Partial melting of UHP calc-gneiss from the Dabie Mountains

Liu, Penglei; Wu, Yao; Liu, Qiang; Zhang, Junfeng; Zhang, Li; Zhang, Jin

doi:10.1016/j.lithos.2014.01.012

Cited by 42 publications

(25 citation statements)

References 111 publications

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“…The discovery of coesite and/or diamond inclusions in various types of rock (e.g., gneiss, eclogite, amphibolite, marble and jadeite quartzite) through the Dabie-Sulu orogen indicates that continental crust has been subducted at a depth of 80-200 km and subsequently exhumed to the Earth's surface. During subduction, dehydration reactions of some hydrous minerals (e.g., lawsonite, phengite and chlorite) and partial melting of other regional metamorphic rocks (e.g., gneiss and eclogite) occur at high temperature and pressure (Xu et al, 2013;Liu et al, 2014). Previous field MT results have found that high conductivity anomalies with magnitudes of 10 −1 S m −1 are widely distributed at 10-20 km in the DabieSulu UHPM belt (Xiao et al, 2007).…”

Section: Geophysical Implicationsmentioning

confidence: 98%

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Dai

Sun

et al. 2018

Solid Earth

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Abstract. The electrical conductivity of gneiss samples with different chemical compositions (W A = Na 2 O + K 2 O + CaO = 7.12, 7.27 and 7.64 % weight percent) was measured using a complex impedance spectroscopic technique at 623-1073 K and 1.5 GPa and a frequency range of 10 −1 to 10 6 Hz. Simultaneously, a pressure effect on the electrical conductivity was also determined for the W A = 7.12 % gneiss. The results indicated that the gneiss conductivities markedly increase with total alkali and calcium ion content. The sample conductivity and temperature conform to an Arrhenius relationship within a certain temperature range. The influence of pressure on gneiss conductivity is weaker than temperature, although conductivity still increases with pressure. According to various ranges of activation enthalpy (0.35-0.52 and 0.76-0.87 eV) at 1.5 GPa, two main conduction mechanisms are suggested that dominate the electrical conductivity of gneiss: impurity conduction in the lower-temperature region and ionic conduction (charge carriers are K + , Na + and Ca 2+ ) in the higher-temperature region. The electrical conductivity of gneiss with various chemical compositions cannot be used to interpret the high conductivity anomalies in the Dabie-Sulu ultrahigh-pressure metamorphic belt. However, the conductivity-depth profiles for gneiss may provide an important constraint on the interpretation of field magnetotelluric conductivity results in the regional metamorphic belt.

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Section: Geophysical Implicationsmentioning

confidence: 98%

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Dai

Sun

et al. 2018

Solid Earth

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“…Significant field evidence exists for substantial fluid flow through deeply subducted sediments and oceanic crustal rocks, as preserved in veins and textures in the Dabie Shan region of China, Zambezi Belt in Zambia, and the Franciscan complex in California (Franz et al, 2001;John and Schenk, 2003;Romer et al, 2003;Sadofsky and Bebout, 2001;review by Bebout, 2007). With only a few exceptions (suites that appear to have experienced melting during exhumation; e.g., see Zheng et al, 2011;Liu et al, 2014), these suites lack field, petrographic, or geochemical evidence for having been partially melted and most or all of them experienced peak metamorphism firmly within the subsolidus P-T region (see discussion by Bebout, 2007). Therefore, it appears that C loss in the deep forearc (60-100 km depths) occurs largely via decarbonation and other devolatilization reactions rather than via melting reactions (except perhaps in particularly warm margins such as Cascadia).…”

Section: Partial Melting Beneath Some Arcs and At Greater Depths In Tmentioning

confidence: 99%

Subduction zone metamorphic pathway for deep carbon cycling: I. Evidence from HP/UHP metasedimentary rocks, Italian Alps

Cook-Kollars¹,

Bebout²,

Collins³

et al. 2014

Chemical Geology

105

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“…These features have been successfully used to identify anatexis in the UHP metamorphic rocks from the Dabie‐Sulu orogenic belt (e.g. Zhao et al ., ; Zeng et al ., ; Gao et al ., ,b; Chen et al ., ,b; Liu et al ., , ).…”

Section: Discussionmentioning

confidence: 99%

“…Metamorphic dehydration and partial melting of high‐pressure (HP) to ultrahigh‐pressure (UHP) metamorphic rocks have different impacts on the physicochemical properties of continental crust at subduction‐zone conditions (Zheng et al ., ). While metamorphic dehydration of the continental crust is common during subduction to and exhumation from mantle depths (Zheng, ), the anatexis of UHP rocks often takes place in their exhumation stage (Zheng et al ., , and references therein; Gao et al ., ,b; Liu et al ., , ; Chen et al ., ,b; Zeng et al ., ; Song et al ., ). However, recent studies found that such anatexis can also occur during subduction at the transition from HP to UHP eclogite facies (Xia et al ., ; Chen et al ., ) and even at the peak UHP stage (Labrousse et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Dehydration and anatexis of UHP metagranite during continental collision in the Sulu orogen

Chen

Zheng

et al. 2014

Journal Metamorphic Geology

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Dehydration and anatexis of ultrahigh-pressure (UHP) metamorphic rocks during continental collision are two key processes that have great bearing on the physicochemical properties of deeply subducted continental crust at mantle depths. Determining the time and P-T conditions at which such events take place is needed to understand subduction-zone tectonism. A combined petrological and zirconological study of UHP metagranite from the Sulu orogen reveals differential behaviours of dehydration and anatexis between two samples from the same UHP slice. The zircon mantle domains in one sample record eclogite facies dehydration metamorphism at 236 AE 5 Ma during subduction, exhibiting low REE contents, steep MREE-HREE patterns without negative Eu anomalies, low Th, Nb and Ta contents, low temperatures of 651-750°C and inclusions of quartz, apatite and jadeite. A second mantle domain records high-T anatexis at 223 AE 3 Ma during exhumation, showing high REE contents, steeper MREE-HREE patterns with marked negative Eu anomalies, high Hf, Nb, Ta, Th and U contents, high temperatures of 698-879°C and multiphase solid inclusions of albite + muscovite + quartz. In contrast, in a second sample, one zircon mantle domain records limited hydration anatexis at 237 AE 3 Ma during subduction, exhibiting high REE contents, steep MREE-HREE patterns with marked negative Eu anomalies, high Hf, Nb, Ta, Th and U contents, medium temperatures of 601-717°C and multiphase solid inclusions of albite + muscovite + hydrohalite. A second mantle domain in this sample records a low-T dehydration metamorphism throughout the whole continental collision in the Triassic, showing low REE contents, steep MREE-HREE patterns with weakly negative Eu anomalies, low Th, Nb and Ta contents, low temperatures of 524-669°C and anhydrite + gas inclusions.Garnet, phengite and allanite/epidote in these two samples also exhibit different variations in texture and major-trace element compositions, in accordance with the zircon records. The distinct P-T-t paths for these two samples suggest separate processes of dehydration and anatexis, which are ascribed to the different geothermal gradients at different positions inside the same crustal slice during continental subduction-zone metamorphism. Therefore, the subducting continental crust underwent variable extents of dehydration and anatexis in response to the change in subduction-zone P-T conditions.

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Partial melting of UHP calc-gneiss from the Dabie Mountains

Cited by 42 publications

References 111 publications

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Subduction zone metamorphic pathway for deep carbon cycling: I. Evidence from HP/UHP metasedimentary rocks, Italian Alps

Dehydration and anatexis of UHP metagranite during continental collision in the Sulu orogen

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