Topic
Granulite
About: Granulite is a research topic. Over the lifetime, 6763 publications have been published within this topic receiving 268925 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: The Itsaq Gneiss Complex of the Nuuk region, southern West Greenland, is dominated by 3850-3690 Ma tonalites intruded into and intercalated with lesser amounts of different ≥3850-3700 Ma supracrustal units as mentioned in this paper.
Abstract: The Itsaq Gneiss Complex of the Nuuk region, southern West Greenland, is dominated by 3850–3690 Ma tonalites intruded into and intercalated with lesser amounts of different ≥3850–3700 Ma supracrustal units. Published whole‐rock Sr and Nd isotopic studies demonstrate that the tonalites are juvenile crustal additions from a depleted mantle source. From our field studies and SHRIMP U/Pb zircon dating, we argue that this juvenile crustal accretion was spread over ca. 170 m.yr. (≥3850–3690 Ma). Following 3850–3690 Ma juvenile crustal accretion events, the evolution of the Itsaq Gneiss Complex continued with numerous crustal‐reworking events between 3670 and 3500 Ma. Examples of these reworking events are as follows: (1) there is intrusion of several generations of geochemically diverse granites (sensu stricto) with subordinate gabbros and diorites; (2) there are superimposed, multiple episodes of amphibolite to granulite facies metamorphism (illustrated with Akilia Island samples by detailed dating of...
80 citations
TL;DR: In this article, the Gibbs method of differential thermodynamics was used to calculate metamorphic paths from zoned garnet and plagioclase for two major groups of migmatites from the Turvo-Cajati Formation.
80 citations
TL;DR: A new Paleoproterozoic high-pressure complex dominated by garnet websterite on the northern margin of the North China Craton is documented and proposed that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northernmargin of the NCC.
Abstract: The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ∼1.90 Ga when it was subducted to eclogite facies at ∼2.4 GPa, then exhumed back to granulite facies at ∼0.9 GPa before ∼1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic.
80 citations
TL;DR: In this paper, a reservoir-flux system model was used to represent the various processes contributing to eclogitization of granulites, which operated at vastly different rates over disparate intervals of time.
Abstract: [1] The transformation of subducted and tectonically buried crustal rocks to denser eclogite plays a fundamental role in the dynamics of mountain building and crustal recycling. However, a complex of partially eclogitized granulites on the island of Holsnoy in the western part of the Norwegian Caledonides reveals that such densification depends in part on the antecedent history of rock masses and that large bodies of untransformed rock can persist metastably even after long residence times in the lower crust. The rocks on Holsnoy suggest that conversion to eclogite was delayed until lower or subcrustal seismic events allowed aqueous fluids to enter the previously dry and unusually strong granulite complex. Metamorphism then occurred in a spatially heterogeneous manner, with several distinct physical processes involving feedbacks between deformation, fluid infiltration, and chemical reactions operating simultaneously in different parts of the rock mass. Field relations show that the introduction of fluids and conversion to eclogite significantly weakened the rocks. A reservoir-flux systems model is used to represent the various processes contributing to eclogitization of the granulites, which operated at vastly different rates over disparate intervals of time. The model suggests that the metamorphic process may have been brief (≪1 Myr), and ultimately self-limiting, arrested by the change in rheology associated with the conversion of brittle granulite to ductile eclogite.
80 citations
TL;DR: In this paper, the authors used the Zr-in-rutile geothermometer to estimate peak metamorphic temperatures in granulite facies rocks from the lowermost part of the Ivrea Zone.
Abstract: The Zr-in-rutile geothermometer is potentially a widely applicable tool to estimate peak metamorphic temperatures in rocks from diverse geological settings. In order to evaluate its usefulness and reliability to record and preserve high temperatures in granulite facies rocks, rutile from UHT rocks was investigated to assess different mechanisms of Zr (re-)distribution following cooling from high temperature. Granulite facies paragneisses from the lowermost part of the Ivrea Zone, Italy, incorporated as thin sheets into the extensive basaltic body of the Mafic Complex were selected for this study. The results show that Zr-in-rutile thermometry, if properly applied, is well suited to identify and study UHT terranes as it preserves a record of temperatures up to 1190 °C, although the thermometer is susceptible to partial post-peak metamorphic resetting by Zr diffusion. Texturally homogeneous rutile grains preserve Zr concentrations corresponding to temperatures of prograde rutile growth. Diverse rutile textures and relationships between some rutile host grains and included or adjacent Zr-bearing phases bear testimony to varying mechanisms of partial redistribution and resetting of Zr in rutile during cooling and link Zr-in-rutile temperatures to different steps of the metamorphic evolution. Rutile grains that equilibrated their Zr concentrations at temperatures above 1070 °C (i.e. 1.1 wt% Zr) could not retain all Zr in the rutile structure during cooling and exsolved baddeleyite (ZrO2). By subsequent reaction of baddeleyite exsolution lamellae with SiO2, zircon needles formed before the system finally closed at 650–700 °C without significant net loss of Zr from the whole host rutile grain. By reintegration of zircon exsolution needles, peak metamorphic temperatures of up to 1190 °C are derived for the studied rocks, which demonstrates the suitability of this solution thermometer to record UHT conditions and also confirms the extraordinary geological setting of the lowermost part of the Ivrea Zone.
80 citations