原地生成宇宙成因核素在地学研究中的应用

传统测年方法(14C、热释光、光释光等)无法直接测量地貌面或基岩面的形成年代,利用宇宙生成核素定出的年代可以直接计算地质、地貌体的暴露年代和埋藏时代。随着测量仪器的长足进步,特别是加速器质谱(AMS)检出限(可测至106原子)的大幅度提高,原地生成宇宙成因核素定年技术给地貌学带来了革命性的变化,因此宇宙生成核素被广泛应用于古气候学、构造地质学、火山年代学及古地磁学等。本文阐释了原地生成宇宙核素定年方法的基本原理,并在地学领域应用的现有基础上,从冰川、断层、阶地等研究对象出发,以沉积物埋藏年龄、地表侵蚀速率、断层滑动速率等为研究内容,具体描述该定年技术在冰川地貌、构造地貌、地貌过程及地貌演化研究中的国内外研究现状,以及应用中尚待解决的诸如核素产生速率与空间、时间关系;样品地质、地貌条件对结果造成的不确定性等问题。

Applications of in-situ Cosmogenic Nuclides in Earth Sciences

Terrestrial in situ cosmogenic nuclide (TCN) techniques can directly measure surface exposure ages and burial events but traditional ¹⁴C dating, thermoluminescence dating, luminescence dating, etc cannot. In addition, the rapid progress of measuring instrumentation accuracy and precision, especially the detection limit of Accelerated Mass Spectrometry (AMS) has greatly improved to 10⁶ atoms. Therefore, TCN dating techniques have led to a revolutionary change, prompting increasing use in the nuclide earth sciences of paleoclimatology, structural geology, tephrochronology and paleomagnetism, for example. In this paper, the principles of TCN are briefly introduced. Based on existing applications, it describes the present field of burial age, erosion rate and faultslip rate for the glacier, fault slip and terrace, etc.. Current research work and problems in several specific earth science areas including glacial geomorphology, tectonic geomorphology, geomorphologic processes and geomorphic evolution are also summarized. In addition, the problem not resolved yet is described, such as the relationship of radionuclide generation rate with time and space, uncertainty of results from geological and geomorphological conditions of sample.