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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 authors studied two areas of exposed basement in northernmost Chile (Belen) and westernmost Bolivia (Cerro Uyarani) and used geothermobarometers to reconstruct the P-T conditions of metamorphism, as well as geochemical analyses and petrological methods to study these rocks.

86 citations

Journal ArticleDOI
TL;DR: In the Bergslagen area of southcentral Sweden, the U-Pb zircon SIMS data presented in this paper complement the previous, regionally scattered TIMS data from this area as mentioned in this paper, which further emphasize previous observations of a major juvenile (< 2.1 Ga) and a minor Archaean provenance.
Abstract: The Svecofennian Domain of the Fennoscandian Shield constitutes a considerable volume of Palaeoproterozoic crustal growth, 2.1-1.86 Ga ago, in between the Archaean craton in the NE and the 1.85-1.65 Ga Transscandinavian Igneous Belt (TIB) in the south and west. The Bergslagen area is a classical ore province located in the southwestern part of the Svecofennian Domain of southcentral Sweden. Its northern part is dominated by volcanic and plutonic rocks of a magmatic are with continental affinity, while the SE part is made up by a sedimentary basin. The Bergslagen area shows a metamorphic zonation from lower to middle amphibolite facies in the north to upper amphibolite facies and locally granulite facies in the south; a small greenschist area exists in the west. Identifying the age spectra of inherited components, magmatic crystallization, as well as metamorphic episodes, provide important constraints on the geodynamic evolution of this centrally located piece of the Shield. U-Pb zircon SIMS data presented in this paper complement the previous, regionally scattered TIMS data from this area. Magmatic zircons from two felsic metavolcanic rocks and two amphibolites (metagabbros) yield 1888 +/- 12, 1892 +/- 7 and 1887 +/- 5, 1895 +/- 5 Ma, respectively; i.e. within the 1.91-1.86 Ga range previously obtained for Early Svecofennian magmatism in Bergslagen. An augen gneiss from southern Bergslagen, assigned to the earliest TIB generation, yield an intrusive age of 1855 6 Ma. Metamorphic monazites from the same rock indicate that deformation and elevated thermal activity prevailed 1.83-1.82 Ga ago (TIMS). Metamorphic zircons in high-grade metasedimentary rocks from the south and west yield ages of 1793 5 and 1804 10 Ma, in accordance with ages for regional peak metamorphism and migmatite formation found elsewhere in the southern Svecofennian province of Sweden. More importantly, a few zircon crystals and overgrowths in rocks from the north indicate an early metamorphic episode at c. 1.87 Ga, indicating that Bergslagen has experienced two major metamorphic events. Detrital and inherited zircons span the range 2.78-1.90 Ga, with an apparent gap at 2.45-2.1 Ga, which further emphasize previous observations of a major juvenile (< 2.1 Ga) and a minor Archaean provenance. This, and in particular the 1.94-1.91 Ga crystals present in the c. 1.89 Ga amphibolites, support the suggestion of a former Palaeoproterozoic pre-1.91 Ga crust in the Bergslagen area. (Less)

86 citations

Journal ArticleDOI
TL;DR: In this article, the authors show that an apparently continuous P-T path inferred for Mg-granulites is actually discontinuous, resulting from the superposition of two distinct metamorphic events at 2 5 Ga and 750Ma.
Abstract: Petrological studies and electron microprobe dating of monazite from the mafic Andriamena unit, north–central Madagascar, indicate that an apparently continuous P–T path inferred for Mg-granulites is actually discontinuous, resulting from the superposition of two distinct metamorphic events at 2 5 Ga and 750Ma. The late Archaean event corresponds to an ultrahigh-temperature metamorphism (1000 C, 10 5 kbar) characterized by a sapphirine–garnet–orthopyroxene–quartz assemblage. Neoproterozoic ages are associated with the development of a sapphirine–cordierite-bearing assemblage, symplectites of orthopyroxene–sillimanite and partial melting at 850 C and 7 kbar. This sequence of reactions and mineral assemblages could be interpreted as the result of near-isothermal decompression to about 4 kbar followed by isobaric cooling to 650 C. However, geodynamic constraints suggest that the granulites underwent a phase of cooling to the stable geotherm following the ultrahightemperature metamorphism at 2 5 Ga. Consequently, we suggest that the ‘petrographical path’ inferred from the Mg-granulites is not representative of the actual P–T–t path. The decompression, in particular, is an artefact of the P–T path with no geological meaning; it results from the equilibration of the refractory late Archaean ultrahigh-temperature assemblages at a lower pressure during the middle Neoproterozoic event.

86 citations

Journal ArticleDOI
TL;DR: In this paper, a geochronological study has been made in the Taihangshan-Wutaishan area, Shanxi Province, on a sequence of Precambrian supracrustal rocks and stratigraphically related intrusives, where the authors employed the U-Pb zircon approach on selected parts of the sequences to provide direct depositional ages or age constraints for the Fuping and Wutai Groups and to find the age(s) of subsequent metamorphic processes.

86 citations

Journal ArticleDOI
TL;DR: In this article, a two-dimensional cross-section of the crust was obtained by forward modeling using ray-tracing techniques, which was obtained from a 440 km long profije on the northern Baltic Shield.

86 citations


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