Carbon enrichment processes in the oceanic upper mantle preserved in peridotites from Sal Island (Cape Verde)

Abstract

This study investigates the petrological and metasomatic processes that lead to carbon enrichment in peridotites from Sal Island, Cape Verde. Geochemical and mineralogical analyses reveal a heterogeneous lithospheric mantle, consisting of harzburgites showing ultrarefractory compositions indicative of 20%-40% melting degrees, as well as fertile spinel lherzolites. Evidence of metasomatism is demonstrated by the formation of reaction coronae around dissolving orthopyroxene, consisting of olivine, clinopyroxene, spinel, and interstitial phonolitic glass, together with trachytic/phonolitic glass + carbonate (calcite, aragonite, and dolomite) microveins associated with CO₂ fluid-rich melt inclusions (Type I and II) cutting through olivine and orthopyroxene. The widely differing proportions of silicate and carbonate components in inclusions likely reflect heterogeneous trapping of melt/fluid and degassing CO₂. Thermobarometric data indicate equilibration temperatures from 950 to 1060 °C in harzburgites and up to 1200 °C for reaction coronas in harzburgites and lherzolites, with pressures reaching the aragonite stability field ( ∼ 2.2-3.5 GPa, or 66-106 km depth). These observations indicate the infiltration at the base of the lithosphere of a silicate-carbonate melt enriched in alkalies, Al, and volatiles (Cl, S, F, N, P). In microveins, the silicate glass composition (e.g., K and Ti content) is consistent with experimental partial melts derived from carbonated sediments with a minor addition of a carbonated eclogite. Enrichments in major and trace elements in clinopyroxene in harzburgites and lherzolites suggest at least two significant metasomatic events involving alkali-rich silicate-carbonate melts at the base of the lithosphere, and CO₂-rich fluid, alkali-rich silicate melts in the deep lithosphere, close to pressure conditions of the carbonate ledge. The introduction of recycled carbon into the upper mantle beneath the Cape Verde archipelago likely occurred during the multiple subduction events that affected the region in the half a billion years leading to the Pangea assembly. Major mobilisation of crustal components, generation of carbonate-rich melts, and subsequent lithospheric metasomatism were triggered by the Oligocene thermal perturbation associated with the Cape Verde mantle plume.

Keywords

Carbon cycle / Ocean Islands / Lithospheric mantle / Mantle metasomatism / Silicate-carbonate metasomatic melt

CRediT authorship contribution statement

Andrea Maffeis: Writing - review & editing, Writing - original draft, Visualization, Methodology, Investigation, Formal analysis, Data curation. Maria Luce Frezzotti: Writing - review & editing, Writing - original draft, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization. Rosario Esposito: Writing - review & editing, Methodology, Investigation. Marco G. Malusà: Writing - review & editing, Validation. Alessandro Aiuppa: Writing - review & editing, Resources. Andrea Luca Rizzo: Writing - review & editing, Resources. Simona Ferrando: Writing - review & editing, Validation, Supervision, Investigation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank Andrea Risplendente and Gianluca Sessa for their support during EPMA and LA-ICP-MS analyses. This work was supported by the Italian Ministry of University and Research (PRIN 2022, project no. 2022HA8XCS) to M.L.F.. Abigail Barker and Joao Mata are kindly thanked for their insightful comments that helped improve the manuscript, as well as the editorial handling of Associate Editor Kristoffer Szilas.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.gsf.2025.102179.

References

[1] Aiuppa, A., Casetta, F., Coltorti, M., Stagno, V., Tamburello, G., 2021. Carbon concentration increases with depth of melting in Earth’s upper mantle. Nat. Geosci. 14 (9), 697-703.

[2] Amsellem, E., Moynier, F., Bertrand, H., Bouyon, A., Mata, J., Tappe, S., Day, J.M., 2020. Calcium isotopic evidence for the mantle sources of carbonatites. Sci. Adv. 6 (23), eaba3269.

[3] Anderson, D., L., 2005. Scoring hotspots:The Plume and Plate Paradigms. In: Foulger G. R., Eds.), Natland J. H., Presnall D. C., D. L. Anderson (Plates, Plumes, and Paradigms. Geological Society of America 388, pp.31-54.

[4] Arai, S., 1994. Characterization of spinel peridotites by olivine-spinel compositional relationships: review and interpretation. Chem. Geol. 113 (3-4), 191-204.

[5] Aulbach, S., Lin, A.B., Weiss, Y., Yaxley, G.M., 2020. Wehrlites from continental mantle monitor the passage and degassing of carbonated melts. Geochem. Perspect. Lett. 15, 30-34.

[6] Barker, A.K., Holm, P.M., Peate, D.W., Baker, J.A., 2010. A 5 million year record of compositional variations in mantle sources to magmatism on Santiago, southern Cape Verde archipelago. Contrib. Mineral. Petrol. 160, 133-154.

[7] Barker, A.K., Holm, P.M., Troll, V.R., 2014. The role of eclogite in the mantle heterogeneity at Cape Verde. Contribut. Mineral. Petrol. 168, 1-15.

