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一、绪言同位素地球化学本身可以分为两个领域,即稳定同位素地球化学和天然放射成因同位素地球化学。前者是研究H、C、O和S等同位素(即D/H,~(12)C/~(13)C,~(16)O/~(18)O,~(32)S/~(34)S在自然界的同位素分馏;后者则是研究天然放射同位素母体及其子体产物,如~(238)U→~(206)Pb,~(235)U→~(207)Pb,~(232)Th→~(208)Pb,~(176)Lu→~(176)Hf,~(147)Sm→~(143)Nd,~(87)Rb→~(87)Sr,~(40)K→~(40)Ar,~(40)K→~(40)Ca等。上述母体-子体系统,有两种应用。其一是通过测定母体和子体同位素丰度,并已知其衰变常数来计算岩石或矿床形成的年龄,如测定沉积矿床和沉积物成岩的时间,沉积盆地中沉积物的源年龄;其二是利用放射成
I. Introduction Isotopes Geochemistry itself can be divided into two areas, namely, stable isotope geochemistry and natural radiogenic isotope geochemistry. The former is to study the isotopes of H, C, O and S (ie D / H, ~ 12 C / ~ 13 C, ~ 16 O / 18 O, ~ 32 S / 34) S isotope fractionation in nature; the latter is the study of natural radioisotope maternal and its daughter products, such as ~ (238) U → 206 Pb, 235 U → 207 Pb, (232) Th → 208 Pb, 176 Lu → 176 Hf ~ 147 Sm → 143 Nd, 87 Rb → 87 Sr, ~ 40 ) K → ~ (40) Ar, ~ (40) K → ~ (40) Ca, etc. The above maternal-daughter system has two applications: one is to determine the abundance of maternal and daughter isotopes Decay constants to calculate the age at which rocks or deposits are formed, such as the timing of diagenesis of sedimentary deposits and sediments, the source age of sediments in sedimentary basins, and the second,