Deep Sourced Fluids for Peridotite Carbonation in the Shallow Mantle Wedge of a Fossil Subduction Zone: Sr and C Isotope Profiles of OmanDP Hole BT1B

Obeso, Juan Carlos de; Kelemen, P. B.; Leong, James M.; Menzel, Manuel D.; Manning, Craig E.; Godard, Marguerite; Cai, Yue; Bolge, Louise

doi:10.1029/2021jb022704

Cited by 15 publications

(25 citation statements)

References 88 publications

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“…These differences in carbon isotope ratios can be understood as the result of temperature dependent carbon isotope fractionation. As discussed in more detail in de Obeso, Kelemen, et al (2022), at temperatures greater than ∼300°C, dissolved CO 2 in aqueous fluids has δ 13 C higher than co-existing calcite and dolomite (Deines, 2002;Horita, 2014). At lower temperatures, calcite and dolomite have δ 13 C higher than co-existing fluids.…”

Section: Source Of Fluid For Listvenite Formationmentioning

confidence: 94%

“…Present day Sr isotope ratios in listvenites and serpentinites from MoD Mtn range from ∼0.708 to 0.715 (de Obeso, Kelemen, et al, 2022;Falk & Kelemen, 2015). Using current Rb/Sr contents in these samples, age corrected 87Sr/86Sr ratios at 96 Ma range from ∼0.708 to 0.714, much higher than the range of Sr ratios in Samail ophiolite peridotites (0.703-0.707, Benoit et al, 1999;Gerbert-Gaillard, 2002;; Lanphere Godard et al, 2000;Hanghoj et al, 2010;Monnier et al, 2006), Banded Unit peridotites near the base of the Samail ophiolite mantle section (small, green open circles, barely visible, Falk & Kelemen, 2015;Khedr et al, 2013Khedr et al, , 2014Takazawa et al, 2003), and listvenites from Hole BT1B and MoD Mtn (open squares, Falk & Kelemen, 2015;Kelemen, Matter, et al, 2020), superimposed on contoured histogram of mineral proportions from shipboard XRF scanner data.…”

Section: Source Of Fluid For Listvenite Formationmentioning

confidence: 99%

“…To quantify this hypothesis, we made thermodynamic calculations with the compositions of solid reactants given in Table S2 in Supporting Information S1, methods described in Section 3, and results outlined in Figure 14 and 15. As the source of fluid, we chose sample OM20-17, a pelitic end-member from among the Hawasina clastic sedimentary rocks analyzed by Falk and Kelemen (2015) and de Obeso, Kelemen, et al (2022). As the peridotite reactant, we used an average Samail harzburgite composition calculated from published studies (Godard et al, 2000;Hanghoj et al, 2010;Monnier et al, 2006).…”

Section: Source Of Fluid For Listvenite Formationmentioning

confidence: 99%

“…The allochthonous sedimentary units below the ophiolite are about 3 km thick. Within these, clastic units comprise at least half the section, and contain about 2300 ppm C, or 0.84 wt% CO 2 on average (de Obeso, Kelemen, et al, 2022), yielding a total of about 35 tons CO 2 per m along strike, per m subducted. (As noted above, rocks composed mainly of calcite and/or dolomite in the subducting sedimentary section would be unlikely to contribute significant amounts of CO 2 to subduction fluids at temperatures less than 800°C.)…”

Section: Listvenite Formationmentioning

confidence: 99%

“…Figure 14. Dissolved carbon concentrations (a) and extent of carbon removal (b) in calculated fluids equilibrated with the compositions of Hawasina sediments in the MoD Mountain area (Supplementary Table1in de Obeso,Kelemen, et al, 2022), at a water/rock ratio of 5%, evolving along cold and hot subduction geotherms. Solid curves are calculated along the cold geotherm (Chile, Marianas) and dashed curves along the hot geotherm (Mexico, Cascades) fromSyracuse et al (2010).…”

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confidence: 99%

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Listvenite Formation During Mass Transfer into the Leading Edge of the Mantle Wedge: Initial Results from Oman Drilling Project Hole BT1B

et al. 2022

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This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic “stratigraphy” of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25–40 km by reaction with CO2‐rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400°–500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites—perhaps facilitated by fluid‐rock reaction—in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, mainly at a serpentinization front.

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Section: Source Of Fluid For Listvenite Formationmentioning

confidence: 94%