摘要
地球表面丰富多样的地形、地貌是地球内外动力相互作用的结果。宇宙射线辐射地表岩石、沉积物等产生的^(10)Be和^(26)Al放射性核素（半衰期分别为1．5Ma和0．71Ma），它们的浓度主要取决于由地理位置和地形、地貌条件所决定的宇宙射线辐射的通量和时间，从而能够记录地表的形成和演化历史。因此，宇宙成因核素是研究地表形成历史和作用过程的有力工具。
The surface of the earth is continuously undergoing changes as a result of weathering and erosion, plate tectonics and volcanic processes. Continental denudation with its complex rock-water interactions is the central process of global biogeochemical cycling of elements. Rates of denudation depend on variety of factors,in particular rock properties and chemical composition, climate (especially rainfall),structure, and elevation. Thus they are quite variable on a regional scale. A primary step in most geomorphological studies is to gain understanding of the location-specific weathering and erosional processes. An important recent contribution to the Earth sciences has been made with the development of a cosmogenic nuclide method applicable for the study of divers geomorphic processes and histories. The basic principle of application of the in situ cosmogenic radionuclides ^(10)Be (half-life = 1. 5Ma)and ^(26)Al (half-life = 0.71Ma) in quartz for study of the processes on the earth surface is given in this paper.The basis of the application of the in situ cosmogenic nuclides in the Earth sciences is their production in solids by particles of the cosmic rays. The production rates of the in situ cosmogenic nuclides depend on the cosmic ray flux at their situation as well as composition and density of the target material. They are different under different irradiation conditions, such as altitude, latitude, irradiation geomeny,and type of rock. Relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons~[3]. Absolute nuclide production rates cannot generally be predicted with any accufacy because of lack of data on excitation functions of nuclides. Based on a natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for about 11 ka were sampled in Sierra Nevada, USA, the absolute production rates of ^(10)Be and ^(26)Al in quartz have been accurately estimated for different mountain altitudes~[11]. Therefore, the absolu
出处
《第四纪研究》
CAS
CSCD
北大核心
1997年第3期211-221,共11页
Quaternary Sciences
基金
中国科学院留学经费择优支持回国工作基金
国家教委留学回国人员科研启动基金
