Chemical geodynamics of continental subduction-zone metamorphism: Insights from studies of the Chinese Continental Scientific Drilling (CCSD) core samples

Zheng, Yong‐Fei; Chen, Ren‐Xu; Zhao, Zi‐Fu

doi:10.1016/j.tecto.2008.09.014

Cited by 308 publications

(236 citation statements)

References 240 publications

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“…The former was generally interpreted as the age of metamorphic dehydration event occurring in the transition from HP to UHP conditions during continental subduction, and the latter as the age of metamorphic dehydration event in the transition from UHP to HP conditions during the exhumation of deeply subducted continental crust [42,50]. The peak UHP metamorphism in the diamond stability field may have took place at 238-235 Ma [12].…”

Section: Interpretation Of Diachroneity Along the Direction Of The Ormentioning

confidence: 99%

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

Liu

Jahn

2013

Chin. Sci. Bull.

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High-pressure (HP) metamorphic terrane in the Tongbai orogen comprises two HP slices (I and II) and a tectonic mélange zone in the northeast and a blueschist-greenschist zone in the southwest. HP slice I is represented by the northern and southern eclogite zones on the two sides of the Tongbaishan antiform. HP slice II is represented by retrograded eclogite-bearing metamorphic enclaves in Cretaceous gneissic granites in the Tongbai Complex. U-Pb, Lu-Hf, Rb-Sr and 40 Ar/ 39 Ar multichronometric data indicate that the peak metamorphism of HP slice I took place at ~255 Ma, whereas the metamorphic ages of HP slice II are as young as 232-220 Ma. By contrast, the tectonic mélange zone near the suture was metamorphosed at ~256 Ma. Such a diachroneity of different slices across the direction of the orogen in the Hong'an-Dabie-Sulu HP/UHP terrane is ubiquitous, and it can be interpreted by a syn-subduction detachment/exhumation model. Furthermore, the metamorphic age of HP slice I in the Tongbai orogen is older than that of the equivalent HP slice in the Hong'an orogen by ~15 Ma, suggesting that the diachroneity may have also existed along the direction of the orogen. A seesaw-type subduction/exhumation model is proposed to explain this age disparity and the subduction of the South China Block becomimg shallower towards the west. The processes and mechanism of exhumation of ultrahighpressure (UHP) metamorphic rocks to the Earth's surface from mantle depths exceeding ~100 km remain as one of the most difficult problems in earth science. It appears that a simple mechanism involving buoyancy and erosion is unable to explain the rapid exhumation required for the preservation of coesite. Much attention should be paid to the deepseated tectonic processes of continental slab. Based on the nature of structural contacts and existence of metamorphic gaps between different HP/UHP metamorphic units in the Dora Maira Massif of the western Alps, Chopin [1] andSchreyer [2] inferred that the end of the downgoing slab might have successively broken to several slices during its subduction along very low geothermal gradients (~7C/km). The earlier subducted slices could be uplifted as the overlying hanging-walls during the subduction of the later underlying slices. Liu and Hu [3] have formerly noticed the similarity of HP/UHP terrane from the Dabie Mountains and the Dora Maira Massif. Lately Liu et al. [4,5] distinguished UHP, HP and low-temperature (LT) HP slices and a tectonic mélange zone with the time difference of exhumation of ~30 Ma in the Hong'an orogen on the basis of thermobaric structure and geochronological data, and proposed a diachronous subduction/exhumation model for the formation of

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Section: Interpretation Of Diachroneity Along the Direction Of The Ormentioning

confidence: 99%

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

Liu

Jahn

2013

Chin. Sci. Bull.

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“…Some of the metabasalts display geochemical features of normal mid-ocean ridge basalts (N-MORB) [13,14]. They underwent metamorphism in the Triassic (242 to 221 Ma) [15], which is consistent with UHP metamorphic ages of 240 to 225 Ma in the Dabie-Sulu orogenic belt [7,[16][17][18][19][20][21][22].…”

Section: Geological Setting and Samplesmentioning

confidence: 87%

“…The Qinling-Dabie-Sulu orogenic belt marks the Triassic suture between the North China Block and and South China Block, with the occurrences of UHP metamorphism rocks in the Dabie-Sulu orogenic belt [3,[5][6][7]10]. The geologic framework of the Qinling orogen is built up through interaction of three blocks, which are the North China (i.e., North Qinling), South Qinling and South China blocks.…”

