Partitioning of Nb and Ta between rutile and felsic melt and the fractionation of Nb/Ta during partial melting of hydrous metabasalt

Xiong, Xiaolin; Keppler, Hans; Audétat, Andreas; Ni, Huaiwei; Sun, Weidong; Li, Yuan

doi:10.1016/j.gca.2010.06.039

Cited by 157 publications

(87 citation statements)

References 61 publications

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“…The good fit of the Nb-Ta (and Zr-Hf) concentrations in the models is related to the phase stability of TiO 2 mineral phases (e.g., rutile and titanomagnetite) in subducted materials (Kimura et al, 2016;Xiong et al, 2011). The ABS5 model uses fixed partition coefficients for these minerals and modal compositions calculated from Perple_X phase equilibria using fixed source compositions.…”

Section: Breakdown Of the Mass Balancementioning

confidence: 91%

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et al. 2013

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Section: Breakdown Of the Mass Balancementioning

confidence: 91%

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et al. 2013

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“…Zircon hosts Zr, Hf and some U, and apatite is the main host for P (e.g., Hermann 2002;Hermann and Rubatto 2009). Rutile preferentially incorporates Ta over Nb during hydration melting (Schmidt et al 2004b;Xiong et al 2011a), with Nb/Ta partition coefficients D Nb/Ta < 1. In contrast, low-Mg amphibole, biotite, and phengite preferentially incorporate Nb over Ta during dehydration melting (Tiepolo et al 2000;Green and Adam 2003;Stepanov and Hermann 2013), with Nb/Ta partition coefficients D Nb/Ta > 1.…”

Section: Composition Of Continental Subduction-zone Fluids Experimentmentioning

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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“…Recent studies, however, suggest that they can be mobile and fractionated during dehydration in ultra-high pressure terranes (Xiao et al, 2006). The detailed mechanism that controls Nb/Ta fractionation remains debated (Ding et al, 2009Xiong et al, 2011;Niu, 2012;Marschall et al, 2013). Gao et al (2014) in this volume demonstrates Nb/Ta fractionation during the growth of metamorphic rutile from aqueous solutions during exhumation of deeply subducted continental crust.…”

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confidence: 88%