[8] Barker, A.K., Rydeblad, E.M., Silva, S.M., 2021. Magma storage at ocean islands:Insights from Cape Verde. In: Masotta M., Beier C., Mollo S. (Eds.), Crustal Magmatic System Evolution: Anatomy, Architecture, and Physico-Chemical Processes. American Geophysical Union, pp. 45-78.

[9] Barker, A.K., Magnusson, E., Troll, V.R., Harris, C., Mattsson, H.B., Holm, P.M., Perez-Torrado, F.J., Carracedo, J.C., Deegan, F.M., 2023. Disequilibrium in historic volcanic rocks from Fogo, Cape Verde traces carbonatite metasomatism of recycled ocean crust. Lithos 456, 107328.

[10] Barnes, J.D., Manning, C.E., Scambelluri, M., Selverstone, J., 2018. The Behavior of Halogens During Subduction-Zone Processes. In: Harlov D., Aranovich L. (Eds.),The Role of Halogens in Terrestrial and Extraterrestrial Geochemical Processes. Springer Geochemistry, Springer, Cham, pp. 545-590.

[11] Begg, G.C., Griffin, W.L., Natapov, L.M., O’Reilly, S.Y., Grand, S.P., O’Neill, C.J., Hronsky, J.M.A., Poudjom Djomani, Y., Swain, C.J., Deen, T., Bowden, P., 2009. The lithospheric architecture of Africa: Seismic tomography, mantle petrology, and tectonic evolution. Geosphere 5 (1), 23-50.

[12] Berkesi, M., Myovela, J.L., Yaxley, G.M., Guzmics, T., 2023. Carbonatite formation in continental settings via high pressure-high temperature liquid immiscibility. Geochim. Cosmochim. Acta 349, 41-54.

[13] Bernstein, S., Hanghøj, K., Kelemen, P.B., Brooks, C.K., 2006. Ultra-depleted, shallow cratonic mantle beneath West Greenland: dunitic xenoliths from Ubekendt Ejland. Contribut. Mineral. Petrol. 152, 335-347.

[14] Boyet, M., Doucelance, R., Israel, C., Bonnand, P., Auclair, D., Suchorski, K., Bosq, C., 2019. New constraints on the origin of the EM-1 component revealed by the measurement of the La-Ce isotope systematics in Gough Island lavas. Geochem. Geophys. Geosyst. 20, 2484-2498.

[15] Bonadiman, C., Beccaluva, L., Coltorti, M., Siena, F., 2005. Kimberlite-like metasomatism and ‘‘garnet signature” in spinel-peridotite xenoliths from Sal, Cape Verde Archipelago: relics of a subcontinental mantle domain within the Atlantic oceanic lithosphere? J. Petrol. 46 (12), 2465-2493.

[16] Bonadiman, C., Coltorti, M., Beccaluva, L., Griffin, W.L., O’Reilly, S.Y., Siena, F., 2011Lithosphere, 2011. Metasomatism versus host magma infiltration: A case study of Sal mantle xenoliths, Cape Verde Archipelago. In: Beccaluva L., Bianchini G., Wilson M. (Eds.). Geol. Soc. Am. 478, 283-305.

[17] Boyd, F.R., 1989. Compositional distinction between oceanic and cratonic lithosphere. Earth Planet. Sci. Lett. 96 (1-2), 15-26.

[18] Brey, G.P., Köhler, T., 1990. Geothermobarometry in four-phase lherzolites II. New thermobarometers, and practical assessment of existing thermobarometers. J. Petrol. 31 (6), 1353-1378.

[19] Carvalho, J., Bonadio, R., Silveira, G., Lebedev, S., Mata, J., Arroucau, P., Meier, T., Celli, N.L., 2019. Evidence for high temperature in the upper mantle beneath Cape Verde archipelago from Rayleigh-wave phase-velocity measurements. Tectonophysics 770, 228225.

[20] Carvalho, J., Silveira, G., Kiselev, S., Custódio, S., Ramalho, R.S., Stutzmann, E., Schimmel, M., 2022. Crustal and uppermost mantle structure of Cape Verde from ambient noise tomography. Geophys. J. Int. 231 (2), 1421-1433.

[21] Castillo, P.R., 2015. The recycling of marine carbonates and sources of HIMU and FOZO ocean island basalts. Lithos 216, 254-263.

[22] Cazenave, A., Souriau, A., Dominh, K., 1988. Global coupling of Earth surface topography with hotspots, geoid and mantle heterogeneities. Nature 340 (6228), 54-57.

[23] Chauvel, C., Hofmann, A.W., Vidal, P., 1992. HIMU-EM: the French Polynesian connection. Earth Planet. Sci. Lett. 110 (1-4), 99-119.

[24] Coltorti, M., Bonadiman, C., Hinton, R.W., Siena, F., Upton, B.G.J., 1999. Carbonatite metasomatism of the oceanic upper mantle: evidence from clinopyroxenes and glasses in ultramafic xenoliths of Grande Comore, Indian Ocean. J. Petrol. 40 (1), 133-165.

[25] Coltorti, M., Bonadiman, C., O’Reilly, S.Y., Griffin, W.L., Pearson, N.J., 2010. Buoyant ancient continental mantle embedded in oceanic lithosphere ( Sal Island, Cape Verde Archipelago). Lithos 120 (1-2), 223-233.

