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从六十年代中期出现的同位素等时线法,目前已在Rb—Sr法、U—Pb法、Th—Pb法、Pb—Pb法、K—Ar法及最近开展的Ar~(40)—Ar~(39)法和Sm—Nd法等年龄测定中得到广泛应用,尤其在Rb—Sr法中应用最广。由于岩石或矿物结晶时总是要捕获一些成因上与岩石矿物结晶时放射性母体同位素无关的初始子体同位素,而且在实验校正时又往往带来很大的误差,造成年龄偏差。采用等时线图解法不需要进行初始子体同位素的校正,可得到真实的年龄和捕获的初始子体同位素值。
Since the mid-1960s isotope isochronism has been in the Rb-Sr method, U-Pb method, Th-Pb method, Pb-Pb method, K-Ar method and the recent development of Ar ~ (40) - Ar ~ (39) method and Sm-Nd method are widely used in the age determination, especially in the Rb-Sr method is the most widely used. Since rocks or minerals are always crystallized, some initial daughter isotopes that are genetically unrelated to the radioactive precursor isotopes in the crystallization of rock minerals are always trapped. However, they often bring about large errors in experimental calibration, resulting in age bias. Using isochronism does not require initial isotopic calibration of the progeny to obtain the true age and initial isotope values captured.