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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 geochemical behavior of detrital zircon and monazite during granulite facies anatexis in metapelites from the Eastern Ghats Belt (EGB), India, is explored using U•Pb geochronology, Hf isotopes, and trace elements.
Abstract: The geochemical behavior of detrital zircon and monazite during granulite facies anatexis in metapelites from the Eastern Ghats Belt (EGB), India, is explored using U‐Pb geochronology, Hf isotopes, and trace elements. In a metapelite from the Ongole Domain, detrital zircon reequilibrated by coupled dissolution‐reprecipitation and diffusion reaction during ultrahigh‐temperature metamorphism at 1.63 Ga. The event completely reset the U‐Pb systems, but Hf isotopes and trace elements were only partially reequilibrated. Overgrowths on the altered cores date migmatization at 1.61 Ga. Monazite yields metamorphic ages similar to those of zircon. In metapelites from the Eastern Ghats Province (EGP), detrital zircon grains give 2.44–1.40‐Ga ages and metamorphic ones 1.2–0.5‐Ga ages. Metamorphic components include detrital grains reequilibrated by coupled dissolution‐reprecipitation in the presence of anatectic melt and newly crystallized overgrowths and grains. In reequilibrated domains, the U‐Pb system wa...
94 citations
TL;DR: In this article, the authors reported U-Pb and 207Pb/206Pb zircon ages for a granulite facies gneiss assemblage exposed in a large quarry at Ihosy, southern Madagascar.
Abstract: We report U—Pb and 207Pb/206Pb zircon ages for a granulite facies gneiss assemblage exposed in a large quarry at Ihosy, southern Madagascar. The granulites are derived from pelitic to arkosic sediments and attained equilibrium conditions at 650–700°C and 4–5 kbar. Higher P—T conditions of 750–800°C and 6 kbar in the presence of low water activities have led to dehydration melting processes. The formation of granitic melts, which (partly) moved away from their source region, intruded into upper parts of the metapelitic gneisses as small granitic veins and left behind granulitic garnet-cordierite-quartz bearing rocks. Detrital zircons in a sample of metapelite and a sample of quartzofeldspathic gneiss yielded ages between ˜720 and ˜1855 Ma, suggesting a chronologically heterogeneous source region and a depositional age of less than ˜720 Ma for these rocks. High-grade metamorphism and anatexis are documented by zircon ages between 526 ±34 and 557 ±2 Ma with a mean age of about 550 Ma. The broad lithologies, metamorphic grades and ages recorded in the Ihosy rocks are similar to those in the Wanni Complex of northwestern Sri Lanka and in high-grade assemblages of southernmost India and support the contention that all these terrains were part of the Mozambique belt which formed as a result of collision of East and West Gondwana in latest Precambrian time.
94 citations
TL;DR: The earliest assemblage at Hakurutale was orthopyroxene + sillimanite + sapphirine as mentioned in this paper, which produced coarse-grained corona-forming continuous reactions.
Abstract: + spinel = sapphirine. This produced coarse-grained coronas of sequence sapphirine around the corundum and spinel. The earliest assemblage at Hakurutale was orthopyroxene + sillimanite + sapphirine. Garnet growth occurred via the reactions orthopyroxene + sillimanite + sapphirine = garnet and orthopyroxene + sillimanite = garnet + quartz. Locally, garnet was partially destroyed by a INTRODUCTION variety of corona-forming continuous reactions. The most important Rocks of highly aluminous and magnesian bulk comare garnet = orthopyroxene + sillimanite + sapphirine and position commonly record a part of the P‐T path close garnet + sillimanite = sapphirine + cordierite (both localities) to peak temperatures (e.g. Hensen, 1987), where the and, at Hakurutale, garnet + quartz = orthopyroxene + sense of the P‐T path—clockwise or counter-clockwise— sillimanite, garnet + sillimanite + quartz = cordierite and may be determined. These rocks generally contain a garnet + quartz = orthopyroxene + cordierite. In places, subset of the minerals garnet (Gar), orthopyroxene (Opx), orthopyroxene + sillimanite + quartz reacted to form cordierite, cordierite (Crd), Al-spinel (Sp) and sapphirine (Spr), in and orthopyroxene + sillimanite reacted to form cordierite + combination with sillimanite (Sil), corundum (Cor) or sapphirine coronas. At Hakurutale, inclusion textures indicate that quartz (Qz). They have been increasingly used in the sapphirine was present in the earliest recorded assemblages (prograde), last few years to deduce parts of the P‐T paths witnessed but also formed later as various corona-forming reactions occurred. by granulite-facies terranes (e.g. Droop & BucherNurminen, 1984; Droop, 1989; Bertrand et al., 1992;
94 citations
TL;DR: Coarse-grained inclusions in Upper Palaeozoic alkali basalts, occurring in over 60 localities in the British Isles, include samples of the underlying mantle and lower crust as discussed by the authors.
Abstract: Coarse-grained inclusions in Upper Palaeozoic alkali basalts, occurring in over 60 localities in the British Isles, include samples of the underlying mantle and lower crust. The ultramafic assemblages imply an extremely heterogeneous upper mantle involving a tectonized spinel lherzolite and harzburgite matrix transected by younger bodies of wehrlite, websterite, clinopyroxenite, orthopyroxenite, garnet-pyroxenite and assorted kaersutite- and biotite-rich ultramafites. Associated megacrysts include anorthoclase, sanidine, clinopyroxene, kaersutite, Ti-biotite, garnet, Ti-magnetite, Mg-ilmenite, apatite, zircon and corundum. These originated in part from disaggregation of pegmatoidal bodies of alkaline felsic rocks, pyroxenites, lherzites and glimmerites. Plagioclase-pyroxene rocks (basic granulites) are probably samples of the lower crust, with quartzo-feldspathic gneisses possibly derived from shallower levels in a chemically-zoned crust. Other inclusions described include apatite-magnetite rocks, biotite- and hornblende-albite rocks and unfoliated tonalites, diorites, trondhjemites and granites. A high-grade (granulite-facies) feldspathic basement is inferred to underlie all the major N British structural provinces, including the Midland Valley and Southern Uplands. Anorthosite xenoliths imply that anorthositic rocks compose some part of the 9basement9 in S and central Scotland.
94 citations
TL;DR: Heimefrontfjella and Mannefallknausane, in Dronning Maud Land, Antarctica, comprise an amphibolite-facies terrain and a granulite terrain, separated by a major mylonite zone as discussed by the authors.
Abstract: Heimefrontfjella and Mannefallknausane, in Dronning Maud Land, Antarctica, comprise an amphibolite-facies terrain and a granulite terrain, separated by a major mylonite zone The amphibolite terrain is made up of mafic to felsic metavolcanics and metasediments, intruded by granitoid plutons: the granulite terrain has supracrustal rocks with similar lithologies, intruded by felsic plutonic rocks that crystallized as charnockites
94 citations