[26] Connolly, J.A.D., 2009. The geodynamic equation of state: what and how. Geochem. Geophys. Geosyst. 10 (10), Q10014.

[27] Courtillot, V., Davaille, A., Besse, J., Stock, J., 2003. Three distinct types of hotspots in the Earth’s mantle. Earth Planet. Sci. Lett. 205 (3-4), 295-308.

[28] Dalton, J.A., Presnall, D.C., 1998. Carbonatitic melts along the solidus of model lherzolite in the system CaO-MgO-Al₂O₃-SiO₂-CO₂ from 3 to 7 GPa. Contribut. Mineral. Petrol. 131, 123-135.

[29] Dasgupta, R., Hirschmann, M.M., 2010. The deep carbon cycle and melting in Earth’s interior. Earth Planet. Sci. Lett. 298 (1-2), 1-13.

[30] Dasgupta, R., Aubaud, C., 2025. Major volatiles in the Earth’s mantle beneath mid-ocean ridges and intraplate ocean islands. In: Anbar A., Weis D. (Eds.), Treatise on Geochemistry (3rd Edition). Elsevier, pp. 381-423.

[31] Dasgupta, R., Hirschmann, M.M., Stalker, K., 2006. Immiscible transition from carbonate-rich to silicate-rich melts in the 3 GPa melting interval of eclogite +CO₂ and genesis of silica-undersaturated ocean island lavas. J. Petrol. 47 (4), 647-671.

[32] Dasgupta, R., Hirschmann, M.M., Smith, N.D., 2007. Partial melting experiments of peridotite+CO₂ at 3 GPa and genesis of alkalic ocean island basalts. J. Petrol. 48 (11), 2093-2124.

[33] Dasgupta, R., Mallik, A., Tsuno, K., Withers, A.C., Hirth, G., Hirschmann, M.M., 2013. Carbon-dioxide-rich silicate melt in the Earth’s upper mantle. Nature 493 (7431), 211-215.

[34] Dautria, J.M., Dupuy, C., Takherist, D., Dostal, J., 1992. Carbonate metasomatism in the lithospheric mantle: peridotitic xenoliths from a melilititic district of the Sahara basin. Contribut. Mineral. Petrol. 111, 37-52.

[35] de Ignacio, C., Muñoz, M., Sagredo, J., 2012. Carbonatites and associated nephelinites from São Vicente, Cape Verde Islands. Mineral. Magaz. 76 (2), 311-355.

[36] DeVitre, C.L., Gazel, E., Ramalho, R.S., Venugopal, S., Steele-MacInnis, M., Hua, J., Allison, C.M., Moore, L.R., Carracedo, J.C., Monteleone, B., 2023. Oceanic intraplate explosive eruptions fed directly from the mantle. Proc. Nat. Acad. Sci. 120 (33), e 2302093120.

[37] Doucelance, R., Escrig, S., Moreira, M., Gariépy, C., Kurz, M.D., 2003. Pb-Sr-He isotope and trace element geochemistry of the Cape Verde Archipelago. Geochim. Cosmochim. Acta 67 (19), 3717-3733.

[38] Doucelance, R., Hammouda, T., Moreira, M., Martins, J.C., 2010. Geochemical constraints on depth of origin of oceanic carbonatites: The Cape Verde case. Geochim. Cosmochim. Acta 74 (24), 7261-7282.

[39] Ducea, M.N., Currie, C.A., Balica, C., Lazar, I., Mallik, A., Petrescu, L., Vlasceanu, M., 2022. Diapirism of carbonate platforms subducted into the upper mantle. Geology 50 (8), 929-933.

[40] Eggler, D.H., 1978a. Stability of dolomite in a hydrous mantle, with implications for the mantle solidus. Geology 6 (7), 397-400.

[41] Eggler, D.H., 1978b. The effect of CO₂ upon partial melting of peridotite in the system Na₂O-CaO-Al₂O₃-MgO-SiO₂-CO₂ to 35 kb, with an analysis of melting in a peridotite-H2O-CO2 system. Am. J. Sci. 278 (3), 305-343.

[42] Escrig, S., Doucelance, R., Moreira, M., Allègre, C.J., 2005. Os isotope systematics in Fogo Island: evidence for lower continental crust fragments under the Cape Verde Southern Islands. Chem. Geol. 219 (1-4), 93-113.

[43] Esposito, R., 2021. Chapter 7:A protocol and review of methods to select, analyze and interpret melt inclusions to determine preeruptive volatile contents of magmas. In: Lecumberri-Sanchez P., Steele-MacInnis, M., Kontak, D., (Eds), Fluid and Melt Inclusions: Applications to Geologic Processes. Mineralogical Association of Canada, Topics in Mineral Sciences, Volume 49, pp. 163-194.

[44] Farsang, S., Louvel, M., Zhao, C., Mezouar, M., Rosa, A.D., Widmer, R.N., Feng, X., Liu, J., Redfern, S.A., 2021. Deep carbon cycle constrained by carbonate solubility. Nat. Commun. 12 (1), 4311.

[45] Foley, S.F., Fischer, T.P., 2017. An essential role for continental rifts and lithosphere in the deep carbon cycle. Nat. Geosci. 10 (12), 897-902.

