A Late Carboniferous-Early Permian slab window in the West Junggar of NW China : Geochronological and geochemical evidence from mafic to intermediate dikes

Jiyuan YIN, Xiaoping LONG*, Chao YUAN, Min SUN, Guochun ZHAO, Hongyan GENG

*Corresponding author for this work

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

69 Citations (Scopus)

Abstract

The Late Carboniferous to Early Permian is a critical period for the formation of particular high-temperature magmatic associations in West Junggar, NW China and the geodynamic processes of ridge subduction and related slab windows in the Central Asian Orogenic Belt. Mafic to intermediate dikes, exposed in the central and southeastern West Junggar extensively, mainly consist of Nb-enriched and magnesian suites. The Nb-enriched dikes (305Ma) are characterized by high Nb contents (5.63-9.08ppm) and large variations of major element contents, exhibiting high-K to medium-K calc-alkaline characteristics with high Na2O/K2O (1.33-3.85) and low Sr/Y (9-32) ratios. The dikes have moderate Mg# (44.6-52.9), LREE-rich and sub-horizontal HREE patterns ((La/Yb)N=3.05-7.18; (Gd/Yb)N=1.43-1.78) with weak Eu anomalies (Eu*/Eu=0.81-1.10) and positive εNd (t) values (+5.2 to +8.0), and likely originate from partial melting of mantle peridotite that was metasomatized by subducted sediment-derived melts and slab fluids. The medium-K magnesian dikes (305Ma) are characterized by high MgO (3.05-7.28wt.%), Cr (22.3-311ppm) and Ni (32.6-199ppm) contents and all plot in the field of high-Mg andesite. Some have very high Mg numbers (Mg#>60), suggesting a primitive melt composition. These samples display positive Ba, Sr, K and negative Nb-Ta-Ti anomalies as well as strongly-depleted HREE patterns with weak positive Eu anomalies. They have high Sr/Y (27-126) and relatively high εNd (t) values (+6.0 to +8.3), which suggest a similar petrogenesis as the Nb-enriched dikes, but were metasomatized by adakitic melts. The high-K magnesian dikes (284Ma) are high-K calc-alkaline and have lower MgO (3.63-5.57wt.%) compared with the medium-K suite. They have high Sr (422-819ppm), Sr/Y (26-62) ratios and εNd (t) values (+7.0 to +7.1) with relatively flat REE patterns ((La/Yb)N=2.4-5.5), probably originating from partial melting of K-enriched mantle wedge peridotite metasomatized by adakitic slab melts. Based on these petrogenetic features, we suggest that a ridge subduction regime likely prevailed in West Junggar in the Late Carboniferous. The opening of related slab windows and upwelling asthenosphere have possibly triggered the formation of Late Carboniferous-Early Permian magmatic associations in West Junggar.

Original languageEnglish
Pages (from-to)146-162
Number of pages17
JournalLithos
Volume175-176
Early online date23 Apr 2013
DOIs
Publication statusPublished - 15 Aug 2013
Externally publishedYes

Fingerprint

Levees
dike
slab
Permian
melt
anomaly
peridotite
partial melting
Melting
subduction
Geodynamics
mantle
asthenosphere
petrogenesis
orogenic belt
andesite
geodynamics
upwelling
Sediments
rare earth element

Keywords

  • Central Asian Orogenic Belt
  • Nb-enriched and magnesian dikes
  • Ridge subduction
  • Slab window
  • West Junggar

