Multiphase solid inclusions in zoisite-bearing eclogite: evidence for partial melting of ultrahigh-pressure metamorphic rocks during continental collision

Chen, Yixiang; Zheng, Yong‐Fei; Gao, Xiao‐Ying; Hu, Zhaochu

doi:10.1016/j.lithos.2014.04.004

Cited by 43 publications

(47 citation statements)

References 108 publications

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“…Subsequently, different amounts of melt would be incorporated into the fluid flow due to the dehydrated melting of phengite (Fig. ) (Gao et al ., , ; Chen et al ., , , ; Wang et al ., ). In this study, both the veins contain minerals that grew from fluid under eclogite facies conditions (Rubatto & Hermann, ; Wu et al ., ).…”

Section: Discussionmentioning

confidence: 97%

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Distinct zircon U–Pb and O–Hf–Nd–Sr isotopic behaviour during fluid flow in UHP metamorphic rocks: evidence from metamorphic veins and their host eclogite in the Sulu Orogen, China

Zhao

Liu

et al. 2016

Journal Metamorphic Geology

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Fluid plays a key role in metamorphism and magmatism in subduction zones. Veins in high-pressure (HP) to ultrahigh-pressure (UHP) rocks are the products of fluid-rock interaction, and can thus provide important constraints on fluid processes in subduction zones. This contribution is an integrated study of zircon U-Pb and O-Hf, as well as whole-rock Nd-Sr isotopic compositions for a quartz vein, a complex vein, and their host eclogite in the Sulu UHP terrane to decipher the timing and source of fluid flow under HP-UHP metamorphic conditions. The inherited magmatic zircon cores from the host eclogite constrain the protolith age at c. 750 Ma. Their variable e Hf (t) values from À1.11 to 2.54 and low d 18 O values of 0.32-3.40& reflect a protolith that formed in a rift setting due to the breakup of the supercontinent Rodinia. The hydrothermal zircon from the quartz and the complex veins shows euhedral shapes, relatively flat HREE pattern, slight or no negative Eu anomaly, low 176 Lu/ 177 Hf ratios, and low formation temperatures of 660-690°C, indicating they precipitated from fluids under HP eclogite facies conditions. This zircon yielded similar U-Pb ages of 217 AE 2 and 213 AE 3 Ma within analytical uncertainty, recording the timing of fluid flow during the exhumation of the UHP rock. It is inferred that the fluids might be of internal origin based on the homogeneity of d 18 O values of the hydrothermal zircon from the quartz (À2.41 AE 0.13&) and complex veins (À2.35 AE 0.12&), and the metamorphic grown zircon of the host eclogite (À2.23 AE 0.16&). The similar e Nd (t) values of the whole rocks also support such a point. Zircon O and whole-rock Nd isotopic compositions are therefore useful to identify the source of fluid, for they are major and trace components in minerals involved in metamorphic reactions during HP-UHP conditions. On the other hand, the hydrothermal zircon from the veins and the metamorphic zircon from the host eclogite exhibit variable e Hf (t) values. Model calculation suggests that the Hf was derived from the breakdown of major rock-forming minerals and recycling of the inherited magmatic zircon. The variable whole-rock initial 87 Sr/ 86 Sr ratios might be caused by subsequent retrograde metamorphism after the formation of the veins.

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Section: Discussionmentioning

confidence: 97%

“…(), Liu & Liou () and Chen et al . (, ). Petrogenetic grids, subdivision of eclogite facies, and reaction curves diamond = graphite, coesite = quartz and jadeite + quartz = albite are from Bundy (), Oh & Liou (), Holland () and Bohlen & Boettcher () respectively.…”

Section: Discussionmentioning

confidence: 99%

Distinct zircon U–Pb and O–Hf–Nd–Sr isotopic behaviour during fluid flow in UHP metamorphic rocks: evidence from metamorphic veins and their host eclogite in the Sulu Orogen, China

Zhao

Liu

et al. 2016

Journal Metamorphic Geology

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“…Discrepancies still exist for phase boundaries of hydrous minerals with respect to solidus conditions in P–T space (Liu et al., ; Rapp & Watson, ; Schmidt, Vielzeuf, & Auzanneau, ; Skjerlie & Patiño Douce, ; Vielzeuf & Schmidt, ). Petrological studies on partial melting of natural UHP eclogite are few (Chen, Zheng, Gao, & Hu, ; Gao, Zheng, & Chen, ; Gao, Zheng, Chen, & Hu, ; Hacker et al., ; Wang et al., ), partly due to limited field occurrence of UHP eclogite with preserved evidence of melting in the textures, which are easily destroyed. Melt may connect and channelize, forming felsic veins or networks on the mesoscale, and segregate, leading to melt escape from the source area (e.g., Brown, ; Kriegsman, ; Rosenberg & Handy, ; Sawyer, ) contributing to relamination of subducted materials (Hacker, Kelemen, & Behn, ).…”

