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Therefore it is more convenient to convert this number to an isotope ratio by dividing through by Sr method was first used in geochronology, the poor precision attainable in mass spectrometry limited the technique to the dating of Rb-rich minerals such as lepidolite.
These minerals develop such high Sr ratio of 0.712 could be assumed in all dating studies without introducing significant errors.
Results are presented for a variety of magmatic rocks with well-established thermal records: a sample each from the Klokken syenodiorite (Greenland; 1161 Ma), the Ulvö alkaligabbro (Sweden; 1256 Ma) and a pegmatite from the Bohus granite (Sweden; 920 Ma).
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An atom with the same number of protons in the nucleus but a different number of neutrons is called an isotope.
For example, uranium-238 is an isotope of uranium-235, because it has 3 more neutrons in the nucleus.
However, discordant dates were often generated by assuming an initial ratio of 0.712 when the real initial ratio was higher.
This problem was first recognised by Compston and Jeffery (1959), and overcome by the invention of the isochron diagram (Nicolaysen, 1961). Strontium isotope stratigraphy: LOWESS Version 3: best fit to the marine Sr-isotope curve for 0-509 Ma, and accompanying look-up table for deriving numerical age.
We present here a simple procedure in which Rb-Sr ages can be obtained from a suite of individual phases in regular thin sections.It has been known for several decades that the lighter elements (notably carbon, oxygen, hydrogen and sulphur) undergo isotopic fractionation under the influence of their physical and chemical environment, and much research has been conducted to understand this behaviour.‘Actually, the question of whether Sr isotopes can be fractionated by nature or not is irrelevant, because all Sr isotope analysis are routinely corrected for all isotopic fractionation effects, be they natural or laboratory-induced.However, this advantage was to date negatively counteracted by the lack of a suitable in-situ technique, as beta decay systems by nature have isobaric interferences of the daughter isotope by their respective parent isotope.A reaction cell sandwiched between two quadrupoles within an inductively coupled plasma mass spectrometer (ICP-MS) allows exactly this, the online chemical separation of two different elements.
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When diffusive isotope fractionation of Sr isotopes is repeated a sufficient number of times by within-mantle processes on isotopically-anomalous mantle xenoliths (each of which originally had low Sr ratios.