Fluid expulsion related to mud extrusion off Costa Rica—A window to the subducting slab

Abstract

Research Article| March 01, 2004 Fluid expulsion related to mud extrusion off Costa Rica—A window to the subducting slab C. Hensen; C. Hensen 1Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany, and GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar K. Wallmann; K. Wallmann 2GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar M. Schmidt; M. Schmidt 3Institute of Geosciences, Kiel University, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar C.R. Ranero; C.R. Ranero 4 GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar E. Suess E. Suess 4 GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Search for other works by this author on: GSW Google Scholar Author and Article Information C. Hensen 1Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany, and GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany K. Wallmann 2GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany M. Schmidt 3Institute of Geosciences, Kiel University, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany C.R. Ranero 4 GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany E. Suess 4 GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany, and Sonderforschungsbereich 574, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Publisher: Geological Society of America Received: 13 Aug 2003 Revision Received: 30 Oct 2003 Accepted: 30 Oct 2003 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (3): 201–204. https://doi.org/10.1130/G20119.1 Article history Received: 13 Aug 2003 Revision Received: 30 Oct 2003 Accepted: 30 Oct 2003 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 C. Hensen, K. Wallmann, M. Schmidt, C.R. Ranero, E. Suess; Fluid expulsion related to mud extrusion off Costa Rica—A window to the subducting slab. Geology 2004;; 32 (3): 201–204. doi: https://doi.org/10.1130/G20119.1 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 A large number of mound-shaped structures that originated from mud extrusions is present along the convergent continental margin off Costa Rica and Nicaragua. Active fluid venting is indicated by the existence of CH4- and H2S-rich pore fluids as well as associated benthic fauna and authigenic carbonates. End-member fluid samples from all mounds are significantly depleted in dissolved Cl and other major elements, suggesting a general process of freshwater addition and thus a common source of the fluids. Our data clearly rule out dilution by gas hydrate dissociation as a dominant source of the freshwater. Enrichments of the fluids in B (up to 2 mmol/L) and inversely correlated δ18O vs. δD values point to clay-mineral dehydration as the cause for these anomalies. Calculations assuming a δ18O vs. δD equilibrium between the pore fluid and clay minerals at depth of formation indicate temperatures of dehydration between 85 and 130 °C. This temperature range is in agreement with the B enrichments and the presence of thermogenically formed CH4. Because temperatures above 50 °C are not reached within the sediment cover of the upper plate, the fluids most likely form within the subducted sediments and flow upward along deep-seated faults from ≥12 km depth. Mound-related fluid expulsion may contribute significantly to the recycling of mineral-bound water. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.