Flow Laws for Quartzo-Feldspathic Aggregates

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The PIs will carry out an experimental determination of flow laws for dislocation and diffusion creep of mono- and polyphase aggregates of quartz of and feldspar which can be reliably extrapolated to crustal conditions. A key element of this study will be use of the molten salt sample assembly developed recently by Green and Borch (1989), which provides the stress sensitivity of a gas apparatus with the capability for high pressure experiments required to induce dislocation creep in quartz and feldspar. They will check this assembly by doing duplicate experiments, on diffusion creep in feldspars, in a gas apparatus. Additional key features of the study are (1) a determination of the fH2O (H+) dependence of dislocation climb and creep in quartz aggregates, which should allow one to take account of the previously observed pressure dependence of hydrolytic weakening in extrapolating flow laws to nature, and (2) delineation of the conditions where different regimes of dislocation creep in quartz are dominant and the experimental materials and conditions necessary to ensure mechanical steady state in each.