藏南裂谷区晚第四纪泉华的ESR测年适用性研究  

Research on the applicability of electron spin resonance dating of the late Quaternary sinter deposits in the rift valley,southern Tibet

作　　者：王晟 吕同艳[2,3,4] 吴中海 白玛多吉[5,6] 叶强 尼玛次仁 沙龙滨 WANG Sheng;LYU Tongyan;WU Zhonghai;BAIMA Duoji;YE Qiang;NIMA Ciren;SHA Longbin(Department of Geography and Spatial Information Techniques,Ningbo University,Ningbo 315211,Zhejiang,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,China;Research Center of Neotectonism and Crustal Stability,China Geological Survey,Beijing 100081,China;Xizang Institute of Geology Survey,Lhasa 850000,Tibet,China;Geothermal and Geological Team,Geology and Mineral Exploration and Development of Tibet Autonomous Region,Lhasa 850000,Tibet,China;Regional Geological Survey Team,Geology and Mineral Exploration and Development of Tibet Autonomous Region,Lhasa 851400,Tibet,China)

机构地区：[1]宁波大学地理与空间信息技术系,浙江宁波315211 [2]中国地质科学院地质力学研究所,北京100081 [3]自然资源部活动构造与地质安全重点实验室,北京100081 [4]中国地质调查局新构造与地壳稳定性研究中心,北京100081 [5]西藏地质调查院,西藏拉萨850000 [6]西藏自治区地质矿产勘查开发局地热地质大队,西藏拉萨850000 [7]西藏自治区地质矿产勘查开发局区域地质调查大队,西藏拉萨851400

出　　处：《地质力学学报》2023年第2期276-289,共14页Journal of Geomechanics

基　　金：中国地质调查局地质调查项目(DD20221644);国家自然科学基金面上项目(41877443,42176226);国家自然科学基金地方联合基金(U2002211-04)。

摘　　要：藏南裂谷区泉华(硅华和钙华)是受区域构造运动控制的水热活动产物,其形成年代对研究该区域水热活动历史有着重要意义。电子自旋共振(ESR)测年法是一种测定泉华年龄的有效测年手段。但存在硅华样品成分复杂,其ESR测年信号具有混合叠加、相互干扰的现象,影响ESR信号的读取;且应用ESR测年法对藏南的钙华样品研究较少,不利于全面掌握藏南水热活动历史等问题。因此对藏南泉华样品ESR测年适用性的研究将有助于指导藏南地区泉华ESR测年的准确性,同时为开展区域构造活动研究提供扎实的年代学基础。该文选取藏南阿里—日喀则地区搭格架热田区的硅华样品和夏康坚温泉区的钙华样品,开展了泉华样品的ESR信号选取和附加剂量影响、钙华ESR信号热稳定性探究,进而得到相对准确的泉华发育年代。研究结果表明:搭格架热田区第三、四级阶地处硅华分别形成于81±16 ka、177±20 ka,夏康坚温泉区河漫滩和第一级阶地处的钙华分别沉积于106±32 ka、264±26 ka。辐照剂量方面,藏南泉华样品在0~7680 Gy范围内对人工附加剂量响应良好;温度方面,硅华受封闭温度影响较小,钙华g=2.0034心信号在20~250℃范围具有良好的稳定性,适合ESR测年。矿物结构方面,藏南钙华的矿物纯度、结晶程度较好,ESR年龄结果相对准确。Sinters in the rift valleys of southern Tibet,including silica sinter and travertine deposits,are the products of hydrothermal activity under regional tectonic movement.Their formation age is significant for studying hydrothermal activity history in this region.Electron spin resonance(ESR)dating is a practical dating method for determining the age of silica sinter and travertine deposits.However,silica sinter’s ESR signals vary due to the complex composition.Meanwhile,these ESR signals are mixed,superimposed,and interfere with each other,affecting the ESR signal’s measurement.Furthermore,ESR dating has been applied less in travertine samples in southern Tibet,which is not conducive to a comprehensive understanding of the hydrothermal activity history in southern Tibet.Studying the applicability of ESR dating of southern Tibetan silica sinter and travertine deposits helps obtain accurate ESR ages.It lays the chronologic foundation for researching tectonic activities in these rift valleys.This research applied ESR dating to the silica sinter and travertine deposits collected separately from the Targejia thermal field area and the Xiakangjian hot spring area,located in the Ngri-Xigaze area in southern Tibet.We performed ESR dating tests,including how to choose ESR signals,the effect of additional doses,and the thermal stability of ESR signals in travertine.Based on these tests,relatively accurate,reliable ESR ages of silica sinter and travertine were obtained.The results show that:According to the ESR dating results,the silica sinter samples collected from the fourth and third terrace of the Targejia geothermal field were formed at 177±20 and 81±16 ka,respectively,and the travertine deposits collected from the floodplain and first terrace of the Xiakangjian hot spring were formed at 106±32 ka and 264±26 ka,respectively.In terms of irradiation dose,sinter samples collected from southern Tibet respond well to irradiation dose in the range of 0~7680 Gy;In terms of temperature,silica sinter samples are less affe

关 键 词：ESR测年 泉华 硅华 钙华 藏南 G值 第四纪 

分 类 号：P533[天文地球—古生物学与地层学] P542[天文地球—地质学] P595