Cite this

@article{ac01f98698184187a1d3da2b35df2db4,
title = "A Late Carboniferous-Early Permian slab window in the West Junggar of NW China : Geochronological and geochemical evidence from mafic to intermediate dikes",
abstract = "The Late Carboniferous to Early Permian is a critical period for the formation of particular high-temperature magmatic associations in West Junggar, NW China and the geodynamic processes of ridge subduction and related slab windows in the Central Asian Orogenic Belt. Mafic to intermediate dikes, exposed in the central and southeastern West Junggar extensively, mainly consist of Nb-enriched and magnesian suites. The Nb-enriched dikes (305Ma) are characterized by high Nb contents (5.63-9.08ppm) and large variations of major element contents, exhibiting high-K to medium-K calc-alkaline characteristics with high Na2O/K2O (1.33-3.85) and low Sr/Y (9-32) ratios. The dikes have moderate Mg# (44.6-52.9), LREE-rich and sub-horizontal HREE patterns ((La/Yb)N=3.05-7.18; (Gd/Yb)N=1.43-1.78) with weak Eu anomalies (Eu*/Eu=0.81-1.10) and positive εNd (t) values (+5.2 to +8.0), and likely originate from partial melting of mantle peridotite that was metasomatized by subducted sediment-derived melts and slab fluids. The medium-K magnesian dikes (305Ma) are characterized by high MgO (3.05-7.28wt.{\%}), Cr (22.3-311ppm) and Ni (32.6-199ppm) contents and all plot in the field of high-Mg andesite. Some have very high Mg numbers (Mg#>60), suggesting a primitive melt composition. These samples display positive Ba, Sr, K and negative Nb-Ta-Ti anomalies as well as strongly-depleted HREE patterns with weak positive Eu anomalies. They have high Sr/Y (27-126) and relatively high εNd (t) values (+6.0 to +8.3), which suggest a similar petrogenesis as the Nb-enriched dikes, but were metasomatized by adakitic melts. The high-K magnesian dikes (284Ma) are high-K calc-alkaline and have lower MgO (3.63-5.57wt.{\%}) compared with the medium-K suite. They have high Sr (422-819ppm), Sr/Y (26-62) ratios and εNd (t) values (+7.0 to +7.1) with relatively flat REE patterns ((La/Yb)N=2.4-5.5), probably originating from partial melting of K-enriched mantle wedge peridotite metasomatized by adakitic slab melts. Based on these petrogenetic features, we suggest that a ridge subduction regime likely prevailed in West Junggar in the Late Carboniferous. The opening of related slab windows and upwelling asthenosphere have possibly triggered the formation of Late Carboniferous-Early Permian magmatic associations in West Junggar.",
keywords = "Central Asian Orogenic Belt, Nb-enriched and magnesian dikes, Ridge subduction, Slab window, West Junggar",
author = "Jiyuan YIN and Xiaoping LONG and Chao YUAN and Min SUN and Guochun ZHAO and Hongyan GENG",
year = "2013",
month = "8",
day = "15",
doi = "10.1016/j.lithos.2013.04.005",
language = "English",
volume = "175-176",
pages = "146--162",
journal = "Lithos",
issn = "0024-4937",
publisher = "Elsevier",

}

A Late Carboniferous-Early Permian slab window in the West Junggar of NW China : Geochronological and geochemical evidence from mafic to intermediate dikes. / YIN, Jiyuan; LONG, Xiaoping; YUAN, Chao; SUN, Min; ZHAO, Guochun; GENG, Hongyan.

In: Lithos, Vol. 175-176, 15.08.2013, p. 146-162.

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

TY - JOUR

T1 - A Late Carboniferous-Early Permian slab window in the West Junggar of NW China : Geochronological and geochemical evidence from mafic to intermediate dikes

