Research Article| April 01, 2012 Hydrothermal circulation and the dike-gabbro transition in the detachment mode of slow seafloor spreading Andrew M. McCaig; Andrew M. McCaig 1Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Michelle Harris Michelle Harris 2National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Geology (2012) 40 (4): 367–370. https://doi.org/10.1130/G32789.1 Article history received: 31 Aug 2011 rev-recd: 19 Nov 2011 accepted: 25 Nov 2011 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Andrew M. McCaig, Michelle Harris; Hydrothermal circulation and the dike-gabbro transition in the detachment mode of slow seafloor spreading. Geology 2012;; 40 (4): 367–370. doi: https://doi.org/10.1130/G32789.1 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 One of the most ubiquitous boundaries within our planet is between sheeted dikes and gabbros in fast-spreading ocean crust. This boundary marks the brittle-ductile transition at the ridge crest, and is localized by a decametric conductive boundary layer between hydrothermal circulation in the sheeted dike layer and a shallow quasi-steady-state melt lens. In contrast, at slow-spreading ridges, the crustal structure appears chaotic, with no consistent sheeted dike layer and widespread occurrences of gabbro and serpentinized peridotite on the seafloor. Recent work suggests that as much as 50% of the Atlantic Ocean crust formed by a detachment mode of seafloor spreading, including the formation of oceanic core complexes capped by long-lived, convex-upward detachment faults. These detachment faults are often associated with large hydrothermal systems in which the location of any magmatic heat source is uncertain. Here we show that detachment faults can act as thermal boundaries between gabbroic melt in the fault footwall and hydrothermal circulation in the fault zone and hanging wall, thus explaining the link between faulting and black smoker systems. We suggest that interaction between magmatism and hydrothermal circulation means that detachment faults can act as the dike-gabbro transition in the detachment mode of spreading, inevitably leading to exposure of gabbros on the seafloor through continued faulting. This concept provides a means of unifying apparently contrasting processes and crustal structures at different spreading rates. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.