Fractionation of Nb and Ta by biotite and phengite: Implications for the “missing Nb paradox”

Stepanov, Aleksandr S.; Hermann, Jörg

doi:10.1130/g33781.1

Cited by 178 publications

(93 citation statements)

References 32 publications

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“…Metasomatic phlogopite has previously been recognized as a major host for elements like Ba, Nb, Sr, and Rb (e.g., Ionov and Hofmann, 1995;Stepanov and Hermann, 2013), whereas apatite can accommodate significant amounts of LREE-MREE, Th, U, and Pb (e.g., Chazot et al, 1996;O'Reilly and Griffin, 2000).…”

Section: Role Of Residual Mineral Assemblages In the Lithospheric Mantlementioning

confidence: 98%

The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: The Eastern Mediterranean case

Kirchenbaur

Münker

2015

Geochimica et Cosmochimica Acta

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Section: Role Of Residual Mineral Assemblages In the Lithospheric Mantlementioning

confidence: 98%

The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: The Eastern Mediterranean case

Kirchenbaur

Münker

2015

Geochimica et Cosmochimica Acta

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“…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. Thus, subduction-zone fluids with elevated Nb/Ta ratios can form either by the breakdown of these hydrous minerals or by the presence of residual rutile in UHP eclogites.…”

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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“…5b), consistent with the accumulation of biotite (e.g. Stepanov and Hermann 2013). The accumulation of aluminous magmatic biotite would also explain the peraluminous composition of the enclaves and the enrichment in Rb.…”

Section: The Middle Triassic Bulunkou Plutonmentioning

confidence: 58%

Origins of Early Mesozoic granitoids and their enclaves from West Kunlun, NW China: implications for evolving magmatism related to closure of the Paleo-Tethys ocean

Wang

Liu

Korhonen

et al. 2015

Int J Earth Sci (Geol Rundsch)

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the melting of a source at middle crustal depths. The AP host and its enclaves from the southeastern part of the West Kunlun have low Rb, Rb/Sr (0.15-1.90) and weakly negative Eu anomalies but high HREE contents indicating limited fractionation of plagioclase without residual garnet in their source. The inferred protolith is an intermediate igneous rock in the middle or lower crust. MEs hosted in the AP have high Mg# (39.7-45.0) and Nb and weakly negative Eu anomalies, as well as high Sr, P and Ti, corresponding to a medium-K basaltic rock, which may have originated from mixing of partial melting of metasomatised mantle wedge that has been modified by upwelling asthenospheric mantle and crustal melting in the deep source. Post-collisional southeasternward younging of Mesozoic granitoids in the West Kunlun records a transition from shallow level, mid-crustal melting to deeper level, lower-crustal melting. The post-collisional granitoids show significant mantle input increasing from northwest to southeast, which was closely associated with mafic magma-driven partial melting of mantle and crustal sources as a consequence of slab break-off. Syn-to post-collisional Early Mesozoic granites emplaced along the Mazar-Kangxiwar suture zone suggest that these tectonomagmatic processes followed the closure of the Paleo-Tethys ocean during the Tarim and Karakorum-Qiangtang continental collision.

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Fractionation of Nb and Ta by biotite and phengite: Implications for the “missing Nb paradox”

Cited by 178 publications

References 32 publications

The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: The Eastern Mediterranean case

The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: The Eastern Mediterranean case

Geochemistry of continental subduction-zone fluids

Origins of Early Mesozoic granitoids and their enclaves from West Kunlun, NW China: implications for evolving magmatism related to closure of the Paleo-Tethys ocean

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