Water follows carbon: CO2 incites deep silicate melting and dehydration beneath mid-ocean ridges

Research Article| February 01, 2007 Water follows carbon: CO2 incites deep silicate melting and dehydration beneath mid-ocean ridges Rajdeep Dasgupta; Rajdeep Dasgupta 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Search for other works by this author on: GSW Google Scholar Marc M. Hirschmann; Marc M. Hirschmann 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Search for other works by this author on: GSW Google Scholar Neil D. Smith Neil D. Smith 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Rajdeep Dasgupta 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Marc M. Hirschmann 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Neil D. Smith 1Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA Publisher: Geological Society of America Received: 05 Apr 2006 Revision Received: 14 Sep 2006 Accepted: 25 Sep 2006 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2007) 35 (2): 135–138. https://doi.org/10.1130/G22856A.1 Article history Received: 05 Apr 2006 Revision Received: 14 Sep 2006 Accepted: 25 Sep 2006 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Rajdeep Dasgupta, Marc M. Hirschmann, Neil D. Smith; Water follows carbon: CO2 incites deep silicate melting and dehydration beneath mid-ocean ridges. Geology 2007;; 35 (2): 135–138. doi: https://doi.org/10.1130/G22856A.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 Hydrous defects in nominally anhydrous minerals influence the physical properties and reduce the melting point of mantle rocks. Consequently, it is believed that extraction of H2O beneath mid-ocean ridges by dehydration melting enhances the creep strength of the upper mantle and produces a chemical lithosphere. However, recent studies show that trace water induces melting at shallower depths beneath ridges than previously believed. Here we explore the hypothesis that incipient melting, dehydration, and strengthening of the subridge mantle is promoted by trace quantities of carbon. Experiments at 3 GPa on carbonated peridotite with 1 and 2.5 wt% CO2 produce partial melts that change from carbonatites with <10 wt% SiO2 to carbonated silicate melts with >25 wt% SiO2 between 1325 and 1350 °C. Enhanced melting of carbonated peridotite relative to volatile free peridotite is parameterized as a simple function of the concentration of CO2in the melt. Application of this model to mantle with 100 ppm bulk CO2 suggests that the subridge mantle undergoes silicate melting ∼130–140 °C below the CO2-free solidus, corresponding to a depth of ∼110 km beneath ridges, and that 0.2 wt% partial melting will be attained at a depth of ∼75 km. The combined effects of H2O and CO2 further enhance deep silicate melting, as H2O partitions from nominally anhydrous silicates to carbonated silicate melts. Thus, the deepest silicate melting beneath ridges will be induced by the combination of H2O and CO2, rather than simply by dehydration melting of nominally anhydrous peridotite, and this combination is likely responsible for dehydration strengthening of the oceanic lithosphere and for geochemical signatures of deep melting in mid-oceanic ridge basalt. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.