Multichronometric Evidence for an In Situ Origin of the Ultrahigh‐Pressure Metamorphic Terrane of Dabieshan, China

Chavagnac, Valérie; Jahn, Bor‐ming; Villa, Igor M.; Whitehouse, Martin J.; Liu, Dunyi

doi:10.1086/321961

Cited by 81 publications

(45 citation statements)

References 46 publications

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“…Firstly, detrital zircons from a metasedimentary rock show two peak ages of ~1.96 and ~1.39 Ga, suggesting that the Yangtze craton not only experienced Paleoproterozoic reworking and Neoproterozoic continental crustal growth [4], but also underwent Mesoproterozoic magmatic activity whose nature needs to be further determined. Secondly, the metamorphic ages of 837 ± 8 Ma and 818 ± 10 Ma on zircon overgrowth rims are obtained from a dioritic gneiss and a metasedimentary rock, which are similar to the metamorphic zircon age of 834 ± 31 Ma for a calc-silicate rocks reported by Zhang et al [28] and also the amphibole 40 Ar/ 39 Ar age of 818 ± 10 Ma obtained for amphibolite by Shen et al [29]. This indicates that the main phase amphibolite facies metamorphism of the Douling Complex occurred during the Neoproterozoic, which is still unreported for the Yangtze craton.…”

Section: Discussionsupporting

confidence: 79%

“…Similar age data were formerly reported in the Dabie-Sulu region. For example, the crystallization age of 2493 ± 13 Ma [38] was obtained for the TTG gneiss underlying the Zhangbaling Group in the eastern Anhui province, and the upper intercept age of 2458 ± 76 Ma [39] was recorded in zircon from the Shuanghe gneiss in the Dabie Mountain. Also in the Dabie Mountains, Chen et al [40] reported another upper intercept zircon age of 2489 ± 25 Ma from an eclogite.…”

Section: Discussionmentioning

confidence: 99%

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A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

et al. 2013

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The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt. Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating, which yielded protolith emplacement ages of 2469 ± 22 Ma, 2479 ± 12 Ma, 2497 ± 21 Ma, 2501 ± 17 Ma and 2509 ± 14 Ma, respectively. An important peak age of ~2.48 Ga was also obtained for a metasedimentary rock in the same region. These discoveries suggest the occurrence of magmatic activity of 2.51-2.47 Ga at the northern margin of the Yangtze craton. The age-corrected ε Hf (t) values obtained from in situ zircon Hf isotopic analysis are mainly between −5.5 and +0.3, and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga. Considering two important periods of ~3.3-3.2 Ga and ~2.95-2.90 Ga for the continental crustal growth in the Yangtze craton, we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo-to Mesoarchean crust at the northern margin of the Yangtze craton at ~2.5 Ga. In addition, metamorphic ages of 837 ± 8 Ma and 818 ± 10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock, indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic, although its geological meaning remains ambiguous. U-

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

et al. 2013

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“…3(a), (b), (d)). Interestingly, these ages fall within, but somewhat later than, the Dabie UHP metamorphic event from 245 to 225 Ma (Ames et al, 1993(Ames et al, , 1996Li, S.-G. et al, 1993Li, S.-G. et al, , 1994Li, S.-G. et al, , 1999Li, S.-G. et al, , 2000Chavagnac and Jahn, 1996;Rowley et al, 1997;Hacker et al, 1998;Chavagnac et al, 2001;Ayers et al, 2002;Zheng et al, 2003b). Amphibolite-facies retrogression may be a major reason to zircon overgrow and associated resetting of U-Pb system to Early Jurassic ages Zheng et al, 2003c).…”

Section: Early Mesozoic Metamorphismmentioning

confidence: 85%

“…But the occurrence of granulite-facies rocks in North Dabie but their absence in South Dabie indicate that the two units experienced differential histories of exhumation subsequent to the peak UHP metamorphism (Zheng et al, 2001). Paleoproterozoic to Archean ages were reported to occur in zircons from the North Dabie granulite-facies rocks (Chen et al, 1996;Jian et al, 1999;Wu et al, 2002) and the South Dabie UHP parametamorphic rocks (Chavagnac et al, 2001;Ayers et al, 2002;Chen et al, 2002Chen et al, , 2003. This indicates the presence of very old basement in the northern margin of the Yangtze Block and thus its involvement during continental deep subduction.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The eclogite-facies metamorphic event has been dated to occur at Triassic with an age range of 245 to 225 Ma (Ames et al, 1993(Ames et al, , 1996Li, S.-G. et al, 1993Li, S.-G. et al, , 1994Li, S.-G. et al, , 1999Li, S.-G. et al, , 2000Chavagnac and Jahn, 1996;Rowley et al, 1997;Hacker et al, 1998;Ayers et al, 2002). However, it is still controversial with respect (Ames et al, 1993(Ames et al, , 1996Rowley et al, 1997;Hacker et al, 1998;Chen et al, 2000Chen et al, , 2003Chavagnac et al, 2001;Zheng et al, 2003aZheng et al, , 2003bZheng et al, , 2004. These data indicate that the metagranites were probably crystallized in the Neoproterozoic and subject to UHP metamorphism in the Triassic.…”

Section: Introductionmentioning

confidence: 99%

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Protolith age and exhumation history of metagranites from the Dabie UHP metamorphic belt in east-central China: A multi-chronological study

Wang

Fang

et al. 2004

Geochem. J.

