| 摘 要： | This paper presents a theoretical study in an attempt to modify the isochron theory. It isshown that isochrons can be obtained for closed systems provided the following linear condition ismet at the initial moment: I_0 = KR_0 + d, where both K and d are constants, R and I standfor the parent and daughter isotopic ratios, respectively. Isochrons established in this way aretermed generalized isochrons, with their equation as I = (K + 1) e~(2t)--1]R + d. Isochronswith uniform initial isotopic ratios (i. e. when K = 0) are called special isochrons; and isochronsobtained from binary-mixing systems, named mix-isochrons, are typical examples of generalizedisochrons. Age calculated from a mix-isochron is excessively high when K>0 and low while K<0.The intercept of a mix-isochron bears no association with isotopic initial values, thus named pseudo-initial values, which are anomalously high when K<0 and low while K>0, sometimes even lowerthan the initial ratio of the earth, e.g. BABI for Sr isotope ratio. The pr
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