Study of non-radiogenic isotopic ratios of selected elements, e.g. D:H, 18O:16O, 32S:34S, which are fractionated in different proportions during different geologic processes (see isotope fractionation). Thus natural waters may be ‘fingerprinted’ by reference to their D:H and 18O:16O ratios as being of meteoric, magmatic, or metamorphic origin; sulphur in sulphide ores may be characterized as sedimentary or igneous by reference to its 32S:34S ratio. See also oxygen-isotope analysis; and oxygen-isotope ratio.
Subjects: Earth Sciences and Geography.