Ages of ultrahigh pressure metamorphism and protolith orthogneisses from the eastern Dabie Shan: U/Pb zircon geochronology

Rowley, David B.; Xue, Feng; Tucker, Robert D.; Peng, Zidong; Baker, Judy; Davis, A. M.

doi:10.1016/s0012-821x(97)81848-1

Cited by 393 publications

(201 citation statements)

References 27 publications

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“…This age is in agreement with the U-Pb concordia upper intercept ages of 700-800 Ma previously obtained on zircons from gneisses (Ames et al 1993;Rowley et al 1997;Xue et al 1997;Hacker et al 1998). The Th/U ratios of gneiss zircon on either core or rim fall within the range, which is identical 1.0 ‫ע‬ 0.4 within error to the observed Th/U ratios in the zircon cores analyzed by Rowley et al (1997), which implies that they have an igneous origin. In contrast, the Bixiling gneisses have much older T DM ages, which range from 1.35 to 1.54 Ga (table 1) and of Ϫ5 (fig.…”

Section: Discussionsupporting

confidence: 91%

“…However, the destabilization of rutile into ilmenite is indicative of an earlier, higher PT condition. The Triassic UHP metamorphic age of the Bixiling Complex was established on the basis of seven Sm-Nd garnet-omphacite-WR isochrons between and Ma (Chavagnac and Jahn 210 ‫ע‬ 9 218 ‫ע‬ 4 1996), which are close to the 220-230 Ma obtained on U-Pb zircon ages (Ames et al 1993;Ames 1995;Maruyama et al 1995;Rowley et al 1997;Hacker et al 1998). The primary intrusive age of the Bixiling Complex was constrained by a Sm-Nd garnetonly isochron (7 points, ; Chavagnac MSWD p 0.7 and Jahn 1996).…”

Section: Geological Setting and Sample Descriptionmentioning

confidence: 84%

“…Our U-Pb data on zircon from the country rock do not emphasize the Triassic UHPM age as did eclogitic zircons. Up to now, only zircons from the Shima and Wumiao eclogite host gneisses, which present extreme metamorphic conditions (pressure up to 41 kbars), recorded the 220-210-Ma event (Ames et al 1993;Rowley et al 1997;Xue et al 1997;Hacker et al 1998). The lack of a record of ∼220-Ma ages in the gneissic zircons may simply be an artifact of sampling, or it may indicate the inability of zircons to accrete new rims during retrograde metamorphism due to a lack of suitable fluids.…”

Section: Discussionmentioning

confidence: 96%

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

Chavagnac

Jahn²,

Villa

et al. 2001

The Journal of Geology

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A B S T R A C TU-Pb zircon data on gneisses indicate a Late Proterozoic protolith at ∼700 Ma at Bixiling and a Late Archean to Early Proterozoic for the Shuanghe sheet within the ultrahigh-pressure metamorphic terrane of Dabieshan (China). U-Pb zircon and Sm-Nd dates on the gneisses of the Shuanghe sheet constrain a metamorphic peak at ∼230 Ma. Rb-Sr and 40 Ar-39 Ar analyses of phengite from five gneisses in the Bixiling Complex yield ages at 198-212 Ma, overlapping the 190-220-Ma age on eclogites. The host gneisses record a similar metamorphic evolution as the coesite-bearing eclogites since both the peak and the retrograde evolution were contemporaneous. This argues for an in situ tectonic relationship.

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Section: Discussionsupporting

confidence: 91%

Section: Geological Setting and Sample Descriptionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 96%

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

Chavagnac

Jahn²,

Villa

et al. 2001

The Journal of Geology

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“…Giorgis et al (2000) suggested that 40 Ar in phengite may represent argon inherited from the protolith of the UHP eclogite, rather than excess, i.e., parentless, argon [nomenclature following McDougall and Harrison (1999)]. Zircon U-Pb ages span a wide range from 210 to 970 Ma with three groups: 210-240 Ma (Ames et al, 1996;Rowley et al, 1997;Hacker et al, 1998;Li et al, 2000;Wan et al, 2005;Xie and Chen, 2005), 420-480 Ma (Jian et al, 1994;Yang et al, 1995;Jian et al, 2000;Gao et al, 2002;Yang et al, 2005) and 650-970 Ma (Liu et al, 1995;Cheng et al, 2000;Wan et al, 2005). A few Early Proterozoic-Late Archean U-Pb ages of 2200-2770 Ma were obtained Zhu, 1995, 1996;Liu et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Paleozoic ages and excess 40Ar in garnets from the Bixiling eclogite in Dabieshan, China: New insights from 40Ar/39Ar dating by stepwise crushing

