UHP-UHT peak conditions and near-adiabatic exhumation path of diamond-bearing garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F16%3A00000263" target="_blank" >RIV/00025798:_____/16:00000263 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216224:14310/16:00087943

Výsledek na webu

<a href="http://www.sciencedirect.com/science/article/pii/S0024493716000621" target="_blank" >http://www.sciencedirect.com/science/article/pii/S0024493716000621</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.lithos.2016.02.001" target="_blank" >10.1016/j.lithos.2016.02.001</a>

Jazyk výsledku

angličtina

Název v původním jazyce

UHP-UHT peak conditions and near-adiabatic exhumation path of diamond-bearing garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif

Popis výsledku v původním jazyce

Intermediate garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif, contain microdiamonds enclosed in garnet and zircon. P-T evolution of the rocks is evaluated using using univariant equilibria and thermodynamic modelling, and ternary feldspar solvus, Ti-in-garnet, Zr-in-rutile and Ti-in-zircon thermometry. Zircon mantle domains with diamond inclusions contain 111-189 ppm Ti, reflecting temperatures of 1037-1117 degrees C at c. 4.5-5.0 GPa. Ti-in-garnet thermometry using the Ti content of diamond-bearing garnet core yielded temperatures of 993-1039 degrees C at c. 5.0 GPa. An omphacite inclusion in garnet (reflecting c. 23-2.4 GPa at c. 1050 degrees C) and metastably preserved kyanite represent relics of eclogite-facies conditions. The dominant high-pressure granulite-facies mineral assemblage of low-Ca garnet, diopsidic clinopyroxene, antiperthitic feldspar and quartz equilibrated at 1.8-2.1 GPa and c. 1050 degrees C. Thermodynamic modelling shows that a steep rimward decrease of XGrs and increase of X-Mg in garnet reflect omphacite and kyanite breakdown reactions producing garnet and plagioclase during decompression without heating. The Ti content in the rim zone of zircon (13-42 ppm), exsolved plagioclase and K-feldspar associated with matrix diopside and garnet rim, matrix rutile grains containing 2028-4390 ppm Zr and late biotite reflect temperatures of c. 830-900 degrees C at c. 1.4 GPa. Our results show that the garnet-clinopyroxene rocks from North Bohemia are UHP-UHT rocks which were extensively overprinted under HP granulite-facies conditions during rapid exhumation along a near-adiabatic P-T path. The UHT peak and UHT-HT exhumation distinguish this area from the other UHP terrains worldwide. The calculated UHP-UHT conditions are similar to those determined for the associated garnet peridotites, providing evidence for juxtaposition of these crustal and mantle rocks during deep Variscan subduction.

Název v anglickém jazyce

UHP-UHT peak conditions and near-adiabatic exhumation path of diamond-bearing garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif

Popis výsledku anglicky

Intermediate garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif, contain microdiamonds enclosed in garnet and zircon. P-T evolution of the rocks is evaluated using using univariant equilibria and thermodynamic modelling, and ternary feldspar solvus, Ti-in-garnet, Zr-in-rutile and Ti-in-zircon thermometry. Zircon mantle domains with diamond inclusions contain 111-189 ppm Ti, reflecting temperatures of 1037-1117 degrees C at c. 4.5-5.0 GPa. Ti-in-garnet thermometry using the Ti content of diamond-bearing garnet core yielded temperatures of 993-1039 degrees C at c. 5.0 GPa. An omphacite inclusion in garnet (reflecting c. 23-2.4 GPa at c. 1050 degrees C) and metastably preserved kyanite represent relics of eclogite-facies conditions. The dominant high-pressure granulite-facies mineral assemblage of low-Ca garnet, diopsidic clinopyroxene, antiperthitic feldspar and quartz equilibrated at 1.8-2.1 GPa and c. 1050 degrees C. Thermodynamic modelling shows that a steep rimward decrease of XGrs and increase of X-Mg in garnet reflect omphacite and kyanite breakdown reactions producing garnet and plagioclase during decompression without heating. The Ti content in the rim zone of zircon (13-42 ppm), exsolved plagioclase and K-feldspar associated with matrix diopside and garnet rim, matrix rutile grains containing 2028-4390 ppm Zr and late biotite reflect temperatures of c. 830-900 degrees C at c. 1.4 GPa. Our results show that the garnet-clinopyroxene rocks from North Bohemia are UHP-UHT rocks which were extensively overprinted under HP granulite-facies conditions during rapid exhumation along a near-adiabatic P-T path. The UHT peak and UHT-HT exhumation distinguish this area from the other UHP terrains worldwide. The calculated UHP-UHT conditions are similar to those determined for the associated garnet peridotites, providing evidence for juxtaposition of these crustal and mantle rocks during deep Variscan subduction.

Druh

J_x - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)

CEP obor

DB - Geologie a mineralogie

OECD FORD obor

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Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2016

Kód důvěrnosti údajů

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

Název periodika

Lithos

ISSN

0024-4937

e-ISSN

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Svazek periodika

248-251

Číslo periodika v rámci svazku

April

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

16

Strana od-do

366-381

Kód UT WoS článku

000373863900026

EID výsledku v databázi Scopus

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