Mineral Inclusions in Zircon from Gneisses in the Ultrahigh‐Pressure Zone of the Dabie Mountains, China

Liu, Jingbo; Yang, Kai; Shegnori, Maruyama; Cong, Bin; Fan, Hong‐Rui

doi:10.1086/320796

Cited by 159 publications

(65 citation statements)

References 25 publications

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“…been proposed to account for the presence of inclusions in zircon [14,75]: ( i ) entrapping concurrent formation minerals during zircon growth (primary inclusion); (ii) squeezing inclusion mineral along fracture into the preexisting zircon (secondary inclusion); (iii) changing precursory mineral inclusion into new mineral inclusion during metamorphism. Once mineral inclusions were entrapped into zircon, their composition can hardly be changed because of the high mineral stability of zircon [75].…”

Section: Reviewsmentioning

confidence: 99%

Genesis of zircon and its constraints on interpretation of U-Pb age

2004

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Zircon V-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon V-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of V-Pb age. Three methods have been proposed to link zircon V-Pb age to metamorphic conditions: ( i ) internal structure; (ii) trace element feature; (iii) mineral inclusion composition. Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances, with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks. Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore, interpretation of zircon V-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.

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Section: Reviewsmentioning

confidence: 99%

Genesis of zircon and its constraints on interpretation of U-Pb age

2004

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“…A few rutile inclusions can be observed in the zircon, and rutile concentrates were separated from the Shuanghe metagranite. Carswell et al (2000), You et al (2000), Liu, F-L. et al (2001) and Liu, J-B. et al (2001) also observed that the above-mentioned mineral assemblages in metagranites (i.e., granitic orthogneisses in their notation) from eastern Dabie were similar to those in the eclogite-bearing paragneisses despite some distinct differences in mineral chemistry.…”

Section: Early Mesozoic Metamorphismmentioning

confidence: 88%

“…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.…”

mentioning

confidence: 95%

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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“…0.7 to 0.8 Ga (e.g., Ishizaka et al, 1994;Guo et al, 2005;Ames et al, 1996;Hacker et al, 1998). This terrain comprises part of the Sulu UHP belt that was subjected to HP-UHP metamorphism during the early Mesozoic (e.g., Cong, 1996;Zhai et al, 2000;Guo et al, 2005;Liu et al, 2001). It is considered as part of the Yangtze block (e.g., Ames et al, 1996;Hacker et al, 1998;Guo et al, 2005).…”

Section: Geological Settingmentioning

confidence: 99%

South China provenance of the lower-grade Penglai Group north of the Sulu UHP orogenic belt, eastern China: Evidence from detrital zircon ages and Nd-Hf isotopic composition

Chen

Guo

et al. 2007

Geochem. J.

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The Dabie-Sulu ultrahigh-pressure orogenic belt resulted from the early Mesozoic collision of the North China block and South China block (comprising the Yangtze and the Cathaysia) and subsequent exhumation of the subducted South China continental slabs. This belt consists of tectonically juxtaposed rock units of different metamorphic grade. Provenance of the low-grade metamorphic terranes exposed along the northern part of the belt can offer useful information about the location of the boundary between these two continental blocks. This study reports detrital zircon ages and Nd-Hf isotopic composition of sedimentary rocks of the low-grade Penglai Group, situated north of the Sulu UHP terrane. Results show that detrital zircon grains mostly crystallized during Mesoproterozoic time, clustering at 1.7 Ga to 1.6 Ga and 1.2 Ga. Nd isotopic composition (T DM value) of the Penglai Group suggests that sedimentary sources are similar to average crustal material of the Yangtze block and mostly formed in Paleo-to Mesoproterozoic. Late Mesoproterozoic detrital zircons probably demonstrate that sedimentary material was derived from the boundary of the Yangtze and Cathaysia blocks, which was formed by the late Mesoproterozoic convergence. Absence of Neoproterozoic detrital zircons from the Penglai sediments probably suggests a late Mesoproterozoic to early Neoproterozoic deposition age (about 1.1 Ga to 0.8 Ga). The age and isotopic evidence implies that the Penglai Group originated from the South China block and probably was thrust onto the basement of the North China block during the early Mesozoic continental collision.

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Mineral Inclusions in Zircon from Gneisses in the Ultrahigh‐Pressure Zone of the Dabie Mountains, China

Cited by 159 publications

References 25 publications

Genesis of zircon and its constraints on interpretation of U-Pb age

Genesis of zircon and its constraints on interpretation of U-Pb age

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

South China provenance of the lower-grade Penglai Group north of the Sulu UHP orogenic belt, eastern China: Evidence from detrital zircon ages and Nd-Hf isotopic composition

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