Geochemical, Sr-Nd and zircon U-Pb-Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang : Implications for ridge subduction?

Hongyan GENG, Min SUN*, Chao YUAN, Wenjiao XIAO, Weisheng XIAN, Guochun ZHAO, Lifei ZHANG, Kenny WONG, Fuyuan WU

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)

290 Citations (Scopus)

Abstract

Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 = 50.4-63.8 wt.%) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.%, Mg# = 0.39-0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu*/Eu = 0.80) and pronounced negative Nb-Ta anomalies. Their Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7035-0.7042, εNd(t) = 4.5-7.9, εHf(t) = 14.1-14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 = 60.0-65.3 wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu*/Eu = 0.75) but pronounced negative Nb-Ta anomalies. Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7037-0.7039, εNd(t) = 5.2-8.0, εHf(t) = 13.9-14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 = 70.0-78.4 wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb-Ta anomalies (average Eu*/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7024-0.7045, εNd(t) = 5.1-8.9, εHf(t) = 13.7-14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma. A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the "slab window" opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian.

Original languageEnglish
Pages (from-to)364-389
Number of pages26
JournalChemical Geology
Volume266
Issue number3-4
DOIs
Publication statusPublished - 30 Aug 2009
Externally publishedYes

Fingerprint

magmatism
zircon
subduction
Rocks
partial melting
alkali feldspar
Alkalies
lower crust
charnockite
isotopic composition
rock
Melting
mantle
mafic rock
anomaly
slab
granite
Chemical analysis
asthenosphere
Petrology

Keywords

  • Central Asian Orogenic Belt
  • Geochemistry
  • Granite
  • Junggar
  • Sr-Nd-Hf isotopes
  • U-Pb zircon

Cite this

GENG, Hongyan ; SUN, Min ; YUAN, Chao ; XIAO, Wenjiao ; XIAN, Weisheng ; ZHAO, Guochun ; ZHANG, Lifei ; WONG, Kenny ; WU, Fuyuan. / Geochemical, Sr-Nd and zircon U-Pb-Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang : Implications for ridge subduction?. In: Chemical Geology. 2009 ; Vol. 266, No. 3-4. pp. 364-389.
@article{38890d8233b040b4aff44624b7d414ac,
title = "Geochemical, Sr-Nd and zircon U-Pb-Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang : Implications for ridge subduction?",
abstract = "Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 = 50.4-63.8 wt.{\%}) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.{\%}, Mg# = 0.39-0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu*/Eu = 0.80) and pronounced negative Nb-Ta anomalies. Their Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7035-0.7042, εNd(t) = 4.5-7.9, εHf(t) = 14.1-14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 = 60.0-65.3 wt.{\%}) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu*/Eu = 0.75) but pronounced negative Nb-Ta anomalies. Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7037-0.7039, εNd(t) = 5.2-8.0, εHf(t) = 13.9-14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 = 70.0-78.4 wt.{\%}) are alkali and Fe-enriched, and have distinct negative Eu and Nb-Ta anomalies (average Eu*/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7024-0.7045, εNd(t) = 5.1-8.9, εHf(t) = 13.7-14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma. A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the {"}slab window{"} opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian.",
keywords = "Central Asian Orogenic Belt, Geochemistry, Granite, Junggar, Sr-Nd-Hf isotopes, U-Pb zircon",
author = "Hongyan GENG and Min SUN and Chao YUAN and Wenjiao XIAO and Weisheng XIAN and Guochun ZHAO and Lifei ZHANG and Kenny WONG and Fuyuan WU",
year = "2009",
month = "8",
day = "30",
doi = "10.1016/j.chemgeo.2009.07.001",
language = "English",
volume = "266",
pages = "364--389",
journal = "Chemical Geology",
issn = "0009-2541",
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number = "3-4",

}

Geochemical, Sr-Nd and zircon U-Pb-Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang : Implications for ridge subduction? / GENG, Hongyan; SUN, Min; YUAN, Chao; XIAO, Wenjiao; XIAN, Weisheng; ZHAO, Guochun; ZHANG, Lifei; WONG, Kenny; WU, Fuyuan.

In: Chemical Geology, Vol. 266, No. 3-4, 30.08.2009, p. 364-389.

Research output: Journal PublicationsJournal Article (refereed)

TY - JOUR

T1 - Geochemical, Sr-Nd and zircon U-Pb-Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang : Implications for ridge subduction?

AU - GENG, Hongyan

AU - SUN, Min

AU - YUAN, Chao

AU - XIAO, Wenjiao

AU - XIAN, Weisheng

AU - ZHAO, Guochun

AU - ZHANG, Lifei

AU - WONG, Kenny

AU - WU, Fuyuan

PY - 2009/8/30

Y1 - 2009/8/30

N2 - Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 = 50.4-63.8 wt.%) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.%, Mg# = 0.39-0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu*/Eu = 0.80) and pronounced negative Nb-Ta anomalies. Their Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7035-0.7042, εNd(t) = 4.5-7.9, εHf(t) = 14.1-14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 = 60.0-65.3 wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu*/Eu = 0.75) but pronounced negative Nb-Ta anomalies. Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7037-0.7039, εNd(t) = 5.2-8.0, εHf(t) = 13.9-14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 = 70.0-78.4 wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb-Ta anomalies (average Eu*/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7024-0.7045, εNd(t) = 5.1-8.9, εHf(t) = 13.7-14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma. A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the "slab window" opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian.

AB - Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 = 50.4-63.8 wt.%) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.%, Mg# = 0.39-0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu*/Eu = 0.80) and pronounced negative Nb-Ta anomalies. Their Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7035-0.7042, εNd(t) = 4.5-7.9, εHf(t) = 14.1-14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 = 60.0-65.3 wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu*/Eu = 0.75) but pronounced negative Nb-Ta anomalies. Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7037-0.7039, εNd(t) = 5.2-8.0, εHf(t) = 13.9-14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 = 70.0-78.4 wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb-Ta anomalies (average Eu*/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr-Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7024-0.7045, εNd(t) = 5.1-8.9, εHf(t) = 13.7-14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma. A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the "slab window" opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian.

KW - Central Asian Orogenic Belt

KW - Geochemistry

KW - Granite

KW - Junggar

KW - Sr-Nd-Hf isotopes

KW - U-Pb zircon

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U2 - 10.1016/j.chemgeo.2009.07.001

DO - 10.1016/j.chemgeo.2009.07.001

M3 - Journal Article (refereed)

AN - SCOPUS:68749092890

VL - 266

SP - 364

EP - 389

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

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