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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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TL;DR: The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low-to high-grade rocks outcropping in the area around Yaounde as mentioned in this paper.
Abstract: The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low- to high-grade rocks outcropping in the area around Yaounde. The fabrics in these rocks are con- sistent with two main ductile deformation events D1 and D2 .D 1 predated emplacement of calc-alkaline dioritic bodies and caused the formation of nappes that resulted in high-pressure granulite metamorphism of soft sediments. A strong overprinting of these nappes during D2 symmetric extension, probably associated with large-scale foliation boudinage and (or) gneissic doming and intense magmatic underplating, gave rise to regional flat-lying fabrics. The latter were further buckled by D3 and D4 folding phases defining a vertical constriction occurring with a major east-west to NW- SE shortening direction. The corresponding F3 and F4 folds trend north-south to NE-SW and east-west to NW-SE, respectively, and represent the main regional strain patterns. Based on the east-west to NW-SE maximum shortening orientation indicated by F3 folds, it is proposed that the nappe-stacking phase D 1 occurred in the same direction. The deformation history in the area can thus be described as corresponding principally to alternating east-west to NW-SE contractions and north-south to NE-SW orogenic-parallel extensions. At the regional scale, this could be due to the Transaharan east-west collisional system.

92 citations

Journal ArticleDOI
TL;DR: Garnet geochronology was used to provide the first direct measurement of the timing of eclogitization in the central Himalaya as discussed by the authors, and the results indicated that Lu-Hf dates from garnet amphibolites from the Arun River Valley in eastern Nepal indicate an age of 20.7 ± 0.4.

92 citations

Journal ArticleDOI
TL;DR: In this article, a direct link is implied between Y, Sm, Eu and Gd in monazite and two major phases in continental lower crust: garnet and plagioclase.
Abstract: Monazite is a common accessory phase in felsic granulite ribbon mylonites exposed in the Upper Deck domain of the Athabasca granulite terrane, western Canadian Shield. Field relationships, bulk rock geochemistry and phase equilibria modelling in the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3 system are consistent with the garnet-rich rocks representing the residual products of ultrahigh temperature melting of biotite-bearing paragneisses driven by intraplating of mafic magma in continental lower crust. The c. 2.64–2.61 Ga Y-rich resorbed monazite cores included in garnet are interpreted as relicts of detrital grains deposited on the Earth's surface after c. 2.61 Ga. Yttrium-poor monazite domains in garnet are depleted in Sm and Gd and linked to fluid-absent melting of biotite + plagioclase + quartz ± sillimanite during a prograde loading path from ≤0.8 to ≥1.4 GPa. The c. 2.61–2.55 Ga Y-depleted, Th-rich monazite domains crystallized in the presence of garnet + ternary feldspar ± orthopyroxene + peraluminous melt. The c. 2.58–2.52 Ga monazite rims depleted in Th + Ca and enriched in Eu are linked to localized melt extraction synchronous with growth of high-pressure (HP) grossular-rich garnet at the expense of plagioclase during crustal thickening, culminating at >950 °C. Re-heating and dextral transpressive lower crustal reactivation at c. 1.9 Ga resulted in syn-kinematic growth of (La + Ce)-enriched monazite and a second generation of garnet, concurrent with recrystallization of feldspar and orthopyroxene at 1.0–1.2 GPa and 600–700 °C. Monazite grains in this study are marked by positive Eu-anomalies relative to chondrite. A direct link is implied between Y, Sm, Eu and Gd in monazite and two major phases in continental lower crust: garnet and plagioclase. Positive Eu-anomalies in lower crustal monazite associated with modally abundant garnet appear to be directly related to Eu-enrichment and depletions of Y, Sm and Gd that are consequences of garnet growth and plagioclase breakdown during HP melting of peraluminous bulk compositions.

92 citations

Journal ArticleDOI
TL;DR: In this paper, the age of granulite facios metamorphism has been defined by coupling whole-rock Sm-Nd analyses of the principal members of the South Harris Igneous Complex, with Sm-nd mineral isochrons on two anothositic gabbros.
Abstract: Sm-Nd geochronology may be used to bracket the age of metamorphism in rocks which are difficult to date by other methods. By coupling whole rock Sm-Nd analyses of the principal members of the South Harris Igneous Complex, with Sm-Nd mineral isochrons on two anothositic gabbros, the age of granulite facios metamorphism has been defined. Whole rock analyses of three pairs of closely spaced samples of the anorthosite give consistent ages averaging 2.18±0.06 Gyr, but in general the data from the anorthosite do not define an isochron as a result of variable contamination of the evolving magma chamber. Whole rock data on the tonalite indicate that it is younger than 2.06 Gyr; its mean TCHUR age is 1.86±0.05 Gyr. Garnet-pyroxene-amphibole-plagioclase mineral isochrons on two anorthosite samples give identical 1.87±0.04 Gyr ages which date cooling after the high pressure granulite facies metamorphism. Together with the tonalite whole rock data this defines the age of that metamorphism and confirms Dearnley's original assignment of an early Laxfordian age.

91 citations

Journal ArticleDOI
TL;DR: A c. 700 km2 area of northern Fiordland (South Island, New Zealand) is described in which Early Cretaceous high-pressure metamorphic rocks and virtually unmetamorphosed plutonic rocks occur as mentioned in this paper.
Abstract: A c. 700 km2 area of northern Fiordland (South Island, New Zealand) is described in which Early Cretaceous high-pressure metamorphic rocks and virtually unmetamorphosed plutonic rocks occur. The dominant rocks are orthogneisses developed from synmetamorphic basic-intermediate intrusive complexes, the youngest and most widespread of which is the Early Cretaceous Western Fiordland Orthogneiss (WFO). The latter has undergone granulite facies metamorphism and occurs throughout much of western Fiordland. In the study area, the WFO protolith intruded a country rock of amphibolite facies metasediments and orthogneisses. Fragments of the country rock are rafted within WFO and are represented by George Sound Paragneiss and Rafted Granitoid Gneisses. External country rock is represented by Arthur River Complex and Jagged Gneiss (possibly related to the Anita Ultramafites); it may also include Indecision Creek Complex and Mount Anau Complex. The George Sound Paragneiss is correlated with the Central Fiordla...

91 citations


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