Trace-element mobilization in slabs due to non steady-state fluid–rock interaction: Constraints from an eclogite-facies transport vein in blueschist (Tianshan, China)

John, Timm; Klemd, Reiner; Gao, Jun; Garbe‐Schönberg, Dieter

doi:10.1016/j.lithos.2007.09.005

Cited by 231 publications

(176 citation statements)

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“…Metamorphic veins Generally, there are two types of metamorphic veins in deeply subducted continental crust, which are mainly formed at subsolidus conditions: (1) felsic veins, which are primarily composed of variable abundances of felsic minerals such as quartz, feldspar, kyanite, and phengite with minor amounts of mafic minerals such as omphacite, garnet, zoisite, and amphibole (e.g., Franz et al 2001;Li et al 2001Zheng et al 2007;Wu et al 2009;Chen et al 2012a;Sheng et al, 2012Sheng et al, , 2013 and (2) mafic veins, which are usually composed of variable abundances of mafic minerals such as omphacite, epidote, zoisite, allanite, and garnet with minor amounts of felsic minerals such as quartz and kyanite (e.g., Gao et al 2007;John et al 2008;Zhang et al 2008;Spandler et al 2011;Guo et al 2012). In addition, the veins contain variable abundances of accessory minerals such as rutile, zircon, and apatite.…”

Section: Natural Constraintsmentioning

confidence: 99%

“…For example, Ti minerals such as titanite, rutile, and ilmenite in Alpine eclogitic veins are precipitated from metamorphic fluids (e.g., Philippot and Selverstone 1991), and metamorphic rutile is common in quartz-dominated veins hosted by UHP eclogites in Dabie-Sulu (Xiao et al 2006;Zhang et al 2008;Zheng et al 2011b) and Chinese Tianshan John et al 2008). These observations suggest that metamorphic fluids can transport Ti at eclogite-facies conditions at least over short distances of a few meters.…”

Section: Action Of Subduction-zone Fluids Accessary Mineral Records Omentioning

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: Action Of Subduction-zone Fluids Accessary Mineral Records Omentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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“…Sr and Nd isotopic analyses used sample solutions from ICP-MS trace element measurements (see John et al (2008) for details of the dissolution procedures) by sequential evaporation of the ca 50ml diluted HNO 3 solution and conversion of the sample matrix into chloride form. The ion exchange procedures followed those described in Hoernle and Tilton (1991).…”

Section: Strontium and Neodymium Isotopic Analysesmentioning

confidence: 99%

“…The direct examination of subduction zone metamorphic rocks provides insight of how mass is redistributed during metamorphism (e.g., Bebout, 1991;Beinlich et al, 2010;Gao et al, 2007;John et al, 2008;King et al, 2004;Sorensen and Grossman, 1989;Spandler et al, 2003Spandler et al, , 2004, about the nature of slab-derived agents added to arc lava sources and about chemical changes in subducting rocks potentially contributing to the geochemical heterogeneity of the upper mantle (e.g., Bebout, 2007;Breeding et al, 2004, John et al, 2004. Increasing attention has been directed towards metasomatic processes within subducted rocks because metasomatic rocks can constitute new bulk compositions that can influence the redistribution of major and trace elements (Bebout, 2007;King et al, 2006King et al, , 2007Scambelluri et al, 2006;Zack and John, 2007).…”

Section: Introductionmentioning

confidence: 99%

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

et al. 2011

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Two distinct types of eclogites from the Raspas Complex (Ecuador), which can be distinguished based on petrography and trace element geochemistry, were analyzed for their stable (Li, O) and radiogenic (Sr, Nd) isotope signature to constrain metasomatic changes due to fluid-overprinting in metabasaltic rocks at high-pressure conditions and to identify fluid sources. MORB-type eclogites are characterized by a relative LREE depletion similar to MORB. High-pressure (HP) minerals from this type of eclogite have highly variable oxygen isotope compositions (garnet: +4.1 to +9.

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“…At this time, in the Permo-Triassic, this entire assemblage was also docked to the Siberian continent further north in present-day co-ordinates [Carroll et al, 1995;Levashova et al 2007] and together these amalgamated terranes formed one of the nuclei of the current Asian continent. This Palaeozoic collision-accretion produced two ophiolite-and UHP-rock bearing suture zones [Allen et al, 1992;Zhang et al, 1993;Gao et al, 1998;Zhang et al 2002a;2002b;Bazhenov et al, 2003;John et al, 2008]. During the various subduction and accretion episodes, the Tien Shan units were vastly intruded by granitoids [Solomovich & Trifonov, 2002;Mao et al, 2004;Konopelko et al, 2007;Solomovich, 2007;Pirajno et al, 2008;Van der Voo et al, 2006;Kröner et al, 2008].…”

Section: Introductionmentioning

confidence: 99%