华南地质2026，Vol.42Issue(4)：573-587,15.DOI:10.3969/j.issn.2097-0013.2026.04.002
桂北地区元宝山韧性剪切带的厘定及其大地构造意义
Determination of the Yuanshan Ductile Shear Zone in Northern Guangxi and Its Tectonic Significance
摘要
Abstract
[Objective]The Yuanshan ductile shear zone in northern Guangxi is located on the southwestern margin of the Early Paleozoic collisional orogenic belt between the Yangtze and Cathaysia blocks.Its strain characteristics and deformation mechanisms are of great significance for understanding the Early Paleozoic tectonic evolution of South China.[Methods]This paper presents systematic macro-and micro-structural analyses,three-dimensional finite strain measurements,and quartz EBSD fabric analysis of the Yuanbaoshan ductile zone.[Results]The shear zone exhibits typical ductile deformation fabrics,including mylonitization,S-C fabrics,rotated porphyroclasts,domino structures,core-mantle structures,and mica fish.Finite strain data and field structural analysis reveal that the ductile shear zone extends more than 30 km in a NNE direction and comprises two roughly parallel belts:the western belt(3.5-5.5 km wide)and the eastern belt(1.5-5.0 km wide).Stereographic projections of mylonitic C-planes show a pole density maximum of 285°∠22° in the western belt,which reverses to a southeast dip at its southern end,and 293°∠45° in the eastern belt.Two deformation episodes are recognized:an early stage characterized by medium-to high-temperature sinistral thrust shearing with flattening strain,and a late stage overprinted by medium-to low-temperature dextral normal slip shearing with constructional strain.Paleodifferential stress and strain rate are relatively low,ranging from 15.38 to 43.83 MPa and from 14.82×10-13 to 977.48×10-13 s-1,respectively.[Conclusions]In-tegrating these results with regional geological data,we propose that the Yuanbaoshan ductile shear zone formed in a back-thrusting setting resulting from the SE-to-NW compression of the Cathaysia block against the Yangtze block during the Caledonian orogeny.The early collision related compression generated medium-to high-temperature sinistral thrust shearing and flattening strain,whereas the late post-orogenic extension produced medium-to low-temperature dextral normal-slip shearing and constructional strain.These findings provide new insights into the deformation temperature,strain characteristics,and geodynamic setting of the Yuanbaoshan ductile shear zone,contributing to a better understanding of the Caledonian tectonic events in South China.关键词
有限应变测量/应变特征/石英EBSD组构/韧性剪切带/桂北元宝山地区Key words
finite strain measurement/strain characteristics/quartz EBSD fabric/ductile shear zone/the Yuanbaoshan area of northern Guangxi分类
天文与地球科学引用本文复制引用
倪战旭,蒋剑,秦亚,苟小芳,冯佐海,郭阿龙..桂北地区元宝山韧性剪切带的厘定及其大地构造意义[J].华南地质,2026,42(4):573-587,15.基金项目
国家自然科学基金项目(42162018)、广西自然科学基金项目(2025GXNSFAA069322)、"赋能"行动计划(广西重点研发计划)(桂科FN2600640052)、地球深部探测与矿产资源勘查国家科技重大专项(2025ZD1005908,2025ZD1009003) （42162018）
