Absence of a high time-integrated 3He/(U+Th) source in the mantle beneath continents

Research Article| September 01, 2005 Absence of a high time-integrated 3He/(U+Th) source in the mantle beneath continents James M.D. Day; James M.D. Day 1Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK Search for other works by this author on: GSW Google Scholar David R. Hilton; David R. Hilton 2Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, California 92093-0244, USA Search for other works by this author on: GSW Google Scholar D. Graham Pearson; D. Graham Pearson 3Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Colin G. Macpherson; Colin G. Macpherson 3Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Bruce A. Kjarsgaard; Bruce A. Kjarsgaard 4Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada Search for other works by this author on: GSW Google Scholar Philip E. Janney Philip E. Janney 5Department of Geology, The Field Museum of Natural History, 1400 Lake Shore Drive, Chicago, Illinois 60605, USA Search for other works by this author on: GSW Google Scholar Author and Article Information James M.D. Day 1Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK David R. Hilton 2Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, California 92093-0244, USA D. Graham Pearson 3Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK Colin G. Macpherson 3Department of Earth Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK Bruce A. Kjarsgaard 4Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada Philip E. Janney 5Department of Geology, The Field Museum of Natural History, 1400 Lake Shore Drive, Chicago, Illinois 60605, USA Publisher: Geological Society of America Received: 15 Feb 2005 Revision Received: 26 May 2005 Accepted: 27 May 2005 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2005) 33 (9): 733–736. https://doi.org/10.1130/G21625.1 Article history Received: 15 Feb 2005 Revision Received: 26 May 2005 Accepted: 27 May 2005 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation James M.D. Day, David R. Hilton, D. Graham Pearson, Colin G. Macpherson, Bruce A. Kjarsgaard, Philip E. Janney; Absence of a high time-integrated 3He/(U+Th) source in the mantle beneath continents. Geology 2005;; 33 (9): 733–736. doi: https://doi.org/10.1130/G21625.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Volcanic rocks from ocean island and continental flood basalt provinces can exhibit 3He/4He ratios greatly in excess of those of mid-oceanic-ridge basalts (MORB). High 3He/4He ratios must indicate derivation from a mantle source with high time-integrated 3He/(U+Th) relative to depleted MORB-source mantle. The location of the high 3He/4He mantle reservoir is a poorly resolved but important issue because of the constraints it places upon the structure and convective style of Earth's mantle. It has been proposed that the high 3He/4He reservoir resides in the upper mantle, rather than the lower mantle, because Earth should be volatile poor and highly differentiated, with incompatible elements (such as He) concentrated in the upper mantle and crust. This hypothesis can be tested using continental intraplate alkaline volcanics (CIAV) that are generated at or near the boundary between the conducting lithospheric and convecting asthenospheric mantle. Olivine and clinopyroxene phenocrysts from Cretaceous to Miocene CIAV from Canada, South Africa, and Uganda have 3He/4He ratios more radiogenic than MORB, strongly arguing against a widespread high 3He/4He source in the continental lithosphere or the underlying convecting upper mantle. Combined with a global data set of CIAV and continental lithosphere mantle xenoliths, these results provide no evidence for high 3He/4He in any samples known to originate from this environment. Therefore, volcanic rocks with 3He/4He greater than MORB 3He/4He are likely to sample a mantle source with high time-integrated 3He/(U+Th) that cannot exist within or below the continents. This reservoir is also unlikely to exist within the upper mantle as defined by the 3He/4He distribution in MORB. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.