Eocene migmatite formation and diachronous burial revealed by petrochronology in NW Himalaya, Zanskar
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F20%3A00000066" target="_blank" >RIV/00025798:_____/20:00000066 - isvavai.cz</a>
Alternative codes found
RIV/67985530:_____/20:00531819 RIV/00216208:11310/20:10476172
Result on the web
<a href="https://doi.org/10.1111/jmg.12534" target="_blank" >https://doi.org/10.1111/jmg.12534</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1111/jmg.12534" target="_blank" >10.1111/jmg.12534</a>
Alternative languages
Result language
angličtina
Original language name
Eocene migmatite formation and diachronous burial revealed by petrochronology in NW Himalaya, Zanskar
Original language description
In this contribution, we highlight the importance of in-situ monazite geochronology linked to P−T modelling for identification of timescales of metamorphic processes. Barrovian-type micaschists, migmatites and augengneiss from the Gumburanjun dome in the southeastern extremity of the Gianbul dome, NW Himalaya, have been studied in order to correlate the early stages of Himalayan metamorphism at different crustallevels and infer the timing of anatexis. P−T−t paths are constrained through combined pseudosection modelling and in-situ and in-mount monazite and xenotime laser ablation– split-stream inductively coupled plasma-mass spectrometry. Petrography and garnet zoning combined with pseudosection modelling show that garnet-staurolite schists record burial from ~530 to 560°C and 5.5 kbar to ~630 to 660°C and 7 kbar; staurolite-kyanite schists from ~530 to 560°C and 5 kbar to ~670 to 680°C and 7−9 kbar; and garnet-kyanite migmatites from 540−570°C and 5 kbar to ~680 to 750°C and 7−10 kbar, probably also to >750°C and >9 kbar above the muscovite stability field. The decompression paths of garnet-staurolite schists indicate cooling on decompression, while garnet rim chemistry and local sillimanite growth point to a stage of re-equilibrationat ~600 to 670°C and 4−6 kbar in some of the staurolite-kyanite schists, and at ~670 to 700°C and 6 kbar in garnet-kyanite migmatites. Some of the staurolite-kyanite schists and garnet-kyanite migmatites also contain andalusite or andalusite-cordierite. Monazite and xenotime were analysed in thin sections in garnet, staurolite and kyanite, and in the matrix; and in mounts. BSE images and compositional maps of monazite(xenotime was too small) show variable internal structures from homogeneous through patchy zoning with embayed to sharp boundaries. Two groups of samples can be identified on the basis of the presence or absence of c. 44 − 37 Ma ages. The first group of samples—two garnet-staurolite schists—recorded only c. 31 − 27 Ma ages in porphyroblastsand no c. 40 Ma ages. The second group (samples of staurolite-kyanite schist,garnet-kyanite migmatites, augengneiss) have both the older, c. 44 − 37 Ma monazite ages in porphyroblasts and younger ages down to c. 22 Ma. These significantly different ranges of ages from porphyroblasts of 44−37 Ma, and 31−27 Ma, are interpreted as the duration of prograde P−T paths in Eocene and Oligocene, and indicate diachronous two-stage burial of rocks. Early migmatization occurred at 38 Ma. The c. 29 Mais interpreted as the time when rocks from the lower and middle crustal levels were partially exhumed and came in to contact with rocks that were downgoing at this time. Localized monazite recrystallization is as young as 26−24 Ma. The youngest ages of 23−22 Ma are related to leucogranite emplacement.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10505 - Geology
Result continuities
Project
<a href="/en/project/GA16-17457S" target="_blank" >GA16-17457S: Melting the metagranitoids: important but poorly understood aspect of crust evolution</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Others
Publication year
2020
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Journal of Metamorphic Geology
ISSN
0263-4929
e-ISSN
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Volume of the periodical
38
Issue of the periodical within the volume
6
Country of publishing house
GB - UNITED KINGDOM
Number of pages
37
Pages from-to
655-691
UT code for WoS article
000540193100001
EID of the result in the Scopus database
2-s2.0-85086412169