Metamorphic P–T path of mafic granulites from Eastern Hebei : Implications for the Neoarchean tectonics of the Eastern Block, North China Craton

Long Ching Jessie KWAN, Guochun ZHAO*, Changqing YIN, Hongyan GENG

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)Researchpeer-review

14 Citations (Scopus)

Abstract

This study documents the metamorphic evolution of mafic granulites from the Eastern Hebei Complex in the Eastern Block of the North China Craton. Mafic granulites from Eastern Hebei occur as boudins or enclaves within Neoarchean high-grade TTG gneisses. Petrographic observations reveal three characteristic metamorphic mineral assemblages in the mafic granulites: the pre-peak hornblende + plagioclase + ilmenite + quartz + sphene assemblage (M1) existing as mineral inclusions within coarse-grained peak assemblage (M2) represented by garnet + clinopyroxene + orthopyroxene + plagioclase + hornblende + ilmenite + quartz, and post-peak assemblage (M3) marked by garnet + quartz ± ilmenite symplectites surrounding the peak pyroxene and plagioclase. Based on pseudosection modeling calculated in the NCFMASHTO model system using the program THERMOCALC, P–T conditions of the pre-peak (M1), peak (M2) and post-peak (M3) assemblages are constrained at 600–715 °C/6.0 kbar or below, 860–900 °C/9.6–10.3 kbar, and 790–810 °C/9.6–10.4 kbar, respectively. These P–T estimates, combined with their mineral compositions and reaction relations, define an anticlockwise P–T path incorporating isobaric cooling subsequent to the peak medium-pressure granulite-facies metamorphism for the mafic granulites from Eastern Hebei. Such an anticlockwise P–T path suggests that the end-Neoarchean metamorphism of the Eastern Hebei Complex correlated closely with underplating and intrusion of voluminous mantle-derived magmas. In conjunction with other geological considerations, a mantle-plume model is favored to interpret the Neoarchean tectonothermal evolution of the Eastern Hebei Complex and other metamorphic complexes in the Eastern Block. The prograde amphibolite-facies metamorphism (M1) was initiated due to the upwelling of the relatively cooler mantle plume head, followed by the peak medium-pressure granulite-facies metamorphism (M2) as triggered by the uprising hotter plume “tail”, and finally when plume activity ceased, the heated metamorphic crust experienced nearly isobaric cooling (M3).

Original languageEnglish
Pages (from-to)20-38
Number of pages19
JournalGondwana Research
Volume37
Early online date14 Jun 2016
DOIs
Publication statusPublished - Sep 2016
Externally publishedYes

Fingerprint

craton
metamorphism
plagioclase
tectonics
mantle plume
granulite facies
ilmenite
hornblende
garnet
mineral
plume
quartz
cooling
underplating
enclave
titanite
orthopyroxene
amphibolite facies
pyroxene
clinopyroxene

Keywords

  • Mafic granulite
  • Mantle plume
  • Metamorphic P–T path
  • Neoarchean
  • North China Craton

Cite this

@article{409c11cd97cf48bc925385a0bbc4c8f2,
title = "Metamorphic P–T path of mafic granulites from Eastern Hebei : Implications for the Neoarchean tectonics of the Eastern Block, North China Craton",
abstract = "This study documents the metamorphic evolution of mafic granulites from the Eastern Hebei Complex in the Eastern Block of the North China Craton. Mafic granulites from Eastern Hebei occur as boudins or enclaves within Neoarchean high-grade TTG gneisses. Petrographic observations reveal three characteristic metamorphic mineral assemblages in the mafic granulites: the pre-peak hornblende + plagioclase + ilmenite + quartz + sphene assemblage (M1) existing as mineral inclusions within coarse-grained peak assemblage (M2) represented by garnet + clinopyroxene + orthopyroxene + plagioclase + hornblende + ilmenite + quartz, and post-peak assemblage (M3) marked by garnet + quartz ± ilmenite symplectites surrounding the peak pyroxene and plagioclase. Based on pseudosection modeling calculated in the NCFMASHTO model system using the program THERMOCALC, P–T conditions of the pre-peak (M1), peak (M2) and post-peak (M3) assemblages are constrained at 600–715 °C/6.0 kbar or below, 860–900 °C/9.6–10.3 kbar, and 790–810 °C/9.6–10.4 kbar, respectively. These P–T estimates, combined with their mineral compositions and reaction relations, define an anticlockwise P–T path incorporating isobaric cooling subsequent to the peak medium-pressure granulite-facies metamorphism for the mafic granulites from Eastern Hebei. Such an anticlockwise P–T path suggests that the end-Neoarchean metamorphism of the Eastern Hebei Complex correlated closely with underplating and intrusion of voluminous mantle-derived magmas. In conjunction with other geological considerations, a mantle-plume model is favored to interpret the Neoarchean tectonothermal evolution of the Eastern Hebei Complex and other metamorphic complexes in the Eastern Block. The prograde amphibolite-facies metamorphism (M1) was initiated due to the upwelling of the relatively cooler mantle plume head, followed by the peak medium-pressure granulite-facies metamorphism (M2) as triggered by the uprising hotter plume “tail”, and finally when plume activity ceased, the heated metamorphic crust experienced nearly isobaric cooling (M3).",
keywords = "Mafic granulite, Mantle plume, Metamorphic P–T path, Neoarchean, North China Craton",
author = "KWAN, {Long Ching Jessie} and Guochun ZHAO and Changqing YIN and Hongyan GENG",
year = "2016",
month = "9",
doi = "10.1016/j.gr.2016.05.004",
language = "English",
volume = "37",
pages = "20--38",
journal = "Gondwana Research",
issn = "1342-937X",
publisher = "Elsevier Inc.",

}

Metamorphic P–T path of mafic granulites from Eastern Hebei : Implications for the Neoarchean tectonics of the Eastern Block, North China Craton. / KWAN, Long Ching Jessie; ZHAO, Guochun; YIN, Changqing; GENG, Hongyan.

