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Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
Isotope fractionation occurs during a phase transition, when the ratio of light to heavy isotopes in the involved molecules changes. When water vapor condenses (an equilibrium fractionation), the heavier water isotopes (18 O and 2 H) become enriched in the liquid phase while the lighter isotopes (16 O and 1 H) tend toward the vapor phase. [1]
Carbon on Earth naturally occurs in two stable isotopes, with 98.9% in the form of 12 C and 1.1% in 13 C. [1] [8] The ratio between these isotopes varies in biological organisms due to metabolic processes that selectively use one carbon isotope over the other, or "fractionate" carbon through kinetic or thermodynamic effects. [1]
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear.
Owing to both of these advantages, the method of isotope dilution is regarded among chemistry measurement methods of the highest metrological standing. [1] Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom.
In geochemistry, paleoclimatology and paleoceanography δ 18 O or delta-O-18 is a measure of the deviation in ratio of stable isotopes oxygen-18 (18 O) and oxygen-16 (16 O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis.
Clay minerals are less than 2 μm thick and cannot easily be irradiated for Ar–Ar analysis because Ar recoils from the crystal lattice. In 2013, the K–Ar method was used by the Mars Curiosity rover to date a rock on the Martian surface, the first time a rock has been dated from its mineral ingredients while situated on another planet. [11] [12]
The amount of liquid-vapor equilibrium fractionation for hydrogen isotopes is about 8x that of oxygen isotopes at Earth surface temperatures, which reflects the relative mass differences of the two isotope systems: 2 H is 100% heavier than 1 H, 18 O is 12.5% heavier than 16 O. Above the boundary layer, there is a transition zone with relative ...