Qiu

Wijbrans

2006

Geochimica et Cosmochimica Acta

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The 40 Ar/ 39 Ar stepwise crushing technique is applied for the first time to date garnet from ultra-high-pressure metamorphic (UHPM) eclogites. Three garnet samples from the Bixiling eclogites analyzed by 40 Ar/ 39 Ar stepwise crushing yield regular, predictable age spectra, and a clear separation between excess 40 Ar and concordant plateau and isochron ages. All three age spectra begin with high apparent ages followed by step by step decreasing ages, and finally age plateaux with apparent ages in the range from 427 ± 20 to 444 ± 10 Ma. The data points constituting the age plateaux yield excellent isochrons with radiogenic intercept ages ranging from 448 ± 34 to 459 ± 58 Ma, corresponding to initial 40 Ar/ 36 Ar ratios from 292.1 ± 4.5 to 294.5 ± 6.7, statistically indistinguishable from the modern air. The high initial ages are interpreted to derive from secondary fluid inclusions containing excess 40 Ar, whereas the plateau ages are attributed to gas from small primary fluid inclusions without significant excess 40 Ar. The plateau ages are interpreted to approximate the time of garnet growth during initial UHPM metamorphism. Phengite analyzed by laser stepwise heating yielded a complicated two-saddle age spectrum with a scattered isochron corresponding to age of 463 ± 116 Ma and initial 40 Ar/ 36 Ar ratio of 1843 ± 1740 indicative of the presence of extraneous 40 Ar within phengite. These concordant isochron ages measured on minerals diagnostic of eclogite grade metamorphism strongly suggest that Dabie UHPM eclogites were first formed in the early Paleozoic, during the same event that caused the Qinling-Northern Qaidam Basin-Altyn Tagh eclogites.

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“…Although recent studies have shown that the North and South China (Yangtze) blocks likely underwent similar thermal events in the early Precambrian, especially in late Archean and early Proterozoic (e.g., Zheng et al, 2006;Zhang et al, 2006), they have had different thermal histories during Late Proterozoic and Early Paleozoic times. During the Late Proterozoic, the evolution of the Yangtze block was associated with magmatic-metamorphic events especially along the northern and western margins (e.g., Chen et al, 2003a, b;Rowley et al, 1997;Xue et al, 1997;Hacker et al, 1998). The southern margin of the North China block, in turn, was characterized by Early Paleozoic magmatism and metamorphism (e.g., Kröner et al, 1993;Zhai et al, 1998;Zhang, 1999, 2000).…”

Section: Discussionmentioning

confidence: 99%

Single-grain detrital muscovite Rb-Sr isotopic composition as an indicator of provenance for the Carboniferous sedimentary rocks in northern Dabie, China

et al. 2009

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Low-grade metamorphic Paleozoic sedimentary rocks are exposed along the northern margin of the Qinling-Dabie orogenic belt that formed by the collision of the North and South China blocks during the Early Mesozoic. Geological provenance and tectonic setting of these low-grade sedimentary rocks are strongly debated. Recent studies have shown that they contain Paleozoic, Late Proterozoic and Late Archean detrital zircons, which points to an origin from different sources including rocks from the South and North China blocks. This study presents single-grain mineral Rb-Sr results for detrital muscovites and biotites from Carboniferous sedimentary sequences of the Beihuaiyang low-grade metamorphic zone exposed along the northern margin of the Dabie Mountains. About 15% of detrital muscovite grains are phengitic in composition with high Si/Al ratios of >3.3. Single grain Rb-Sr isotopic analyses show that both muscovites and phengites give a pooled age of about 420 Ma, implying Middle Paleozoic thermal and high-pressure metamorphic events in the source area(s). Rb-Sr isotopic evidence from detrital biotites suggests at least two different sedimentary sources of old crustal rocks and juvenile material. The latter probably comprised magmatic rocks related to the Paleozoic convergence along the southern margin of the North China block. Whole-rock Sm-Nd isotopic composition of the sedimentary rocks also demonstrates a mixture of sedimentary sources of different ages that confirm conclusions proposed previously from evidence of detrital zircon ages. We conclude that the Paleozoic detrital phengites originate from Paleozoic subduction and subsequent collision proposed for the North Qinling terrane. Our study shows that, single-grain detrital mica Rb-Sr isotopic characteristics can be a potential indicator for the provenance of geological complex terranes.

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Ages of ultrahigh pressure metamorphism and protolith orthogneisses from the eastern Dabie Shan: U/Pb zircon geochronology

Cited by 393 publications

References 27 publications

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

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

Paleozoic ages and excess 40Ar in garnets from the Bixiling eclogite in Dabieshan, China: New insights from 40Ar/39Ar dating by stepwise crushing

Single-grain detrital muscovite Rb-Sr isotopic composition as an indicator of provenance for the Carboniferous sedimentary rocks in northern Dabie, China

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