Pan-African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica

2009 ◽  
Vol 27 (5) ◽  
pp. 335-347 ◽  
Author(s):  
T. ROMER ◽  
K. MEZGER ◽  
E. SCHMÄDICKE
Keyword(s):  
Ultramafic Rocks ◽  
Pan African ◽  
Facies Metamorphism ◽  
Eclogite Facies

scholarly journals High pressure metamorphism in the peridotitic cumulate of the Marun-Keu complex, Polar Urals

2019 ◽  
Vol 27 (2) ◽  
pp. 138-160
Author(s):  
Y. Y. Liu ◽  
A. L. Perchuk ◽  
A. A. Ariskin
Keyword(s):  
High Pressure ◽  
Crystallization Process ◽  
Ultramafic Rocks ◽  
Magmatic Chamber ◽  
Polar Urals ◽  
Tectonic Model ◽  
Facies Metamorphism ◽  
Formation Conditions ◽  
Eclogite Facies ◽  
Cumulate Texture

The Marun-Keu Complex of high-pressure rocks comprises granitoids, gneisses, schists, gabbroids and peridotites, which are unevenly and variably metamorphosed to the eclogite facies. A representative sample of garnet–amphibole lherzolite from the Mount Slyudyanaya area shows a cumulate texture and well preserved magmatic mafic minerals (olivine and pyroxenes) but practically no preserved plagioclase. The eclogite-facies metamorphism produced corona textures of newly formed minerals: amphibole, garnet, orthopyroxene and spinel. The metamorphic parameters of the garnet–amphibole lherzolite were estimated by geothermobarometry and by modeling phase equilibria at Р ~ 2.1 GPa and T ~ 640–740°C and are well consistent with our earlier estimate of the formation conditions of eclogites in the area. Computer simulation of the crystallization process of the gabbroic melt with the COMAGMAT program package, using literature data on the composition of the least altered plagioclase peridotites and gabbroids from the Marun-Keu Complex, shows that the mafic and ultramafic rocks are genetically interrelated: they crystallized in a single magmatic chamber. According to the modeling, the origin of the cumulate texture in the lherzolite was controlled by the peritectic reaction Ol + melt → Opx at a pressure of 0.7–0.8 GPa and a temperature of 1255–1268°C. Differences between thermodynamic parameters in the eclogites and garnet peridotites are discussed within the framework of a tectonic model for subduction and subsequent exhumation of the Baltica paleocontinent.

Timing of eclogite-facies metamorphism of mafic and ultramafic rocks from the Pohorje Mountains (Eastern Alps, Slovenia) based on Lu–Hf garnet geochronometry

Lithos ◽  
2016 ◽  
Vol 262 ◽  
pp. 576-585 ◽  
Author(s):  
Sascha Sandmann ◽  
Daniel Herwartz ◽  
Frederik Kirst ◽  
Nikolaus Froitzheim ◽  
Thorsten J. Nagel ◽  
...  
Keyword(s):  
Eastern Alps ◽  
Ultramafic Rocks ◽  
Facies Metamorphism ◽  
Eclogite Facies

AGE OF ECLOGITE-FACIES METAMORPHISM AND EXHUMATION IN NORTHWESTERN BHUTAN

2016 ◽  
Author(s):  
David J. Young ◽  
◽  
Daniele Regis ◽  
Clare Warren ◽  
Andrew R.C. Kylander-Clark
Keyword(s):  
Facies Metamorphism ◽  
Eclogite Facies

A garnet peridotite and a garnet-amphibole pyroxenite from South Harris, Outer Hebrides, and their bearing on the South Harris eclogite facies status

1967 ◽  
Vol 36 (279) ◽  
pp. 380-388 ◽  
Author(s):  
A. Livingstone
Keyword(s):  
Optical Properties ◽  
Granulite Facies ◽  
Garnet Peridotite ◽  
Ultramafic Rocks ◽  
Chemical Analyses ◽  
The South ◽  
Outer Hebrides ◽  
Eclogite Facies

SummaryA garnet-olivine metaperidotite and a garnet-amphibole pyroxenite are described. Chemical analyses are presented for six rocks and optical properties and chemical analyses are tabulated for clinopyroxene, almandine-pyrope garnet, and hastingsitie amphibole from the garnet-amphibole pyroxenite. A possible origin for the garnet peridotite and chemically similar granulite facies ultramafic rocks is suggested. The eclogite facies in South Harris is reinstated in the light of the data presented.

scholarly journals Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xu Kong ◽  
Xueyuan Qi ◽  
Wentian Mi ◽  
Xiaoxin Dong
Keyword(s):  
Regional Metamorphism ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Isotopic Data ◽  
Metamorphic Condition ◽  
Eu Anomaly ◽  
Facies Metamorphism ◽  
Eclogite Facies ◽  
Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

Zircon geochronology and trace element characteristics of eclogites and granulites from the Orlica-Śnieżnik complex, Bohemian Massif

2009 ◽  
Vol 147 (3) ◽  
pp. 339-362 ◽  
Author(s):  
MICHAEL BRÖCKER ◽  
REINER KLEMD ◽  
ELLEN KOOIJMAN ◽  
JASPER BERNDT ◽  
ALEXANDER LARIONOV
Keyword(s):  
Trace Element ◽  
Bohemian Massif ◽  
Trace Element Analysis ◽  
Amphibolite Facies ◽  
Zircon Geochronology ◽  
Metamorphic Zircon ◽  
Element Analysis ◽  
Large Variability ◽  
Facies Metamorphism ◽  
Eclogite Facies

AbstractU–Pb zircon geochronology and trace element analysis was applied to eclogites and (ultra)high-pressure granulites that occur as volumetrically subordinate rock bodies within orthogneisses of the Orlica-Śnieżnik complex, Bohemian Massif. Under favourable circumstances such data may help to unravel protolith ages and yet-undetermined aspects of the metamorphic evolution, for example, the time span over which eclogite-facies conditions were attained. By means of ion-probe and laser ablation techniques, a comprehensive database was compiled for samples collected from prominent eclogite and granulite occurrences. The 206Pb/238U dates for zircons of all samples show a large variability, and no single age can be calculated. The protolith ages remain unresolved due to the lack of coherent age groups at the upper end of the zircon age spectra. The spread in apparent ages is interpreted to be mainly caused by variable and possibly multi-stage Pb-loss. Further complexities are added by metamorphic zircon growth and re-equilibration processes, the unknown relevance of inherited components and possible mixing of different aged domains during analysis. A reliable interpretation of igneous crystallization ages is not yet possible. Previous studies and the new data document the importance of a Carboniferous metamorphic event at c. 340 Ma. The geological significance of this age group is controversial. Such ages have previously either been related to peak (U)HP conditions, the waning stages of eclogite-facies metamorphism or the amphibolite-facies overprint. This study provides new arguments for this discussion because, in both rock types, metamorphic zircon is characterized by very low total REE abundances, flat HREE patterns and the absence of an Eu anomaly. These features strongly suggest contemporaneous crystallization of zircon and garnet and strengthen interpretations proposing that the Carboniferous ages document late-stage eclogite-facies metamorphism, and not amphibolite-facies overprinting.

Sign in / Sign up

Export Citation Format

Share Document