Felsic veins within UHP eclogite at xitieshan in North Qaidam, NW China: Partial melting during exhumation

Chen, Danling; Liu, Liang; Sun, Yong; Sun, Weidong; Zhu, Xinming; Liu, Xiaoming; Cailian, Guo

doi:10.1016/j.lithos.2011.11.006

Cited by 82 publications

(51 citation statements)

References 75 publications

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“…Nevertheless, metamorphic veins and migmatic leucosomes within UHP rocks can be used to retrieve information about the composition of deep fluids. Advanced micro-analytical methods are applied to acquire the geochemical composition of metamorphic and anatectic veins in UHP metamorphic terranes (Zheng et al 2008;Chen et al, 2012aChen et al, , 2012bGuo et al 2012;Yu et al 2012;Song et al 2014). This leads to a better understanding of the role of fluids for mass transfer at the slab-mantle interface in subduction channels.…”

Section: Natural Constraintsmentioning

confidence: 99%

“…Geochemical analyses of migmatic leucosomes from UHP metamorphic terranes provide a proxy for the composition of anatectic melts Chen et al 2012b;Yu et al 2012;Gao et al 2013;Liu et al 2013;Song et al 2014). This is delineated by plotting the calcalkalinity index (MALI = NaO + K 2 O − CaO in weight percentage) against SiO 2 content ( Figure 3a Table S2).…”

Section: Migmatic Leucosomes and Multiphase Solid Inclusionsmentioning

confidence: 99%

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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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Section: Natural Constraintsmentioning

confidence: 99%

Section: Migmatic Leucosomes and Multiphase Solid Inclusionsmentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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“…Thereby, the study of natural partially molten eclogite can give us precious information about the mechanism of continental crust formation and is important for the elucidation of the evolution process of the Earth. However, evidence for partial melting of natural eclogite has been rarely reported, except for a few examples (e.g., Konilov et al, 2011;Chen et al, 2012;Gao et al, 2012). Konilov et al (2011) and Chen et al (2012) reported the presence of felsic veins in eclogite and interpreted that the felsic veins were products of partial melting of eclogite.…”

Section: Introductionmentioning

confidence: 99%

“…However, evidence for partial melting of natural eclogite has been rarely reported, except for a few examples (e.g., Konilov et al, 2011;Chen et al, 2012;Gao et al, 2012). Konilov et al (2011) and Chen et al (2012) reported the presence of felsic veins in eclogite and interpreted that the felsic veins were products of partial melting of eclogite. Konilov et al (2011) showed that the trace element compositions of the felsic veins were very similar to those of the average TTG and experimental melt of eclogite, whereas the trace-element compositions of the felsic veins reported by Chen et al (2012) are quite different from the natural TTG compositions.…”

Section: Introductionmentioning

confidence: 99%

“…Konilov et al (2011) and Chen et al (2012) reported the presence of felsic veins in eclogite and interpreted that the felsic veins were products of partial melting of eclogite. Konilov et al (2011) showed that the trace element compositions of the felsic veins were very similar to those of the average TTG and experimental melt of eclogite, whereas the trace-element compositions of the felsic veins reported by Chen et al (2012) are quite different from the natural TTG compositions. Other works (e.g., Gao et al, 2012) treated the presence of multiphase solid (MS) inclusions as evidence for partial melting of eclogite, although Gao et al (2012) did not estimate the chemical composition of the melt from the MS inclusions.…”

Section: Introductionmentioning

confidence: 99%

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Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic

Miyazaki

Nakamura

Tamura

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Eclogites from the Moldanubian Zone of the Bohemian Massif (Czech Republic) have experienced ultrahighpressure (UHP) and ultrahigh-temperature (UHT) metamorphic conditions (P > 4.0 GPa, T > 1000°C). One eclogite sample collected from Nové Dvory, eastern part of Czech Republic, contains leucocratic pockets. The mineral assemblage of the melanocratic part of the eclogite is garnet + omphacite + rutile + later-stage minerals (biotite + amphibole + plagioclase). The leucocratic pockets mainly consist of plagioclase and include moderate amounts of garnet and clinopyroxene + small amounts of biotite and amphibole. Garnet and clinopyroxene grains in the leucocratic pockets display faceted shapes whereas those in the melanocratic part show irregular shapes. These are consistent with the idea that garnet and clinopyroxene grains in the leucocratic pockets had been surrounded by melt, as melt can provide free space for the formation of such faceted shapes. The major and trace element composition of garnet grains in the melanocratic part are the same as those in the leucocratic pockets. Clinopyroxene also shows the same major and trace element composition for irregular shape grains in the melanocratic part as faceted grains in the leucocratic pockets. If the melt had originated from the gneiss surrounding the peridotite body with eclogite lenses or layers, the composition of clinopyroxene in the leucocratic pockets would have been completely different from that in the melanocratic part. In addition, the trace element composition of melt estimated from clinopyroxene composition resembles that of TonaliteTrondjhemite -Granodiorite (TTG), which can be produced by partial melting of eclogite. Thus, these observational and analytical data suggest that the leucocratic pockets were originally melt that was internally produced by partial melting of the eclogite.

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Geochronology and geochemistry of volcanic rocks from the Tanjianshan Group, NW China: Implications for the early Palaeozoic tectonic evolution of the North Qaidam Orogen

Sun

Algeo

et al. 2018

Geological Journal

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The widely exposed Tanjianshan volcanic rocks in the North Qaidam Orogen (NW China) encode abundant information about early Palaeozoic magma origin and tectonic evolution. This research utilizes petrological, geochemical, and geochronological methods to investigate the last volcanic cycle (Formation d) of the Tangjianshan Group, aiming to reveal the tectonic evolutionary processes of the North Qaidam Orogen. Formation d can be further divided into two major volcanic sequences, that is, Formation

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Felsic veins within UHP eclogite at xitieshan in North Qaidam, NW China: Partial melting during exhumation

Cited by 82 publications

References 75 publications

Geochemistry of continental subduction-zone fluids

Geochemistry of continental subduction-zone fluids

Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic

Geochronology and geochemistry of volcanic rocks from the Tanjianshan Group, NW China: Implications for the early Palaeozoic tectonic evolution of the North Qaidam Orogen

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