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The role of plumes in mantle helium fluxes

Kellogg, L. H. and Wasserburg, G. J. (1990) The role of plumes in mantle helium fluxes. Earth and Planetary Science Letters, 99 (3). pp. 276-289. ISSN 0012-821X. https://resolver.caltech.edu/CaltechAUTHORS:20131028-104549067

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Abstract

We present a simple model of ^3He and ^4He transport in the mantle using the appropriate rates of mass and species transfer and ^4He production. Previous workers have shown the presence of excess ^3He in hotspots such as Hawaii and Iceland and inferred that these hotspots tap a source with a higher ^3He ^4He ratio than the source region of mid-ocean ridge basalts (MORB). Hotspot ocean islands probably originate over upwelling plumes which carry material from the lower mantle to the upper mantle. Melting at hotspots and at mid-ocean ridges degasses the mantle of volatiles such as helium. The upper mantle is outgassed largely of helium due to melting at mid-ocean ridges and hotspots. We postulate that the excess ^3He seen in MORB originates in material that was carried from the lower mantle in plumes but not completely outgassed at hotspots. This helium is incorporated into the depleted upper mantle. Assuming that the upper mantle is in a quasi-steady-state with respect to helium, a simple model balancing ^3He and ^4He fluxes in the upper mantle indicates that the hotspots significantly outgas the lower mantle of ^3He. The concentration of ^4He in the plume source reservoir is 2–3 orders of magnitude lower than the concentration in carbonaceous chondrites. The residence time of helium in the upper mantle depends on the outgassing efficiency at hotspots, since the hotspots may outgas some upper mantle material which has been entrained in the plumes. The residence time of He in the upper mantle is about 1.4 × 10^9 yr. We conclude that the efficiency of outgassing of He from plumes is high and that the plumes dominate the present ^3He loss to the atmosphere. The ^4He in the less depleted layer of the mantle is not trapped “primordial” but is predominantly from in situ decay of U and Th in the depleted layer over ∼ 1.4 × 10^9 yr. The ^4He in the lower mantle is dominantly from in situ decay of U and Th over 4.4 × 10^9 yr. This model appears to explain the total Ar in the atmosphere as there is about the same amount of K in the depleted mantle as is in the continents.


Item Type:Article
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http://dx.doi.org/10.1016/0012-821X(90)90116-FDOIArticle
http://www.sciencedirect.com/science/article/pii/0012821X9090116FPublisherArticle
Additional Information:© 1990 Elsevier Science Publishers B.V. Received August 4, 1989; revised version accepted December 23, 1989. L.H. Kellogg was supported during this work by a Bantrell Research Fellowship in Geochemistry and Geophysics. The authors thank Brad Hager for discussions of the model and Ivan Tolstikhin and Norman Sleep for reviews of the manuscript. L.H. Kellogg thanks John Stone for several suggestions. G.J. Wasserburg thanks his colleagues of the Max Planck Institute for Chemistry in Mainz for the opportunity to repeatedly present this study. In particular, discussions with L. Schultz, A. Hoffman, F. Begeman, and H. Wänke have proven most helpful. This is contribution 4779 (680) of the Division of Geological and Planetary Sciences.
Funders:
Funding AgencyGrant Number
Bantrell Research Fellowship in Geochemistry and GeophysicsUNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences4779
Lunatic Asylum Lab680
Issue or Number:3
Record Number:CaltechAUTHORS:20131028-104549067
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131028-104549067
Official Citation:L.H. Kellogg, G.J. Wasserburg, The role of plumes in mantle helium fluxes, Earth and Planetary Science Letters, Volume 99, Issue 3, August 1990, Pages 276-289, ISSN 0012-821X, http://dx.doi.org/10.1016/0012-821X(90)90116-F. (http://www.sciencedirect.com/science/article/pii/0012821X9090116F)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42094
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:28 Oct 2013 18:24
Last Modified:03 Oct 2019 05:55

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