[46] Frezzotti, M.L., Ferrando, S., 2018. The role of halogens in the lithospheric mantle. In: Harlov D., Aranovich L. (Eds.),The Role of Halogens in Terrestrial and Extraterrestrial Geochemical Processes. Springer Geochemistry, Springer, Chambridge, pp. 805-845.

[47] Frezzotti, M.L., Touret, J.L., 2014. CO₂, carbonate-rich melts, and brines in the mantle. Geosci. Front. 5 (5), 697-710.

[48] Frezzotti, M.L., 2001. Silicate-melt inclusions in magmatic rocks: applications to petrology. Lithos 55 (1-4), 273-299.

[49] Frezzotti, M.L., Andersen, T., Neumann, E.R., Simonsen, S.L., 2002a. Carbonatite melt-CO₂ fluid inclusions in mantle xenoliths from Tenerife, Canary Islands: a story of trapping, immiscibility and fluid-rock interaction in the upper mantle. Lithos 64 (3-4), 77-96.

[50] Frezzotti, M.L., Touret, J.L., Neumann, E.R., 2002b. Ephemeral carbonate melts in the upper mantle: carbonate-silicate immiscibility in microveins and inclusions within spinel peridotite xenoliths, La Gomera, Canary Islands. Eur. J. Mineral. 14 (5), 891-904.

[51] Frezzotti, M.L., Tecce, F., Casagli, A., 2012. Raman spectroscopy for fluid inclusion analysis. J. Geochem. Explor. 112, 1-20.

[52] Gaillard, F., Malki, M., Iacono-Marziano, G., Pichavant, M., Scaillet, B., 2008. Carbonatite melts and electrical conductivity in the asthenosphere. Science 322 (5906), 1363-1365.

[53] Gerbode, C., Dasgupta, R., 2010. Carbonate-fluxed melting of MORB-like pyroxenite at 2.9 GPa and genesis of HIMU ocean island basalts. J. Petrol. 51 (10), 2067-2088.

[54] Gerlach, D.C., Cliff, R.A., Davies, G.R., Norry, M., Hodgson, N., 1988. Magma sources of the Cape Verdes archipelago: isotopic and trace element constraints. Geochim. Cosmochim. Acta 52 (12), 2979-2992.

[55] Gibson, S.A., McKenzie, D., 2023. On the role of Earth’s lithospheric mantle in global volatile cycles. Earth Planet. Sci. Lett. 602, 117946.

[56] Grassi, D., Schmidt, M.W., 2011. The melting of carbonated pelites from 70 to 700 km depth. J. Petrol. 52 (4), 765-789.

[57] Green, D.H., Wallace, M.E., 1988. Mantle metasomatism by ephemeral carbonatite melts. Nature 336 (6198), 459-462.

[58] Grégoire, M., Moine, B.N., O’Reilly, S.Y., Cottin, J.Y., Giret, A., 2000. Trace element residence and partitioning in mantle xenoliths metasomatized by highly alkaline, silicate-and carbonate-rich melts (Kerguelen Islands, Indian Ocean). J. Petrol. 41 (4), 477-509.

[59] Hammouda, T., Laporte, D., 2000. Ultrafast mantle impregnation by carbonatite melts. Geology 28 (3), 283-285.

[60] Hammouda, T., Keshav, S., 2015. Melting in the mantle in the presence of carbon: Review of experiments and discussion on the origin of carbonatites. Chem. Geol. 418, 171-188.

[61] Harris, B.J.R., De Hoog, J.C.M., Halama, R., 2022. The behaviour of nitrogen during subduction of oceanic crust: insights from in situ SIMS analyses of high-pressure rocks. Geochim. Cosmochim. Acta 321, 16-34.

[62] Hart, S.R., 1988. Heterogeneous mantle domains: signatures, genesis and mixing chronologies. Earth Planet. Sci. Lett. 90 (3), 273-296.

[63] Hart, S.R., Hauri, E.H., Oschmann, L.A., Whitehead, J.A., 1992. Mantle plumes and entrainment—Isotopic evidence. Science 256, 517-520.

[64] Hoernle, K., Tilton, G., Le Bas, M.J., Duggen, S., Garbe-Schönberg, D., 2002. Geochemistry of oceanic carbonatites compared with continental carbonatites: mantle recycling of oceanic crustal carbonate. Contribut. Mineral. Petrol. 142 (5), 520-542.

[65] Holm, P.M., Wilson, J.R., Christensen, B.P., Hansen, L., Hansen, S.L., Hein, K.M., Mortensen, A.K., Pedersen, R., Plesner, S., Runge, M.K., 2006. Sampling the Cape Verde mantle plume: evolution of melt compositions on Santo Antão, Cape Verde Islands. J. Petrol. 47 (1), 145-189.

[66] Holm, P.M., Grandvuinet, T., Friis, J., Wilson, J.R., Barker, A.K., Plesner, S., 2008. An ⁴⁰Ar-³⁹Ar study of the Cape Verde hot spot: Temporal evolution in a semistationary plate environment. J. Geophys. Res. Solid Earth 113, B08201.

[67] Ionov, D.A., O’Reilly, S.Y., Genshaft, Y.S., Kopylova, M.G., 1996. Carbonate-bearing mantle peridotite xenoliths from Spitsbergen: phase relationships, mineral compositions and trace-element residence. Contributi. Mineral. Petrol. 125 (4), 375-392.

