MIX-ISOCHRON AND ITS SIGNIFICANCE IN ISOTOPIC CHRONOLOGY

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     

中国某些花岗岩δD与H_2O的关系

花岗岩类岩石δD与HH_2O(wt％)的关系可分为三种类型:封闭结晶型(大容山型),呈平缓正相关关系;开放去气型(崂山型),呈近于垂直的相关关系;大气降水热液交换型(告乌型),呈不规则略具负相关趋势。     

混合等时线及其在同位素年代学中的意义

本文对等时线理论进行了修改,一封闭体系在初始时刻只要满足线性条件:I_0=KR_0+d(K,d为常数,R和I分别为同位素母、子体比值),便能获得等时线,称广义等时线,其方程为:I=[(K+1)e~(λt)—1]R+d。初始值均—(K=0时)的等时线称狭义等时线,两元混合体系构成的混合等时线是广义等时线的范例,其年龄当K>0时偏高;K<0时偏低.截距d已无初始值意义,称假初始值,可异常地高(K<0时)或低(K>0时),甚至低于地球初始值,许多异常的等时线可望由本模式得到合理解释。     

CORRELATION BETWEEN δD AND H_2O IN SOME GRANITOID OF CHINA

The correlation between δD and H_2O content in granitoid can be divided into threetypes: closed-system crystallization type (Darongshan type): a flat positive linear corre-lation; open-system degassing type (Laoshan type): a nearly vertical linear positive cor-relation; meteoric hydrothermal exchange type (Gabug type): an irregular negative trendcorrelation.