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Iodine-129 in terrestrial ores
Science (New York, N.Y.)
|July 23, 1971
Summary
Natural xenon from Australian silver iodide reveals pre-nuclear iodine-129 to iodine-127 ratios. This research estimates the equilibrium ratio of these isotopes before the nuclear age.
Area of Science:
- Geochemistry
- Isotope Geology
- Nuclear Chemistry
Background:
- Iodine-129 is a long-lived cosmogenic and radiogenic isotope.
- Natural iodine isotope ratios provide insights into Earth's history.
- Xenon isotopes are valuable tracers in geochemical studies.
Purpose of the Study:
- To determine the pre-nuclear equilibrium ratio of iodine-129 to iodine-127 in terrestrial iodine.
- To utilize xenon isotopes as indicators of iodine isotopic composition.
Main Methods:
- Extraction of xenon from natural iodyrite (silver iodide) samples.
- Analysis of excess xenon-129 (from iodine-129 decay) and xenon-128 (from neutron capture on iodine-127).
- Calculation of iodine isotope ratios based on measured xenon excesses.
Main Results:
- Xenon extracted from Broken Hill iodyrite showed excesses of both xenon-129 and xenon-128.
- The amount of radiogenic xenon-129 allowed for estimation of the initial iodine-129 abundance.
- Estimated pre-nuclear equilibrium ratio of iodine-129 to iodine-127 ranged from 3.3 x 10^-15 to 2.2 x 10^-15.
Conclusions:
- The study successfully estimated the natural abundance of iodine-129 relative to iodine-127 before human nuclear activities.
- Xenon isotope analysis in iodine-rich minerals is a viable method for reconstructing past iodine isotopic compositions.
- These findings contribute to our understanding of the natural iodine cycle and its isotopic variations over geological timescales.
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