伊利石K-Ar/Ar-Ar年龄约束浅地表断层活动时间:原理和潜力  

Dating of Shallow Crusted Faults by Illite K-Ar/Ar-Ar Ages:Principles and Potential

作　　者：赵奇 闫义[1,2,4,5] ZHAO Qi;YAN Yi(Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Center for Excellence in Deep Earth Science,Chinese Academy of Sciences,Guangzhou 510640,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou 511458,China;Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China)

机构地区：[1]中国科学院广州地球化学研究所,中国科学院边缘海与大洋地质重点实验室,广东广州510640 [2]中国科学院深地科学卓越创新中心,广东广州510640 [3]中国科学院大学地球与行星科学学院,北京100049 [4]南方海洋科学与工程广东省实验室,广东广州511458 [5]中国科学院南海生态环境工程创新研究院,广东广州510301

出　　处：《地球科学进展》2021年第7期671-683,共13页Advances in Earth Science

基　　金：国家自然科学基金项目“华南陆壳结构与南海北部地质过程研究”(编号:U1701641);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项“南海北部陆缘岩石圈薄化—破裂过程及其资源效应”(编号:GML 2019ZD0205)资助。

摘　　要：地壳脆性区断层的定年工作是地质学面临的一个重大瓶颈问题。尽管绝大多数脆性断层在活动时会产生可以用于放射性测年的自生/同运动学伊利石,但同时也会混入影响放射性年龄的碎屑矿物,如2M1多型伊利石或云母,从而使得自生/同运动学伊利石年龄数据受到质疑。随着伊利石年龄分析法及年龄牵引子法的提出,利用分离提纯的各粒级伊利石年龄与颗粒尺度的关系约束近地表脆性断层活动时间的方法逐渐变得可靠。首先介绍了伊利石定年的原理和假设,其次回顾了伊利石年龄限定断层活动时间的研究历史,并总结了关于伊利石年龄数据解释的2种方法及其原理和运用背景。然后评价了影响伊利石定年的可能因素,认为Ar损失在近地表脆性断层域中可以忽略不计,而2M1多型伊利石或云母是否自生对讨论断层泥伊利石年龄的地质意义至关重要。最后指出伊利石定年技术不仅仅局限于浅地表断层定年,还可以约束高应变褶皱及构造混杂岩的变形时间。另外,如果识别俯冲带中与俯冲、增生、剥蚀相关的各构造主控域并分别开展伊利石定年工作,将有助于从时空上对整个俯冲带循环过程(俯冲—增生—剥蚀)的还原。Dating of shallow crusted faults has remained difficult. Although most brittle faults produce authigenic/synkinetic illite that can be used for radiometric dating,the fault gouges always retain detrital minerals,such as high-temperature 2 M1 polytype illite/mica that make the radioactive age data questioned.However,with the introduction of the Illite Age Analysis method and the "Age-Attractor" method,illite K-Ar/Ar-Ar ages of each grain size fraction can be used for constraining the activity time of near-surface brittle faults.This paper first introduces the principles and assumptions of illite dating,and then reviews the history of the study of fault gouge dating,including the principles and background of the Illite Age Analysis method and "AgeAttractor" method. Then,the factors affecting the dating of illite are evaluated,and it is believed that Ar loss is negligible in the near-surface brittle fault domain,and whether the 2 M1 polytype illite/mica is authigenic mineral is crucial for discussing the geological significance of illite age. Finally,it is pointed out that the illite dating method is not only used for shallow crusted fault dating,but can also constrain the deformation time of highstrain folds and tectonic mélange as well. In addition,if the main structural domains of subduction,accretion,and denudation in subduction zones are identified and dated,a complete temporal and spatial evolution process of the subduction zone can be obtained.

关 键 词：断层定年 K-Ar/Ar-Ar年龄 伊利石 伊利石年龄分析 年龄牵引子 

分 类 号：P597.3[天文地球—地球化学]