Petrology and geochronology of ultrahigh-pressure granitic gneiss from South Dulan, North Qaidam belt, NW China

Ren, Yushan; Chen, Danling; Hauzenberger, Christoph; Liu, Liang; Liu, Xiaoming; Zhu, Xinming

doi:10.1080/00206814.2015.1058729

Cited by 24 publications

(21 citation statements)

References 106 publications

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“…Our results indicate that the Dulan eclogites experienced a retrograde P–T path to temperatures of ~580–660°C, enough to obliterate any evidence of lawsonite, but cold enough to preclude partial melting (Figures d, d, and c; Clarke et al., ; Wei & Clarke, ). These results contrast with the hypothesis that eclogites from the south part of the Dulan area experienced wide‐spread granulite facies conditions during exhumation (Ren et al., ; Song et al., , ; Zhang et al., ). Furthermore, phengite in metabasic rocks is expected to disappear on the solidus (Schmidt & Poli, ; Schmidt, Vielzeuf, & Auzanneau, ); the presence of this mineral in the eclogites from the southern part of the Dulan area is inconsistent with the idea that these eclogites experienced retrogression to granulite facies conditions and partial melting.…”

Section: Discussioncontrasting

confidence: 86%

“…Our P–T path of the Dulan eclogites contrasts with the nearly isothermal prograde P–T path from ~10 to ~30 kbar proposed by Ren et al. () and Zhang, Ellis, et al. () (Figure ).…”

Section: Discussioncontrasting

confidence: 82%

“…457–422 Ma have been interpreted to indicate a protracted residence at HP–UHP depths (Mattinson, Wooden, Zhang, & Bird, ; Mattinson et al., ; Zhang, Mattinson, et al., ; Zhang et al., ). Other authors have interpreted this age range as two different eclogite facies events involving oceanic and continental crust respectively (Ren et al., ; Song et al., , ; Zhang, Zhang, et al., ). Eclogite retrogression is characterized by amphibolite facies overprinting at P–T conditions of ~7–9 kbar and ~645–720°C (Song et al., ; Zhang, Zhang, et al., ).…”

Section: Geological Settingmentioning

confidence: 87%

“…The red area corresponds to the P–T conditions for the HP granulites (Yu et al., , ). The grey area represents previous P–T estimates using conventional thermobarometry for eclogites of the Dulan area (Ren et al., ; Song et al., ; Zhang, Ellis, et al., ; Zhang, Mattinson, et al., ; Zhang, Meng, et al., ; Zhang, Zhang, et al., ). Metamorphic facies and abbreviations follow Liou, Tsujimori, Zhang, Katayama, and Maruyama ()…”

Section: Discussionmentioning

confidence: 99%

“…Eclogites from the Dulan area occur as foliated and unfoliated lenses, blocks, and layers within foliated paragneisses (Mattinson et al., ; Song et al., , ). Conventional garnet+omphacite+phengite±kyanite thermobarometry of eclogites records peak P–T conditions of ~27–35 kbar and ~610–830°C (Ren et al., ; Song et al., , , ; Zhang, Mattinson, et al., ; Zhang, Meng, et al., ; Zhang, Zhang, ), and zircon U–Pb ages are c . 457–422 Ma (Mattinson et al., ; Song et al., , ; Zhang, Ellis, Christy, Zhang, & Song, ; Zhang, Mattinson, et al., ; Zhang, Meng, et al., ).…”

Section: Geological Settingmentioning

confidence: 99%

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Phase equilibrium modelling and implications forP–Tdeterminations of medium‐temperature UHP eclogites, North Qaidam terrane, China

Hernández‐Uribe

Mattinson

Zhang

2018

Journal Metamorphic Geology

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In contrast to low‐T eclogites (garnet growth zoning preserved) or high‐T eclogites (garnet diffusionally homogenized at peak conditions), medium‐temperature eclogites pose additional challenges to P–T determinations due to the partial preservation of garnet zoning. The Dulan area, in the southeastern part of North Qaidam ultrahigh‐pressure terrane, exposes minor eclogites hosted by ortho‐ and paragneisses. Four fresh, medium‐temperature eclogites contain the paragenesis Grt+Omp+Rt+Qz/Coe+Ph±Ky±Zo. In all samples, garnet XMg shows little zoning, suggesting diffusional modification, and precludes the use of pyrope+almandine+grossular isopleth intersections to determine a P–T path. However, in one sample, sharp zoning in grossular content suggests that grossular growth compositions are preserved. Since garnet pyrope+almandine compositions appear to be modified, we instead use the intersections of grossular and garnet volume isopleths to define a prograde P–T path. This approach yields a path from ~17 kbar and ~410°C to ~35 kbar and ~625°C with a gradient of ~5–9°C/km through the lawsonite stability field. Peak P–T conditions determined from the intersection between Si pfu in phengite and Zr‐in‐rutile isopleths are ~26–33 kbar and ~625–700 °C for the four eclogites. These conditions are close to the limit of the lawsonite stability field, suggesting that fluid released from lawsonite breakdown may have promoted re‐equilibration at these conditions. These peak conditions are also in good agreement (within 3 kbar and 50°C) with garnet–omphacite–phengite (±kyanite) thermobarometry in three of the four samples. We regard the phengite–rutile constraints as more reliable, because they are less sensitive to uncertainties associated with ferric iron compared to conventional thermobarometry. Phase equilibrium modelling predicts that the retrograde assemblage of amphibole+zoisite formed at ~60 km. Infiltration of external fluids was likely required for the growth of these hydrous minerals. Based on the comparison of P–T estimation methods applied in this study, we propose that the garnet grossular+volume isopleths can recover the prograde P–T path of medium‐temperature eclogites, and that the combination of phengite+rutile isopleths represents a more robust approach to constrain peak P–T conditions.

