High‐Pressure Single‐Crystal Elasticity and Thermal Equation of State of Omphacite and Their Implications for the Seismic Properties of Eclogite in the Earth's Interior

Hao, Ming; Zhang, Jin S.; Pierotti, Caroline; Ren, Z.M.; Zhang, D.

doi:10.1029/2018jb016964

Cited by 18 publications

(20 citation statements)

References 71 publications

(134 reference statements)

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“…This is the major revision to what was found in Hao et al. (2019). The difference is caused by the use of diopside’s ∂ K S0 /∂T and ∂ G 0 /∂T for omphacite in the calculation in Hao et al.…”

Section: Discussionsupporting

confidence: 71%

“…Our ability to trace the eclogitic materials in the deep Earth through seismic methods is substantially restricted by the lack of knowledge on the temperature‐dependent single‐crystal elasticity of omphacite at high‐pressure condition. Thus, building up on our previous high‐pressure study on omphacite single crystals at 300 K (Hao et al., 2019), we further conducted single‐crystal Brillouin spectroscopy experiments on the same crystals at simultaneously high pressure‐temperature conditions up to 18 GPa and 700 K, and then modeled the isotropic and anisotropic seismic properties of the undeformed and deformed eclogite samples after combining the laboratory determined LPO with the updated pressure‐temperature dependent single‐crystal elastic properties of omphacite. The results presented in this study will serve as the basis for detecting the recycled oceanic crust in the Earth’s upper mantle.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

et al. 2021

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The Earth's oceanic crust is primarily made of basalt. When the oceanic lithosphere is subducted, the basaltic oceanic crust metamorphizes into eclogite when the pressure and temperature exceed 2 GPa and 1073 K (Ito & Kennedy, 1971). Due to its high density, the formation of eclogite further helps the slab subduction (Moghadam et al., 2010;Xu et al., 2008). Omphacite, the solid solution of diopside (CaMgSi 2 O 6 ) and jadeite (NaAlSi 2 O 6 ), is the major mineral phase in eclogite (up to 75 vol%) and can stably exist at depths up to 500 km. Due to the slow mixing and diffusion process within the Earth's interior, the recycled eclogitic materials can be preserved over the geological time as chemical heterogeneities in the deep Earth (Ballmer et al., 2017;Xu et al., 2008). To seismically identify those heterogeneities, the high pressure-temperature elastic properties of relevant minerals are needed.Seismologists have found complex seismic anisotropy features near subduction zones (e.g., Long & Silver, 2008;Niday & Humphreys, 2020), which are generally explained as the result of the flow-induced lattice-preferred orientation (LPO) of the elastically anisotropic minerals. Understanding the seismic anisotropy observations as well as the mantle flow field requires knowledge of the single-crystal elasticity and the LPO of relevant minerals, such as omphacite in the subducted slab crust.

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Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

et al. 2021

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“…The omphacite SBB-46 had a C2/c symmetry based on its high T thermal history. The difference in cation ordering was not found to have a resolvable effect on the elastic properties beyond experimental uncertainties [37].…”

Section: Resultsmentioning

confidence: 78%

Hydrogen Effect on the Sound Velocities of Upper Mantle Omphacite

et al. 2019

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Clinopyroxene (Cpx) is commonly believed to be the best structural water (hydrogen) carrier among all major upper mantle nominally anhydrous minerals (NAMs). In this study, we have measured the single-crystal elastic properties of a Cpx, a natural omphacite with~710 ppm water at ambient pressure (P) and temperature (T) conditions. Utilizing the single-crystal X-ray diffraction (XRD) and electron microprobe data, the unit cell parameters and density were determined as a = 9.603(9) Å, b = 8.774(3) Å, c = 5.250(2) Å, β = 106.76(5) o , V = 255.1(4) Å 3 , and = 3.340(6) g/cm 3 . We performed Brillouin spectroscopy experiments on four single crystals along a total of 52 different crystallographic directions. The best-fit single-crystal elastic moduli (C ij s), bulk and shear moduli were determined as: C 11 = 245(1) GPa, C 22 = 210(2) GPa, C 33 = 249.6(9) GPa, C 44 = 75.7(9) GPa, C 55 = 71.2(5) GPa, C 66 = 76(1) GPa, C 12 = 85(2) GPa, C 13 = 70(1) GPa, C 23 = 66(2) GPa, C 15 = 8.0(6) GPa, C 25 = 6(1) GPa, C 35 = 34.7(6) GPa, and C 46 = 8.7(7) GPa, K S0 = 125(3) GPa, and G 0 = 75(2) GPa, respectively. Compared with the anticipated elastic properties of an anhydrous omphacite with the same chemical composition, our results indicate that the incorporation of~710 ppm structural water has no resolvable effect on the aggregate elastic properties of omphacite, although small differences (up to~9 GPa) were observed in C 13 , C 25 , C 44 , and C 66 .

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“…Many studies have focused on the thermoelastic properties of omphacite (Hao et al, 2019;Nishihara et al, 2003;Pandolfo et al, 2012bPandolfo et al, , 2012aXu et al, 2019;Zhang et al, 2016) (Table S3). Most of the results are obtained by the single-crystal XRD method, except for the result of Nishihara et al (2003), which was obtained from powder XRD.…”

Section: Omphacitementioning

confidence: 99%

Delamination in Tibet: Deriving constraints from the density of eclogite

Fan

et al. 2021

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Abstract. Tibet, which is characterized by collisional orogens, has undergone the process of delamination or convective removal. The lower crust and mantle lithosphere appear to have been removed through delamination during orogenic development. Numerical and analog experiments demonstrate that the metamorphic eclogitized oceanic subduction slab or lower crust may promote gravitational instability due to its increased density. The eclogitized oceanic subduction slab or crustal root is believed to be denser than the underlying mantle and tends to sink. However, the density of eclogite under high-pressure and high-temperature conditions and density differences from the surrounding mantle is not preciously constrained. Here, we offer new insights into the derivation of eclogite density with a single experiment to constrain delamination in Tibet. Using in situ synchrotron X-ray diffraction combined with diamond anvil cell, experiments focused on minerals (garnet, omphacite, and epidote) of eclogite are conducted under simultaneous high-pressure and high-temperature conditions, which avoids systematic errors. Fitting the pressure-temperature-volume data with the third-order Birch-Murnaghan equation of state, the thermal equation of state (EoS) parameters, including the bulk modulus (KT0), its pressure derivative (KT0′), the temperature derivative ((KT/T)P), and the thermal expansion coefficient (α0), are derived. The densities of rock-forming minerals and eclogite are modeled along with the geotherms of two types of delamination. The delamination processes of subduction slab breakoff and the removal of the eclogitized lower crust in Tibet are discussed. The Tibetan eclogite which containing 40–60 vol. % garnet and 37–64 % degrees of eclogitization can promote the delamination of slab break-off in Tibet. Our results indicate that eclogite is a major controlling factor in the initiation of delamination. A high abundance of garnet, a high Fe-content, and a high degree of eclogitization are more conducive to instigating the delamination.

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High‐Pressure Single‐Crystal Elasticity and Thermal Equation of State of Omphacite and Their Implications for the Seismic Properties of Eclogite in the Earth's Interior

Cited by 18 publications

References 71 publications

Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

Hydrogen Effect on the Sound Velocities of Upper Mantle Omphacite

Delamination in Tibet: Deriving constraints from the density of eclogite

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