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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: In this paper, the first detailed study of oxygen isotope ratios in zircon has been carried out and the results show that high-magnetism zircons are up to 2 ǫ lower in δ18O than low magnetism zirons from the same rock, consistent with the hypothesis that they represent nearly pristine samples of the parent magma.
331 citations
TL;DR: Pattison et al. as mentioned in this paper applied a thermobarometry method to 414 granulites of mafic, intermediate and aluminous bulk compositions and found that they are much hotter than traditionally assumed and that the P±T conditions of the amphibolite±granulite transition portrayed in current petrology textbooks are significant underestimates by over 100 C.
Abstract: This study assesses temperatures of formation of common granulites by combining experimental constraints on the P±T stability of granulite-facies mineral associations with a garnet± orthopyroxene (Grt±Opx) thermobarometry scheme based on Al-solubility in Opx, corrected for late Fe±Mg exchange. We applied this scheme to 414 granulites of mafic, intermediate and aluminous bulk compositions. Our findings suggest that granulites are much hotter than traditionally assumed and that the P±T conditions of the amphibolite±granulite transition portrayed in current petrology textbooks are significant underestimates by over 100 C. For aluminous and intermediate granulites, mean corrected temperatures based on our method are 890 17 and 841 11 C, respectively (uncertainties reported as 95% confidence limits on the mean), consistent with minimum temperatures for orthopyroxene production by fluid-absent partial melting in these bulk compositions. In contrast, mean temperatures based on Grt±Opx Fe±Mg exchange equilibria, using the same thermodynamic data, are 732 22 and 723 11 C, respectively, well below the minimum temperatures for Opx stability. For mafic granulites, the mean corrected temperature using our method is 816 12 C, similar to the mean temperature of 793 13 C from Fe±Mg exchange. Reasons for the differences between the mafic granulites and aluminous±intermediate granulites are unclear but may be due to the lower Al concentrations in Opx in the mafic rocks and possible deficiencies in the thermodynamic modelling of these low concentrations. We discuss a number of well-known granulite terrains in the context of our findings, including the Adirondacks, the Acadian granulites of New England, the incipient charnockites of southern India and Sri Lanka, and the Kerala Khondalite Belt. Our findings carry implications for thermotectonic models of granulite formation. A computer program to perform our thermobarometry calculations, RCLC, is available from the Journal of Petrology website at http://www.petrology.oupjournals.org or from the authors at http://www.geo.ucalgary.ca/ pattison/drm_pattison-rclc.htm.
330 citations
TL;DR: In the early Silurian low-pressure greenschist to granulite facies regional metamorphism of Ordovician flysch at Cooma, southeastern Australia, had different effects on detrital zircon and monazite and their U-Pb isotopic systems as mentioned in this paper.
Abstract: Progressive Early Silurian low‐pressure greenschist to granulite facies regional metamorphism of Ordovician flysch at Cooma, southeastern Australia, had different effects on detrital zircon and monazite and their U–Pb isotopic systems. Monazite began to dissolve at lower amphibolite facies, virtually disappearing by upper amphibolite facies, above which it began to regrow, becoming most coarsely grained in migmatite leucosome and the anatectic Cooma Granodiorite. Detrital monazite U–Pb ages survived through mid‐amphibolite facies, but not to higher grade. Monazite in the migmatite and granodiorite records only metamorphism and granite genesis at 432.8 ± 3.5 Ma. Detrital zircon was unaffected by metamorphism until the inception of partial melting, when platelets of new zircon precipitated in preferred orientations on the surface of the grains. These amalgamated to wholly enclose the grains in new growth, characterised by the development of {211} crystal faces, in the migmatite and granodiorite. New growth,...
323 citations
TL;DR: In this paper, high-pressure granulites, gneisses and marbles were used to determine the timing of metamorphism of the high-temperature and high pressure granulite and associated gneises and marble cores in the Jiao-Liao-Ji Belt.
323 citations
TL;DR: In this article, low-pressure charnockites, their tonalitic precursors, and syn-metamorphic granites in the granulite facies transition zone south of Krishnagiri, Tamil Nadu, India, define single Rb-Sr and Sm-Nd isochrons at, respectively, $$2463 \pm 65$$ and $$2455 \pm 121 Ma.
Abstract: Low-pressure charnockites, their tonalitic precursors, and syn-metamorphic granites in the granulite facies transition zone south of Krishnagiri, Tamil Nadu, India, define single Rb-Sr and Sm-Nd isochrons at, respectively, $$2463 \pm 65$$ and $$2455 \pm 121 Ma$$. Rb depletion occurred at this time, while Sm/Nd ratios were not significatively changed. Common lead ratios are identical for the granitic and tonalitic gneisses as well as the low-pressure charnockites; they are very unradiogenic ($$^{206}Pb/^{204}Pb$$: 14.5 to 15.5), indicating U depletion around 2500 Ma ago. These data suggest (1) that granulites in this part of the transition zone, as well as some high-grade charnockites south of the zone (Nilgiris and Sheravoy Hills) that yield similar results, derive from a 2.5 Ga-old crust and (2) the time elapsed between the crust-forming event and the metamorphism was short. The high-pressure charnockites of the Biligirirangan Hills, Karnataka, are different from those in the transition zone near Krishna...
322 citations