Syn-exhumation magmatism during continental collision: Evidence from alkaline intrusives of Triassic age in the Sulu orogen

Zhao, Zi‐Fu; Zheng, Yong‐Fei; Zhang, Juan; Dai, Li-Qun; Li, Qiuli; Liu, Xiaoming

doi:10.1016/j.chemgeo.2011.11.002

Cited by 154 publications

(82 citation statements)

References 140 publications

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“…The hydrous melts may originate from two types of continental crustal sources, one is the metagranite and other is the metasediment. Low-degree partial melting of the UHP crustal rocks yields alkaline igneous rocks of felsic composition (Zhao et al 2012), and it is also a key to geochemical differentiation of subducted crustal rocks, because it can result in significant enrichment of meltmobile incompatible trace elements relative to meltimmobile compatible trace elements in hydrous melts (McKenzie 1989). In contrast, high-degree partial melting of the deeply subducted continental crust gives rise to postcollisional granitoids (Zhao et al 2007c).…”

Section: Crust-mantle Interaction In Subduction Channelmentioning

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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Section: Crust-mantle Interaction In Subduction Channelmentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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“…Such fluid/melt would flow along the slab-mantle interface and rise into the overlying SCLM wedge, leading to chemical reaction with the mantle wedge peridotite to generate mafic to ultramafic metasomes [7]. The mantle metasomes may be stored in orogenic lithospheric mantle for few to tens of millions of years, serving as mantle sources for synexhumation alkali magmatism [20] and postcollisional mafic magmatism [21][22][23][24][25][26]. The dynamic structure of the jelly sandwich that formed during continental subduction would become a static structural of the jelly sandwich in the orogenic lithosphere subsequent to the exhumation of deeply subducted continental crust.…”

Section: Subduction Channel Processesmentioning

confidence: 99%

Continental subduction channel processes: Plate interface interaction during continental collision

2013

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The study of subduction-zone processes is a key to development of the plate tectonic theory. Plate interface interaction is a basic mechanism for the mass and energy exchange between Earth's surface and interior. By developing the subduction channel model into continental collision orogens, insights are provided into tectonic processes during continental subduction and its products. The continental crust, composed of felsic to mafic rocks, is detached at different depths from subducting continental lithosphere and then migrates into continental subduction channel. Part of the subcontinental lithospheric mantle wedge, composed of peridotite, is offscrapped from its bottom. The crustal and mantle fragments of different sizes are transported downwards and upwards inside subduction channels by the corner flow, resulting in varying extents of metamorphism, with heterogeneous deformation and local anatexis. All these metamorphic rocks can be viewed as tectonic melanges due to mechanical mixing of crust-and mantle-derived rocks in the subduction channels, resulting in different types of metamorphic rocks now exposed in the same orogens. The crust-mantle interaction in the continental subduction channel is realized by reaction of the overlying ancient subcontinental lithospheric mantle wedge peridotite with aqueous fluid and hydrous melt derived from partial melting of subducted continental basement granite and cover sediment. The nature of premetamorphic protoliths dictates the type of collisional orogens, the size of ultrahigh-pressure metamorphic terranes and the duration of ultrahigh-pressure metamorphism. In continental collision orogens, exposed ultrahigh-pressure (UHP) metamorphic terranes contain the lithotectonic records of Alpine-type subduction [1]. These records highlight metamorphic P-T conditions and mass transfers, indicating subduction of continental crustal rocks to mantle depths of over 100 km. The UHP terranes are characterized by minor occurrences of mafic eclogites and ultramafic peridotites that are hosted by felsic gneisses. Such UHP eclogite-facies parageneses are absent in Pacific-type subduction zones [2]. These UHP rocks are of crustal and mantle protoliths and now occur together with their lower pressure counterparts in continental collision orogens [3]. It is intriguing how the continental crust is subducted to mantle depths for UHP metamorphism, how UHP slices are exhumed from mantle depths to crustal levels, and how metamorphic rocks of different P-T conditions occur together in the same orogens. The property of plate interface in subduction zones is a key to physical and chemical interactions at interplate boundaries. Physical and chemical transfers at convergent plate margins can occur on various spatial and temporal scales, which is fundamental to subduction-zone processes. Like the plate tectonic theory, the concept of subduction channel was originally developed from the tectonics of oceanic subduction zone [4][5][6]. It was primarily focused on the plate interface interaction in ocean...

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“…Ziron Hf isotope studies of igneous and metamorphic rocks also reveal two episodes of crustal growth in the YZC, late Mesoproterozoic to early Neoproterozoic and middle Paleoproterozoic (Zheng et al, 2006b;Chen et al, 2007;Zhao et al, 2008), whereas the NCC primarily exhibits Archean ages of crustal growth (Wu et al, 2005a;Geng et al, 2012). These features have been successfully used to constrain source of the Mesozoic intermediate-mafic igneous rocks along the Dabie-Sulu Orogen (Yang et al, 2012c;Zhao et al, 2012).…”

Section: Nature Of the Mantle Sourcementioning

confidence: 94%