[68] Ionov, D.A., Bodinier, J.L., Mukasa, S.B., Zanetti, A., 2002. Mechanisms and sources of mantle metasomatism: major and trace element compositions of peridotite xenoliths from Spitsbergen in the context of numerical modelling. J. Petrol. 43 (12), 2219-2259.

[69] Ionov, D.A., Hofmann, A.W., Merlet, C., Gurenko, A.A., Hellebrand, E., Montagnac, G., Gillet, P., Prikhodko, V.S., 2006. Discovery of whitlockite in mantle xenoliths: Inferences for water-and halogen-poor fluids and trace element residence in the terrestrial upper mantle. Earth Planet. Sci. Lett. 244 (1-2), 201-217.

[70] Jørgensen, J.Ø., Holm, P.M., 2002. Temporal variation and carbonatite contamination in primitive ocean island volcanics from São Vicente, Cape Verde Islands. Chem. Geol. 192 (3-4), 249-267.

[71] Kamenetsky, V.S., Yaxley, G.M., 2015. Carbonate-silicate liquid immiscibility in the mantle propels kimberlite magma ascent. Geochim. Cosmochim. Acta 158, 48-56.

[72] Kelemen, P.B., Manning, C.E., 2015. Re-evaluating carbon fluxes in subduction zones: What goes down, mostly comes up. Proc. Nat. Acad. Sci. 112 (30), E3997-E4006.

[73] Kiseeva, E.S., Yaxley, G.M., Hermann, J., Litasov, K.D., Rosenthal, A., Kamenetsky, V.S., 2012. An experimental study of carbonated eclogite at 3.5-5.5 GPa—implications for silicate and carbonate metasomatism in the cratonic mantle. J. Petrol. 53 (4), 727-759.

[74] Kogarko, L.N., Henderson, C.M.B., Pacheco, H., 1995. Primary Ca-rich carbonatite magma and carbonate-silicate-sulphide liquid immiscibility in the upper mantle. Contribut. Mineral. Petrol. 121 (3), 267-274.

[75] Köhler, T.P., Brey, G., 1990. Calcium exchange between olivine and clinopyroxene calibrated as a geothermobarometer for natural peridotites from 2 to 60 kb with applications. Geochim. Cosmochim. Acta 54 (9), 2375-2388.

[76] Le Maitre, R.W., Streckeisen, A., Zanettin, B., Le Bas, M.J., Bonin, B., Bateman, P., 2002. Igneous Rocks: A Classification and Glossary of Terms:Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. Cambridge University Press, Cambridge, p. 236.

[77] Li, J.L., Schwarzenbach, E.M., John, T., Ague, J.J., Huang, F., Gao, J., Klemd, R., Whitehouse, M.J., Wang, X.S., 2020. Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective. Nat. Commun. 11 (1), 514.

[78] Litasov, K.D., Podgornykh, N.M., 2017. Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite. J. Raman Spectros. 48 (11), 1518-1527.

[79] Liu, X., Zhao, D., 2021. Seismic evidence for a plume-modified oceanic lithosphere-asthenosphere system beneath Cape Verde. Geophys. J. Int. 225 (2), 872-886.

[80] Lo Forte, F.M.L., Schiavi, F., Rose-Koga, E.F., Rotolo, S.G., Verdier-Paoletti, M., Aiuppa, A., Zanon, V., 2024a. High CO₂ in the mantle source of ocean island basanites. Geochim. Cosmochim. Acta 368, 93-111.

[81] Lo Forte, F.M.L., Boudoire, G., Frezzotti, M.L., Rotolo, S.G., Sandoval-Velasquez, A., Viveiros, F., Zanon, V., Aiuppa, A., Rizzo, A.L., 2024b. The helium and carbon isotopic signature of Ocean island basalts: Insights from Fogo volcano (Cape Verde archipelago). Earth Planet. Sci. Lett. 645, 118930.

[82] Lodge, A., Helffrich, G., 2006. Depleted swell root beneath the Cape Verde Islands. Geology 34 (6), 449-452.

[83] Lodhia, B.H., Roberts, G.G., Fraser, A.J., Fishwick, S., Goes, S., Jarvis, J., 2018. Continental margin subsidence from shallow mantle convection: Example from West Africa. Earth Planet. Sci. Lett. 481, 350-361.

[84] Luth, R.W., Stachel, T., 2014. The buffering capacity of lithospheric mantle: implications for diamond formation. Contribut. Mineral. Petrol. 168, 1-12.

[85] Madeira, J., Mata, J., Mourão, C., Brum da Silveira, A., Martins, S., Ramalho, R., Hoffmann, D.L., 2010. Volcano-stratigraphic and structural evolution of Brava Island (Cape Verde) based on ⁴⁰Ar/³⁹Ar, U-Th and field constraints. J. Volcanol. Geotherm. Res. 196, 219-235.

[86] Maffeis, A., Ferrando, S., Connolly, J.A.D., Frezzotti, M.L., Castelli, D., 2023. Fluid redox fingerprint of the CaCO₃ + antigorite dehydration reaction in subducted metacarbonate sediments. Geosciences 13 (5), 130.

