摘要
矿物晶体中累积的释光信号与其暴露在辐射环境中的时间相关,可用于测定沉积物年代.近年来,依托石英和长石 2 种矿物释光信号的测年方法日臻成熟,但这 2 种矿物的释光信号过早饱和,限制了其测年上限(通常<300ka).前人研究表明,方解石亦有可能成为热释光测年材料,因为其热释光信号对剂量响应的灵敏度高,且特征饱和剂量约可达 3000～5000Gy,有望将释光测年范围扩展至第四纪尺度.特别地,这一技术的发展也将拓展目前仅限于剥露速率极高地区的释光低温热年代学的应用范围,使其更好地贡献于地貌演化和构造活动的研究.文中对方解石热释光的基本原理和测年流程进行了简要概括,总结了方解石热释光测年应用及动力学参数的研究成果.此外,利用方解石热释光技术对虎跳峡段的基岩样品进行了测试,结果表明,ITL-235℃释光信号可用于该地区剥露历史的恢复工作.同时,文中基于上述内容讨论了方解石热释光技术的应用潜力和待解决问题,以期为该技术在构造地貌领域的应用提供帮助.
Abstract
The accumulation of luminescence signals in mineral crystals correlates with the duration of exposure to radiation.This phenomenon has been utilized as a tool for measuring sediment age and has found extensive application in various research endeavors.While quartz and feldspar luminescence signals have been utilized for dating in recent years,their effectiveness is constrained by early saturation,limiting their dating range to less than 300ka.In contrast,calcite exhibits high sensitivity to dose responses of thermoluminescence signals and possesses a characteristic saturation dose that can reach levels of 3000-5000Gy,making it a promising material for thermoluminescence dating.This has the potential to extend the age range of luminescence dating to the Quaternary period and broaden the application scope of low-temperature thermochronology.Providing quantitative descriptions of bedrock exhumation history through low-temperature thermochronology can offer crucial data support for understanding the interconnected relationship between tectonic activity,climate influences,and geomorphic evolution.Low-temperature thermoluminescence thermochronology,characterized by its high resolution and low closure temperature,presents advantages over commonly used apatite U-Th/He thermochronology in elucidating the excavation history of the Earth's crust surface(approximately 1～2km).However,traditional minerals utilized for reconstructing bedrock cooling history,such as quartz and feldspar,exhibit rapid saturation,limiting the study period to less than 200ka.In contrast,calcite boasts an exceptionally high characteristic saturation dose and lower dose rate,making it a promising new dating mineral that extends the upper limit of low-temperature thermoluminescence thermochronology beyond 0.5Ma.This paper begins by introducing the principle and application of thermoluminescence dating,followed by an overview of commonly used techniques for measuring dose rate and equivalent dose.The thermoluminescence dating process primarily involves equivalent dose measurement and dose rate measurement.Considerable research has been conducted on equivalent dose,and newly developed methods such as single aliquot regenerative dose,multiple aliquot regenerative dose,and multiple aliquot-additive dose have addressed issues related to sensitivity changes caused by heating,thereby enhancing the accuracy of dating results.Additionally,the paper summarizes recent advancements in calcite thermoluminescence dating and kinetic parameters.To validate the method,we performed thermoluminescence dating analysis on calcite grains in bedrock samples collected from the Tiger Leap Gorge of the Jinsha river.After passing through Shigu,the Jinsha river experiences a sudden change in flow direction,carving its way through the Yulong-Haba mountain range to create the renowned"Tiger Leaping Gorge."This geographic feature is characterized by active tectonics and intense river erosion,making it an ideal site for investigating the interplay among tectonics,climate,and surface processes.However,the Tiger Leaping Gorge primarily comprises limestone and griotte,lacking minerals such as apatite and zircon necessary for traditional low-temperature thermochronology dating(only exposed in the Upper Tiger Leaping Gorge).Consequently,it presents an ideal setting for exploring calcite low-temperature thermoluminescence thermochronology.SAR-ITL can detect the 280℃thermolu-minescence peak signal of calcite at 235℃,effectively mitigating the influence of spurious thermolu-minescence.Moreover,the number of calcite grains required is lower than that of the MAAD test.The findings highlight the potential of this method for estimating the exhumation rate of carbonate rock.To facilitate its more effective utilization in the field of tectonic geomorphology,we address the challenges and potential applications of calcite thermoluminescence dating.
基金项目
国家自然科学基金(42030305)
国家自然科学基金(42202212)
中国博士后国际交流计划引进项目(YJ20210146)
中国博士后科学基金项目(2021M702425)
天津市自然科学基金青年项目(23JCQNJC02000)
NETL
NSTL
万方数据