Sound velocities of natural clinohumite at high pressures and implications for seismic velocities of subducted slabs in the upper mantle

Elasticity of Single‐Crystal Clinohumite at High Pressures and Temperatures: Implication for the H2O and F Circulation in the Earth's Mantle

“…Here, we derived the ∂K S /∂T value of 0.024(1) GPa/K. Converting our obtained ∂K S /∂T to ∂K T /∂T yields a value of 0.028(1) GPa/K, showing a smaller temperature effect on the bulk modulus than the literature results with V P ; triangles: V S , lines: the fitting results from third-or fourth-order finite-strain equations (Birch, 1978); blue: this study; orange: Phan (2008); green: Fritzel and Bass (1997); gray: Zhang et al (2023). Uncertainties of the elastic moduli are smaller than the symbols if not shown.…”

“…We calculated the sound velocity of clinohumite with varying F content along the normal mantle geotherm (see Supporting Information S1 for details) (Brown & Shankland, 1981;Ehlers & Hoinkes, 1987;Friedrich et al, 2002). Based on aforementioned discussion, varying F content between 37 and 45 mol.% has a minor effect on the K S0 ′ and G 0 ′ (Table S6 in Supporting Information S1) (Fritzel & Bass, 1997;Phan, 2008;Zhang et al, 2023Zhang et al, , 2024. Here we considered that F-bearing clinohumite has the same K S0 ′ of 4.2 and G 0 ′ of 1.3.…”

“…Experimental studies on the elasticity of clinohumite at relevant pressure and temperature conditions of the mantle help to identify the potential occurrence of clinohumite within the Earth's interior. Previous studies have shown that the elasticity of clinohumite exhibits a strong dependence on composition at ambient conditions (Fritzel & Bass, 1997;Phan, 2008;Qin et al, 2017;Ross & Crichton, 2001;Zhang et al, 2023). For synthetic OHclinohumite (Mg 9 Si 4 O 16 (OH) 2 ), the isothermal bulk modulus K T0 determined by X-ray diffraction (XRD), is 119.4(7) GPa with a fixed pressure derivative K T0 ′ = 4.8(2), which is consistent with Ultrasonic measurements with the adiabatic bulk modulus, K S0 , of 119(2) GPa and its pressure derivative K S0 ′ = 4.8(1) (Phan, 2008;Ross & Crichton, 2001).…”

“…The substitution of OH by F leads to an increase in the K S0 and shear modulus, G 0 (Fritzel & Bass, 1997;Phan, 2008;Zhang et al, 2023). Elevating the F content to 78 mol.% increases the K S0 and G 0 by 8.0% and 3.7%, respectively (Ehlers & Hoinkes, 1987;Friedrich et al, 2002;Fritzel & Bass, 1997;Phan, 2008;Zhang et al, 2023). High-pressure ultrasonic experiments have shown that the pressure derivative of the bulk (K S ′) and shear modulus (G′) of OH-clinohumite are 4.8(1) and 1.9(2), greater than those of clinohumite with 37 mol.% F, where K S ′ and G′ are 3.9(1) and 1.1(1), respectively (Phan, 2008;Zhang et al, 2023).…”

“…Elevating the F content to 78 mol.% increases the K S0 and G 0 by 8.0% and 3.7%, respectively (Ehlers & Hoinkes, 1987;Friedrich et al, 2002;Fritzel & Bass, 1997;Phan, 2008;Zhang et al, 2023). High-pressure ultrasonic experiments have shown that the pressure derivative of the bulk (K S ′) and shear modulus (G′) of OH-clinohumite are 4.8(1) and 1.9(2), greater than those of clinohumite with 37 mol.% F, where K S ′ and G′ are 3.9(1) and 1.1(1), respectively (Phan, 2008;Zhang et al, 2023). However, the effect of temperature on the elasticity of clinohumite is only available for the isothermal bulk modulus (Qin et al, 2017).…”