Heidelberg 2015 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 9: Applied Noble Gas Physics Part 2

UP 9.1: Hauptvortrag

Donnerstag, 26. März 2015, 14:30–15:00, C/gHS

Using Noble Gases to Understand the History of Terrestrial Volatiles — •Don Porcelli — Oxford University, Dept Earth Sciences, Oxford, UK

Noble gas isotopes provide essential information on the origin and distribution of terrestrial volatiles. The 3He/4He ratios measured in mantle-derived volcanics indicate that the noble gases initially incorporated into the Earth remains heterogeneously distributed, although it is not yet clear how this relates to mantle structure. Xe isotopes indicate that separate noble gas reservoirs were established during Earth formation, with variations that must have been created before complete decay of short-lived 129I and 244Pu. Further, Ne isotopes suggest that there have been several different solar system sources of noble gases. Also, Xe isotopes indicate that substantial quantities of noble gases were incorporated into the Earth and lost soon after. A number of key questions remain, as data are limited due to the subtle variations and low concentrations involved, and the presence of atmospheric contamination. More precise measurements of all noble gases, and with greater sensitivity, are essential to better identify how many sources of noble gases there have been; the extent of isotope variability within the Earth and so the history of early losses and subsequent reservoir isolation; the role of the core in storing noble gases; and the relationship between variations of the different noble gases and so the history of each separate reservoir. With such data, the history of terrestrial volatiles can be understood within the context of evolving theories of planetary accretion.

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