城市活断层探测中钻孔岩心光释光样品的采集

钻孔岩心测年样品具有较一般地质样品更为复杂的影响因素,样品特征对年龄可靠性有非常重要的影响,且主要受钻进方法和采样过程的制约。采用回转钻进取全心的方法,对光释光测年带来的不确定性影响因素主要有扰动导致软弱土层、砂层的混染;泥浆渗入对样品的污染;挤压和摩擦生热对释光信号的可能影响等。除样品特征外,含水量的变化及放射性平衡状况等对钻孔岩心样品的年龄可能存在影响。释光测年样品的基本要求、测试技术和方法是野外正确采样的依据,针对城市活断层探测工作中钻探任务的一般要求,文中提出了岩心光释光样品采集的建议,并对年代测试时需要考虑的不确定性因素进行了讨论

OPTICAL STIMULATED LUMINESCENCE SAMPLING AND DATING OF BORING CORE IN URBAN ACTIVE FAULT EXPLORATION

The reliability of ages from optically stimulated luminescence (OSL) dating of boring core has a stringent dependence on characteristic of samples, and on motheds of boring and sampling. When using a full core collected at boring, the uncertainty of estimation to equivalent dose at OSL dating is affected by some factors, such as mixture occurring in soft soil and sand, contamination due to mud penetrating into sample, the possible influence of heat from pressure and attrition on luminescence signals. In addition, a potential effect on dose rate of samples from boring cores should be emphasized, that is, the effect of change of water content and equilibrium of radioactivity. The basic conditions for sampling, protocols and methods of luminescence dating are important to for sampling correctly in the field. As general requirements for drilling in urban active fault exploration, this paper gives suggestions on sampling from boring core for OSL dating, and factors affecting results of measurement are also discussed.