Eclogite-facies rocks in the Saxonian Erzgebirge, Germany: high pressure metamorphism under contrasting P-T conditions

1992 ◽  
Vol 110 (2-3) ◽  
pp. 226-241 ◽  
Author(s):  
Esther Schm�dicke ◽  
Martin Okrusch ◽  
Wolfgang Schmidt
Keyword(s):  
High Pressure ◽  
High Pressure Metamorphism ◽  
Eclogite Facies

scholarly journals Eclogites and related high-pressure rocks from North-East Greenland

1994 ◽  
Vol 162 ◽  
pp. 77-90
Author(s):  
J.A Gilotti
Keyword(s):  
High Pressure ◽  
Northern Limit ◽  
Medium Temperature ◽  
East Greenland ◽  
High Pressure Metamorphism ◽  
North East ◽  
Gneiss Complex ◽  
Facies Metamorphism ◽  
Eclogite Facies

Eclogite, gamet clinopyroxenite, gamet websterite and websterite bodies were discovered within the Skærfjorden gneiss complex during recent mapping in North-East Greenland. These eclogitic pods extend from Danmarkshavn (c. 76° 40'N) to the northern limit of the area mapped (78°N), and attest to widespread high-pressure metamorphism. Eclogites with the assemblage omphacite + garnet ± quartz ± futile are common. The protoliths of some of the eclogites were xenoliths within the precursor batholiths to the gneisses. Field relations, regional correlations and preliminary geochronology indicate that the eclogite facies metamorphism is Caledonian. The eclogites formed at minimum pressures between 10-15 kilobars and temperatures between 600–900°C, and hence are the medium-temperature type typically formed in over-thickened crust during continent collision.

Mechanism of formation of atoll garnet during high-pressure metamorphism

2010 ◽  
Vol 74 (1) ◽  
pp. 111-126 ◽  
Author(s):  
S. W. Faryad ◽  
H. Klápová ◽  
L. Nosál
Keyword(s):  
High Pressure ◽  
Short Distance ◽  
Mechanism Of Formation ◽  
Medium Temperature ◽  
High Pressure Metamorphism ◽  
The Core ◽  
Fluid Infiltration ◽  
Garnet Core ◽  
Facies Metamorphism ◽  
Eclogite Facies

AbstractAtoll garnet has been found in metabasites and quartz- and mica-rich rocks that have experienced low- to medium-temperature, high-pressure eclogite facies metamorphism in the Krušné Hory (Erzgebirge). They occur in several localities but are restricted to thin, texturally distinct zones, even on a thin-section scale. The mechanism of atoll garnet formation is documented by a series of micrographs and compositional maps and profiles of atoll garnet in combination with textural relations to other phases in the rocks. The core of full garnet or its relics in the atoll garnet have larger Ca and Fe, but smaller Mg contents, compared with the thin rim (ring). In addition to quartz, Na-Ca amphibole and phengite, the atoll cores are filled by a new garnet that has a composition similar to the outer rim. Formation of the atoll garnet is interpreted as resulting from fluid infiltration and element exchange between the garnet core and matrix, a process facilitated by a temperature increase during eclogite facies metamorphism. In addition to fluid access, the primary textures, mainly grain size, were also effective for the atoll garnet formation. Small grain fractions with thin rims were easily infiltrated by fluid, which used the short distance for element exchange between core and matrix. The core garnet was gradually dissolved and replaced by new garnet having the same crystallographic orientation as the rim or relics in the core.

U–Pb zircon geochronology of unusual eclogite-facies rocks from Syros and Tinos (Cyclades, Greece)

1999 ◽  
Vol 136 (2) ◽  
pp. 111-118 ◽  
Author(s):  
MICHAEL BRÖCKER ◽  
MICHAEL ENDERS
Keyword(s):  
High Pressure ◽  
Discrete Event ◽  
White Mica ◽  
Zircon Geochronology ◽  
Metasomatic Alteration ◽  
Zircon Age ◽  
High Pressure Metamorphism ◽  
Eclogite Facies ◽  
Tectonic Mélange ◽  
Very High

Low-temperature eclogite-facies rocks from Syros and Tinos (Cyclades, Greece) include meta-igneous blocks of unclear origin (meta-olistostrome or tectonic mélange) with very high trace element concentrations (e.g. Zr up to 4850 ppm; Y up to 475 ppm). The unusual geochemistry is considered to be the result of metasomatic alteration in a subduction-zone environment. Locally, metasomatic exchange with an ultramafic matrix further enhanced compositional anomalies. A concordant U–Pb zircon age of 78±1 Ma recorded for an omphacitite from Syros is interpreted as the time of pre-Eocene high-pressure metamorphism in the Cyclades. Zircon dates of 61 and 63 Ma for a jadeitite from Tinos possibly indicate an additional discrete event (deformation?). These results are a first geochronological indication that high-pressure metamorphism in the Cyclades commenced significantly earlier than indicated by previous white mica chronology which provided ages between c. 50 and 40 Ma.

The occurrence and timing of high-pressure metamorphism on Margarita Island, Venezuela: a constraint on Caribbean-South America interaction

2009 ◽  
Vol 328 (1) ◽  
pp. 705-741 ◽  
Author(s):  
Walter V. Maresch ◽  
Rolf Kluge ◽  
Albrecht Baumann ◽  
James L. Pindell ◽  
Gabriela Krückhans-Lueder ◽  
...  
Keyword(s):  
High Pressure ◽  
South America ◽  
High Pressure Metamorphism
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