Geochemical and Re–Os isotope constraints on the origin and age of the Songshugou peridotite massif in the Qinling orogen, central China

Nie, Hu; Yang, Jianghai; Zhou, Guangyan; Liu, Chuan-Zhou; Zheng, Jianping; Zhang, Wenxiang; Zhao, Yujie; Wang, Hao; Wu, Yuan–Bao

doi:10.1016/j.lithos.2017.09.009

Cited by 23 publications

(9 citation statements)

References 74 publications

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“…The formation age of the Songshugou ophiolite has been constrained by maximum Re depletion model ages (T RD ) of 1.0-0.8 Ga from the ultramafic rocks (Nie et al, 2017;Yu et al, 2017;Sun et al, 2019), zircon U-Pb ages of 973-729 Ma from the mafic rocks (Liu et al, 2004;Qian et al, 2013;Li et al, 2014;Chen et al, 2015;Yu et al, 2016), and a 40 Ar-39 Ar age of 848 ± 4 Ma from the diopside vein (Chen et al, 2002).…”

Section: Researchmentioning

confidence: 99%

Fabrics, geothermometry, and geochronology of the Songshugou ophiolite: Insights into the tectonic evolution of the Shangdan suture, Qinling orogen, China

et al. 2019

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The Songshugou ophiolite, located in the northern Qinling belt, consists mainly of metamorphosed mafic and ultramafic rocks recording details of deformation and metamorphism that occurred during subduction, accretion, and collision along the Shangdan suture in the Qinling orogenic belt. Electron backscatter diffraction measurements revealed that the harzburgites are dominated by olivine C-type crystal preferred orientations (CPOs), which were possibly induced by high pressure during slab subduction. Olivine A-type CPOs were also observed in some harzburgites, representing the remnants of the original fabric in oceanic mantle rocks formed in the spreading center of the Shangdan ocean. Coarse-grained dunites are characterized by B-type CPOs, which may have been caused by melt-rock reactions and/or high water contents in a suprasubduction-zone setting during exhumation. Fine-grained dunites are also dominated by B-type CPOs, suggesting that grain-size reduction related to mylonitization did not result in fabric variations. Combined with the mineral assemblages, application of geothermometry suggested that the Songshugou ophiolite has experienced metamorphism and deformation under amphibolite-facies conditions. Zircons from garnet-bearing amphibole schist are characterized by flat heavy rare earth element (HREE) patterns and low Th/U ratios and yielded a mass spectrometry U-Pb age of 500.5 ± 8.8 Ma, representing the peak metamorphic age of the metamafic rocks. Other zircons displayed relative HREE enrichment and a clearly negative Eu anomaly and gave an age of 492.5 ± 3.0 Ma, constraining the time of the exhumation of the ophiolite. Integrated with all the available regional geology, our new fabric, geochemical, and geochronological data suggest that the tectonic evolution of the Songshugou ophiolite can be proximately constrained as subduction at ca. 500 Ma and exhumation at ca. 492 Ma.

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Section: Researchmentioning

confidence: 99%

Fabrics, geothermometry, and geochronology of the Songshugou ophiolite: Insights into the tectonic evolution of the Shangdan suture, Qinling orogen, China

et al. 2019

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“…Eclogite protoliths and ultramafic rocks could not have mixed in the subduction channel or entered it coherently, because (a) the largest ultramafic body of the Songshugou Complex is, despite its margin, where serpentinization likely occurred during D3, serpentine‐free, (b) the eclogites reached pressures, which trigger garnet growth in ultramafic rocks (Klemme, 2004), but there is no indication for that, and (c) U/Pb zircon protolith ages of eclogites ( c . 0.78 Ga; Table ) and maximal Re depletion model ages of spinel dunite (1.2–1.1 Ga; Nie et al, 2017) differ distinctly. Furthermore, the structures and thermobarometry of eclogites and HP granulites imply that both were only juxtaposed at conditions equivalent to non‐thickened lower crust (see section “The HP granulites and contemporaneous rocks”; Figure 13).…”

Section: Discussionmentioning

confidence: 95%

“…The ultramafic rocks are fragments of highly refractory uppermost mantle. Rhenium depletion model ages imply partial melt extraction before 1.2 to ~0.8 Ga (Nie et al, 2017; Sun, Dong, Sun, et al, 2019; Yu, Zhang, & Santosh, 2017). A Re–Os isochron age of roughly 500 Ma dates a younger modification by boninitic melt percolation above a subduction zone (Sun, Dong, Sun, et al, 2019).…”

Section: Regional Geologymentioning

confidence: 99%

High‐P granulites of the Songshugou area (Qinling Orogen, east‐central China): Petrography, phase relations, and U/Pb zircon geochronology

