Majoritic garnets monitor deep subduction fluid flow and mantle dynamics

Scambelluri, Marco; Pettke, Thomas; Roermund, H.L.M. van

doi:10.1130/g24056a.1

Cited by 134 publications

(105 citation statements)

References 33 publications

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“…The garnet megacrysts contain sparse exsolved clinopyroxene and orthopyroxene needles (Fig. 1b) with similar size, abundance and distribution to the exsolution previously reported for M3 garnet (Scambelluri et al, 2008). MSI are abundant in the garnet (Fig.…”

Section: Lettersupporting

confidence: 75%

“…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).…”

Section: Lettermentioning

confidence: 99%

“…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 al, 2008). The Bardane peridotite represents the best-known analogue for the study of fluid-related redox processes at sub-arc depth.…”

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confidence: 99%

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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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Section: Lettersupporting

confidence: 75%

Section: Lettermentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…UHP nappes may be exhumed because of regional mantle upwelling, subduction channel backflow, or underplating combined with extensional collapse . Exhumation of majoritic (garnet-pyroxene solid solution) peridotites indicates that material subducted to >200 km depth may be returned to the surface (Liou et al 2007;Scambelluri et al 2008). The return of deeply subducted material to the surface often does not occur, as shown by the fact that no UHP terranes have been identified in North America despite many collisions over geologic time and an abundance of metamorphic petrologists hungry to make the discovery.…”

Section: Continent Subductionmentioning

confidence: 98%

Yin and yang of continental crust creation and destruction by plate tectonic processes

Stern

Scholl

2010

International Geology Review

200

107

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Earth's continental crust today is both created and destroyed by plate tectonic processes, a balance that is encapsulated by the traditional Chinese concept of yin-yang, whereby dualities act in concert as well as in opposition. Yin-yang conceptualizations of crustal growth and destruction are mostly related to plate tectonics; both occur mostly at subduction zones, by arc magmatic creation and by subduction removal. Crust is also created and destroyed by processes unrelated to plate tectonics, including losses by lower crust foundering and additions at hotspots. At present, creation and destruction of continental crust is either in balance (∼3.2 km 3 /year, or 3.2 AU) or more crust is being destroyed than created; the uncertainty comes from unknown deep losses of continental crust at collision zones and due to lower crustal foundering. The yinyang creation-destruction balance changes over a supercontinent cycle, with crustal growth being greatest during supercontinent break-up due to high magmatic flux at new arcs and crustal destruction being greatest during supercontinent amalgamation due to subduction of continental material and increased sediment flux due to orogenic uplift. These conclusions challenge the widely held view that continental crust volume has increased over time due to plate tectonic activity; it is just as likely that this volume has decreased.

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“…Some MSI are trapped in UHP minerals such as coesite, diamond, and majoritic garnet (Stöckhert et al 2001;van Roermund et al 2002;Scambelluri et al, 2008;Zhang et al 2008), indicating that they were included as supercritical fluids at UHP conditions. Different sizes of felsic MSI in the garnet of UHP eclogites from the Dabie orogen (east-central China) exhibit very large variations in composition (Gao et al 2013), with SiO 2 = 63.78 to 94.43 wt %, Al 2 O 3 = 1.89 to 18.26 wt %, MALI = 0.19 to 15.21, A/CNK = 0.18 to 1.54, Si/Al = 2.86 to 42.40, and (Na + K)/Al = 0.48 to 3.30 (Additional file 3: Table S2).…”

Section: Migmatic Leucosomes and Multiphase Solid Inclusionsmentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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The composition of continental subduction-zone fluids varies dramatically from dilute aqueous solutions at subsolidus conditions to hydrous silicate melts at supersolidus conditions, with variable concentrations of fluid-mobile incompatible trace elements. At ultrahigh-pressure (UHP) metamorphic conditions, supercritical fluids may occur with variable compositions. The water component of these fluids primarily derives from structural hydroxyl and molecular water in hydrous and nominally anhydrous minerals at UHP conditions. While the breakdown of hydrous minerals is the predominant water source for fluid activity in the subduction factory, water released from nominally anhydrous minerals provides an additional water source. These different sources of water may accumulate to induce partial melting of UHP metamorphic rocks on and above their wet solidii. Silica is the dominant solute in the deep fluids, followed by aluminum and alkalis. Trace element abundances are low in metamorphic fluids at subsolidus conditions, but become significantly elevated in anatectic melts at supersolidus conditions. The compositions of dissolved and residual minerals are a function of pressure-temperature and whole-rock composition, which exert a strong control on the trace element signature of liberated fluids. The trace element patterns of migmatic leucosomes in UHP rocks and multiphase solid inclusions in UHP minerals exhibit strong enrichment of large ion lithophile elements (LILE) and moderate enrichment of light rare earth elements (LREE) but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE), demonstrating their crystallization from anatectic melts of crustal protoliths. Interaction of the anatectic melts with the mantle wedge peridotite leads to modal metasomatism with the generation of new mineral phases as well as cryptic metasomatism that is only manifested by the enrichment of fluid-mobile incompatible trace elements in orogenic peridotites. Partial melting of the metasomatic mantle domains gives rise to a variety of mafic igneous rocks in collisional orogens and their adjacent active continental margins. The study of such metasomatic processes and products is of great importance to understanding of the mass transfer at the slab-mantle interface in subduction channels. Therefore, the property and behavior of subduction-zone fluids are a key for understanding of the crust-mantle interaction at convergent plate margins.

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Majoritic garnets monitor deep subduction fluid flow and mantle dynamics

Cited by 134 publications

References 33 publications

Evidence of sub-arc mantle oxidation by sulphur and carbon

Evidence of sub-arc mantle oxidation by sulphur and carbon

Yin and yang of continental crust creation and destruction by plate tectonic processes

Geochemistry of continental subduction-zone fluids

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