scispace - formally typeset
Search or ask a question
Topic

Granulite

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


Papers
More filters
Journal ArticleDOI
TL;DR: Petrological and isotopic investigations were undertaken on high pressure granulites of granitic to mafic composition from the Prachatice and Blanský les granulite complexes of southern Bohemia, Czech Republic as mentioned in this paper.
Abstract: Petrological and isotopic investigations were undertaken on high pressure granulites of granitic to mafic composition from the Prachatice and Blanský les granulite complexes of southern Bohemia, Czech Republic. The predominant felsic granulites are quartz + ternary feldspar (now mesoperthite)-rich rocks containing minor garnet, kyanite and rutile, and most show a characteristic mylonitic fabric formed during retrogression along the exhumation path. Three high temperature reaction stages at distinctly different pressures are recognized. Rare layers of intermediate to mafic composition, containing clinopyroxene, best record a primary high pressure–high temperature stage (>15 kbar, >900 °C), and a well-defined overprint at medium pressure granulite facies conditions (6–8 kbar, 700–800 °C) during which orthopyroxene (+plagioclase) formed from garnet and clinopyroxene. A further high temperature overprint at lower pressure (ca. 4 kbar) is reflected in the development of cordierite- and/or andalusite-bearing partial-melt patches in some felsic granulites. Conventionally separated zircons from the granulites were measured on a SHRIMP II ion microprobe. Near-spherical, multifaceted grains interpreted to be metamorphic, and short prismatic grains from the cordierite-bearing melt patch, are all concordant and yielded indistinguishable results producing an average age, for 83 individual grain spots, of 339.8 ± 2.6 Ma (2σ). Metamorphic grains from a meta-granodiorite associated with the granulites gave the same age (339.6 ± 3.1 Ma, mean of 9), whereas inherited magmatic grains of the same sample yielded 367.8 ± 1.4 Ma. A mean age of 469.3 ± 3.8 Ma was obtained for two short prismatic concordant grains in one of the granulites, whereas several of the rounded grains with ca. 340 Ma metamorphic zircon overgrowths had much older (207Pb/206Pb minimum ages up to 1771 Ma) discordant cores. In addition to analysis of conventionally separated grains, ion-microprobe measurements were also made on zircons extracted from thin sections (drilled-out, mounted and repolished) such that a direct relationship between the dated zircons and petrographic position could be made. Identical results were obtained from both preparation methods, thus showing that the considerable advantage in petrological control is not offset by any appreciable lack of precision when compared to conventionally prepared ion-microprobe samples. All these isotopic results are identical to those previously obtained by conventional multigrain and single-grain evaporation techniques, but rather than allowing a greater resolution of the age of the petrographically obvious different metamorphic stages the results document, for the first time, the apparent short time scale for high, medium and low pressure metamorphism in the granulites. The short time period between the 340 Ma age for the high pressure granulites, as derived here and from studies of similar rocks elsewhere in the European Variscides, and the 320–330 Ma ages for regional low pressure–high temperature metamorphism, migmatization and granite magmatism, strongly suggests an important link between these two high temperature processes.

184 citations

Journal ArticleDOI
TL;DR: In this article, a review of the evidence for tectonic boundaries within the Arunta Inlier suggests that no major structural discontinuity exists between the northern and central Australia, but that the Redbank Thrust Zone is, at least in part, a province boundary.

183 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed that all HP/UHP events in the Scandinavian Caledonides occurred through the subduction of crustal slabs into the mantle and their subsequent buoyancy-enhanced exhumation toward the surface (eduction).
Abstract: [1] The evolution of the Caledonides of Scandinavia included at least four events that resulted in high-pressure (HP) and ultrahigh-pressure (UHP) eclogite facies metamorphism and the introduction of peridotite from the mantle into the crust. Two are the classic Finnmarkian orogeny at ∼500 Ma and the Scandian orogeny between 400 and 425 Ma. We have dated a third HP metamorphism in the Seve Nappe Complex in Jamtland, central Sweden, at ∼454 Ma. Identical Upper Ordovician ages from eclogite of the Troms region, northern Norway, date a simultaneous fourth HP event that occurred in a different tectonic setting, probably western Iapetus. Recently reported Late Silurian ages from eclogite of the Bergen Arcs District, southern Norway, suggest a possible fifth event. We propose that all HP/UHP events in the Scandinavian Caledonides occurred through the subduction of crustal slabs into the mantle and their subsequent buoyancy-enhanced exhumation toward the surface (eduction). The slabs are recognized as intensely deformed, high-grade (eclogite and HP granulite facies) metamorphic rocks although HP metamorphism is not necessarily penetrative and retrogression to medium grade assemblages is common. The HP/UHP metamorphic terranes are bounded by thrust faults at the base and low-angle normal detachments at the top and are separated by these shear zones from less deformed terranes of lower pressure metamorphic grade. The peridotite bodies were introduced from the overlying mantle wedge during subduction or eduction. The evolution of metamorphic terranes in other orogens might be better understood through successive subduction/eduction events, a process we provisionally call “dunk” tectonics.

183 citations

Journal ArticleDOI
TL;DR: The Dabieshan area between the Sino-Korean and Yangtze cratons in east-central China has become the focus of much recent attention because of the discovery of abundant coesite and rare micro-diamond inclusions in both eclogites and their enclosing country rocks as mentioned in this paper.

183 citations

Journal ArticleDOI
01 Feb 2001-Geology
TL;DR: The Qinling-Dabieshan belt as mentioned in this paper consists of several stacked units: from top to bottom, these are (1) a weakly metamorphosed slate-sandstone unit of Neoproterozoic-Paleozoic age, (2) a gneiss-quartzite unit metamorphoses under high-pressure (P ) conditions, (3) a marble-amphibolite unit, (4) an ultrahigh-P unit that was very deeply subducted and then exhumed, and (5) a migmatitic
Abstract: The Qinling-Dabieshan belt results from the collision of the North China and South China blocks. The eastern extension of the belt (the Sulu area) consists of several stacked units: from top to bottom, these are (1) a weakly metamorphosed slate-sandstone unit of Neoproterozoic-Paleozoic age, (2) a gneiss-quartzite unit metamorphosed under high-pressure ( P ) conditions, (3) a marble-amphibolite unit, (4) an ultrahigh- P unit that was very deeply subducted and then exhumed, and (5) a migmatitic dome resulting from the melting of ultrahigh- P rocks. All these units underwent the same deformation, which was characterized by a top-to-the-northwest extensional ductile shearing, during their exhumation. Granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh- P rocks. The migmatite exhibits the same structural and petrologic evolution as that determined for the other units. The resemblance of petrologic and structural features and the lack of ocean-basin rock shows that the boundary between the North China block and South China block must be placed north of the Sulu area.

183 citations


Network Information
Related Topics (5)
Metamorphism
18.3K papers, 655.8K citations
97% related
Zircon
23.7K papers, 786.6K citations
95% related
Continental crust
11.1K papers, 677.5K citations
94% related
Basalt
18.6K papers, 805.1K citations
93% related
Subduction
22.4K papers, 1.1M citations
92% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023126
2022301
2021177
2020203
2019148
2018142