[87] Maffeis, A., Frezzotti, M.L., Connolly, J.A.D., Castelli, D., Ferrando, S., 2024. Sulfur disproportionation in deep COHS slab fluids drives mantle wedge oxidation. Sci. Adv. 10 (12), eadj2770.

[88] Malusà M.G., Frezzotti, M.L., Ferrando, S., Brandmayr, E., Romanelli, F., Panza, G.F., 2018. Active carbon sequestration in the Alpine mantle wedge and implications for long-term climate trends. Sci. Rep. 8 (1), 4740.

[89] Manning, C.E., Frezzotti, M.L., 2020. Subduction-zone fluids. Elements Int. Mag. Mineral. Geochem. Petrol. 16 (6), 395-400.

[90] Martins, S., Mata, J., Munhá J., Mendes, M.H., Maerschalk, C., Caldeira, R., Mattielli, N., 2010. Chemical and mineralogical evidence of the occurrence of mantle metasomatism by carbonate-rich melts in a n oceanic environment (Santiago Island, Cape Verde). Mineral. Petrol. 99, 43-65.

[91] Mata, J., Moreira, M., Doucelance, R., Ader, M., Silva, L.C., 2010. Noble gas and carbon isotopic signatures of Cape Verde oceanic carbonatites: implications for carbon provenance. Earth Planet. Sci. Lett. 291 (1-4), 70-83.

[92] McDonough, W.S., 1990. Constraints on the composition of the continental lithospheric mantle. Earth Planet. Sci. Lett. 101 (1), 1-18.

[93] McKenzie, D.A.N., O’nions, R. K, 1991. Partial melt distributions from inversion of rare earth element concentrations. J. Petrol. 32 (5), 1021-1091.

[94] Mendes, M.H., Caldeira, R., Silva, L., Munhá J., 2004. Petrology of spinel peridotite xenoliths from Santo Antao, Cape Verde Islands. Comunicações Geológicas 91, 99-116.

[95] Mercier, J.C., Nicolas, A., 1975. Textures and fabrics of upper-mantle peridotites as illustrated by xenoliths from basalts. J. Petrol. 16 (1), 454-487.

[96] Miller, W.G., Maclennan, J., Shorttle, O., Gaetani, G.A., Le Roux, V., Klein, F., 2019. Estimating the carbon content of the deep mantle with Icelandic melt inclusions. Earth Planet. Sci. Lett. 523, 115699.

[97] Mitchell, J.G., Le Bas, M.J., Zielonka, J., Furnes, H., 1983. On dating the magmatism of Maio, Cape Verde Islands. Earth Planet. Sci. Lett. 64, 61-76.

[98] Moine, B.N., Grégoire, M., O’Reilly, S.Y., Delpech, G., Sheppard, S.M.F., Lorand, J.P., Renac, C., Giret, A., Cottin, J.Y., 2004. Carbonatite melt in oceanic upper mantle beneath the Kerguelen Archipelago. Lithos 75 (1-2), 239-252.

[99] Mourão, C., Moreira, M., Mata, J., Raquin, A., Madeira, J., 2012a. Primary and secondary processes constraining the noble gas isotopic signatures of carbonatites and silicate rocks from Brava Island: evidence for a lower mantle origin of the Cape Verde plume. Contribut. Mineral. Petrol. 163, 995-1009.

[100] Mourão, C., Mata, J., Doucelance, R., Madeira, J., Millet, M.-A., Moreira, M., 2012b. Geochemical temporal evolution of Brava Island magmatism: constraints on the variability of Cape Verde mantle sources and on the carbonatite-silicate magma link. Chem. Geol. 334, 44-61.

[101] Neumann, E.R., Simon, N.S., 2009. Ultra-refractory mantle xenoliths from ocean islands: How do they compare to peridotites retrieved from oceanic sub-arc mantle? Lithos 107 (1-2), 1-16.

[102] Nishio, I., Morishita, T., Tamura, A., Itano, K., Takamizawa, S., Ichiyama, Y., Arai, S., Barrett, N., Zilas, K., 2023. Formation of ultra-depleted mantle peridotites and their relationship with boninitic melts: An example from the Kamuikotan Unit, Hokkaido, Japan. J. Geophys. Res. Solid Earth 128 (2), e2022JB 025066.

[103] Oliveira, B., Afonso, J.C., Tilhac, R., 2020. A disequilibrium reactive transport model for mantle magmatism. J. Petrol. 61 (9), egaa067.

[104] O’Reilly, S.Y., Zhang, M., Griffin, W.L., Begg, G., Hronsky, J., 2009. Ultradeep continental roots and their oceanic remnants: a solution to the geochemical ‘‘mantle reservoir” problem? Lithos 112, 1043-1054.

[105] Palme, H., O’Neill, H. S. T. C., 2014. 3.1 Cosmochemical estimates of mantle composition. In: Holland H.D., Turekian K.K. (Eds.),Treatise on Geochemistry ( 2nd Edition). Volume 3 The Mantle and Core. Elsevier, pp. 1-39.

[106] Pearson, D.G., Canil, D., Shirey, S.B., 2003. Mantle samples included in volcanic rocks: xenoliths and diamonds. Treatise Geochem. 2, 568.

[107] Plank, T., Manning, C.E., 2019. Subducting carbon. Nature 574 (7778), 343-352.

