Oxygen isotope geochemistry of ultrahigh-pressure metamorphic rocks from 200–4000 m core samples of the Chinese Continental Scientific Drilling

Chen, Ren‐Xu; Zheng, Yong‐Fei; Gong, Bing; Zhao, Zi‐Fu; Gao, Tianshan; Chen, Bin; Wu, Yuqi

doi:10.1016/j.chemgeo.2007.03.008

Cited by 51 publications

(26 citation statements)

References 75 publications

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“…Its Pb isotope compositions lie between upper and lower parts, probably resulting from the mixing between the two units. In view of the lowest δ 18 O values of the middle unit [107,108] , the detachment zone might have developed along an ancient Figure 4 Common Pb profiles of omphacite in eclogite and feldspar in gneiss from the CCSD (100-2000 m) [106] . fault zone, which was a channel of cold meteoric water activity in the Neoproterozoic, resulting in lower δ 18 O values and weak mechanical strength on the rocks due to water-rock interaction.…”

Section: Evidence From the Ccsd Core Samples In North Jiangsumentioning

confidence: 99%

Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt

Liu

2008

Sci. Bull.

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Section: Evidence From the Ccsd Core Samples In North Jiangsumentioning

confidence: 99%

Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt

Liu

2008

Sci. Bull.

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“…During exhumation of the deeply subducted continental crust, hydrous fluid (especially retrograde fluid) commonly exist in the UHPM rocks [64,65]. However, preservation of heterogeneous oxygen isotopic compositions for the UHPM rocks suggests that the fluid only play a role in local scale [66], likely resulting in partial melting of UHPM rocks at small scales [67,68]. This implies the limited role of fluid in the continental subduction zones relative to the oceanic subduction zone [65], consistent with the dry LCC.…”

Section: Chemical Composition Of the Mafic Lcc: Wet Or Dry?mentioning

confidence: 73%

“…Because the main minerals in eclogites, garnet and cpx, do not contain K, the small amount of K may be accommodated in some minor minerals such as phengite and amph (e.g. [64][65][66][67][68][69]). As mentioned above, these two water-bearing minerals (especially phengite) are enriched in K. Therefore, the dry mafic UHPM rocks should also be depleted in K, similar to the mafic LCC (Table 1).…”

Section: Chemical Composition Of the Mafic Lcc: Wet Or Dry?mentioning

confidence: 99%

“…Although metamorphic rocks from the Dabie-Sulu orogenic belt contain many hydrous minerals such as phengite and amphibole (e.g. [64][65][66][67][68][69]), the volume of these minerals is still limited. This makes the water content in the eclogitic LCC of the Dabie orogen much lower than that of the hydrous altered oceanic crust.…”

Section: Chemical Composition Of the Mafic Lcc: Wet Or Dry?mentioning

confidence: 99%

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Partial melting of the dry mafic continental crust: Implications for petrogenesis of C-type adakites

Huang

2010

Chin. Sci. Bull.

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“…Previous studies have demonstrated that although fluid activity during the exhumation of deep-subducted continental crust has various ways and effects, it did not occur in large-scale fluid flow but in limited and local-scale [28][29][30] . This local-scale fluid activity can result in not only oxygen isotope difference between nearby outcrops, but also oxygen isotope heterogeneous and dis-equilibration in mm-scale in one specimen [31] . Likewise, this local-scale fluid activity can result in retrograde and recrystallization of rutilezircon-quartz systems in different specimens or even in different position of one specimen to various extents.…”

Section: The Criterion For Equilibrium Of Zr Distribution In Rutilementioning

confidence: 99%

Zr-in-rutile thermometry in eclogite at Jinheqiao in the Dabie orogen and its geochemical implications

Chen

2008

Chin. Sci. Bull.

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Trace element analysis was made by an electron microprobe on rutiles from ultrahigh-pressure eclogite at Jinheqiao in the Dabie orogen. The results show Zr contents of 37 to 118 μg·g −1 , with significant variations between grains within the same thin section. Zr-in-rutile temperatures were calculated by the pressure-dependent thermometer, yielding 595 to 678℃ at 4.1 GPa for the upper limit of metamorphic pressures. The temperatures are about 200 to 250℃ lower than temperatures of 846±70℃ calculated from garnet-omphacite Fe-Mg partition geothermometry, but 150 to 200℃ higher than ~460℃ from quartz-rutile O isotope temperatures and rutile Pb diffusion closure temperature for the same specimen. This indicates that the diffusion rate of Zr in rutile is remarkably slower than that of Pb and O in rutile, and that the temperature of Zr-in-rutile is higher than the closure temperature corresponding to cooling age as dated by rutile U-Pb radiometric system. The latter is consistent with experimental result of Zr diffusion in rutile. Diffusion and re-crystallization with intensive retrograde fluid during exhumation of UHP metamorphic rocks may be the major reason why the Zr contents in rutile decreased and thus did not provide the record of the peak metamorphic temperatures. The remarkable difference in Zr content between rutile grains suggests that the distribution of Zr in rutile was in the state of disequilibrium due to differential diffusion and retrograde resetting.rutile, thermometer, Jinheqiao eclogite, differential diffusion and retrograde, disequilibrium, U-Pb ageThe Dabie-Sulu ultrahigh-pressure metamorphic (UHPM) belt in east-central China is known to be the largest UHP terrane in the world. It has attracted worldwide attention and active research due to its large-scale and abundant UHPM rocks, and has become a new hotspot of geological studies in the world during the last two decades [1,2] . Because the changes in P-T conditions and metamorphic style during the subduction-exhumation of UHPM rocks may have significant influence on the opening/closure and equilibrium/disequilibrium of element and isotope systems in various minerals [3,4] , the UHPM rocks have provided a natural laboratory for us to study the behaviors of their geochemistry at subduction-zone metamorphism. Rutile is a common accessory mineral in eclogite. Because of its significant geochemical characteristics such as the most important carrier of HFSE, suitable object for U-Pb isotope dating, and Zr-in-rutile thermometer, rutile has attracted more and more attention from geochemists (see [5] and reference therein).Zr-in-rutile thermometer is a newly developed approach by use of the temperature dependence of trace element distribution in single mineral [6][7][8][9] . It has attracted wide interest soon after its come out due to its simpleness and practicality, and has been applied to several high-grade metamorphic rocks [10][11][12][13][14][15][16] . Further

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Oxygen isotope geochemistry of ultrahigh-pressure metamorphic rocks from 200–4000 m core samples of the Chinese Continental Scientific Drilling

Cited by 51 publications

References 75 publications

Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt

Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt

Partial melting of the dry mafic continental crust: Implications for petrogenesis of C-type adakites

Zr-in-rutile thermometry in eclogite at Jinheqiao in the Dabie orogen and its geochemical implications

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