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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 authors showed that LILE deficiency is not a pre-condition of granulite facies metamorphism: granulites may have either "depleted" or "normal"chemistries.
Abstract: The orthopyroxene-clinopyroxene, garnet-orthopyroxene and garnet-clinopyroxene geothermometers, and the garnet-orthopyroxene-plagioclase, garnet-clinopyroxene-plagioclase and anorthite-ferrosilite-grossular-almandine-quartz geobarometers are applied to metabasites and the garnetplagioclase-sillimanite-quartz geobarometer is applied to a metapelite from the Proterozoic Arendal granulite terrain, Bamble sector, Norway. P–T conditions of metamorphism were 7.3 ± 0.5 kbar and 800 ± 60°C.
This terrain shows a regional gradation from the amphibolite facies, into normal LILE content granulite facies rocks and finally strongly LILE deficient granulite facies gneisses. Neither P nor T vary significantly across the entire transition zone. The change in ‘grade’parallels the increasing dominance of CO2 over H2O in the fluid phase.
LILE-depletion is not a pre-condition of granulite facies metamorphism: granulites may have either ‘depleted’or ‘normal’chemistries. The results presented herein show that LILE-deficiency in granulite facies orthogneisses is not necessarily related to variations in either P or T. The important mechanisms in the Arendal terrain were (a) direct synmetamorphic crystallization from magma, with primary LILE-poor mineralogies imposed by the prevailing fluid regime, and (b) metamorphic depletion, involving scavenging of LILEs during flushing by mantle-derived CO2-rich fluids. The latter process is constrained by U–Pb and Rb–Sr isotopic work to have occurred no later than 50 Ma after intrusion of the acid-intermediate gneisses, and was probably associated with contemporary basic magmatism in a tectonic environment similar to a present day cordilleran continental margin.
75 citations
TL;DR: In situ UPb ages of zircons from crustal rocks have been measured by laser ablation ICP-MS as discussed by the authors, and these results, together with previously published ages for Man Shield rocks, indicate an early Archean crust formation event followed by major crustal growth at 2.9-3.0 Ga.
75 citations
TL;DR: The Lewisian complex of the Scourie-Badcall area is composed predominantly of banded tonalitic gneiss which intrudes layered gabbro-ultramafic complexes.
Abstract: The Lewisian complex of the Scourie-Badcall area is composed predominantly of banded tonalitic gneiss which intrudes layered gabbro-ultramafic complexes. Intrusive into both gabbro and tonalitic gneiss are homogeneous acid sheets which are trondhjemitic to granitic in composition. All rocks were subjected to granulite facies metamorphism.
75 citations
TL;DR: In this paper, the core of a garnet porphyroblast, along with fine-grained inclusions of biotite+plagioclase+k-feldspar+quartz+granulites, defines the prograde metamorphic (M1) stage.
75 citations
TL;DR: In this paper, the authors show evidence for granulite-facies metamorphism older than the 1930±30 Ma-old Nyika Granite and constrain the end of regional high-temperature conditions.
75 citations