Granulite

About: Granulite is a research topic. Over the lifetime, 6763 publications have been published within this topic receiving 268925 citations.

Queen Maud block: A newly recognized Paleoproterozoic (2.4–2.5 Ga) terrane in northwest Laurentia

Abstract: The Queen Maud block of Arctic Canada is central to understanding the Proterozoic tectonic history of northwestern Laurentia, but its crustal history is largely unknown. Results of an in situ U-Pb zircon, monazite, and whole-rock Sm-Nd study through the central and eastern Queen Maud block indicate: (1) widespread 2.46–2.50 Ga magmatism derived from Neoarchean source rocks, (2) an extensive NE-trending 2.44–2.39 Ga sedimentary belt characterized by 2.45–2.50 Ga detritus, and (3) regional ca. 2.39 Ga granulite metamorphism. There is no evidence of metamorphic or magmatic activity at 1.9–2.0 Ga, concurrent with orogenesis in the adjacent Taltson-Thelon belt. We propose that the eastern Queen Maud block was the site of an incipient continental rift ca. 2.5 Ga. Exhumation of 2.46–2.50 Ga granitoids produced in the early stages of rifting provided detritus to a short-lived basin that underwent granulite metamorphism ca. 2.39 Ga.

Rare earth element geochemistry of the Scourian complex N.W. Scotland — Evidence for the granite-granulite link

Abstract: Medium-to high-pressure granulite facies complexes represent samples of lower crustal material and are, therefore, important in the study of crustal processes. New rare earth element data for the Scourian granulite facies terrain of the Precambrian Lewisian complex of N.W. Scotland indicate that: These new data, along with previously reported major and trace element data, isotopic abundances, and trace element modelling support the hypothesis that the Scourian terrain is the residuum left after genesis and removal of granitic melts.

Petrological evidence for stepwise accretion of metamorphic soles during subduction infancy (Semail ophiolite, Oman and UAE)

Abstract: Metamorphic soles are tectonic slices welded beneath most large-scale ophiolites. These slivers of oceanic crust metamorphosed up to granulite facies conditions are interpreted as forming during the first million years of intra-oceanic subduction following heat transfer from the incipient mantle wedge towards the top of the subducting plate. This study reappraises the formation of metamorphic soles through detailed field and petrological work on three key sections from the Semail ophiolite (Oman and United Arab Emirates). Based on thermobarometry and thermodynamic modelling, it is shown that metamorphic soles do not record a continuous temperature gradient, as expected from simple heating by the upper plate or by shear heating as proposed in previous studies. The upper, high-temperature metamorphic sole is subdivided in at least two units, testifying to the stepwise formation, detachment and accretion of successive slices from the down-going slab to the mylonitic base of the ophiolite. Estimated peak pressure-temperature conditions through the metamorphic sole, from top to bottom, are 850°C and 1 GPa, 725°C and 0.8 GPa and 530°C and 0.5 GPa. These estimates appear constant within each unit but differing between units by 100 to 200°C and ~0.2 GPa. Despite being separated by hundreds of kilometres below the Semail ophiolite and having contrasting locations with respect to the ridge axis position, metamorphic soles show no evidence for significant petrological variations along strike. These constraints allow us to refine the tectonic–petrological model for the genesis of metamorphic soles, formed via the stepwise stacking of several homogeneous slivers of oceanic crust and its sedimentary cover. Metamorphic soles result not so much from downward heat transfer (ironing effect) as from progressive metamorphism during strain localization and cooling of the plate interface. The successive thrusts originate from rheological contrasts between the sole, initially the top of the subducting slab, and the peridotite above as the plate interface progressively cools. These findings have implications for the thickness, the scale and the coupling state at the plate interface during the early history of subduction/obduction systems. This article is protected by copyright. All rights reserved.

Garnet Granulite Xenoliths from the Northern Baltic Shield—the Underplated Lower Crust of a Palaeoproterozoic Large Igneous Province?

Abstract: a second plume that arrived beneath the region at this time. Evidence Garnet granulite facies xenoliths hosted in Devonian lamprophyres for partial melting of mafic crust exists in the presence of migmatitic from the Kola Peninsula are interpreted to represent the high-grade granulites. The timing of migmatization overlaps that of metametamorphic equivalents of continental flood tholeiites, emplaced somatism, and it is suggested that migmatization was facilitated into the Baltic Shield Archaean lower crust in early Proterozoic by the metasomatism. The metamorphism, metasomatism and time. Geochronological data and similarities in major and trace migmatization recorded in the Kola granulite xenoliths may be element geochemistry suggest that the xenoliths formed during the representative of the processes responsible for converting Archaean same plume-related magmatic event that created a widespread LIP-generated proto-continents into continental crust. Palaeoproterozoic large igneous province (LIP) at 2·4–2·5 Ga. They are, thus, the first samples of the lower crust of a Palaeoproterozoic LIP to be studied in petrological detail. The suite includes mafic granulites (gar + cpx + rutile ± plag ± opx