The fate of zircon during UHT-UHP metamorphism: isotopic (U/Pb, δ18O, Hf) and trace element constraints
Identifikátory výsledku
Kód výsledku v IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F16%3A00000253" target="_blank" >RIV/00025798:_____/16:00000253 - isvavai.cz</a>
Výsledek na webu
<a href="http://onlinelibrary.wiley.com/doi/10.1111/jmg.12206/full" target="_blank" >http://onlinelibrary.wiley.com/doi/10.1111/jmg.12206/full</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1111/jmg.12206" target="_blank" >10.1111/jmg.12206</a>
Alternativní jazyky
Jazyk výsledku
angličtina
Název v původním jazyce
The fate of zircon during UHT-UHP metamorphism: isotopic (U/Pb, δ18O, Hf) and trace element constraints
Popis výsledku v původním jazyce
Garnet-clinopyroxene ultrahigh-pressure rocks from N Bohemian Massif contain zircons with micro-diamond inclusions. Trace element concentrations, oxygen and hafnium isotopic composition and U-Pb age of distinct textural domains in zircons characterize their growth conditions and temporal evolution. Uniform Th/U ratios (c. 0.1-0.2), high Ti contents (110-190 ppm), and preserved steep HREE patterns with a weak negative Eu anomaly of the diamond-bearing zircon mantle domains with relics of oscillatory zoning are consistent with crystallization from a melt under UHP/UHT conditions. The bright-CL rims with Th/U ratios of c. 0.3-0.4), lower Ti contents (20-40ppm), flat HREE patterns and negative Eu anomalies have formed through recrystallization in solid state during the exhumation of the rock, when garnet and plagioclase are stable. The three zircon domains, i.e. cores, mantles and rims, yield U-Pb concordia ages of 340.9 ± 1.5 Ma, 340.3 ± 1.5 Ma and 341.2 ± 3.4 Ma, respectively. When linked to the previously reconstructed P-T path of the rock, the error limits of the zircon mantle and rim ages constrain the exhumation of the rocks from depth of c. 140 km (UHP) to c. 80 km (HP) to a minimum rate of 1.5 cm/year. The scattering εHf values (-15.7 to +4.8) possibly reflect the presence of a heterogeneous population of old zircons. The uniform and young 238U/206Pb ages may thus represent (near-)complete resetting of the U-Pb geochronometer during the UHP-UHT event at ca. 340 Ma through dissolution-reprecipitation process. In contrast to Hf, the oxygen isotope composition of zircons is homogeneous, ranging between 7.8 and 9.6 ‰ VSMOW, reflecting a source containing upper crustal material and homogenization at UHP-UHT conditions. Our study documents that continental crust was subducted to mantle depths at c. 340 Ma during the Variscan orogeny and subsequent very rapidly exhumed, implying that the sequence of events was faster than can be resolved by the SIMS technique.
Název v anglickém jazyce
The fate of zircon during UHT-UHP metamorphism: isotopic (U/Pb, δ18O, Hf) and trace element constraints
Popis výsledku anglicky
Garnet-clinopyroxene ultrahigh-pressure rocks from N Bohemian Massif contain zircons with micro-diamond inclusions. Trace element concentrations, oxygen and hafnium isotopic composition and U-Pb age of distinct textural domains in zircons characterize their growth conditions and temporal evolution. Uniform Th/U ratios (c. 0.1-0.2), high Ti contents (110-190 ppm), and preserved steep HREE patterns with a weak negative Eu anomaly of the diamond-bearing zircon mantle domains with relics of oscillatory zoning are consistent with crystallization from a melt under UHP/UHT conditions. The bright-CL rims with Th/U ratios of c. 0.3-0.4), lower Ti contents (20-40ppm), flat HREE patterns and negative Eu anomalies have formed through recrystallization in solid state during the exhumation of the rock, when garnet and plagioclase are stable. The three zircon domains, i.e. cores, mantles and rims, yield U-Pb concordia ages of 340.9 ± 1.5 Ma, 340.3 ± 1.5 Ma and 341.2 ± 3.4 Ma, respectively. When linked to the previously reconstructed P-T path of the rock, the error limits of the zircon mantle and rim ages constrain the exhumation of the rocks from depth of c. 140 km (UHP) to c. 80 km (HP) to a minimum rate of 1.5 cm/year. The scattering εHf values (-15.7 to +4.8) possibly reflect the presence of a heterogeneous population of old zircons. The uniform and young 238U/206Pb ages may thus represent (near-)complete resetting of the U-Pb geochronometer during the UHP-UHT event at ca. 340 Ma through dissolution-reprecipitation process. In contrast to Hf, the oxygen isotope composition of zircons is homogeneous, ranging between 7.8 and 9.6 ‰ VSMOW, reflecting a source containing upper crustal material and homogenization at UHP-UHT conditions. Our study documents that continental crust was subducted to mantle depths at c. 340 Ma during the Variscan orogeny and subsequent very rapidly exhumed, implying that the sequence of events was faster than can be resolved by the SIMS technique.
Klasifikace
Druh
J<sub>x</sub> - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)
CEP obor
DB - Geologie a mineralogie
OECD FORD obor
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Návaznosti výsledku
Projekt
<a href="/cs/project/GA13-21450S" target="_blank" >GA13-21450S: Severočeské granulity obsahující diamant a coesit: studium médií vzniku diamantu v hluboké subdukční zóně a důsledky pro geodynamické modely</a><br>
Návaznosti
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Ostatní
Rok uplatnění
2016
Kód důvěrnosti údajů
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Údaje specifické pro druh výsledku
Název periodika
Journal of Metamorphic Geology
ISSN
0263-4929
e-ISSN
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Svazek periodika
34
Číslo periodika v rámci svazku
7
Stát vydavatele periodika
GB - Spojené království Velké Británie a Severního Irska
Počet stran výsledku
20
Strana od-do
719-739
Kód UT WoS článku
000382959200005
EID výsledku v databázi Scopus
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