Data Series 202
Introduction
Noble gases in rocks, minerals, and fluids provide unique insights to the degassing history of the Earth, the chemical heterogeneity of the mantle, and volcanic processes. The utility of noble gases towards the study of these topics is summarized in several books (Alexander and Ozima 1978; Ozima and Podosek 2002; Mamyrin and Tolstikhin 1984; Matsuda 1994) and review articles (Lupton 1983; Farley and Neroda 1998; Ozima 1994; McDougall and Honda 1998; Graham, 2002). Their value for Earth science problems arises from their lack of chemical reactivity, systematic variation in physical characteristics (e.g., solubility, diffusivity) with mass, and production by numerous radioactive decay schemes. The abundances of noble gases within Earth materials are modified only by radioactive decay and physical processes such as melting and vapor-phase transport. Measurable changes in the isotopic compositions of noble gases are closely related to the geochemical processes controlling the distribution of K, U and Th, the major heat-producing nuclides in the Earth.
In an ascending magma the noble gases will partition strongly into the first-formed vapor phase, usually nearly pure CO2. Because noble gas solubilities in silicate liquids decrease significantly with increasing atomic mass, the heavier gases will preferentially be enriched in the vapor phase. The strong partitioning of noble gases into the gas and vapor phase makes them especially useful as early indicators of magma ascent towards the ground surface. However, with the exception of He, the mantle component in geothermal gases is difficult to detect in the presence of admixed atmospheric gases. Therefore, helium isotopes are most often used in the study of magmatic degassing.
The extent to which ocean islands are derived from the deep mantle (mantle plumes), or from chemical heterogeneities embedded within the mantle convective flow has long been debated. Noble gases have unique properties that enable them to provide significant information regarding this debate and make them important geodynamic tracers. Whereas traditional models based on noble gas data hypothesized that MORB represents a broad sampling of the convecting upper mantle, the He-Ne isotope systematics of Ocean Island Basalts (OIBs) provide strong evidence of melting anomalies related to mantle upwelling from a thermal boundary layer in the deep mantle. In recent years alternatives to this model were developed around a different interpretation of mantle He isotope data.
The database (Version 1.0) is a MS-Excel file that contains close to 5,000 entries of published information on noble gas concentrations and isotopic ratios from volcanic systems in Mid-Ocean ridges, ocean islands, seamounts, and oceanic and continental arcs (location map). Where they were available we also included the isotopic ratios of strontium, neodymium, and carbon. The database is sub-divided both into material sampled (e.g., volcanic glass, different minerals, fumarole, spring), and into different tectonic settings (MOR, ocean islands, volcanic arcs). Included is also a reference list in MS-Word and pdf from which the data was derived. The database extends previous compilations by Ozima (1994), Farley and Neroda (1998), and Graham (2002). The extended database allows scientists to test competing hypotheses, and it provides a framework for analysis of noble gas data during periods of volcanic unrest.
There are six spreadsheets in the MS-Excel file:
Sample abbreviation in the database
The entries in the in the master spreadsheet appear in the following columns:
References
Alexander E.C. and Ozima, M., 1978, Terrestrial Rare Gases: Advances in Earth and Planetary Science, v. 3, Center for Academic Publications, Japan , Tokyo.
Farley, K.A., and Neroda, E., 1998, Noble gases in the Earth's mantle: Annual Review of Earth and Planetary Sciences, v. 26, p. 189-218.
Graham, D. W., 2002, Noble gas isotope geochemistry of mid-ocean ridge and ocean island basalts; characterization of mantle source reservoirs. In: Noble Gases in Geochemistry and Cosmochemistry, eds. D. Porcelli, R. Wieler and C. Ballentine. Reviews in Mineralogy and Geochemistry, Mineral. Soc. Amer., Washington , D.C. , pp. 247-318.
Lupton, J.E., 1983, Terrestrial inert gases: isotope tracer studies and clues to primordial components in the mantle: Annual Review of Earth & Planetary Sciences, v. 11, p. 371-414.
Mamyrin, B.A., and Tolstikhin, I.N., 1984, Helium Isotopes in Nature (Developments in Geochemistry 3), Amsterdam & New York (Elsevier Science Publishers).
Matsuda J., 1994, Noble Gas Geochemistry and Cosmochemistry: Terra Scientific Publishing Co, Tokyo.
McDougall I., and Honda M., 1998, Primordial solar noble-gas component in the Earth: consequences for the origin and evolution of the Earth and its atmosphere. In Jackson I (ed) The Earth’s mantle: composition, structure and evolution: Cambridge University Press, Cambridge , p 159-187.
Ozima M., and Podosek F.A., (2002) Noble Gas Geochemistry: Cambridge University Press. Cambridge, UK, 286 pp.
Ozima, M., and Alexander Jr, E.C., 1976, Rare gas fractionation patterns in terrestrial samples and the Earth-atmosphere evolution model: Rev Geophys Space Phys, v. 14, no. 3, p. 385-390.
Plots of the data
The data base is intended to be updated periodically with new information. If relevant data are missing from the database we would appreciate any contribution. Please contact Atosa A. Abedini.
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