84 Sr Sr Sr Sr

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Andra Dalton
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$Stable isotope Relative atomic mass Mole fraction 84 Sr 83.913 419 0.0056 86 Sr 85.909 261 0.0986 87 Sr 86.908 878 0.0700 88 Sr 87.905 613 0.$ $Also, strontium is not subject to oxidation-reduction reactions in normal terrestrial environments, which would cause isotopic fractionation to be more evident.$

1 Stable isotope Relative atomic mass Mole fraction 84 Sr Sr Sr Sr Strontium isotopes in Earth/planetary science Stable isotopic fractionation of strontium is small because the relative differences between the masses of stable strontium isotopes are small (mass numbers are 86, 87, and 88 for the most abundant stable isotopes). Also, strontium is not subject to oxidation-reduction reactions in normal terrestrial environments, which would cause isotopic fractionation to be more evident. Nevertheless, current studies are exploring potential applications of stable strontium isotopic fractionation; for example, it has been used as a proxy for temperature during coral growth and for insights into the diets of ancient populations [ ].

2 The relative abundance of natural radiogenic 87 Sr in seawater is related to the relative rates of processes that add or remove strontium in the ocean (seafloor spreading, mid-oceanridge hydrothermal activity, and continental weathering). Over geologic time, these processes have fluctuated and the isotope-amount ratio n( 87 Sr)/n( 86 Sr) has changed systematically. By measuring the n( 87 Sr)/n( 86 Sr) ratio in marine fossils of known age, it is possible to identify when such environmental changes occurred. Conversely, it is possible to estimate the ages of marine deposits by comparing measured n( 87 Sr)/n( 86 Sr) ratios with the global time chart; this process is known as strontium isotope stratigraphy [ ]. Strontium isotopes in forensic science and anthropology The isotope-amount ratio n( 87 Sr)/n( 86 Sr) is highly variable in rocks, minerals, soils, and waters, and it can be transmitted to plants (Figure 1), animals, and manufactured materials. Measurements of n( 87 Sr)/n( 86 Sr) ratios can be used for forensic applications in food authentication (determining where food came from), archaeology, crime-scene investigation, and human migration [ ]. Fig. 1: Variation in strontium isotope-amount ratios of twenty species of exotic wood from thirteen countries (modified from [300]). Strontium isotopes in geochronology The 87 Rb- 87 Sr dating technique utilizes the fact that 87 Sr is a product of radioactive 87 Rb decay (half-life = years) and is a useful tool for determining ages of rocks and minerals spanning the age of the Earth (Figure 2) [ ].

3 Fig. 2: Cross plot of n( 87 Sr)/n( 86 Sr) isotope-amount ratio and n( 87 Rb)/n( 86 Sr) mole ratio of sphalerites (zinc sulfide mineral) from the Kipushi base metal deposit, Democratic Republic of Congo (modified from [301]). 87 Sr is produced by decay of radioactive 87 Rb. Rock containing higher amounts of 87 Rb will over time produce higher amounts of 87 Sr, for example sample KI 1270/128 R. Rock containing lower amounts of 87 Rb will over time produce smaller amounts of 87 Sr, for example sample KI 1270/113 R. Assuming all the sphalerites in this figure were formed at the same time, one can determine the age of formation of the sulfides from the slope of the line through the data points (here ± 6.0 million years), and this line is called an isochron.

4 Glossary atomic number (Z) The number of protons in the nucleus of an atom. electron elementary particle of matter with a negative electric charge and a rest mass of about kg. element (chemical element) a species of atoms; all atoms with the same number of protons in the atomic nucleus. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus [703]. gamma rays (gamma radiation) a stream of high-energy electromagnetic radiation given off by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher than those of X-rays; thus, gamma rays have greater penetrating power. half-life (radioactive) the time interval that it takes for the total number of atoms of any radioactive isotope to decay and leave only one-half of the original number of atoms. [return] isochron a line indicating age of formation of a suite of rock or mineral samples on a cross plot of amount ratios of isotopes of the same element and mole ratios of isotopes of different elements (one of which is radioactive and decays to an isotope of the other element). The time formed can indicate time since metamorphism, crystallization, shock events, differentiation of precursor melts, etc. For examples, see neodymium Figure 1, samarium Figure 1, rhenium Figure 1, and osmium Figure 2.[return] isotope one of two or more species of atoms of a given element (having the same number of protons in the nucleus) with different atomic masses (different number of neutrons in the nucleus). The atom can either be a stable isotope or a radioactive isotope. isotope-amount ratio (r) amount (symbol n) of an isotope divided by the amount of another isotope of the chemical element in the same system [706]. [return] isotopic fractionation (stable-isotope fractionation) preferential enrichment of one isotope of an element over another, owing to slight variations in their physical, chemical, or biological properties [706]. [return] mass number (A) total number of heavy particles (protons and neutrons, jointly called nucleons) in the nucleus of an atom [703]. [return] neutron an elementary particle with no net charge and a rest mass of about kg, slightly more than that of the proton. All atoms contain neutrons in their nucleus except for protium ( 1 H). proton an elementary particle having a rest mass of about kg, slightly less than that of a neutron, and a positive electric charge equal and opposite to that of the electron. The number of protons in the nucleus of an atom is the atomic number.

5 proxy a measured quantity that can be used to represent the value of another quantity in a calculation. [return] radioactive decay the process by which unstable (or radioactive) isotopes lose energy by emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma radiation, neutrons or protons to reach a final stable energy state. radioactive isotope (radioisotope) an atom for which radioactive decay has been experimentally measured (also see half-life). radiogenic produced by the decay of a radioactive isotope, but which itself may or may not be radioactive. [return] reduction-oxidation (redox) - reduction gain of an electron by an atom, oxidation loss of an electron by an atom. [return] stable isotope an atom for which no radioactive decay has ever been experimentally measured. [return] X-rays electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers shorter than those of UV rays and typically longer than those of gamma rays. References 294. A. Rüggeberg, Fietzke, J., Liebetrau, V., Eisenhauer, A., Dullo, W.C., and Freiwald, A. Earth and Planetary Science Letters. 269 (3-4), 570 (2008) K. J. Knudson, Williams, H.M., Buikstra, J.E., Tomczak, P.D., Gordon, G.W., and Anbar, A.D. Journal of Archaeological Science. 37 (9), 2352 (2010) J. M. McArthur, Howarth, R.J., and Bailey, T.R. Journal of Geology. 109, 155 (2001) B. L. Beard, and Johnson, C.M. Journal of Forensic Sciences. 45, 1049 (2000) K. M. Frei, and Frei, R. Applied Geochemistry. 26 (3), 326 (2011) G. Faure. Principles of Isotope Geology, 2nd Edition Wiley (1986) K. Miller, Coplen, T.B., and Wieser, M. In Goldschmidt 22nd Conference, Montreal, Canada (2012) F. M. J. Schneider, and M. Brauns. Miner Deposita. 42, 791 (2007) I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Blackwell Scientific Publications, Oxford (1997) Coplen. Rapid Communications in Mass Spectrometry. 25 (2011).

Stable isotope. Relative atomic mass. Mole fraction 203 Tl Tl Thallium isotopes in Earth/planetary science

$Stable isotope. Relative atomic mass. Mole fraction 203 Tl Tl Thallium isotopes in Earth/planetary science$ Stable isotope Relative atomic mass Mole fraction 203 Tl 202.972 345 0.2952 205 Tl 204.974 428 0.7048 Thallium isotopes in Earth/planetary science Because molecules, atoms, and ions of the stable isotopes