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Metagranites (granitic orthogneisses) constitute one of the important lithologic units in the Dabie ultrahigh pressure metamorphic belt. They often display direct contact with paragneisses and eclogites. TIMS zircon U-Pb dating on the metagranites reveal that their protolith was crystallized as granitoids in Neoproterozoic ages of 755 to 611 Ma and thus correspond to rift magmatism associated with breakup of the Rodinia supercontinent in the northern margin of the Yangtze Block. Zircon U-Pb age and Ar-Ar ages of amphibole and biotite indicate that the granitoids experienced eclogite-facies metamorphism in Early Mesozoic with rapid exhumation at cooling rates of 8.7 to 10.2°C/Ma from 225 ± 6 to 181 ± 3 Ma in response to amphibolite-facies retrogression. Fission track ages of sphene, zircon and apatite indicate that the metagranites experienced slow exhumation with cooling rates of 0.88 to 1.25°C/Ma in Late Mesozoic. It is possible that in the first period of exhumation, the metagranites were uplifted from the mantle depth to lower crustal level at ca. 225 Ma, then rapidly reached middle to upper crustal levels between 204 Ma and 180 Ma. After the intensive magmatism in Early Cretaceous, the Dabie terrane was uplifted at the slow rate in response to unroofing. Either the rapid exhumation in the Early Mesozoic or the slow uplift in the Late Mesozoic in the Dabie terrane were contemporaneous with two rapid subsidence and sedimentation of the Hefei Basin in Early Jurassic and Paleogene, respectively. This suggests that the orogeny and basin-forming events were closely related to each other rather than independently separated.Keywords: metagranite, geochronology, cooling history, eclogite-facies, amphibolite-facies to the exact timing of UHP metamorphic event at either Early-middle Triassic or Late Triassic.In the Dabie UHP metamorphic belt, granitic orthogneisses are widespread Cong, 1996), which is termed as metagranites in this paper following the nomenclature of Xu et al. (1998). It was suggested that these metagranites did not experience the UHP metamorphism because no UHP index mineral was found until 2001. However, this suggestion was questioned by Carswell et al. (2000), who deduced from mineralogy and mineral chemistry that the metagranites were metamorphosed at P-T conditions of 36 to 18 kbar and 750 to 690°C. Furthermore, coesite inclusions were observed in zircons by Liu, F-L. et al. (2001) and Liu, J-B. et al. (2001), demonstrating that the metagranites did experience the UHP metamorphism.With respect to ages of metagranite protolith and UHP event in the Dabie terrane, a number of zircon U-Pb dating was carried out by the TIMS technique. The results show discordia upper and lower intercept ages of 800 to

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Basement evolution of the Sulu orogenic belt: Constraints on zircon U–Pb ages and trace elements from the Weihai gneisses

Lei

Xiang

2019

Geological Journal

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Early Paleoproterozoic rocks occur sporadically in the Sulu ultrahigh‐pressure (UHP) belt. The tectonic affinity and evolution of these rocks are still disputed. Two magmatic events (Early Paleoproterozoic and Neoproterozoic) and two metamorphic events (Late Paleoproterozoic and Triassic) were revealed by the zircon U–Pb ages and trace elements from the Weihai gneisses, which provide a key clue to understand the evolution of the Sulu orogen. The Early Paleoproterozoic zircons occur as residual zircons or zircon‐inherited cores in the two gneisses. They generally show oscillation zoning and enriched HREE patterns. The weighted mean age of the upper intercept age of these zircons is ~2.46 Ga, suggesting that the protolith of the ancient gneisses formed at ~2.46 Ga. The Late Paleoproterozoic zircons occur as metamorphic zircon core or mantle domains in the two gneisses and a quartzite. They generally show planar zoning or no zoning, with relative lower Th/U ratios. These zircons yield metamorphic ages of 1.8–1.84 Ga, which are consistent with the age of the Paleoproterozoic ultrahigh‐temperature metamorphism of the northern Sulu orogenic belt. The Neoproterozoic zircons occur as magmatic cores or mantles in the zircon grains of the two gneisses and their wall rocks. They show typical oscillatory zoning and enriched HREE patterns, yielding magmatic ages of ca. 740–787 Ma. The Neoproterozoic igneous rocks are the dominant basement rocks in the Sulu orogenic belt. Triassic UHP metamorphism has been well studied in the Sulu orogenic belt. Two Triassic age groups were also recognized here: 228–229 and 208 Ma, respectively. The Triassic zircons occur as metamorphic rims of the two ancient gneisses and their wall rocks. These two age ranges correspond to the time of subduction and exhumation of the the South China Craton (SCC) during the Triassic orogeny. This study provides solid evidence that the Weihai ancient gneisses have a strong affinity with the Yangtze Block. The protoliths of them are Paleoproterozoic (ca. 2.46 Ga) magmatic rocks. They were subsequently suffered from ca. 1.8‐ to 1.84‐Ga metamorphism, new crustal materials overgrowth during ca. 740‐ to 787‐Ma magmatism, and then experienced Triassic continental deep subduction and exhumation process to build the Sulu orogenic belt.

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Multichronometric Evidence for an In Situ Origin of the Ultrahigh‐Pressure Metamorphic Terrane of Dabieshan, China

Cited by 81 publications

References 46 publications

A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

Protolith age and exhumation history of metagranites from the Dabie UHP metamorphic belt in east-central China: A multi-chronological study

Basement evolution of the Sulu orogenic belt: Constraints on zircon U–Pb ages and trace elements from the Weihai gneisses

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