Abstract
Mineral assemblages and microstructures of a newly identified (retrogressed) eclogite (sensu lato) in the North Dabie Complex (NDC), central-eastern China, indicate early very high-pressure metamorphic relics preserved in a dominant amphibolite-facies host, where no eclogite (sensu stricto) has been positively identified before. The investigated eclogitic rock shows distinct multistage recrystallization, with granulite- and amphibolite-facies assemblages overprinting eclogite-facies relics. The minimum temperature for the eclogite-facies metamorphism is estimated to be ~800-820 °C. A spectacular microstructure of oriented quartz needles (~2-20 μm wide, ~5-200 μm long) in matrix Ca-Na clinopyroxene implies the prior existence of a non-stoichiometric “supersilicic” omphacite stabilized at ultrahigh-pressure (UHP, ³25 kbar) conditions, although no coesite or coesite pseudomorphs have been found in the samples. The absence of coesite may be due to the lack of free silica at UHP conditions or the consumption of silica during retrograde reactions. The inferred UHP conditions metamorphism is further supported by Sm-Nd ages that are equivalent to Triassic metamorphic ages from UHP eclogites in the southeastern Dabie Mountains. This finding expands the UHP terrane northward about 50 km; spatial distribution of subduction/collision-related UHP rocks includes parts of the NDC.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China
- Application of INVEQ to the geothermobarometry of metamorphic rocks near a kyanite-sillimanite isograd, Mica Creek, British Columbia
- Microstructural characterization of metamorphic magnetite crystals with implications for oxygen isotope distribution
- Coexisting monazite and allanite in peraluminous granitoids of the TribečMountains, Western Carpathians
- Effect of alkalis, phosphorus, and water on the surface tension of haplogranite melt
- Direct observation of immiscibility in pyrope-almandine-grossular garnet
- On the cluster analysis of grains and crystals in rocks
- Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
- Estimation and testing of standard molar thermodynamic properties of tourmaline end-members using data of natural samples
- An investigation of matrix effects in the analysis of fluorine in humite-group minerals by EMPA, SIMS, and SREF
- New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis
- Effect of aluminum on Ti-coordination in silicate glasses: A XANES study
- XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase
- Oxidation-reduction mechanism of iron in dioctahedral smectites: I. Crystal chemistry of oxidized reference nontronites
- Oxidation-reduction mechanism of iron in dioctahedral smectites: II. Crystal chemistry of reduced Garfield nontronite
- 15N NMR study of nitrate ion structure and dynamics in hydrotalcite-like compounds
- 29Si and 27Al MAS-NMR spectroscopy of b-eucryptite (LiAlSiO4): The enthalpy of Si,Al ordering
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- In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures
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- Optical properties of natural and cation-exchanged heulandite group zeolites
- The crystal structure of gearksutite, CaAlF4(OH)· H2O
- A new anhydrous amphibole from the Eifel region, Germany: Description and crystal structure of obertiite, NaNa2(Mg3Fe3+Ti4+)Si8O22O2
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Articles in the same Issue
- Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China
- Application of INVEQ to the geothermobarometry of metamorphic rocks near a kyanite-sillimanite isograd, Mica Creek, British Columbia
- Microstructural characterization of metamorphic magnetite crystals with implications for oxygen isotope distribution
- Coexisting monazite and allanite in peraluminous granitoids of the TribečMountains, Western Carpathians
- Effect of alkalis, phosphorus, and water on the surface tension of haplogranite melt
- Direct observation of immiscibility in pyrope-almandine-grossular garnet
- On the cluster analysis of grains and crystals in rocks
- Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
- Estimation and testing of standard molar thermodynamic properties of tourmaline end-members using data of natural samples
- An investigation of matrix effects in the analysis of fluorine in humite-group minerals by EMPA, SIMS, and SREF
- New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis
- Effect of aluminum on Ti-coordination in silicate glasses: A XANES study
- XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase
- Oxidation-reduction mechanism of iron in dioctahedral smectites: I. Crystal chemistry of oxidized reference nontronites
- Oxidation-reduction mechanism of iron in dioctahedral smectites: II. Crystal chemistry of reduced Garfield nontronite
- 15N NMR study of nitrate ion structure and dynamics in hydrotalcite-like compounds
- 29Si and 27Al MAS-NMR spectroscopy of b-eucryptite (LiAlSiO4): The enthalpy of Si,Al ordering
- The nuclear and magnetic structure of “white rust”—Fe(OH0.86D0.14)2
- In-situ study of the R3̅ to R3̅c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron powder diffraction
- In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures
- A shell model for the simulation of rhombohedral carbonate minerals and their point defects
- Optical properties of natural and cation-exchanged heulandite group zeolites
- The crystal structure of gearksutite, CaAlF4(OH)· H2O
- A new anhydrous amphibole from the Eifel region, Germany: Description and crystal structure of obertiite, NaNa2(Mg3Fe3+Ti4+)Si8O22O2
- Kinoshitalite, Ba(Mg)3(Al2Si2)O10(OH,F)2, a brittle mica from a manganese deposit in Oman: Paragenesis and crystal chemistry
- The crystal structure of parisite-(Ce), Ce2CaF2(CO3)3
- High-pressure synthesis of Na2Mg6Si6O18(OH)2—a new hydrous silicate phase isostructural with aenigmatite