Carbonatite Metasomatism of the Oceanic Upper Mantle: Evidence from Clinopyroxenes and Glasses in Ultramafic Xenoliths of Grande Comore, Indian Ocean

Coltorti, Massimo; Bonadiman, Costanza; Hinton, R. W.; Siena, Franca; Upton, B. G. J.

doi:10.1093/petroj/40.1.133

Cited by 387 publications

(130 citation statements)

References 81 publications

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“…Analyses of mantle xenoliths brought to the surface by such magmas have yielded a range of fO 2 which have been compiled by Foley (2012): the oceanic and continental lithosphere xenoliths equilibrated at FMQ-0.7/-1, very similar to the riftinfluenced mantle (FMQ-0.4); xenoliths from within plate oceanic settings are significantly more oxidized (FMQ+0.6) which, along with the rare findings of high fO 2 conditions in OIB basalts (see above), hint at more oxidized source regions (but see Rhodes and Vollinger, 2005). This slightly more oxidized nature of the intraplate mantle can be related to metasomatic events (Woodland et al, 1996;McCammon et al, 2001;Coltorti et al, 1999;Creighton et al, 2009), which involve infiltration-reaction of carbon dioxide and water-rich low degree melts prior to basalt production. The involvement of such low degree melts in the source regions of MORBs has been also suggested (Wallace and Green, 1988;Gaillard et al, 2008;Dasgupta et al, 2013), including for the formation of the enriched MORBs (E-MORBs)…”

Section: Magmatic Production From Up-welling Mantle Regionsmentioning

confidence: 90%

The redox geodynamics linking basalts and their mantle sources through space and time

et al. 2015

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International audienceThe Earth's mantle redox state regulates the fate and transfer of metals by magmatism, buffers the igneous inputs of volcanic gases in the atmosphere and controls the depth of mantle melting. It therefore strongly affects ore forming processes, biogeochemical cycles and deep geodynamic processes. This paper reviews the current knowledge on the redox state of the upper mantle and of magmas produced by mantle melting. The geochemical processes likely to control and modify it through space and time are discussed.We analyze the link between the redox state of magma and that of their mantle source and we conclude that melts produced in the mantle may well all equilibrate in a narrow range of oxidation state, where the speciation of sulfur in basalts shifts from sulfide to sulfate, that is, FMQ+1 ± 1 (1 log unit below and above the oxygen fugacity buffered by the assemblage fayalite–magnetite–quartz). Subsequently, degassing and partial crystallization of melts can affect their redox states, producing most of the range of redox states observed on magmas reaching Earth's surface. The asthenosphere sourcing basaltic magmas may therefore be more oxidized than the FMQ−1 value generally assumed.We also discuss redox transfers from the mantle to the atmosphere via volcanic degassing and the backward fluxes via subduction processes of the hydrothermalized oceanic lithosphere. Arc-magmas are oxidized (up to FMQ+4) but it is unclear when this feature is acquired since strongly oxidized primary arc-basalts have yet to be found. The oxidizing event may be the assimilation of slab-derived SO3-rich fluids by primary basalt generated by decompression melting in the mantle-wedge.Overall, subduction must result in a transfer of oxygen from the Earth's surface down to the mantle. This must imply that subduction and its initiation can hardly be the trigger of the great oxidation event at the end of the Archaean. In contrast, the cooling of the Earth's interior through time must have impacted on the redox state of basalts, by decreasing the depth of mantle melting. According to the long-established vertical stratification of the Earth's mantle, ancient primary magmas are therefore likely to have been more reduced (i.e. < FMQ−3) than present-day ones. However, geochemical observations on ancient basalts suggest a constant oxidation state since the early Archaean.We conclude that large uncertainties in the calibration of mineralogical oxygen barometer probably explains why we have difficulties in identifying (i) ancient primary basalts being more reduced than recent ones and (ii) primary basalts from subduction zones being as oxidized as arc-lavas reaching the surface. Finally, the degree of mantle melting is certainly a key issue for the interpretation of the mantle oxidation state. Extremely oxidized melts, enriched in C–H–S volatile species, produced by very low degrees of mantle melting may be indicative of an Earth's mantle more oxidized than usually considered

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Section: Magmatic Production From Up-welling Mantle Regionsmentioning

confidence: 90%

The redox geodynamics linking basalts and their mantle sources through space and time

et al. 2015

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“…8) and are comparatively poor in HFSE. The major and trace element compositions of such clinopyroxenes closely resemble those of clinopyroxenes resulting from carbonatitic metasomatism (Hauri et al 1993;Coltorti et al 1999;Delpech et al 2004;Yaxley et al 1991Yaxley et al , 1998. Metasomatism by a carbonatitic melt or fluid should produce extensive reaction zones around the primary orthopyroxene in harzburgites, because orthopyroxene is unstable in the presence of carbonatitic melt at low pressures and will form secondary clinopyroxene, olivine and Cr-rich spinel associated with release of CO 2 (Wyllie & Huang 1976;Yaxley et al 1991Yaxley et al , 1998Dalton & Wood 1993;Coltorti et al 1999;Laurora et al 2001;Dawson 2002).…”

Section: Metasomatic Historymentioning

confidence: 94%

“…Smallfilled circles on curves are 1% increments of melting. between distinctive mineral parageneses and the occurrence of minerals in mantle xenoliths such as amphibole, phlogopite or plagioclase, in association with major and trace element enrichments, are indicative of metasomatic processes (O'Reilly & Griffin 1988;Fabriès et al 1989Fabriès et al , 1991Ionov et al 1994;Wulff-Pedersen et al 1996;Coltorti et al 1999;Grégoire et al 2000;Frezzotti et al 2002;Delpech et al 2004;Moine et al 2004).…”

