植硅体释光信号特征及其对测年应用的启示  

THE LUMINESCENCE SIGNAL CHARACTERISTICS OF PHYTOLITH AND ITS APPLICATION IN DATING

作　　者：李兆宁 尹金辉[1] 杨会丽[1] 石文芳 郑勇刚[1] LI Zhao-ning;YIN Jin-hui;YANG Hui-li;SHI Wen-fang;ZHENG Yong-gang(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029

出　　处：《地震地质》2024年第1期101-116,共16页Seismology and Geology

基　　金：国家重点研发计划项目(2021YFC3000600);中国地震局地质研究所基本科研业务专项(IGCEA1903);中国地震局地震科技星火计划项目(XH20074);国家自然科学基金(42102267)共同资助。

摘　　要：中国西部青藏高原等地区往往缺乏可供AMS^(14)C测年的炭屑、植物残体等物质,开展传统的^(14)C测年有一定难度。然而,这些地区的现代地表常生长着大量草本植物,在其第四纪沉积物中均发现了丰富的植硅体。探索新的植硅体测年技术流程,可为中国西部地区的第四纪沉积物提供新的有效测年途径。植硅体以其自身的广泛分布性、结构稳定性和保存完整性,在测年应用中具有特殊优势,尤其是植硅体碳可用于^(14)C测年。然而,植硅体碳的^(14)C年龄存在高估问题,这可能是由于前处理过程中的快速氧化作用和高温作用破坏了其结构的稳定性和封闭性,需依据其化学组成和某些物理性质变化识别其结构在高温环境下的细微改变。植硅体作为特殊的非晶质含水SiO_(2),其热释光(Thermoluminescence,TL)与光释光(Optically stimulated luminescence,OSL)信号具有测年潜力,可作为直接比对和替代植硅体^(14)C测年法的另一测年手段,同时其释光性质变化可能对识别其物理结构变化具有参考价值。文中以从干稻草中提取的现代植硅体样品为例,对其进行了一系列条件实验,从而确定了植硅体OSL与ITL_(165)信号的具体测试流程,并进行了不同给定剂量的剂量恢复实验,以探讨其剂量-信号的响应关系及测试流程的可行性和可靠性。结果表明,天然植硅体颗粒存在稳定且易晒退的OSL信号,在较高给定剂量(850Gy)的条件下植硅体存在较显著且稳定的_(165)℃TL峰,OSL信号与ITL_(165)信号均有潜力应用于测年研究,但需要已知年龄的样品进行检验。与此同时,不同退火温度加热后的ITL_(500)曲线具有识别植硅体释光性质和物理结构变化的潜力,退火温度升高至300~350℃时植硅体的结构开始发生改变,至约600℃时已发生不可逆的结构改变且逐渐敏化。这也意味着在提取植硅体的过程中应尽可能使用湿式氧化法而非干�Phytoliths have shown a lot of advantages in dating due to their widespread distribution,structural stability,and preservation integrity,especially since phytolith carbon was used in radiocarbon dating.However,there is a problem of overestimation of phytolith carbon 14 C ages,which may be due to its structure destruction during pre-treatment processes of the rapid oxidation and high temperature.It is necessary to identify the subtle changes in its structure under high-temperature conditions based on its chemical composition and certain physical properties.As a special amorphous hydrated SiO 2,using their luminescence signals for thermoluminescence(TL)or optically stimulated luminescence(OSL)dating can be directly compared with their 14 C ages even as an alternative dating method,and the luminescence property changes of phytoliths may have a reference value for identifying the physical structure changes.In this paper,modern phytolith samples extracted from dry rice straw were taken as an example to study the stability of OSL and isothermal TL(ITL)signals.We conducted a series of conditional experiments to determine the specific experimental process of OSL and ITL_(165)signals,and discussed the feasibility and reliability of the dose-signal response relationship and test process under different given doses of dose recovery experiments.Moreover,the OSL signal were tested by a conventional single-aliquot regenerative-dose(SAR)protocol which firstly preheated at 200℃/180℃to remove the instability signal and then blue excited at 125℃.The OSL signal of phytolith sample rapidly decays under blue light and is basically reset within 5s of excitation.The sensitivity corrected OSL signal intensity and regeneration dose can respond one by one and a growth curve can be established,indicating that there is also a trap structure within the phytolith particles that can generate relatively stable OSL signals.However,there are still some problems which need further to be solved such as relatively weak signal intensity and poo

关 键 词：植硅体 光释光信号 等温热释光 植硅体碳 退火实验 

分 类 号：P597[天文地球—地球化学]