Section: Introductionmentioning

confidence: 99%

“…On the micro‐scale, UHP eclogite may contain features, such as cusps, graphic intergrowths, inclusions of melt, and triple junctions among equant minerals (e.g., Fenn, ; Holness, Cesare, & Sawyer, ; Holness & Sawyer, ; Sawyer, ), among which the inclusions of melt are most commonly used to decipher partial melting of metabasites. Inclusions of K‐feldspar+quartz±plagioclase±albite±calcite±barite in garnet, omphacite, and clinopyroxene in UHP eclogite from the Sulu‐Dabie and Kokchetav areas are interpreted as crystallized melt (Chen et al., ; Gao et al., ; Hwang et al., ; Wang et al., ). Partial melting of eclogite is inferred to be due to the breakdown of hydrous minerals, phengite (Gao et al., ; Liu, Hermann, & Zhang, ; Wang et al., ; Zeng, Liang, Asimow, Chen, & Chen, ), or phengite, paragonite, and zoisite (Chen et al., ) on the retrograde path.…”

Section: Introductionmentioning

confidence: 99%

“…Inclusions of K‐feldspar+quartz±plagioclase±albite±calcite±barite in garnet, omphacite, and clinopyroxene in UHP eclogite from the Sulu‐Dabie and Kokchetav areas are interpreted as crystallized melt (Chen et al., ; Gao et al., ; Hwang et al., ; Wang et al., ). Partial melting of eclogite is inferred to be due to the breakdown of hydrous minerals, phengite (Gao et al., ; Liu, Hermann, & Zhang, ; Wang et al., ; Zeng, Liang, Asimow, Chen, & Chen, ), or phengite, paragonite, and zoisite (Chen et al., ) on the retrograde path.…”

Section: Introductionmentioning

confidence: 99%

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Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Cao

Gilotti

Massonne

et al. 2018

Journal Metamorphic Geology

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In the North‐East Greenland Caledonides, P–T conditions and textures are consistent with partial melting of ultrahigh‐pressure (UHP) eclogite during exhumation. The eclogite contains a peak assemblage of garnet, omphacite, kyanite, coesite, rutile, and clinozoisite; in addition, phengite is inferred to have been present at peak conditions. An isochemical phase equilibrium diagram, along with garnet isopleths, constrains peak P–T conditions to be subsolidus at 3.4 GPa and 940°C. Zr‐in‐rutile thermometry on inclusions in garnet yields values of ~820°C at 3.4 GPa. In the eclogite, plagioclase may exhibit cuspate textures against surrounding omphacite and has low dihedral angles in plagioclase–clinopyroxene–garnet aggregates, features that are consistent with former melt–solid–solid boundaries and crystallized melt pockets. Graphic intergrowths of plagioclase and amphibole are present in the matrix. Small euhedral neoblasts of garnet against plagioclase are interpreted as formed from a peritectic reaction during partial melting. Polymineralic inclusions of albite+K‐feldspar and clinopyroxene+quartz±kyanite±plagioclase in large anhedral garnet display plagioclase cusps pointing into the host, which are interpreted as crystallized melt pockets. These textures, along with the mineral composition, suggest partial melting of the eclogite by reactions involving phengite and, to a large extent, an epidote‐group mineral. Calculated and experimentally determined phase relations from the literature reveal that partial melting occurred on the exhumation path, at pressures below the coesite to quartz transition. A calculated P–T phase diagram for a former melt‐bearing domain shows that the formation of the peritectic garnet rim occurred at 1.4 GPa and 900°C, with an assemblage of clinopyroxene, amphibole, and plagioclase equilibrated at 1.3 GPa and 720°C. Isochemical phase equilibrium modelling of a symplectite of clinopyroxene, plagioclase, and amphibole after omphacite, combined with the mineral composition, yields a P–T range at 1.0–1. 6 GPa, 680–1,000°C. The assemblage of amphibole and plagioclase is estimated to reach equilibrium at 717–732°C, calculated by amphibole–plagioclase thermometry for the former melt‐bearing domain and symplectite respectively. The results of this study demonstrate that partial melt formed in the UHP eclogite through breakdown of an epidote‐group mineral with minor involvement of phengite during exhumation from peak pressure; melt was subsequently crystallized on the cooling path.

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Partial melting and crust-mantle interaction in subduction channels: Constraints from experimental petrology

Zhang

Wang

et al. 2015

Sci. China Earth Sci.

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Multiphase solid inclusions in zoisite-bearing eclogite: evidence for partial melting of ultrahigh-pressure metamorphic rocks during continental collision

Cited by 43 publications

References 108 publications

Distinct zircon U–Pb and O–Hf–Nd–Sr isotopic behaviour during fluid flow in UHP metamorphic rocks: evidence from metamorphic veins and their host eclogite in the Sulu Orogen, China

Distinct zircon U–Pb and O–Hf–Nd–Sr isotopic behaviour during fluid flow in UHP metamorphic rocks: evidence from metamorphic veins and their host eclogite in the Sulu Orogen, China

Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Partial melting and crust-mantle interaction in subduction channels: Constraints from experimental petrology

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