[108] Rudnick, R.L., McDonough, W.F., Chappell, B.W., 1993. Carbonatite metasomatism in the northern Tanzanian mantle: petrographic and geochemical characteristics. Earth Planet. Sci. Lett. 114 (4), 463-475.

[109] Ryabchikov, J.D., Ntaflos, T., Kurat, G., Kogarko, L.N., 1995. Glass-bearing xenoliths from Cape Verde: evidence for a hot rising mantle jet. Mineral. Petrol. 55, 217-237.

[110] Rychert, C.A., Shearer, P.M., 2009. A global view of the lithosphere-asthenosphere boundary. Science 324 (5926), 495-498.

[111] Scambelluri, M., Cannaò E., Gilio, M., 2019. The water and fluid-mobile element cycles during serpentinite subduction. A review. Eur. J. Mineral. 31 (3), 405-428.

[112] Schmerr, N., 2012. The Gutenberg discontinuity: Melt at the lithosphere-asthenosphere boundary. Science 335 (6075), 1480-1483.

[113] Scott, J.M., Liu, J., Pearson, D.G., Harris, G.A., Czertowicz, T.A., Woodland, S.J., Riches, A.J.V., Luth, R.W., 2019. Continent stabilisation by lateral accretion of subduction zone-processed depleted mantle residues; insights from Zealandia. Earth Planet. Sci. Lett. 507, 175-186.

[114] Sharygin, I.S., Litasov, K.D., Shatskiy, A., Safonov, O.G., Golovin, A.V., Ohtani, E., Pokhilenko, N.P., 2017. Experimental constraints on orthopyroxene dissolution in alkali-carbonate melts in the lithospheric mantle: Implications for kimberlite melt composition and magma ascent. Chem. Geol. 455, 44-56.

[115] Shaw, C.S., Heidelbach, F., Dingwell, D.B., 2006. The origin of reaction textures in mantle peridotite xenoliths from Sal Island, Cape Verde: the case for ‘‘metasomatism” by the host lava. Contribut. Mineral. Petrol. 151 (6), 681-697.

[116] Shaw, D.M., 2006. Trace Elements in Magmas:A Theoretical Treatment. Cambridge University Press, Cambridge, p. 243.

[117] Shcheka, S.S., Wiedenbeck, M., Frost, D.J., Keppler, H., 2006. Carbon solubility in mantle minerals. Earth Planet. Sci. Lett. 245 (3-4), 730-742.

[118] Shejwalkar, A., Coogan, L.A., 2013. Experimental calibration of the roles of temperature and composition in the Ca-in-olivine geothermometer at 0.1 MPa. Lithos 177, 54-60.

[119] Silva, L., Serralheiro, A., Macedo, J., Gomes, A., Torres, P., 1990. Carta Geológica de Cabo Verde, Ilha do Sal, na escala de 1/25 000 ( folhas 1-2). Instituto Investigação Científica Tropical-Instituto de Cooperação Económica, Lisboa (in Portuguese).

[120] Simon, N.S., Neumann, E.R., Bonadiman, C., Coltorti, M., Delpech, G., Grégoire, M., Widom, E., 2008. Ultra-refractory domains in the oceanic mantle lithosphere sampled as mantle xenoliths at ocean islands. J. Petrol. 49 (6), 1223-1251.

[121] Stagno, V., Frost, D.J., 2010. Carbon speciation in the asthenosphere: Experimental measurements of the redox conditions at which carbonate-bearing melts coexist with graphite or diamond in peridotite assemblages. Earth Planet. Sci. Lett. 300 (1-2), 72-84.

[122] Stagno, V., Ojwang, D.O., McCammon, C.A., Frost, D.J., 2013. The oxidation state of the mantle and the extraction of carbon from Earth’s interior. Nature 493 (7430), 84-88.

[123] Stone, R.S., Luth, R.W., 2016. Orthopyroxene survival in deep carbonatite melts: implications for kimberlites. Contribut. Mineral. Petrol. 171, 1-9.

[124] Stracke, A., Bizimis, M., Salters, V.J., 2003. Recycling oceanic crust: Quantitative constraints. Geochem. Geophys. Geosyst. 4 (3), 8003.

[125] Sun, S.S., 1982. Chemical composition and origin of the Earth’s primitive mantle. Geochim. Cosmochim. Acta 46 (2), 179-192.

[126] Sun, C., Dasgupta, R., 2023. Carbon budget of Earth’s deep mantle constrained by petrogenesis of silica-poor ocean island basalts. Earth Planet. Sci. Lett. 611, 118135.

[127] Takahashi, E., 1986. Origin of basaltic magmas—implications from peridotite melting experiments and an olivine fractionation model. Bull. Volcanol. Soc. Japan 30, S17-S40 (in Japanese with English abstract).

[128] Tamburello, G., Pondrelli, S., Chiodini, G., Rouwet, D., 2018. Global-scale control of extensional tectonics on CO₂ Earth degassing. Nat. Commun. 9 (1), 4608.

[129] Thomsen, T.B., Schmidt, M.W., 2008. Melting of carbonated pelites at 2.5-5.0 GPa, silicate-carbonatite liquid immiscibility, and potassium-carbon metasomatism of the mantle. Earth Planet. Sci. Lett. 267 (1-2), 17-31.

