lower reaches of the Yangtze River:Evidence from Yindian‑Malong shear zone

作　　者：张刚[1] 王辉[1] 扈志勇[1] 弓永峰[1] 何小锋[1] 王国瑞 唐存智 方璐[1] 高世昌 杨睿青 Zhang Gang;Wang Hui;Hu Zhiyong;Gong Yongfeng;He Xiaofeng;Wang Guorui;Tang Cunzhi;Fang Lu;Gao Shichang;Yang Ruiqing(Institute of Land and Resources Investigation and Monitoring of Ningxia Hui Autonomous Region,Yinchuan 750002)

机构地区：[1]宁夏回族自治区自然资源厅,国土资源调查监测院,银川750002

出　　处：《地质科学》2023年第3期723-763,共41页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:41272222);宁夏回族自治区自然科学基金项目(编号:2021AAC03426)资助。

摘　　要：殷店—马垅剪切带位于大别造山带南侧,它不仅是一条划分大别造山带南侧岩性界线的剪切带,更是长江中下游地区“蝴蝶结”几何学形态的西侧边界断裂。本文通过该剪切带几何学、运动学、年代学和动力学特征深入了解整个区域的演化过程和动力学背景。剪切带宏观与显微构造均指示其运动学特征为右行剪切。纵向上,越靠近剪切带,呈现出分形维数值越大的变化趋势,差异应力值σ和应变速率ε也表现出此规律。横向上,剪切带东段岩石有限应变RXZ在1.91~2.46之间,大于剪切带西段的值。表明剪切带越靠近“蝴蝶结”结点部位时,构造作用力的影响越深,剪应力和应变强度越大。显微构造特征估算、角闪石单矿物温压计和黑云母单矿物压力计计算,获得其形成时温压条件为:T=588℃~640℃,P=0.45~0.52 GPa,属于中低角闪岩相变质范围。剪切带涡度值Wk远大于0.75,以简单剪切变形为主。构造应力场指示了以190°向180°~170°的转变,可能代表了华南华北板块碰撞后产生的南北向挤压应力场逐渐转变为受太平洋构造体制影响下的应力场。锆石U-Pb定年获得了剪切带在153.5±2.9 Ma存在剪切活动,属于中生代构造活动的一部分,结合前人研究成果,认为剪切带活动时间约从176 Ma开始,到130 Ma左右结束。中生代以来,受太平洋构造体制的影响,殷店—马垅剪切带与脉动式左行剪切的郯庐断裂带在几何学、运动学、年代学上十分吻合,共同构成了整个区域构造系统下的共轭剪切作用。二者的构造活动使得桐柏—大别造山带内物质由西向东深层次有序流动,运动方向转变为向南,在桐柏—大别造山带最南缘处成为理论上最佳的应力集中点,这种应力方式在与扬子板块相互挤压的共同作用下,可能造成了如今长江中下游地区表现为中间窄,两侧渐宽的“蝴蝶结”状几何学形态。The Yindian‑Malong shear zone is located in the south of the Dabie orogenic belt.It is not only a shear zone dividing the lithologic boundary of the southern Dabie orogenic belt,but also the western boundary fault of the“bowknot”geometry in the middle and lower reaches of the Yangtze River.In this paper,the geometry,kinematics,chronology and dynamics characteristics of the shear zone are used to further understand the evolution process and dynamic background of the whole region.Both macroscopic and microscopic structures of the shear zone indicate that its kinematic characteristics are dextral shear.In the longitudinal direction,the closer the shear zone,the larger the fractal dimension is(1.16~1.14 to 1.16~1.18),and the differential stress valueσand strain rateεalso show this pattern.Laterally,the finite strain RXZ of rock in the eastern is between 1.91 and 2.46,which is larger than that in the western.The results show that the closer to the“bowknot”junction,the deeper the influence of tectonic forces and the greater the shear stress and strain strength.According to the microstructural characteristics,amphibolite single mineral temperature and pressure gauge calculation and biotite single mineral pressure gauge calculation,the temperature and pressure conditions of its formation are T=588℃~640℃,P=0.45~0.52 GPa,which belongs to the metamorphic range of middle and low amphibolite facies.The vorticity value Wk of the shear zone is much larger than 0.75,which is mainly caused by simple shear deformation.The tectonic stress field indicates the transition from 190°to 180°~170°,which may represent the gradual change of the north‑south compressive stress caused by the collision of the South China and North China plates to the stress field change under the Pacific tectonic system.Zircon U‑Pb dating shows for the first time that the shear zone has shear activity at 153.5±2.9 Ma,which is a part of the Mesozoic tectonic activity.Combined with previous research results,it is believed that the shear zo

关 键 词：殷店—马垅剪切带 中生代 构造年代学 构造意义 

分 类 号：P542[天文地球—构造地质学]