Mass Fractionation Laws, Mass-Independent Effects, and Isotopic Anomalies

摘要: Isotopic variations usually follow mass-dependent fractionation, meaning that the relative in isotopic ratios scale with difference mass of isotopes involved (e.g., δ17O ≈ 0.5×δ18O). In detail, however, dependence is not always same, and different natural processes can define distinct slopes three-isotope diagrams. These are subtle, but improvements analytical capabilities now allow precise measurement these effects make it possible to draw inferences about caused them reaction kinetics versus equilibrium isotope exchange). Some elements, some sample types, do conform regularities fractionation. Oxygen sulfur display a rich phenomenology mass-independent documented laboratory, rock record, modern atmosphere. meteorites shows slope-one line (δ17O δ18O) whose origin may ...