The mechanism of heat extraction from the lower oceanic crust near the ridge axis is poorly constrained despite its importance for understanding both the process of accretion of the plutonic complex and the mass fluxes associated with ridge hydrothermal systems. We have investigated the role of zones of focussed fluid flow in the plutonic complex of the Oman ophiolite in the near-axis cooling of the oceanic crust. Lineaments identified on aerial photographs, that occur at ∼1 km spacing, show evidence for extensive hydrothermal fluid flow through regions ∼10 to 50 m wide. Fluid flow is initiated in these regions at ∼800°C and continues at least into the lower greenschist facies. Strontium-isotope analyses indicate that the fluid flux through these zones is sufficient to transport a metasomatic front from the base of the sheeted dike complex to close to the Moho. Computed *minimum* fluid fluxes to transport a metasomatic front through the focussed fluid flow zones are ∼1x10^8^ kgm^−2^. Modeling of diffusive exchange of calcium from olivine to clinopyroxene indicates enhanced cooling rates adjacent to the focussed fluid flow zones. Heat fluxes estimated from the enhanced cooling rates are broadly consistent with the fluid fluxes determined from modeling the Sr-isotopic composition of samples from the focussed fluid flow zones. The combination of independent estimates of the fluid and heat fluxes, such as these, can provide more rigorous constraints on the thermal history than either approach used in isolation. Our results show that focussed fluid flow could play a major role in the cooling in the lower oceanic crust. Significant focussed fluid flow in the lower oceanic crust has important implications for predicting the total mass flux associated with hydrothermal circulation at mid-ocean ridges. This is because fluids flowing through channels become chemically rock-buffered at smaller fluid fluxes than those flowing pervasively through a rock mass. Thus, if focussed fluid flow is an important mechanism of heat loss from the lower oceanic crust the chemical fluxes from ridge hydrothermal systems into the oceans may be smaller than currently thought.
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Research Article| September 01, 1999 Continental extensional setting for the Archean Belingwe Greenstone Belt: Comment and Reply T. M. Kusky; T. M. Kusky 1Center for Remote Sensing, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar W. S. F. Kidd; W. S. F. Kidd 2Department of Geological Sciences, University at Albany, Albany, NewYork 12222, USA Search for other works by this author on: GSW Google Scholar M. A. Hunter; M. A. Hunter 3Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK. Present address: British Antarctic Survey, High Cross, Madingley Road, Cambridge CB30ET, UK. Search for other works by this author on: GSW Google Scholar M. J. Bickle; M. J. Bickle 4Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK. Search for other works by this author on: GSW Google Scholar E. G. Nisbet; E. G. Nisbet 5Department of Geology, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK Search for other works by this author on: GSW Google Scholar A. Martin; A. Martin 66, Autumn Close, Greendale, Harare, Zimbabwe Search for other works by this author on: GSW Google Scholar H. J. Chapman H. J. Chapman 7Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK Search for other works by this author on: GSW Google Scholar Geology (1999) 27 (9): 861–862. https://doi.org/10.1130/0091-7613(1999)027<0861:CESFTA>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 MailTo Tools Icon Tools Get Permissions Search Site Citation T. M. Kusky, W. S. F. Kidd, M. A. Hunter, M. J. Bickle, E. G. Nisbet, A. Martin, H. J. Chapman; Continental extensional setting for the Archean Belingwe Greenstone Belt: Comment and Reply. Geology 1999;; 27 (9): 861–862. doi: https://doi.org/10.1130/0091-7613(1999)027<0861:CESFTA>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 No Abstract Available. 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.
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