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Section: Discussioncontrasting

confidence: 86%

“…Our P–T path of the Dulan eclogites contrasts with the nearly isothermal prograde P–T path from ~10 to ~30 kbar proposed by Ren et al. () and Zhang, Ellis, et al. () (Figure ).…”

Section: Discussioncontrasting

confidence: 82%

Section: Geological Settingmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Phase equilibrium modelling and implications forP–Tdeterminations of medium‐temperature UHP eclogites, North Qaidam terrane, China

Hernández‐Uribe

Mattinson

Zhang

2018

Journal Metamorphic Geology

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Tracking the timing and nature of protolith, metamorphism, and partial melting of tourmaline‐bearing migmatites by zircon U–Pb and Hf isotopic compositions in the Yuka terrane, North Qaidam UHP metamorphic belt

Gao

Chen

et al. 2018

Geological Journal

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An integrated study using cathodoluminescence (CL) images, U–Pb geochronology, and Hf isotopic characterization of zircons was performed on migmatites from the Yuka terrane to provide insights into the timing and nature of the protoliths, metamorphism, and partial melting of these rocks. Zircon grains separated from the migmatites have three distinct domains. Residual zircon cores in samples YKT01 and YKT02 exhibit oscillatory zoning, high Th/U ratios (0.10–0.79), steep heavy rare earth element (HREE) patterns, and mean ages of 936 ± 5 Ma and 927 ± 11 Ma, respectively, indicating that they are igneous in origin and record Neoproterozoic magmatism during the Grenvillian Orogeny. CL‐grey cores record an ultrahigh‐pressure (UHP) peak metamorphism age of 435 ± 5 Ma and have low Th/U and 176Lu/177Hf ratios, weak negative Eu anomalies, and relatively flat HREE patterns. The CL‐bright rims have steep HREE patterns with lower middle rare earth element (MREE) concentrations but higher HREE concentrations compared with the metamorphic cores and a weighted average age of 422 ± 4 Ma, which records the timing of melt crystallization. The migmatites incorporate garnet relicts coexisting with fluid inclusions and hydrous minerals like peritectic phengite and peritectic large anhedral poikilitic tourmaline in the leucosomes. Peak temperatures are less than 750°C, suggesting that the anatectic melts may be derived from melting of felsic gneiss in the presence of water. The timing of melt crystallization is ca. 13 Ma later than UHP metamorphism, indicating that the partial melting took place during the exhumation stage. The metamorphic zircon cores have higher 176Hf/177Hf(t) ratios than the residual magmatic cores, which provides powerful evidence for the generation of the metamorphic zircons through the incorporation of internal high Hf minerals other than zircon in a closed system. Anatectic rims with lower 176Hf/177Hf(t) ratios but higher 176Lu/177Hf ratios than metamorphic cores suggest that the main formation mechanism is dissolution‐reprecipitation of pre‐existing zircons. In conclusion, the elevated 176Hf/177Hf(t), TDM2 age and decreasing 176Lu/177Hf(t) ratios in the metamorphic and anatectic domains imply that the new zircons in some migmatites and granites may not reflect the Hf isotope compositions of their source rocks, accounting for the variable Hf isotope compositions in S‐type granites.

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Metamorphic evolution of the East Tethys tectonic domain and its tectonic implications

Zhang,

Gao,

Chen

et al. 2023

Sci. China Earth Sci.

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Petrology and geochronology of ultrahigh-pressure granitic gneiss from South Dulan, North Qaidam belt, NW China

Cited by 24 publications

References 106 publications

Phase equilibrium modelling and implications forP–Tdeterminations of medium‐temperature UHP eclogites, North Qaidam terrane, China

Phase equilibrium modelling and implications forP–Tdeterminations of medium‐temperature UHP eclogites, North Qaidam terrane, China

Tracking the timing and nature of protolith, metamorphism, and partial melting of tourmaline‐bearing migmatites by zircon U–Pb and Hf isotopic compositions in the Yuka terrane, North Qaidam UHP metamorphic belt

Metamorphic evolution of the East Tethys tectonic domain and its tectonic implications

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