TY - ABST
T1 - Thermal effects of metamorphic reactions in a three-component slab
AU - Chemia, Zurab
AU - Dolejš, David
AU - Steinle-Neumann, Gerd
PY - 2010/5/1
Y1 - 2010/5/1
N2 - Thermal evolution of a subducting crust is of primary importance for
understanding physical properties, phase transformations, fluid
migration and melting regimes at convergent plate boundaries. Various
factors influencing the thermal structure of a subduction zone have been
considered previously: age, geometry and rate of subducting lithosphere,
shear stress across the subduction interface, radioactive heating, etc.
Recently, emphasis has been placed on significant heating of the slab
due to rheologically favourable convection in the mantle wedge. However,
substantial heat production or consumption can occur due to metamorphic
reactions, including endothermic devolatilization. We investigate
enthalpy budget in a subducting slab using a self-consistent
thermodynamic model. Petrological model of a subducting slab consists of
three layers: oceanic subducting sediment (GLOSS), oceanic basalt (OB),
and moderately serpentinized harzburgite (SHB). These layers are
examined over the range of pressure-temperature conditions of interest
by computing metamorphic phase diagrams and retrieving whole-rock
thermodynamic properties. Our results suggest that metamorphic reactions
consume a significant amount of slab heat budget and induce substantial
cooling. In contrast to previous thermal models of subduction zones,
actual slab temperatures may be lower by as much as 250 °C.
AB - Thermal evolution of a subducting crust is of primary importance for
understanding physical properties, phase transformations, fluid
migration and melting regimes at convergent plate boundaries. Various
factors influencing the thermal structure of a subduction zone have been
considered previously: age, geometry and rate of subducting lithosphere,
shear stress across the subduction interface, radioactive heating, etc.
Recently, emphasis has been placed on significant heating of the slab
due to rheologically favourable convection in the mantle wedge. However,
substantial heat production or consumption can occur due to metamorphic
reactions, including endothermic devolatilization. We investigate
enthalpy budget in a subducting slab using a self-consistent
thermodynamic model. Petrological model of a subducting slab consists of
three layers: oceanic subducting sediment (GLOSS), oceanic basalt (OB),
and moderately serpentinized harzburgite (SHB). These layers are
examined over the range of pressure-temperature conditions of interest
by computing metamorphic phase diagrams and retrieving whole-rock
thermodynamic properties. Our results suggest that metamorphic reactions
consume a significant amount of slab heat budget and induce substantial
cooling. In contrast to previous thermal models of subduction zones,
actual slab temperatures may be lower by as much as 250 °C.
M3 - Conference abstract in journal
VL - 12
SP - 5768
JO - EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p.5768
JF - EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p.5768
ER -