Section: Geological Setting and Samplesmentioning

confidence: 99%

“…The Qinling orogen is an important part of the central orogenic belt in China, and experienced three main evolutionary stages: (1) the formation of Precambrian basements from Archean to Neoproterozoic; (2) the evolution of plate tectonics from oceanic subduction to continental collision during the Early Paleozoic to Early Mesozoic; and (3) intracontinental orogeny during the Jurassic to Cretaceous [1][2][3][4][5][6][7]. The Triassic collision between the South China Block and the North China Block caused the Mianlue suture *Corresponding author (email: peini@nju.edu.cn) in the Qinling orogen, widespread high-pressure (HP) to ultrahigh-pressurer (UHP) metamorphism but few syn-collisional magmatic rocks in the Dabie-Sulu orogenic belt [5][6][7].…”

mentioning

confidence: 99%

“…The Triassic collision between the South China Block and the North China Block caused the Mianlue suture *Corresponding author (email: peini@nju.edu.cn) in the Qinling orogen, widespread high-pressure (HP) to ultrahigh-pressurer (UHP) metamorphism but few syn-collisional magmatic rocks in the Dabie-Sulu orogenic belt [5][6][7]. In contrast, there are widespread occurrences of Triassic granitic rocks in the Qinling orogen (Figure 1), forming a belt of 400-km-long granitoids along the Mianlue suture [1,3].…”

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confidence: 99%

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Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Wang

Sun

et al. 2011

Chin. Sci. Bull.

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Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma, respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the Changba intrusion, yielding a weighted mean of 206 Pb/ 238 U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO 2 and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process may be coupled with exhumation of the subducted continental crust in the stage of late collision.Qinling orogen, continental collision, granite, zircon U-Pb dating, whole-rock geochemistry, syn-exhumation magmatism Citation:Wang T G, Ni P, Sun W D, et al. Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature.

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Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

Dai

Zhao

Zheng

et al. 2015

Geochem. Geophys. Geosyst.

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Postcollisional mafic igneous rocks commonly exhibit petrological and geochemical heterogeneities, but their origin still remains enigmatic. While source mixing is substantial due to the crustmantle interaction during continental collision, magma mixing is also significant during postcollisional magmatism. The two processes are illustrated by Early Cretaceous mafic igneous rocks in the Dabie orogen. These mafic rocks show arc-like trace element distribution patterns and enriched Sr-Nd-Pb isotope compositions, indicating their origination from enriched mantle sources. They have variable whole-rock e Nd (t) values of 217.6 to 25.2 and zircon e Hf (t) values of 229.0 to 27.7, pointing to source heterogeneities. Such whole-rock geochemical features are interpreted by the source mixing through melt-peridotite reaction in the continental subduction channel. Clinopyroxene and plagioclase megacrystals show complex textural and compositional variations, recording three stages of mineral crystallization during magma evolution. Cpx-1 core has low Cr and Ni but high Ba, Rb and K, indicating its crystallization from a mafic melt (Melt 1) derived from partial melting of hydrous peridotite rich in phlogopite. Cpx-1 mantle and Cpx-2 exhibit significantly high Cr, Ni and Al 2 O 3 but low Rb and Ba, suggesting their crystallization from pyroxenite-derived mafic melt (Melt 2). Whole-rock initial 87 Sr/ 86 Sr ratios of gabbro lies between those of Pl-1core (crystallized from Melt 1) and Pl-1 mantle and Pl-2 core (crystallized from Melt 2), providing isotopic evidence for magma mixing between Melt 1 and Melt 2. Taken together, a heterogeneously enriched mantle source would be generated by the source mixing due to reaction of the overlying subcontinental lithospheric mantle wedge peridotite with felsic melts derived from partial melting of different rocks of the deeply subducted continental crust during the continental collision. The magma mixing would occur between mafic melts that were derived from partial melting of the heterogeneously metasomatic mantle domains in the postcollisional stage. As a consequence, the source and magma mixing processes in the continental subduction factory are responsible for the significant variations in the whole-rock and mineral geochemistries of postcollisional mafic igneous rocks.

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Chemical geodynamics of continental subduction-zone metamorphism: Insights from studies of the Chinese Continental Scientific Drilling (CCSD) core samples

Cited by 308 publications

References 240 publications

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

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