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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
Ralph Kretz1
01 Jan 1969-Lithos
TL;DR: The distribution of crystals and crystal boundaries in a thin-section of a pyroxene-scapolite-sphene granulite from Quebec is examined in detail in this paper.

103 citations

Journal ArticleDOI
TL;DR: The amphibolite-facies gneisses consist of quartz, biotite, plagioclase, garnet, K-feldspar, sillimanite and were identified as metapelites, metagreywackes and quarzites with minor carbonates as mentioned in this paper.

103 citations

Journal ArticleDOI
TL;DR: The coastal terrane of the Three Palms Mylonite Zone as discussed by the authors contains evidence for an arc-backarc wrench-shear system that developed inboard an E-dipping subduction system where the Adamastor Ocean was subducted beneath the leading edge of the attenuated Congo Craton.

103 citations

Journal ArticleDOI
TL;DR: In this article, the contaminant is also shown to have been enriched in Ba with respect to Rb and K. The results of this study can be explained by melting of granulite-facies paragneiss, which had previously been depleted in K and Rb by an earlier melting event.
Abstract: The Ivrea-Verbano and adjacent Strona-Ceneri zones have been described collectively as a section through the continental crust. While resident in the lower crust, amphibolite to granulite-facies paragneiss of the Ivrea-Verbano Zone was intruded by huge volumes of mafic to intermediate plutonic rocks grouped as the Mafic Complex. Growth of the Mafic Complex involved hypersolidus deformation in an extensional environment. Isotopic and trace element variations close to the axis of this structure indicate crystallization from mantle-derived melts that were extensively contaminated by crustal material. Previous investigations determined that the contaminant was fingerprinted by 87Sr/86Sr > 0.71, δ18O = 10–12.5‰, and a positive Eu anomaly. In the present study, the contaminant is also shown to have been enriched in Ba with respect to Rb and K. Charnockites associated with paragneiss septa in the lower part of the Mafic Complex have the appropriate chemistry to be samples of the contaminating material. These chemical features can be explained by melting of granulite-facies paragneiss, which had previously been depleted in K and Rb by an earlier melting event. The Ba enrichment in the core of the Mafic Complex can be modeled by a replenishment-tapping-fractional-crystallization (RTF) process operating within a small magma chamber is repeatedly replenished by mantle melts and contaminated by Ba-rich charnockite. Very high Ba/K in the lower part of the complex are tentatively attributed to chemical exchange between the cumulate framework and infiltrating anatectic melts from underlying paragneiss septa. In contrast to the Mafic Complex, the chemistry of coeval granites in the adjacent Strona-Ceneri zone reflect a component derived from crustal rocks that had not been significantly depleted by a previous melting event. Significantly, the incompatible trace element abundances in the Mafic Complex and Strona-Ceneri granites are similar to model compositions for the lower and upper crust, respectively.

103 citations

Journal ArticleDOI
TL;DR: For example, in this article, the authors show that extensional shear zones are common in central Madagascar, locally controlling amphibolite-facies retrogression of granulite facies and the emplacement of crustal melt granites.
Abstract: New 207 Pb/ 206 Pb single zircon evaporation ages for granulites, gneisses and granites in southern and central Madagascar record a widespread Pan-African metamorphic and magmatic event in the period c. 650–556 Ma, but also earlier ages in the range 1890–1710 Ma, inherited from protolith material and reflecting heterogeneous crustal sources. South of the Ranotsara shear zone, metasedimentary gneisses and granulites contain an early population of detrital zircons with ages in the range 1890–1740 Ma; a detrital grain with an age of 899 ± 2 Ma suggests that some sedimentary protoliths were deposited later than c. 900 Ma. Metamorphic zircons have a mean age of 564.2 ± 0.9 Ma. North of the Ranotsara shear zone, our data provide information on the age of source material of metamorphic rocks: 788.6 ± 0.7 Ma for the time of emplacement of the granitic precursor of a granulite-facies charnockite and 650.9 ± 0.9 Ma for the protolith age of an amphibolite-facies migmatitic gneiss. A structurally conformable alkali granite sheet with a crystallization age of 568.7 ±1.6 Ma contains xenocrystic zircons, one of which has an age of 1229.6 ± 1.0 Ma, inherited from the source of the anatectically derived material. The post-tectonic, alkalic Carion granite has an emplacement age of 556.0 ± 1.7 Ma and provides a minimum age for granulite- and amphibolite-facies metamorphism. Our field data indicate that extensional shear zones are common in central Madagascar, locally controlling amphibolite-facies retrogression of granulite-facies rocks and the emplacement of crustal melt granites. These events record the widespread extensional collapse of the Pan-African orogen in Madagascar.

103 citations


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