TY - JOUR
T1 - Effects of chemical composition, water and temperature on physical properties of continental crust
AU - Guerri, Mattia
AU - Cammarano, Fabio
AU - Connolly, James A. D.
PY - 2015/7/1
Y1 - 2015/7/1
N2 - We explore the influence of major elements chemistry and H2O-content on the density and seismic velocity of crustal rocks by computing stable and metastable crustal mineralogy and elastic properties as a function of pressure and temperature (P-T). Proposed average compositions of continental crust result in significantly different properties, for example a difference in computed density of is obtained at a given P-T. Phase transformations affect crustal properties at the point that crustal seismic discontinuities can be explained with mineral reactions rather than chemical stratification. H2O, even if introduced in small amount in the chemical system, has an effect on physical properties comparable to that attributed to variations in major elements composition. Thermodynamical relationships between physical properties differ significantly from commonly used empirical relationships. Density models obtained by inverting CRUST 1.0 compressional wave velocity are different from CRUST 1.0 density and translate into variations in isostatic topography and gravitational field that ranges ±600 m and ±150 mGal respectively. Inferred temperatures are higher than reference geotherms in the upper crust and in the deeper portions of thick orogenic crust, consistently with presence of metastable rocks. Our results highlight interconnections/dependencies among chemistry, pressure, temperature, seismic velocities and density that need to be addressed to better understand the crustal thermo-chemical state.
AB - We explore the influence of major elements chemistry and H2O-content on the density and seismic velocity of crustal rocks by computing stable and metastable crustal mineralogy and elastic properties as a function of pressure and temperature (P-T). Proposed average compositions of continental crust result in significantly different properties, for example a difference in computed density of is obtained at a given P-T. Phase transformations affect crustal properties at the point that crustal seismic discontinuities can be explained with mineral reactions rather than chemical stratification. H2O, even if introduced in small amount in the chemical system, has an effect on physical properties comparable to that attributed to variations in major elements composition. Thermodynamical relationships between physical properties differ significantly from commonly used empirical relationships. Density models obtained by inverting CRUST 1.0 compressional wave velocity are different from CRUST 1.0 density and translate into variations in isostatic topography and gravitational field that ranges ±600 m and ±150 mGal respectively. Inferred temperatures are higher than reference geotherms in the upper crust and in the deeper portions of thick orogenic crust, consistently with presence of metastable rocks. Our results highlight interconnections/dependencies among chemistry, pressure, temperature, seismic velocities and density that need to be addressed to better understand the crustal thermo-chemical state.
U2 - 10.1002/2015gc005819
DO - 10.1002/2015gc005819
M3 - Journal article
SN - 1525-2027
VL - 16
SP - 2431
EP - 2449
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
IS - 7
ER -