方解石LA-(MC-)ICP-MS U-Pb定年技术及其在脆性构造中的应用  

LA-(MC-)ICP-MS U-Pb Dating Technique of Calcite and Its Application in Brittle Structures

作　　者：赵子贤 施炜[1,2] ZHAO Zi-xian;SHI Wei(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Neotectonic Movement and Geohazard,Ministry of Natural Resources,Beijing 100081,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部新构造运动与地质灾害重点实验室,北京100081

出　　处：《地球科学与环境学报》2019年第5期505-516,共12页Journal of Earth Sciences and Environment

基　　金：中国地质调查局地质调查项目(DD20190018);国家重点研发计划项目(2017YFC0601402)

摘　　要：脆性构造形成于地壳浅层,记录了地壳浅层构造变形过程,精确限定浅层地壳变形时代是构造地质研究的热点和难点之一。由于脆性构造变形发生于较低的温压环境,岩石应变速率快,变质和交代作用相对较弱,难以形成韧性构造变形中可定年的同构造新生矿物,所以脆性构造的精确定年一直是学界难题。近年来,方解石U-Pb定年技术取得重要进展,通过脆性构造变形同构造方解石脉U-Pb定年可以精确限定构造变形时代。对近几年方解石LA-(MC-)ICP-MS U-Pb定年技术研究进展进行总结,系统地介绍了同构造方解石脉特征、方解石U-Pb定年基本原理、方解石LA-(MC-)ICP-MS U-Pb定年方法及应用实例,指出该方法目前存在的关键问题和技术难点在于方解石U-Pb年龄代表的地质意义和其定年的成功率。野外识别同构造方解石脉,划分不同期次方解石,确定原生域和次生域能够准确揭示其年龄的地质意义;圈定最优待测靶区,选择合适的普通铅校正方法以及寻找理想的方解石标样有利于提高定年结果精度和准确性。Brittle structures are formed in the shallow crust and record the deformation process of shallow crust structures.How to precisely define the age of shallow crustal deformation is one of the hotspots and difficulties in structural geology research.Brittle structural deformation occurs in a lower temperature and pressure environment,which results in a faster rock strain rate and a relatively weaker metamorphism and metasomatism.As a result,it is difficult to form syntectonic new minerals similar to the measurable age of ductile deformation,which makes precise dating of brittle structures become a difficult problem in the field of earth science.In recent years,the calcite U-Pb dating technology has made important progress,and the calcite U-Pb dating from brittle structural deformation can accurately date the age of structural deformation.The research progress of the calcite LA-(MC-)ICP-MS U-Pb dating technique in recent years was summarized,the characteristics of the syntectonic calcite vein,the theoretical basis of U-Pb isotope dating of calcite,the LA-(MC-)ICP-MS U-Pb dating technique of calcite and its examples of application were systematically introduced.Furthermore,pointing out the key problems and technical difficulties of this method at present depends on the geological significance of calcite U-Pb age and the success rate of age determination.Identifying syntectonic calcite veins in the field,dividing different stages of calcite and determining primary and secondary domains,can accurately reveal the geological significance of its age;besides,the accuracy of dating results can be improved by delineating the optimal target area to be measured,choosing reasonable common lead correction method and searching for ideal calcite reference materials.

关 键 词：脆性构造 构造变形 方解石 U-Pb定年 LA-(MC-)ICP-MS 同位素年代学 普通铅 标准样品 

分 类 号：P597[天文地球—地球化学]