Bader

Zhang

et al. 2020

Journal Metamorphic Geology

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High-pressure (HP) granulites provide telling records of mineral reactions at upper mantle to lower crustal levels and key information on the fate of material in subduction systems. The latter especially applies when they abut eclogite and mantle dunite because such rock associations are crucial for understanding the incompletely known processes at the interface of converging plates. A continental arc, active c. 520-395 Ma ago, formed an enigmatic example of such a rock association in the Songshugou area, Qinling Orogen. To unravel the juxtaposition of the distinct rocks, this study combines petrography, phase equilibria modelling, conventional thermobarometry, and zircon U-Th-Pb-Ti-REE analysis. Two mafic HP granulites, which contain the mineral assemblages garnet-clinopyroxene-plagioclase-rutile-mesoperthite-quartz and garnet-clinopyroxene-plagioclase-rutile, experienced peak metamorphic conditions of ≤1.4 GPa, 860°C and ~1.3 GPa, ≥910°C, respectively. During decompression and cooling, at 489 ± 4 Ma, amphibole lamellae unmixed from a clinopyroxene solid solution and orthopyroxene in part replaced garnet. A felsic HP granulite shows equilibration of garnet, perthite, antiperthite, kyanite, quartz, and rutile at 810-860°C, ~1.2 GPa, sillimanite growth during decompression, and upper amphibolite facies cooling at 510 ± 4 Ma. Though the thermobarometric data are just within the methodological errors, the U/Pb zircon ages imply the HP granulites did not evolve coherently. The HP granulites either represent foundered lower arc crust or originated from subduction erosion because their geochemistry is indistinguishable from that of the hanging-wall plate. Published and new pressure-temperature-time-deformation paths converge at ~710°C, ~0.9 GPa, and ≲470 Ma, implying exhumation tectonics juxtaposed the HP granulites with a mélange of eclogite and mantle dunite at lower crustal levels. This study highlights that lower arc crust can comprise material of diverse evolution. K E Y W O R D S high-P granulite, phase equilibria modelling, Qinling Orogen, zircon petrochronology 422 |

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“…500–490 Ma were identified to occur as discontinuous bands, lenses and blocks in the Qinling Complex (Chen et al, 2004; Hu et al, 1994; Liu et al, 1995, 2016; Liu, Steel, & Zhang, 2005). The Songshugou Ophiolite consists mainly of metamorphosed ultramafic and mafic rocks, representing relics of an oceanic crust in the mid‐ocean ridge (Dong et al, 2008; Dong, Zhang, Hauzenberger, et al, 2011; Sun et al, 2019) or forearc mantle wedge (Cao et al, 2016; Nie et al, 2017).…”

Section: Geological Backgroundmentioning

confidence: 99%

Ordovician tectonic transition from passive margin into peripheral foreland in the southern Ordos: A diagnostic insight into the closure of Erlangping Ocean between the North Qinling Arc and North China Block

et al. 2022

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Achieving a reliable closure time of a back-arc ocean is an essential aspect in studies on detailed tectonic processes of an active continental margin and arc-continent collision. This is particularly the case for the northern Qinling Orogen, which records the accretion of the North Qinling Arc (NQA) onto the North China Block (NCB) after the Erlangping back-arc ocean closure. Sedimentological, petrological and geochronological signatures from the Ordovician successions in the southern Ordos reveal a tectonic transition from passive continental margin to peripheral foreland in the southern NCB at the beginning of Katian. Sedimentological and geochronological investigations reveal an abrupt shift of accelerating basin subsidence and deepening at the earliest Katian, separating ca. 300-m-thick shallow-marine carbonate shelf assemblages from overlying ca. 2000-m-thick deep-water carbonate slope and turbidite associations. Zircon age spectra of the Katian turbidites are characterized by early-Palaeozoic and Neoproterozoic age clusters, which are different from those of the Middle Ordovician quartz arenites sourced merely from the NCB basement. Instead, these age patterns match well with those of the coeval successions in the northern NQA, indicating a spatially linked abyssal deposystem. Stratigraphic architecture deciphers a typical foreland basin geometry, involving, from south to north, northward-propagating turbiditic wedge, northward-backstepping carbonate slope and progressively shoaling carbonate platform, embodying foredeep, forebulge and backbulge, respectively. These characteristics of basin-fill evolution reflect the northward migration of the flexural wave as a dynamic response to the northward expansion of the thickened NQA thrust wedge. Together with the other geological and geochronological data, our new insights indicate a southward subduction polarity of the Erlangping back-arc oceanic crust followed by its termination at ca. 450 Ma, which was earlier than that of the main Proto-Tethyan Shangdan Ocean between

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Geochemical and Re–Os isotope constraints on the origin and age of the Songshugou peridotite massif in the Qinling orogen, central China

Cited by 23 publications

References 74 publications

Fabrics, geothermometry, and geochronology of the Songshugou ophiolite: Insights into the tectonic evolution of the Shangdan suture, Qinling orogen, China

Fabrics, geothermometry, and geochronology of the Songshugou ophiolite: Insights into the tectonic evolution of the Shangdan suture, Qinling orogen, China

High‐P granulites of the Songshugou area (Qinling Orogen, east‐central China): Petrography, phase relations, and U/Pb zircon geochronology

Ordovician tectonic transition from passive margin into peripheral foreland in the southern Ordos: A diagnostic insight into the closure of Erlangping Ocean between the North Qinling Arc and North China Block

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