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Granulite

About: Granulite is a research topic. Over the lifetime, 6763 publications have been published within this topic receiving 268925 citations.


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Journal ArticleDOI
TL;DR: In this article, the authors show that rutile has a well-defined temperature of closure and that volume diffusion is the most probable mechanism responsible for the ages being younger than the time of peak metamorphism.

267 citations

Journal ArticleDOI
01 Apr 1997-Geology
TL;DR: In this article, a case study of felsic granulites from the Bohemian massif of Variscan central Europe, it appears likely that most zircons in the rocks would have grown after they were exhumed to medium pressure levels, thus, zircon growth related to high-grade metamorphism should not be automatically assumed as reflecting the age of peak P-T conditions.
Abstract: Granulite facies metamorphic events are constrained commonly through application of U-Pb zircon geochronometry. Zircon growth related to high-grade metamorphism is interpreted as reflecting the age of peak pressure-temperature ( P-T ) conditions. However, these ages obtained from granulites need to be interpreted with considerable care. Under conditions of high-grade metamorphism, it is important that the possible presence of melt is considered. Our modeling of partial melting and its impact on zircon stability implies that zircon crystallization in hot, isothermally uplifted granulites could postdate the pressure peak of the P-T path. In a case study of felsic granulites from the Bohemian massif of Variscan central Europe, it appears likely that most zircons in the rocks would have grown after they were exhumed to medium pressure levels. Thus, zircon growth related to high-grade metamorphism should not be automatically assumed as reflecting the age of peak P-T conditions.

262 citations

Journal ArticleDOI
TL;DR: The Qinling and Tongbai granulites were previously regarded as Archean to early Proterozoic in age and belonging to the southern margin of the North China plate (craton).
Abstract: The Tongbai area of the eastern Qinling belt in China includes granulite-grade metamorphic assemblages (Qinling Complex) which were previously regarded as Archean to early Proterozoic in age and belonging to the southern margin of the North China plate (craton) Our petrological and geochemical data characterize these rocks as two-pyroxene granulites and garnet granulites which formed at temperatures of 757°–840°C and pressures of about 95 kbar and are now found as xenoliths in granodioritic gneisses The protoliths of these rocks were granodiorites and tholeiitic basalt or gabbro The 207Pb/206Pb ratios derived from evaporation of single zircons yield ages of 470±20 and 470±14 Ma, respectively, for the basic granulites which we interpret to reflect the time of protolith emplacement These are intruded by a 435±14 Ma granodioritic gneiss post-dating granulite formation A metaquartzite sample contains detrital zircons as old as 2555±8 Ma Two samples of granitoid gneiss from the Tongbai Complex S of the Qinling granulites have single-zircon 207Pb/206Pb evaporation ages of 776±8 and 746±10 Ma, respectively, and document late Proterozoic igneous activity We suggest that the Qinling granulites document an important and hitherto unknown phase of early Silurian crustal thickening following subduction and continental collision and that both the Qinling and Tongbai Complexes were part of the southern margin of the North China craton prior to this event and record late Proterozoic igneous activity

259 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effects of H2O and CO2 in cordierite on phase equilibria and reaction texture analysis in UHT metamorphism.
Abstract: Ultra-high-temperature (UHT) metamorphism occurs when the continental crust is subjected to temperatures of greater than 900 °C at depths of 20–40 km. UHT metamorphism provides evidence that major tectonic processes may operate under thermal conditions more extreme than those generally produced in numerical models of orogenesis. Evidence for UHT metamorphism is recorded in mineral assemblages formed in magnesian pelites, supported by high-temperature indicators including mesoperthitic feldspar, aluminous orthopyroxene and high Zr contents in rutile. Recent theoretical, experimental and thermodynamic data set constraints on metamorphic phase equilibria in FMAS, KFMASH and more complex chemical systems have greatly improved quantification of the P–T conditions and paths of UHT metamorphic belts. However, despite these advances key issues that remain to be addressed include improving experimental constraints on the thermodynamic properties of sapphirine, quantifying the effects of oxidation state on sapphirine, orthopyroxene and spinel stabilities and quantifying the effects of H2O–CO2 in cordierite on phase equilibria and reaction texture analysis. These areas of uncertainty mean that UHT mineral assemblages must still be examined using theoretical and semi-quantitative approaches, such as P(–T)–μ sections, and conventional thermobarometry in concert with calculated phase equilibrium methods. In the cases of UHT terranes that preserve microtextural and mineral assemblage evidence for steep or ‘near-isothermal’ decompression P–T paths, the presence of H2O and CO2 in cordierite is critical to estimates of the P–T path slopes, the pressures at which reaction textures have formed and the impact of fluid infiltration. Many UHT terranes have evolved from peak P–T conditions of 8–11 kbar and 900–1030 °C to lower pressure conditions of 8 to 6 kbar whilst still at temperature in the range of 950 to 800 °C. These decompressional P–T paths, with characteristic dP/dT gradients of ∼25 ± 10 bar °C−1, are similar in broad shape to those generated in deep-crustal channel flow models for the later stages of orogenic collapse, but lie at significantly higher temperatures for any specified pressure. This thermal gap presents a key challenge in the tectonic modelling of UHT metamorphism, with implications for the evolution of the crust, sub-crustal lithosphere and asthenospheric mantle during the development of hot orogens.

259 citations

Journal ArticleDOI
01 Dec 1982-Nature
TL;DR: An experimentally calibrated geobarometer based on the solubility of alumina in orthopyroxene coexisting with garnet is presented in this article, which is based on experiments in the FeO-MgO-Al2O3-SiO2 systems performed at high temperatures and pressures (800-1,200 °C and 5-20 kbar).
Abstract: An experimentally calibrated geobarometer based on the solubility of alumina in orthopyroxene coexisting with garnet is presented. This geobarometer is based on experiments in the FeO–MgO–Al2O3–SiO2 and CaO–FeO–MgO–Al2O3–SiO2 systems performed at high temperatures and pressures (800–1,200 °C and 5–20 kbar). Applying the geobarometer to a variety of natural garnet–orthopyroxene assemblages from granulite facies terrains and other occurrences, yields reliable and consistent pressure estimates for these samples.

258 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023126
2022301
2021177
2020203
2019148
2018142