[130] Tomlinson, E.L., Holland, T.J., 2021. A thermodynamic model for the subsolidus evolution and melting of peridotite. J. Petrol. 62 (1), egab012.

[131] Torres, P.C., Silva, L.C., Serralheiro, A., Tassinari, C., Munhá J., 2002. Enquadramento geocronológico pelo método K/Ar das principais sequências vulcano-estratigráficas da Ilha do Sal - Cabo Verde. Garcia de Orta. Série de Geologia 18 (1-2), 9-13 (in Portuguese).

[132] Torres, P., Silva, L.D., Munhá J., Caldeira, R., Mata, J., Tassinari, C.C.G., 2010. Petrology and geochemistry of lavas from Sal Island: implications for the variability of the Cape Verde magmatism. Comun. Geol. 97, 35-61.

[133] Tsuno, K., Dasgupta, R., 2011. Melting phase relation of nominally anhydrous, carbonated pelitic-eclogite at 2.5-3.0 GPa and deep cycling of sedimentary carbon. Contribut. Mineral. Petrol. 161, 743-763.

[134] Uenver-Thiele, L., Woodland, A.B., Seitz, H.M., Downes, H., Altherr, R., 2017. Metasomatic processes revealed by trace element and redox signatures of the lithospheric mantle beneath the Massif Central, France. J. Petrol. 58 (3), 395-422.

[135] Villaseca, C., Orejana, D., Huertas, M.J., Ancochea, E., de Ignacio, C., Mata, J., Caldeira, R., García-Rodríguez, M., Moreno, J.A., Pérez-Sob, C., 2025. The old central igneous complexes of Sal, Boa Vista and Maio islands: Implications for 17 Ma of isotopic evolution of the Cape Verde archipelago. Lithos 498-499, 107975.

[136] Villeneuve, M., Gärtner, A., Mueller, P. A., Guillou, O., Linnemann, U., 2024. Colliding cratons:linking the Variscan orogeny in West Africa and North America. In: Nance R.D., Strachan R.A., Quesada C., Lin S. (Eds.),Supercontinents, Orogenesis and Magmatism. Geol. Soc. London Spe. Publ. 542, 359-377.

[137] Villeneuve, M., Marcaillou, B., 2013. Pre-Mesozoic origin and paleogeography of blocks in the Caribbean, South Appalachian and West African domains and their impact on the post ‘‘variscan” evolution. Bull. Societe Geol. France 184 (1-2), 5-20.

[138] Vinnik, L., Silveira, G., Kiselev, S., Farra, V., Weber, M., Stutzmann, E., 2012. Cape Verde hotspot from the upper crust to the top of the lower mantle. Earth Planet. Sci. Lett. 319, 259-268.

[139] Viti, C., Frezzotti, M.L., 2001. Transmission electron microscopy applied to fluid inclusion investigations. Lithos 55 (1-4), 125-138.

[140] Wilson, D.J., Peirce, C., Watts, A.B., Grevemeyer, I., Krabbenhöft, A., 2010. Uplift at lithospheric swells—I: seismic and gravity constraints on the crust and uppermost mantle structure of the Cape Verde mid-plate swell. Geophys. J. Int. 182 (2), 531-550.

[141] Winter, J.D., 2014. Principles of Igneous and Metamorphic Petrology, 2. UK Pearson Education, Harlow.

[142] Wojdyr, M., 2010. Fityk: a general-purpose peak fitting program. Appl. Crystallograp. 43 (5), 1126-1128.

[143] Wong, K., Mason, E., Brune, S., East, M., Edmonds, M., Zahirovic, S., 2019. Deep carbon cycling over the past 200 million years: a review of fluxes in different tectonic settings. Front. Earth Sci. 7, 263.

[144] Workman, R.K., Hart, S.R., 2004. Major and trace element composition of the depleted MORB mantle (DMM). Earth Planet. Sci. Lett. 231 (1-2), 53-72.

[145] Wu, S., Wörner, G., Jochum, K.P., Stoll, B., Simon, K., Kronz, A., 2019. The preparation and preliminary characterisation of three synthetic andesite reference glass materials (ARM-1, ARM-2, ARM-3) for in situ microanalysis. Geostandard. Geoanalyt. Res. 43 (4), 567-584.

[146] Yaxley, G.M., Crawford, A.J., Green, D.H., 1991. Evidence for carbonatite metasomatism in spinel peridotite xenoliths from western Victoria, Australia. Earth Planet. Sci. Lett. 107 (2), 305-317.

[147] Yaxley, G.M., Green, D.H., Kamenetsky, V., 1998. Carbonatite metasomatism in the southeastern Australian lithosphere. J. Petrol. 39 (11-12), 1917-1930.

[148] Yaxley, G.M., Anenburg, M., Tappe, S., Decree, S., Guzmics, T., 2022. Carbonatites: classification, sources, evolution, and emplacement. Ann. Rev. Earth Planet. Sci. 50 (1), 261-293.

[149] Zhao, S., Schettino, E., Merlini, M., Poli, S., 2019. The stability and melting of aragonite: An experimental and thermodynamic model for carbonated eclogites in the mantle. Lithos 324, 105-114.