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dc.contributor.authorKolandaivelu, Kannikha Parameswarien
dc.contributor.authorHarris, Robert N.en
dc.contributor.authorLowell, Robert P.en
dc.contributor.authorRobinson, Adam H.en
dc.contributor.authorWilson, Dean J.en
dc.contributor.authorHobbs, Richard W.en
dc.description.abstractWe analyse 67 new conductive heat-flow measurements on the southern flank of the Costa Rica Rift (CRR). Heat-flow measurements cover five sites ranging in oceanic crustal age between approximately 1.6 and 5.7 Ma, and are co-located with a high-resolution multichannel seismic line that extends from slightly north of the first heat-flow site (1.6 Ma) to beyond ODP Hole 504B in 6.9 Ma crust. For the five heat-flow sites, the mean observed conductive heat flow is approximate to 85 mW m(-2). This value is approximately 30 per cent of the mean lithospheric heat flux expected from a half-space conductive cooling model, indicating that hydrothermal processes account for about 70 per cent of the heat loss. The advective heat loss fraction varies from site to site and is explained by a combination of outcrop to outcrop circulation through exposed basement outcrops and discharge through faults. Supercritical convection in Layer 2A extrusives occurs between 1.6 and 3.5 Ma, and flow through a thinly sedimented basement high occurs at 4.6 Ma. Advective heat loss diminishes rapidly between approximate to 4.5 and approximate to 5.7 Ma, which contrasts with plate cooling reference models that predict a significant deficit in conductive heat flow up to ages approximate to 65 +/- 10 Ma. At approximate to 5.7 Ma the CRR topography is buried under sediment with an average thickness of approximate to 150 m, and hydrothermal circulation in the basement becomes subcritical or perhaps marginally critical. The absence of significant advective heat loss at approximate to 5.7 Ma at the CRR is thus a function of both burial of basement exposure under the sediment load and a reduction in basement permeability that possibly occurs as a result of mineral precipitation and original permeability at the time of formation. Permeability is a non-monotonic function of age along the southern flank of the CRR, in general agreement with seismic velocity tomography interpretations that reflect variations in the degree of ridge-axis magma supply and tectonic extension. Hydrothermal circulation in the young oceanic crust at the southern flank of CRR is affected by the interplay and complex interconnectedness of variations in permeability, sediment thickness, topographical structure, and tectonic and magmatic activities with age.en
dc.description.sponsorshipNSFNational Science Foundation (NSF) [OCE 1353114, 1558797, NSF OCE 1353003, 1558824]; NERC OSCAR project [NE/I027010/1]en
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.subjectPermeability and porosityen
dc.subjectHeat flowen
dc.subjectHydrothermal systemsen
dc.titleEvolution of heat flow, hydrothermal circulation and permeability on the young southern flank of the Costa Rica Riften
dc.typeArticle - Refereeden
dc.description.notesThe authors would like to thank the thorough and constructive reviews from Dr Keir Becker and one other anonymous reviewer that helped improve this manuscript. This research was supported in part by NSF Grants OCE 1353114 and 1558797 to RPL and Grants NSF OCE 1353003 and 1558824 to RNH. The NERC OSCAR project grant NE/I027010/1 (Hobbs & Peirce 2015) underpinned this work. The authors would like to thank the officers, crew, technicians and science party on board the RRS JamesCook during cruises JC112, JC113 and JC114. TheMCS datawere processed using GNS Globe Claritas at Durham University. The swath bathymetry was cleaned and processed using QPS Fledermaus by Gavin Haughton from the National Oceanographic Centre and Emma Gregory from Durham University. Yang Li, Durham University, UK, provided the Monte Carlo Matlab code for calculation of uncertainties. The heat-flow data have been placed on the IEDA data portal, doi:, seismic data are available on request through the British Oceanographic Data Center or the author RWH.en
dc.title.serialGeophysical Journal Internationalen

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Creative Commons Attribution 4.0 International
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