In: Gondwana Research, Vol. 37, 09.2016, p. 20-38.

Research output: Journal PublicationsJournal Article (refereed)Researchpeer-review

TY - JOUR

T1 - Metamorphic P–T path of mafic granulites from Eastern Hebei : Implications for the Neoarchean tectonics of the Eastern Block, North China Craton

AU - KWAN, Long Ching Jessie

AU - ZHAO, Guochun

AU - YIN, Changqing

AU - GENG, Hongyan

PY - 2016/9

Y1 - 2016/9

N2 - This study documents the metamorphic evolution of mafic granulites from the Eastern Hebei Complex in the Eastern Block of the North China Craton. Mafic granulites from Eastern Hebei occur as boudins or enclaves within Neoarchean high-grade TTG gneisses. Petrographic observations reveal three characteristic metamorphic mineral assemblages in the mafic granulites: the pre-peak hornblende + plagioclase + ilmenite + quartz + sphene assemblage (M1) existing as mineral inclusions within coarse-grained peak assemblage (M2) represented by garnet + clinopyroxene + orthopyroxene + plagioclase + hornblende + ilmenite + quartz, and post-peak assemblage (M3) marked by garnet + quartz ± ilmenite symplectites surrounding the peak pyroxene and plagioclase. Based on pseudosection modeling calculated in the NCFMASHTO model system using the program THERMOCALC, P–T conditions of the pre-peak (M1), peak (M2) and post-peak (M3) assemblages are constrained at 600–715 °C/6.0 kbar or below, 860–900 °C/9.6–10.3 kbar, and 790–810 °C/9.6–10.4 kbar, respectively. These P–T estimates, combined with their mineral compositions and reaction relations, define an anticlockwise P–T path incorporating isobaric cooling subsequent to the peak medium-pressure granulite-facies metamorphism for the mafic granulites from Eastern Hebei. Such an anticlockwise P–T path suggests that the end-Neoarchean metamorphism of the Eastern Hebei Complex correlated closely with underplating and intrusion of voluminous mantle-derived magmas. In conjunction with other geological considerations, a mantle-plume model is favored to interpret the Neoarchean tectonothermal evolution of the Eastern Hebei Complex and other metamorphic complexes in the Eastern Block. The prograde amphibolite-facies metamorphism (M1) was initiated due to the upwelling of the relatively cooler mantle plume head, followed by the peak medium-pressure granulite-facies metamorphism (M2) as triggered by the uprising hotter plume “tail”, and finally when plume activity ceased, the heated metamorphic crust experienced nearly isobaric cooling (M3).

AB - This study documents the metamorphic evolution of mafic granulites from the Eastern Hebei Complex in the Eastern Block of the North China Craton. Mafic granulites from Eastern Hebei occur as boudins or enclaves within Neoarchean high-grade TTG gneisses. Petrographic observations reveal three characteristic metamorphic mineral assemblages in the mafic granulites: the pre-peak hornblende + plagioclase + ilmenite + quartz + sphene assemblage (M1) existing as mineral inclusions within coarse-grained peak assemblage (M2) represented by garnet + clinopyroxene + orthopyroxene + plagioclase + hornblende + ilmenite + quartz, and post-peak assemblage (M3) marked by garnet + quartz ± ilmenite symplectites surrounding the peak pyroxene and plagioclase. Based on pseudosection modeling calculated in the NCFMASHTO model system using the program THERMOCALC, P–T conditions of the pre-peak (M1), peak (M2) and post-peak (M3) assemblages are constrained at 600–715 °C/6.0 kbar or below, 860–900 °C/9.6–10.3 kbar, and 790–810 °C/9.6–10.4 kbar, respectively. These P–T estimates, combined with their mineral compositions and reaction relations, define an anticlockwise P–T path incorporating isobaric cooling subsequent to the peak medium-pressure granulite-facies metamorphism for the mafic granulites from Eastern Hebei. Such an anticlockwise P–T path suggests that the end-Neoarchean metamorphism of the Eastern Hebei Complex correlated closely with underplating and intrusion of voluminous mantle-derived magmas. In conjunction with other geological considerations, a mantle-plume model is favored to interpret the Neoarchean tectonothermal evolution of the Eastern Hebei Complex and other metamorphic complexes in the Eastern Block. The prograde amphibolite-facies metamorphism (M1) was initiated due to the upwelling of the relatively cooler mantle plume head, followed by the peak medium-pressure granulite-facies metamorphism (M2) as triggered by the uprising hotter plume “tail”, and finally when plume activity ceased, the heated metamorphic crust experienced nearly isobaric cooling (M3).

KW - Mafic granulite

KW - Mantle plume

KW - Metamorphic P–T path

KW - Neoarchean

KW - North China Craton

UR - http://www.scopus.com/inward/record.url?scp=84976565414&partnerID=8YFLogxK

U2 - 10.1016/j.gr.2016.05.004

DO - 10.1016/j.gr.2016.05.004

M3 - Journal Article (refereed)

VL - 37

SP - 20

EP - 38

JO - Gondwana Research

JF - Gondwana Research

SN - 1342-937X

ER -