The Oxidation State of Metasomatized Mantle Wedge: Insights from C-O-H-bearing Garnet Peridotite

Malaspina, Nadia; Poli, Stefano; Fumagalli, P.

doi:10.1093/petrology/egp040

Cited by 83 publications

(50 citation statements)

References 71 publications

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“…BDN03 and other natural samples from the mantle wedge that have been metasomatised by slab fluids display fO 2 values higher than the depleted mantle curve estimated here (Malaspina et al, 2009(Malaspina et al, , 2010 (Fig. 4).…”

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confidence: 62%

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Evidence of sub-arc mantle oxidation by sulphur and carbon

Rielli¹,

Tomkins²,

Nebel³

et al. 2017

Geochem. Persp. Let.

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The oxygen fugacity ( fO 2 ) of the Earth's mantle at subduction zones exerts a primary control on the genesis of mineral deposits in the overlying magmatic arcs and on speciation of volcanic gases emitted into the atmosphere. However, the processes governing mantle fO 2 such as the introduction of oxidised material by subduction are still unresolved. Here, we present evidence for the reduction of oxidised fluid-borne sulphur and carbon during alteration of depleted mantle by slab fluids at ultra-high pressure in the Bardane peridotite (Western Gneiss Region, Norway). Elevated ferric iron in metasomatic garnet, determined using synchrotron X-ray absorption near edge structure (XANES) spectroscopy, indicates that this process drove oxidation of the silicate assemblage. Our finding indicates that subduction oxidises the Earth's mantle by cycling of sulphur and carbon. LetterPlate tectonics drives recycling of surface material into the Earth's interior, introducing hydrated and oxidised oceanic lithosphere into the mantle at subduction zones (Wood et al., 1990;Evans, 2012). Fluids liberated during dehydration of subducted crust trigger partial melting of the overlying mantle leading to the formation of volcanic arcs, dominated by oxidised rocks (Ballhaus, 1993;Kelley and Cottrell, 2009). Correlation between oxidation of arc lavas and addition of slab material by aqueous fluids to their mantle source has been quantitatively established (Kelley and Cottrell, 2009; Brounce et al., 2014) fluids are somehow responsible for the observed oxidation. However, although calculations suggest that fluid-borne oxidised sulphur may be important (Evans and Tomkins, 2011), the process has not been resolved with physical evidence. Determination of redox processes associated with fluid-mantle interaction cannot be indisputably resolved by studying the product of the arc system (i.e. arc lavas); it is best approached by examining rocks from the deep portion of mantle wedge close to the slab-mantle interface that have been altered by slab fluids, which are preserved as orogenic peridotites.The Western Gneiss Region of Norway hosts several orogenic peridotite bodies that represent a portion of transition zone mantle that upwelled, melted (Stage M1) and accreted to cratonic lithosphere (Stage M2;Spengler et al., 2006). Subsequently, during the Caledonian orogeny, fluids derived from subducting slab locally promoted metasomatism (Stage M3), as recorded by the Bardane peridotite on Fjørtoft island (Brueckner et al., 2002;Van Roermund et al., 2002;Scambelluri et al., 2008). Other portions have not been infiltrated by slab fluids and preserve the original mantle assemblage (M1-M2), exemplified by the Ugelvik peridotite on the island of Otrøy (Brueckner et al., 2002;Spengler et al., 2006). Although there is debate on the origin of metasomatism at Bardane, the trace element and isotopic signature of the metasomatic assemblage are comparable to the effects of typical subduction zone fluids sensu lato (cf. Brueckner et al., 2002;Scambelluri et...

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confidence: 62%

“…fO 2 for UGL01 is represented by green dots and the green bold line represents the variation range. BDN03 fO 2 is reported in yellow while in orange is the fO 2 of metasomatised orogenic peridotites from Malaspina et al (2009) and Malaspina et al (2010). Literature data have been recalculated using the Miller et al (2016) oxybarometer.…”

mentioning

confidence: 99%

Evidence of sub-arc mantle oxidation by sulphur and carbon

Rielli¹,

Tomkins²,

Nebel³

et al. 2017

Geochem. Persp. Let.

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“…These include HP and UHP ultramafic bodies dominated by garnet peridotites. These rocks have attracted much attention recently as a potential source of information on relatively deep mantle processes such as accretion of lithospheric roots, transport, reaction and storage of fluids/melts in suprasubduction mantle wedges, and subduction/exhumation mechanisms Brueckner and Medaris, 2000;Brueckner et al, 2004;Ernst and Liou, 2008;Green et al, 1997;Green et al, 2010;Katayama et al, 2003Katayama et al, , 2005Kotkova et al, 2011;Liou et al, 2002aLiou et al, ,b, 2007Liou et al, , 2009Liu et al, 2007Liu et al, , 2009MacKenzie et al, 2005;Malaspina et al, 2009Malaspina et al, , 2010Paquin et al, 2004;Sapienza et al, 2009;Scambelluri et al, 2006Scambelluri et al, , 2008Scambelluri et al, , 2010Song et al, 2004;van Roermund et al, 2001;Yoshida et al, 2004;Zhang and Liou, 1998;Zhang et al, 2005;Zhang et al, 2003Zhang et al, , 2004aZheng et al, 2003Zheng et al, , 2011. Numerous studies were published, mostly in the last decade, providing data on the petrology, geochronology, and geochemistry of HP/UHP garnet peridotites and related rocks from four principal regions: Liati and Gebauer, 2009;Medaris et al, 1995Medaris et al, , 2005Medaris et al, , 2006Massonne and Bautsch, 2002;Masso...…”

Section: Orogenic Peridotite Massifsmentioning

confidence: 99%

Orogenic, Ophiolitic, and Abyssal Peridotites

Bodinier

Godard

2014

Treatise on Geochemistry

181

148

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“…The fate of these species in subduction zones is documented by petrological and geochemical studies, although the details of the reaction paths involved are unkown (Wallace, 2005;Evans, 2012). It is generally accepted that carbonates by-pass the region of dehydration/melting beneath arc-volcanoes (Connolly, 2005;Malaspina et al, 2008;Poli et al, 2009) and are buried in the deep mantle (Hammouda, 2003;Dasgupta and Hirschmann, 2010,). A few arc-volcanoes produce elevated amount of CO 2 , but it is unclear whether this CO 2 has really been processed through the mantle wedge or is simply assimilated during magma transport and storage in the upper crust (Iacono-Marziano et al, 2009).…”

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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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The Oxidation State of Metasomatized Mantle Wedge: Insights from C-O-H-bearing Garnet Peridotite

Cited by 83 publications

References 71 publications

Evidence of sub-arc mantle oxidation by sulphur and carbon

Evidence of sub-arc mantle oxidation by sulphur and carbon

Orogenic, Ophiolitic, and Abyssal Peridotites

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

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