深海碳酸盐岩ESR测年信号的热力学特征

THERMODYNAMIC PROPERTIES OF ESR SIGNALS OF DEEP-SEA CARBONATE

ESR测年方法的年代范围可以从数百年到几百万年,但在较老的深海碳酸盐岩测年研究中,ESR测年信号的平均寿命较短,其年龄极限受到质疑。利用较老的深海碳酸盐岩进行了ESR测年信号的热力学特征研究,同时估算了深海碳酸盐岩的平均寿命。研究结果表明:单一级热动力学模式不适于深海碳酸盐岩样品的平均寿命估算,而双一级动力学模式是一种较好的估算方法。经估算,深海碳酸盐岩试样的平均寿命为5.14 Ma,年龄为320±50ka,与铀系不平衡法测得的365±49ka具有较好的一致性。

The ESR dating method could date the samples within a time span from hundreds of years to millions of years.However,the average lifetime of ESR signals from deep-sea carbonate rocks are relatively shorter.In this regard,the age limit of the deep-sea carbonate rocks dating need to be further studied.In this paper,we studied the thermodynamic characteristics of ESR dating signals acquired from old deep-sea carbonate rocks and the average lifetime of those deep-sea carbonate rocks is estimated.The results of the thermodynamic properties of deep-sea carbonate suggests that the single first-order kinetic equation might not be suitable to calculate the average lifetime,and the double firstorder kinetic equation is more effective.The average lifetime of the deep-sea samples we calculated is about 5.14×10~6 years by using the double first-order kinetic equation.Thus the estimated age is 320±50 ka,which is in good agreement with the unbalanced U system dating result of 365±49 ka.