Deep fluid circulation in fault zones

Research Article| October 01, 1988 Deep fluid circulation in fault zones Andrew M. McCaig Andrew M. McCaig 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, England Search for other works by this author on: GSW Google Scholar Author and Article Information Andrew M. McCaig 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, England Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1988) 16 (10): 867–870. https://doi.org/10.1130/0091-7613(1988)016<0867:DFCIFZ>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 Andrew M. McCaig; Deep fluid circulation in fault zones. Geology 1988;; 16 (10): 867–870. doi: https://doi.org/10.1130/0091-7613(1988)016<0867:DFCIFZ>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 Massive fluid circulation in retrogressive ductile shear zones is a well-established but poorly understood phenomenon. In some cases, surface-derived fluids, which must initially have been at hydrostatic pressures, can be shown to have entered shear zones in which fluids would normally be expected to be at lithostatic pressure. In these circumstances, thermal convection is an unlikely driving force for fluid movement. Underthrusting of a surficial fluid reservoir beneath shear zones is a viable mechanism in some cases, but not for metasomatic shear zones in the Pyrenees where insufficient underthrusting has occurred. Seismic pumping provides an alternative mechanism to explain the paradox of fluid access into ductile shear zones; a kinematic analysis of a hypothetical fault zone shows that stress and dilatancy cycles will be out of phase above and below the frictional/quasiplastic transition. If this effect is sufficiently large, hydraulic gradients may force fluid downward across the transition immediately after earthquake rupture through highly permeable microcrack networks. Between earthquake cycles, plastic creep in mylonites will overprint microcrack networks, increase fluid pressure, and promote slow upward movement of fluid at low permeability. For smaller shear zones, such as those in the Pyrenees, seismic pumping could occur down a shallow decollement with subsequent upward fluid flow through shear zones in the hanging wall of the decollement. 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.