Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985831%3A_____%2F22%3A00563140" target="_blank" >RIV/67985831:_____/22:00563140 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.jstage.jst.go.jp/article/jmps/117/1/117_220221/_article" target="_blank" >https://www.jstage.jst.go.jp/article/jmps/117/1/117_220221/_article</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.2465/jmps.220221" target="_blank" >10.2465/jmps.220221</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

Popis výsledku v původním jazyce

The origins of eclogite associated with garnet peridotite in continent–continent collision belts are still debated. We performed petrological studies of eclogites collected from a garnet peridotite block from Nové Dvory in the Gföhl Unit of the Moldanubian Zone in the Variscan orogenic belt, Czech Republic. The eclogite was divided into three types: one kyanite (Ky)–bearing and two Ky–free types. Garnet and omphacite in the Ky–bearing eclogite have lower Fe contents than those in the Ky–free eclogite. Furthermore, the Ky–free eclogite was divided into two types on the basis of Ca content in garnet: Ca–rich (Xgrs > 0.32) and Ca–poor (Xgrs < 0.32) types, except for Ca–poor rim compositions. Application of conventional geothermobarometers to the Ky–bearing type and the Ky–free type with Ca–rich garnet yielded similar pressure–temperature (P–T) conditions (3.2–4.8 GPa and 920– 1160 °C) to those of previous studies, whereas the Ky–free type with Ca–poor garnet yielded slightly lower P–T conditions (3.1–3.4 GPa and 950–990 °C) than the other two types. The observed chemical variation of garnet is probably due to the difference in origins, whereby, according to our new results and previous findings, the Ky– bearing eclogite was derived from plagioclase–bearing crustal gabbro, whereas the Ky–free eclogite with Ca–rich garnet was derived from a crystal cumulate possibly in the mantle wedge. In the Ky–free eclogite samples with Ca–poor garnet, chemical compositions of garnet and omphacite are different from those in the other Ky–free samples, and those samples with Ca–poor garnet would have a different origin from the others. One of the Ky– free type with Ca–poor garnet retains garnet grains with chemical zonings probably created during the prograde history, although the eclogite underwent the extremely high temperature (~ 1000 °C) metamorphism. Calculated diffusion distances in garnet reach 0.5 mm during 2 million years, even if we adopted a low value of diffusion coefficient data. Thus, the residence time of the eclogite at the peak meatamorphic conditions would have been shorter than at least 2 million years. The subsequent decompression and cooling after the peak metamorphism were also probably very fast to avoid the chemical homogenization of garnet.

Název v anglickém jazyce

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

Popis výsledku anglicky

The origins of eclogite associated with garnet peridotite in continent–continent collision belts are still debated. We performed petrological studies of eclogites collected from a garnet peridotite block from Nové Dvory in the Gföhl Unit of the Moldanubian Zone in the Variscan orogenic belt, Czech Republic. The eclogite was divided into three types: one kyanite (Ky)–bearing and two Ky–free types. Garnet and omphacite in the Ky–bearing eclogite have lower Fe contents than those in the Ky–free eclogite. Furthermore, the Ky–free eclogite was divided into two types on the basis of Ca content in garnet: Ca–rich (Xgrs > 0.32) and Ca–poor (Xgrs < 0.32) types, except for Ca–poor rim compositions. Application of conventional geothermobarometers to the Ky–bearing type and the Ky–free type with Ca–rich garnet yielded similar pressure–temperature (P–T) conditions (3.2–4.8 GPa and 920– 1160 °C) to those of previous studies, whereas the Ky–free type with Ca–poor garnet yielded slightly lower P–T conditions (3.1–3.4 GPa and 950–990 °C) than the other two types. The observed chemical variation of garnet is probably due to the difference in origins, whereby, according to our new results and previous findings, the Ky– bearing eclogite was derived from plagioclase–bearing crustal gabbro, whereas the Ky–free eclogite with Ca–rich garnet was derived from a crystal cumulate possibly in the mantle wedge. In the Ky–free eclogite samples with Ca–poor garnet, chemical compositions of garnet and omphacite are different from those in the other Ky–free samples, and those samples with Ca–poor garnet would have a different origin from the others. One of the Ky– free type with Ca–poor garnet retains garnet grains with chemical zonings probably created during the prograde history, although the eclogite underwent the extremely high temperature (~ 1000 °C) metamorphism. Calculated diffusion distances in garnet reach 0.5 mm during 2 million years, even if we adopted a low value of diffusion coefficient data. Thus, the residence time of the eclogite at the peak meatamorphic conditions would have been shorter than at least 2 million years. The subsequent decompression and cooling after the peak metamorphism were also probably very fast to avoid the chemical homogenization of garnet.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10504 - Mineralogy

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2022

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of Mineralogical and Petrological Sciences

ISSN

1345-6296

e-ISSN

1349-3825

Svazek periodika

117

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

JP - Japonsko

Počet stran výsledku

18

Strana od-do

220221

Kód UT WoS článku

000879375600001

EID výsledku v databázi Scopus

2-s2.0-85143750071