P–T–t–D records of Early Palaeozoic Andean-type shortening of a hot active margin: The Dunhuang block in NW China

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F22%3A00000164" target="_blank" >RIV/00025798:_____/22:00000164 - isvavai.cz</a>

Výsledek na webu

<a href="https://onlinelibrary.wiley.com/doi/10.1111/jmg.12688" target="_blank" >https://onlinelibrary.wiley.com/doi/10.1111/jmg.12688</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1111/jmg.12688" target="_blank" >10.1111/jmg.12688</a>

Jazyk výsledku

angličtina

Název v původním jazyce

P–T–t–D records of Early Palaeozoic Andean-type shortening of a hot active margin: The Dunhuang block in NW China

Popis výsledku v původním jazyce

High-pressure (HP) granulites form either in the domain of the subductedplate during continental collision or in supra-subduction systems where thethermally softened upper plate is shortened and thickened. Such a discrepancy in tectonic setting can be evaluated by metamorphic pressure–temperature–time-deformation (P–T–t–D) paths. In the current study, P–T–t–D paths of Early Palaeozoic HP granulite facies rocks, in the form of metabasic lenses enclosed in migmatitic metapelite, from the Dunhuang block, NW China, are investigated in order to constrain the nature of the HP rocks and shed light on he geodynamic evolution of a modern hot orogenic system in an active margin setting. The rocks show a polyphase evolution characterized by (1) relics of horizontal or gently dipping fabric (S1) preserved in cores of granulite lenses and in garnet porphyroblasts, (2) a N-S trending sub-vertical fabric (S2) preserved in low-strain domains and (3) upright folds (F3) associated with ubiquitous steep E-W striking axial planar foliation (S3). Garnet in the granulites preserves relics of a prograde mineral assemblage M1a equilibrated at11.5 kbar and 770–780C, whereas the matrix granulite assemblage (M1b)from the S1 fabric attained peak pressure at 13.5 kbar and 850C. The granuliteswere overprinted at 8–11 kbar and 850–900C during crustal melting(M2) followed by partial re-equilibration (M3) at 8 kbar and 625C. A garnetLu–Hf age of 421.6 1.2 Ma dates metamorphism M1, while a garnet Sm–Nd age of 385.3 4.0 Ma reflects M3 cooling of the granulites. The mineralassemblage, M1, of the host migmatitic metapelite formed at 9–12.5 kbarand 760–810C, partial melting and migmatization (M2) occurred at 7 kbarand 760C and re-equilibration (M3) at 5–6 kbar and 675C. A garnetLu–Hf age of 409.7 2.3 Ma dates thermal climax (M2) and a garnet Sm–Ndage of 356 11 Ma constrains M3 for the migmatitic metapelites. The timingof this late phase is also bracketed by an emplacement age of syntectonicgranite dated at c. 360 Ma. Decoupling of M1 and M2 P–T evolutions betweenthe mafic granulites and migmatitic metapelites indicates their differentpositions in the crustal column, while the shared pressure–temperature (P–T)evolution M3 suggests formation of a mélange-like association during the latestages of orogeny. The high-pressure event D1-M1 is interpreted as a result ofLate Silurian–Early Devonian moderate crustal thickening of a thermallysoftened and thinned pre-orogenic crust. The high-temperature (HT) reequilibrationD2-M2 is interpreted as a result of Mid-Devonian shortening ofthe previously thickened crust, possibly due to ‘Andean-type’ underthrusting.The D3-M3 event reflects Late Devonian supra-subduction shortening andcontinuous erosion of the sub-crustal lithosphere. This tectono-metamorphicsequence of events is explained by polyphased Andean-type deformation of a‘Cascadia-type’ active margin, which corresponds to a supra-subductiontectonic switching paradigm.

Název v anglickém jazyce

P–T–t–D records of Early Palaeozoic Andean-type shortening of a hot active margin: The Dunhuang block in NW China

Popis výsledku anglicky

High-pressure (HP) granulites form either in the domain of the subductedplate during continental collision or in supra-subduction systems where thethermally softened upper plate is shortened and thickened. Such a discrepancy in tectonic setting can be evaluated by metamorphic pressure–temperature–time-deformation (P–T–t–D) paths. In the current study, P–T–t–D paths of Early Palaeozoic HP granulite facies rocks, in the form of metabasic lenses enclosed in migmatitic metapelite, from the Dunhuang block, NW China, are investigated in order to constrain the nature of the HP rocks and shed light on he geodynamic evolution of a modern hot orogenic system in an active margin setting. The rocks show a polyphase evolution characterized by (1) relics of horizontal or gently dipping fabric (S1) preserved in cores of granulite lenses and in garnet porphyroblasts, (2) a N-S trending sub-vertical fabric (S2) preserved in low-strain domains and (3) upright folds (F3) associated with ubiquitous steep E-W striking axial planar foliation (S3). Garnet in the granulites preserves relics of a prograde mineral assemblage M1a equilibrated at11.5 kbar and 770–780C, whereas the matrix granulite assemblage (M1b)from the S1 fabric attained peak pressure at 13.5 kbar and 850C. The granuliteswere overprinted at 8–11 kbar and 850–900C during crustal melting(M2) followed by partial re-equilibration (M3) at 8 kbar and 625C. A garnetLu–Hf age of 421.6 1.2 Ma dates metamorphism M1, while a garnet Sm–Nd age of 385.3 4.0 Ma reflects M3 cooling of the granulites. The mineralassemblage, M1, of the host migmatitic metapelite formed at 9–12.5 kbarand 760–810C, partial melting and migmatization (M2) occurred at 7 kbarand 760C and re-equilibration (M3) at 5–6 kbar and 675C. A garnetLu–Hf age of 409.7 2.3 Ma dates thermal climax (M2) and a garnet Sm–Ndage of 356 11 Ma constrains M3 for the migmatitic metapelites. The timingof this late phase is also bracketed by an emplacement age of syntectonicgranite dated at c. 360 Ma. Decoupling of M1 and M2 P–T evolutions betweenthe mafic granulites and migmatitic metapelites indicates their differentpositions in the crustal column, while the shared pressure–temperature (P–T)evolution M3 suggests formation of a mélange-like association during the latestages of orogeny. The high-pressure event D1-M1 is interpreted as a result ofLate Silurian–Early Devonian moderate crustal thickening of a thermallysoftened and thinned pre-orogenic crust. The high-temperature (HT) reequilibrationD2-M2 is interpreted as a result of Mid-Devonian shortening ofthe previously thickened crust, possibly due to ‘Andean-type’ underthrusting.The D3-M3 event reflects Late Devonian supra-subduction shortening andcontinuous erosion of the sub-crustal lithosphere. This tectono-metamorphicsequence of events is explained by polyphased Andean-type deformation of a‘Cascadia-type’ active margin, which corresponds to a supra-subductiontectonic switching paradigm.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

<a href="/cs/project/GX19-27682X" target="_blank" >GX19-27682X: Hlavní mechanismy periferálního kontinentálního růstu během superkontinentálního cyklu</a><br>

Návaznosti

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

Rok uplatnění

2022

Kód důvěrnosti údajů

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

Název periodika

Journal of Metamorphic Geology

ISSN

0263-4929

e-ISSN

—

Svazek periodika

41

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

38

Strana od-do

1-38

Kód UT WoS článku

000852195200001

EID výsledku v databázi Scopus

2-s2.0-85137437649