@article{fdi:010093603,
  title = {{T}he effect of {CO}2 on the partitioning of {H}2{O} between clinopyroxene and melts and melting of volatile-bearing eclogites},
  author = {{C}urtolo, {A}. and {C}ondamine, {P}. and {S}chiavi, {F}ederica and {B}olfan-{C}asanova, {N}. and {N}ovella, {D}.},
  editor = {},
  language = {{ENG}},
  abstract = {{H}2{O} and {CO}2 are critical components for the development and sustainment of life on {E}arth and affect a wide variety of geological processes. {I}t has been suggested that the presence of {CO}2 in the mantle could alter how {H}2{O} is stored and partitioned between minerals and melts, implying dramatic effects on both melting processes and {H}2{O} storage capacities of the {E}arth's mantle. {E}clogites, which are present as heterogeneities in the mantle, have been shown to participate in the production of oceanic island basalts such as the {HIMU} ({H}igh-mu, mu = {U}-238/{P}b-204). {T}hey can host significant amounts of {H}2{O} in clinopyroxenes and their {H}2{O} storage capacity and melting temperature can be significantly influenced by the presence of {CO}2. {H}ere, the effect of {CO}2 on the partition coefficient of {H}2{O} between clinopyroxene and melt ({D}-{H}2{O}(cpx/melt )= {C}-{H}2{O}(cpx)/{C}-{H}2{O}(melt)) was explored at high-pressure and high-temperature by conducting piston cylinder experiments at 1200 degrees {C} and 2 {GP}a. {T}he experiments employed a basaltic starting mixture with different concentrations of {H}2{O} and {CO}2 and produced an assemblage consisting of more than 60 wt% basaltic-andesitic melt in equilibrium with high-{A}l ({A}l2{O}3 = 7.83-11.18 wt%) clinopyroxene crystals. {T}he {H}2{O} concentration in clinopyroxene, measured by {F}ourier {T}ransform {I}nfrared spectroscopy, ranges from 869 +/- 71 to 1950 +/- 134 ppm wt, and shows a negative correlation with the concentration of {CO}2 in the system and a positive correlation with tetrahedrally-coordinated {A}l3+ in the clinopyroxene. {T}he quenched melts have {H}2{O} and {CO}2 concentrations ranging from 5.18 to 6.97 wt% and from 0.19 to 2.59 wt%, respectively. {T}he calculated {D}-{H}2{O}(cpx/melt) varies from 0.031 +/- 0.005 at {XCO}2 = 0.03 to 0.017 +/- 0.003 at {XCO}2 = 0.34 (where {XCO}2 = {CO}2/[{H}2{O}+{CO}2 in wt). {T}he variation of {D}-{H}2{O}(cpx/melt) as a function of {XCO}2 is described by a power law in the form: {D}-{H}2{O}(cpx/melt )= 0.0123 & lowast;{XCO}2-0.237, with an extrapolated {D}-{H}2{O}(cpx/melt) of 0.033 at {XCO}2 = 0. {T}he calculated {D}-{H}2{O}(cpx/melt) is combined with {DH}2{O}grt/cpx to constrain the effect of {CO}2 on the {H}2{O} partition coefficient between an eclogite and a melt ({D}-{H}2{O}(eclo/melt)), which is then used to predict the melting temperature of eclogite in a hydrous-carbonated system. {T}he results show that melting of hydrous-carbonated eclogite (600 ppm wt {H}2{O}-300 ppm wt {CO}2) occurs at temperatures drastically lower than those of both purely hydrous and purely carbonated melting. {I}n this scenario, the temperature of hydrous carbonated melting of eclogite remains lower than the mantle adiabat and crosses the geotherm of the hottest subduction zones at {P} > 5.8 {GP}a, indicating that the oceanic crust in a subducting slab could undergo partial melting at this pressure. {I}n addition, {D}-{H}2{O}(eclo/melt) is used in a simple mass balance model to constrain the {H}2{O} content of a mantle source lithology of {HIMU} melts, suggested to be made mainly of recycled oceanic crust. {T}he model, using {D}-{H}2{O}(eclo/melt) at {XCO}2 values of 0, 0.1 and 0.3, indicates that partial melting of eclogite with a bulk {H}2{O} content ranging from similar to 300 to similar to 720 ppm wt can potentially explain the {H}2{O} abundance measured in magmas originating from the {HIMU} mantle reservoir.},
  keywords = {{E}clogite ; {M}antle ; {H}2{O} ; {P}artitioning ; {CO}2 ; {HIMU}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {398},
  numero = {},
  pages = {54--66},
  ISSN = {0016-7037},
  year = {2025},
  DOI = {10.1016/j.gca.2025.03.013},
  URL = {https://www.documentation.ird.fr/hor/fdi:010093603},
}