Section: Metasomatic Historymentioning

confidence: 99%

“…Many recent petrological and geochemical studies on mantle metasomatism have focused on the major and trace element compositions of upper mantle xenoliths to decipher the nature of percolating melts or fluids (O'Reilly & Griffin 1988;Hauri et al 1993;Ionov et al 1994;Wulff-Pedersen et al 1996;Coltorti et al 1999;Grégoire et al 2000;Moine et al 2001Moine et al , 2004Frezzotti et al 2002;Delpech et al 2004). These studies have described a wide range of melt or fluid compositions as metasomatic media ranging from H 2 O-rich to CO 2 -rich melts and basaltic to carbonatitic melts occurring in oceanic and continental settings.…”

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confidence: 99%

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Petrological and geochemical constraints on the composition of the lithospheric mantle beneath the Syrian rift, northern part of the Arabian plate

Ismail

Delpech

Cottin

et al. 2007

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“…The latter consist of spongy clinopyroxene, and reaction rims/patches around orthopyroxenes and spinel with 'secondary' microcrysts of olivine, clinopyroxene, feldspar, and rarely phlogopite, apatite and carbonate, as well as interstitial glassy blebs. These reaction textures, recorded in different xenolith suites from various localities of Calatrava (Humphreys et al 2008a;Villaseca et al 2010), do not reflect interaction with the host basalts and were plausibly formed at mantle depths before FE-LHERZOLITE XENOLITHS FROM CALATRAVA the exhumation of the xenoliths (Siena et al 1991;Coltorti et al 1999Coltorti et al , 2000Beccaluva et al 2001bBeccaluva et al , 2008Delpech et al 2004;Bonadiman et al 2005).…”

Section: Petrography and Mineral Chemistry Of Lherzolite Xenoliths Frmentioning

confidence: 98%

Mantle metasomatism by melts of HIMU piclogite components: new insights from Fe-lherzolite xenoliths (Calatrava Volcanic District, central Spain)

Bianchini

Beccaluva

Bonadiman

et al. 2010

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Mantle xenoliths from the Calatrava Volcanic District (CLV), central Spain, are characterized by a wide compositional range that includes lherzolites (prevalent), as well as minor amounts of wehrlite, olivine (ol)-websterite and rare dunites. They generally have a bulkrock Mg# of less than 89, lower than any primordial mantle estimates. Intra-suite variations in modal proportions are inconsistent with those predicted by melting models irrespective of the starting composition; mineral and bulk-rock variation diagrams show inconsistencies between the CLV compositions (anomalously enriched in Fe-Ti) and those predicted from the partial melting of primordial mantle material. Processes other than pure melt extraction are confirmed by the whole-rock REE (rare earth element) budget, typically characterized by LREE enrichments, with La N /Yb N (up to 6.7), probably related to pervasive metasomatism. CLV mantle clinopyroxenes (cpx) generally display fractionated REE patterns with upwards-convex shapes, characterized by low HREE (Tm-Lu) concentrations (typically ,6Â chondrite) and enrichments in middle-light REE (MREE-LREE) (Nd N /Yb N up to 7, La N /Yb N up to 5). These 'enriched' cpx compositions either result from re-equilibration of primary mantle cpx with an incoming melt, or represent cpx crystallization directly from the metasomatic agent. The latter was plausibly generated at greater depths in the presence of residual garnet (from peridotite or eclogite starting materials). Separated cpx have homogeneous 87 Sr/ 86 Sr compositions between 0.7031 and 0.7032; 143 Nd/ 144 Nd ranges from 0.51288 to 0.51295 (1Nd 4.74-6.07) and 176 Hf/ 177 Hf is in the range 0.28302-0.28265 (1Hf 23.6 to 9.0). Unlike mantle xenoliths and alpine-type peridotites from other Iberian occurrences, which range in composition from the depleted mantle (DM) to the enriched mantle (EM), the CLV mantle cpx approach the composition of the HIMU mantle end member, the genesis of which is generally interpreted as the result of long-term recycling of oceanic basalts/gabbros (or their eclogitic equivalent) via ancient subduction. A model is proposed for the mantle evolution under central Iberia, where sublithospheric convective instabilities -possibly triggered by the neighbouring subduction along the Betic collisional belt -could have remobilized deep domains from the mantle 'transition zone' (410-660 km), which may include relicts of older subducted slabs. Within these remobilized domains, characterized by the coexistence of peridotite and eclogite and referred to as a 'piclogite' association, the eclogites melt preferentially generating Fe-Ti rich melts characterized by a HIMU isotopic signature that infiltrates and metasomatizes the shallower lithospheric mantle.

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Carbonatite Metasomatism of the Oceanic Upper Mantle: Evidence from Clinopyroxenes and Glasses in Ultramafic Xenoliths of Grande Comore, Indian Ocean

Cited by 387 publications

References 81 publications

The redox geodynamics linking basalts and their mantle sources through space and time

The redox geodynamics linking basalts and their mantle sources through space and time

Petrological and geochemical constraints on the composition of the lithospheric mantle beneath the Syrian rift, northern part of the Arabian plate

Mantle metasomatism by melts of HIMU piclogite components: new insights from Fe-lherzolite xenoliths (Calatrava Volcanic District, central Spain)

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