Compositional dependence of lower crustal viscosity
MetadataShow full item record
We calculate the viscosity structure of the lower continental crust as a function of its bulk composition using multiphase mixing theory. We use the Gibbs free-energy minimization routine Perple_X to calculate mineral assemblages for different crustal compositions under pressure and temperature conditions appropriate for the lower continental crust. The effective aggregate viscosities are then calculated using a rheologic mixing model and flow laws for the major crust-forming minerals. We investigate the viscosity of two lower crustal compositions: (i) basaltic (53 wt % SiO2) and (ii) andesitic (64 wt % SiO2). The andesitic model predicts aggregate viscosities similar to feldspar and approximately 1 order of magnitude greater than that of wet quartz. The viscosity range calculated for the andesitic crustal composition (particularly when hydrous phases are stable) is most similar to independent estimates of lower crust viscosity in actively deforming regions based on postglacial isostatic rebound, postseismic relaxation, and paleolake shoreline deflection.
Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 8333–8340, doi:10.1002/2015GL065459.
Suggested CitationGeophysical Research Letters 42 (2015): 8333–8340
Showing items related by title, author, creator and subject.
Rioux, Matthew; Lissenberg, C. Johan; McLean, Noah M.; Bowring, Samuel A.; MacLeod, Christopher J.; Hellebrand, Eric; Shimizu, Nobumichi (2011-12)Formation of the oceanic crust at mid-ocean ridges is a fundamental component of plate tectonics. A majority of the crust at many ridges is composed of plutonic rocks that form by crystallization of mantle-derived magmas ...
Three-dimensional seismic structure of the Mid-Atlantic Ridge (35°N) : evidence for focused melt supply and lower crustal dike injection Dunn, Robert A.; Lekic, Vedran; Detrick, Robert S.; Toomey, Douglas R. (American Geophysical Union, 2005-09-09)We gathered seismic refraction and wide-angle reflection data from several active source experiments that occurred along the Mid-Atlantic Ridge near 35°N and constructed three-dimensional anisotropic tomographic images of ...
Lower crustal variability and the crust/mantle transition at the Atlantis Massif oceanic core complex Blackman, Donna K.; Collins, John A. (American Geophysical Union, 2010-12-18)Seismic refraction data provide new constraints on the structure of the lower oceanic crust and its variability across the Atlantis Massif oceanic core complex, ∼30°N on the Mid-Atlantic Ridge. A 40 km-long spreading-parallel ...