Fluid-present melting of ocean crust in subduction zones

Abstract

Research Article| December 01, 1999 Fluid-present melting of ocean crust in subduction zones G. Prouteau; G. Prouteau 1UMR 6538, UBO, 6, avenue Le Gorgeu, B.P. 809, 29285 Brest, France Search for other works by this author on: GSW Google Scholar B. Scaillet; B. Scaillet 2Institut des Sciences de la Terre d'Orléans, CRSCM-CNRS, 1A rue de la Férollerie, 45071 Orléans, France Search for other works by this author on: GSW Google Scholar M. Pichavant; M. Pichavant 2Institut des Sciences de la Terre d'Orléans, CRSCM-CNRS, 1A rue de la Férollerie, 45071 Orléans, France Search for other works by this author on: GSW Google Scholar R. C. Maury R. C. Maury 1UMR 6538, UBO, 6, avenue Le Gorgeu, B.P. 809, 29285 Brest, France Search for other works by this author on: GSW Google Scholar Author and Article Information G. Prouteau 1UMR 6538, UBO, 6, avenue Le Gorgeu, B.P. 809, 29285 Brest, France B. Scaillet 2Institut des Sciences de la Terre d'Orléans, CRSCM-CNRS, 1A rue de la Férollerie, 45071 Orléans, France M. Pichavant 2Institut des Sciences de la Terre d'Orléans, CRSCM-CNRS, 1A rue de la Férollerie, 45071 Orléans, France R. C. Maury 1UMR 6538, UBO, 6, avenue Le Gorgeu, B.P. 809, 29285 Brest, France Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (12): 1111–1114. https://doi.org/10.1130/0091-7613(1999)027<1111:FPMOOC>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation G. Prouteau, B. Scaillet, M. Pichavant, R. C. Maury; Fluid-present melting of ocean crust in subduction zones. Geology 1999;; 27 (12): 1111–1114. doi: https://doi.org/10.1130/0091-7613(1999)027<1111:FPMOOC>2.3.CO;2 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 Phase equilibria were investigated in the pressure range 400–2000 MPa on the Pinatubo dacite, a representative example of natural Cenozoic adakites (slab melts), to constrain the temperature versus wt% H2O conditions of magma genesis. The experimental results suggest that water contents of the melt were at least 10 wt% and temperatures were ∼900 °C during magma ascent from the slab. Natural aluminous amphiboles present in the dacite crystallized at pressures of ∼1000 MPa, fixing an upper temperature limit of 950 °C for the slab melts at the crust-mantle boundary. Amphiboles experimentally crystallized at 1000 MPa are identical to those found in melt inclusions in metasomatized mantle xenoliths. These natural inclusions represent samples of slab melts and contain glasses with a dacitic bulk composition, which requires an H2O content in the melt of >10 wt% at 1000 MPa and 900 °C. For conditions of magma generation of 800–900 °C at 2000–2300 MPa, melt H2O contents close to 15 wt% are needed to generate melts with dacitic bulk composition. Overall, these constraints are inconsistent with slab melts being produced by dehydration melting of amphibolite, a mechanism unable to produce dacite melt compositions that are both hydrous and cool. Slab melting in modern subduction zones must occur under fluid-present conditions at temperatures below 900 °C, in agreement with the thermal regime of subducted oceanic crust as deduced from numerical simulation of heat transfer using the present-day mantle geotherm. At such low temperatures, Ti-bearing phases are stable during melting; thus any metasomatizing slab melt will be strongly depleted in Nb, Ta, and Ti, a major characteristic of arc magmas produced in the mantle wedge. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.