A journey towards the forbidden zone: a new, cold, UHP unit in the Dora‐Maira Massif (Western Alps)
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F22%3A00000152" target="_blank" >RIV/00025798:_____/22:00000152 - isvavai.cz</a>
Result on the web
<a href="https://link.springer.com/article/10.1007/s00410-022-01923-8" target="_blank" >https://link.springer.com/article/10.1007/s00410-022-01923-8</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1007/s00410-022-01923-8" target="_blank" >10.1007/s00410-022-01923-8</a>
Alternative languages
Result language
angličtina
Original language name
A journey towards the forbidden zone: a new, cold, UHP unit in the Dora‐Maira Massif (Western Alps)
Original language description
The distribution of ultrahigh-pressure metamorphism (UHP) at the scale of a mountain belt is of prime importance for deciphering its past subduction history. In the Western Alps, coesite has been recognized in the southern Dora-Maira Massif, in the lens-shaped Brossasco-Isasca Unit, but has not been found up to now in the other parts of the massif. We report the discovery of a new UHP unit in the northern Dora-Maira Massif (Western Alps), named Chasteiran Unit. It is only a few tens of metres thick and consists of graphite-rich, garnet–chloritoid micaschists, whose protoliths may be black shales of Silurian age. Garnet inclusions (chloritoid, rutile) and its growth zoning allow to precisely model the P–T evolution. Coesite crystals, which are pristine or partially transformed to palisade quartz occur as inclusions in the garnet outer cores. According to thermodynamic modelling, garnet displays a continuous record of growth during the prograde increase in P and T (25–27 kbar 470–500 °C) (stage 1), up to the coesite stability field (27–28 kbar 510–530 °C) (stage 2), as well as sub-isothermal decompression of about 10 kbar (down to 15 kbar 500–515 °C) (stage 3). The main regional, composite, foliation, marked by chloritoid and rutile, began to develop during this stage, and was then overprinted by chlorite–ilmenite (stage 4). The Chasteiran Unit is discontinuously exposed in the immediate hangingwall of the Pinerolo Unit, and it is located far away from, and without physical links to the classic UHP Brossasco-Isasca Unit. Moreover, it records a different, much colder, P–T evolution, showing that different slices were detached from the downgoing subduction slab. The Chasteiran Unit is the fourth and the coldest Alpine UHP unit known so far in the entire Alpine belt. Its P–T conditions are comparable to the ones of the Tian Shan coesite–chloritoid-bearing rocks.
Czech name
—
Czech description
—
Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
—
OECD FORD branch
10505 - Geology
Result continuities
Project
—
Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2022
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Contributions to Mineralogy and Petrology
ISSN
0010-7999
e-ISSN
—
Volume of the periodical
177
Issue of the periodical within the volume
6 : 59
Country of publishing house
DE - GERMANY
Number of pages
22
Pages from-to
nestránkováno
UT code for WoS article
000808343800001
EID of the result in the Scopus database
2-s2.0-85131765173