摘要
宇宙成因核素地表暴露测年方法,是近年来迅速发展起来的一种新的同位素地质年代学方法.宇宙成因核素主要是由来源于银河系的宇宙射线与暴露于地表的物质作用形成的,作用机制主要包括裂变、中子捕获和介子反应.产生宇宙成因核素宇宙射线粒子主要是次生快中子、热中子和负慢介子,由于这些宇宙射线粒子在空间分布上的不同,地球上不同纬度、海拔高度和深度处的宇宙成因核素生成速率也表现出较大的差异.地表物质中宇宙成因核素浓度除了受到核素生成速率和地表物质的暴露时间制约外,还与地表侵蚀速率密切相关,此外,地磁场强度、遮蔽、化学风化及样品的几何位置等也会对核素浓度产生一定影响,在求算样品的地表暴露年代时,应对这些因素进行相应的校正.宇宙成因核素地表暴露测年技术的理论和方法日臻完善,目前它已被广泛到第四纪冰川、撞击坑、火山地貌、断层面等地学问题中来.
Cosmogenic nuclide surface exposure dating is a newly developed isotopic dating technique in the past few years. Cosmogenic nuclides are primarily generated by reaction of target nuclei exposed near earth surface and galactic cosmic radiation. The reactions producing cosmogenic nuclides mainly involve spallation, capture of neutrons and muon reaction. The reacting cosmic particles producing nuclides primarily include secondary fast neutrons, thermal neutrons and slow negative muons. Due to the differential special distribution of these reacting particles, the production rates of cosmogenic nuclides at different latitude,altitude and depth are different. The concentration of cosmogenic nuclides is not only constrained by production rates and exposure time, and also closely related to surface erosion. Furthermore, the concentration is affected by geomagnetic intensity, shielding, chemical weathering, and sample geometry as well. These factors affecting cosmogenic nuclide concentration should be calibrated when surface exposure age is calculated. With the progress of the theory and methodology of cosmogenic surface exposure dating, the technique has been widely used in studies of Quaternary glaciations, impact craters, volcanic surfaces, and fault faces.
出处
《冰川冻土》
CSCD
北大核心
2006年第4期577-585,共9页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目(40371013)资助
关键词
宇宙成因核素
地表暴露测年
宇宙射线
侵蚀
cosmogenic nuclides
surface exposure dating
cosmic radiation
erosion
