Water in the deep Earth’s interior has important and profound impacts on the geodynamical properties at high-temperature(T)and high-pressure(P)conditions.A series of dense hydrous Mg-silicate(DHMS)phases are generate...Water in the deep Earth’s interior has important and profound impacts on the geodynamical properties at high-temperature(T)and high-pressure(P)conditions.A series of dense hydrous Mg-silicate(DHMS)phases are generated from dehydration of serpentines in subduction slabs below the lithosphere,including phase A,chondrodite,clinohumite,phase E,superhydrous phase B and phase D.On the other hand,olivine and its high-P polymorphs of wadsleyite and ringwoodite are dominant nominally anhydrous minerals(NAMs)in the upper mantle and transition zone,which could contain significant amount of water in the forms of hydroxyl group(OH-)defects.The water solubilities in wadsleyite and ringwoodite are up to about 3 weight percent(wt.%),making the transition zone a most important layer for water storage in the mantle.Hydration can significantly affect the pressure-volumetemperature equations of state(P-V-T EOSs)for the DHMS and NAM phases,including the thermal expansivities and isothermal bulk moduli.In this work,we collected the reported datasets for the DHMS and NAM phases,and reconstruct internally consistent EOSs.Next,we further evaluated the thermodynamic Grüneisen parameters,which are fundamental for constraining the temperature distribution in an isentropic process,such as mantle convection.The adiabatic temperature profiles are computed for these minerals in the geological settings of normal mantle and subduction zone,and our calculation indicates that temperature is the dominant factor in determining the gradient of a geotherm,rather than the mineralogical composition.展开更多
基金supported by the National Natural Science Foundation of China(No.42072050)the Science Fund for Distinguished Young Scholars of Hubei Province(No.2020CFA104)。
文摘Water in the deep Earth’s interior has important and profound impacts on the geodynamical properties at high-temperature(T)and high-pressure(P)conditions.A series of dense hydrous Mg-silicate(DHMS)phases are generated from dehydration of serpentines in subduction slabs below the lithosphere,including phase A,chondrodite,clinohumite,phase E,superhydrous phase B and phase D.On the other hand,olivine and its high-P polymorphs of wadsleyite and ringwoodite are dominant nominally anhydrous minerals(NAMs)in the upper mantle and transition zone,which could contain significant amount of water in the forms of hydroxyl group(OH-)defects.The water solubilities in wadsleyite and ringwoodite are up to about 3 weight percent(wt.%),making the transition zone a most important layer for water storage in the mantle.Hydration can significantly affect the pressure-volumetemperature equations of state(P-V-T EOSs)for the DHMS and NAM phases,including the thermal expansivities and isothermal bulk moduli.In this work,we collected the reported datasets for the DHMS and NAM phases,and reconstruct internally consistent EOSs.Next,we further evaluated the thermodynamic Grüneisen parameters,which are fundamental for constraining the temperature distribution in an isentropic process,such as mantle convection.The adiabatic temperature profiles are computed for these minerals in the geological settings of normal mantle and subduction zone,and our calculation indicates that temperature is the dominant factor in determining the gradient of a geotherm,rather than the mineralogical composition.
