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Digitale Medien

Mineral parageneses and metamorphic P-T paths of ultrahigh-pressure eclogites from Kyrghyzstan Tien-Shan (1995)

Tagiri, M. ; Yano, T. ; Bakirov, A. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

The @island arc 4 (1995), S. 0

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ISSN: 1440-1738

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie

Notizen: Abstract Eclogites occur in three districts of the northern and southern parts of Tien-Shan. Three eclogites collected from the Aktyuz, Makbal and Atbashy districts were analyzed; the P-T paths of three eclogites were estimated by analyzing compositional growth zoning and retrograde reaction of garnet and omphacite. Aktyuz and Makbal eclogites have not preserved the prograde path. An Aktyuz eclogite that underwent a quartz eclogite facies metamorphism (about T = 600°C, P = 12 kbar) has recorded three stages of retrograde metamorphism. Four stages of retrograde metamorphism were recognized in a Makbal eclogite; the garnet-omphacite geothermometer gave about T = 560°C at 20 kbar as the highest metamorphic condition. Garnet from a garnetchloritoid-talc schist of the Makbal district includes quartz pseudomorphs after coesite; some units evidently underwent a low-temperature part of coesite eclogite fades metamorphism. Prograde and retrograde paths were recognized in an Atbashy eclogite; five stages of metamorphic reaction were observed in the Atbashy sample. The prograde path from stage I to stage III has been recorded in garnet and omphacite in which quartz pseudomorphs after coesite are included. The peak metamorphism of stage III took place at about 660°C at 25 kbar. The stages IV and V are retrograde. UHP eclogite facies metamorphism took place twice in Kyrghyzstan. The Aktyuz and Atbashy eclogites gave Rb-Sr mineral-isochron ages of about 750 Ma and 270 Ma, respectively. The K-Ar age of paragonite from the Makbal eclogite is about 480 Ma.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1440-1738.1995.tb00150.x

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Digitale Medien

Evidence for late Proterozoic subduction from 700-Myr-old blueschists in China (1990)

Nakajima, T. ; Maruyama, S. ; Uchiumi, S. ; [weitere]

[s.l.] : Nature Publishing Group

Nature 346 (1990), S. 263-265

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ISSN: 1476-4687

Quelle: Nature Archives 1869 - 2009

Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik

Notizen: [Auszug] Possible occurrences in the USSR and China of Precambrian blueschists have been reported7'13. Unfortunately these are not well documented because the data from the isotope analyses and the geological and petrographic descriptions were not provided. Although radiometric ages of 1,600, 1,100 and ...