An experimental study of the brittle-ductile transition of basalt at oceanic crust pressure and temperature conditions

摘要: Received 21 September 2011; revised 10 January 2012; accepted 1 February published 23 March 2012. [1] The brittle to ductile transition (BDT) in rocks may strongly influence their transport properties (i.e., permeability, porosity topology…) and the maximum depth temperature where hydrothermal fluids circulate. To examine this context of Icelandic crust, we conducted deformation experiments on a glassy basalt (GB) glass-free (GFB) under oceanic crust conditions. Mechanical micro-structural observations at constant strain rate � 5 s confining pressure 100–300 MPa indicate that are dilatant up 700–800 C. At higher temperatures effective pressures mode becomes macroscopically ductile, i.e., is distributed throughout sample no localized shear rupture plane develops. presence glass key component reducing strength lowering BDT. In field, consistent with Mohr-Coulomb failure criterion an internal coefficient friction 0.42 for both samples. rate- temperature-dependent samples were characterized by same stress exponent range 3 < n 4.2 but very different activation energy QGB =5 9� 15 KJ/mol QGFB = 456 4 KJ/mol. Extrapolation these results Iceland conditions predicts BDT 100 C basalt, whereas might occur non-glassy basalts deeper conditions, than 550 C, agreement