AU - YIN, Jiyuan

AU - LONG, Xiaoping

AU - YUAN, Chao

AU - SUN, Min

AU - ZHAO, Guochun

AU - GENG, Hongyan

PY - 2013/8/15

Y1 - 2013/8/15

N2 - The Late Carboniferous to Early Permian is a critical period for the formation of particular high-temperature magmatic associations in West Junggar, NW China and the geodynamic processes of ridge subduction and related slab windows in the Central Asian Orogenic Belt. Mafic to intermediate dikes, exposed in the central and southeastern West Junggar extensively, mainly consist of Nb-enriched and magnesian suites. The Nb-enriched dikes (305Ma) are characterized by high Nb contents (5.63-9.08ppm) and large variations of major element contents, exhibiting high-K to medium-K calc-alkaline characteristics with high Na2O/K2O (1.33-3.85) and low Sr/Y (9-32) ratios. The dikes have moderate Mg# (44.6-52.9), LREE-rich and sub-horizontal HREE patterns ((La/Yb)N=3.05-7.18; (Gd/Yb)N=1.43-1.78) with weak Eu anomalies (Eu*/Eu=0.81-1.10) and positive εNd (t) values (+5.2 to +8.0), and likely originate from partial melting of mantle peridotite that was metasomatized by subducted sediment-derived melts and slab fluids. The medium-K magnesian dikes (305Ma) are characterized by high MgO (3.05-7.28wt.%), Cr (22.3-311ppm) and Ni (32.6-199ppm) contents and all plot in the field of high-Mg andesite. Some have very high Mg numbers (Mg#>60), suggesting a primitive melt composition. These samples display positive Ba, Sr, K and negative Nb-Ta-Ti anomalies as well as strongly-depleted HREE patterns with weak positive Eu anomalies. They have high Sr/Y (27-126) and relatively high εNd (t) values (+6.0 to +8.3), which suggest a similar petrogenesis as the Nb-enriched dikes, but were metasomatized by adakitic melts. The high-K magnesian dikes (284Ma) are high-K calc-alkaline and have lower MgO (3.63-5.57wt.%) compared with the medium-K suite. They have high Sr (422-819ppm), Sr/Y (26-62) ratios and εNd (t) values (+7.0 to +7.1) with relatively flat REE patterns ((La/Yb)N=2.4-5.5), probably originating from partial melting of K-enriched mantle wedge peridotite metasomatized by adakitic slab melts. Based on these petrogenetic features, we suggest that a ridge subduction regime likely prevailed in West Junggar in the Late Carboniferous. The opening of related slab windows and upwelling asthenosphere have possibly triggered the formation of Late Carboniferous-Early Permian magmatic associations in West Junggar.

AB - The Late Carboniferous to Early Permian is a critical period for the formation of particular high-temperature magmatic associations in West Junggar, NW China and the geodynamic processes of ridge subduction and related slab windows in the Central Asian Orogenic Belt. Mafic to intermediate dikes, exposed in the central and southeastern West Junggar extensively, mainly consist of Nb-enriched and magnesian suites. The Nb-enriched dikes (305Ma) are characterized by high Nb contents (5.63-9.08ppm) and large variations of major element contents, exhibiting high-K to medium-K calc-alkaline characteristics with high Na2O/K2O (1.33-3.85) and low Sr/Y (9-32) ratios. The dikes have moderate Mg# (44.6-52.9), LREE-rich and sub-horizontal HREE patterns ((La/Yb)N=3.05-7.18; (Gd/Yb)N=1.43-1.78) with weak Eu anomalies (Eu*/Eu=0.81-1.10) and positive εNd (t) values (+5.2 to +8.0), and likely originate from partial melting of mantle peridotite that was metasomatized by subducted sediment-derived melts and slab fluids. The medium-K magnesian dikes (305Ma) are characterized by high MgO (3.05-7.28wt.%), Cr (22.3-311ppm) and Ni (32.6-199ppm) contents and all plot in the field of high-Mg andesite. Some have very high Mg numbers (Mg#>60), suggesting a primitive melt composition. These samples display positive Ba, Sr, K and negative Nb-Ta-Ti anomalies as well as strongly-depleted HREE patterns with weak positive Eu anomalies. They have high Sr/Y (27-126) and relatively high εNd (t) values (+6.0 to +8.3), which suggest a similar petrogenesis as the Nb-enriched dikes, but were metasomatized by adakitic melts. The high-K magnesian dikes (284Ma) are high-K calc-alkaline and have lower MgO (3.63-5.57wt.%) compared with the medium-K suite. They have high Sr (422-819ppm), Sr/Y (26-62) ratios and εNd (t) values (+7.0 to +7.1) with relatively flat REE patterns ((La/Yb)N=2.4-5.5), probably originating from partial melting of K-enriched mantle wedge peridotite metasomatized by adakitic slab melts. Based on these petrogenetic features, we suggest that a ridge subduction regime likely prevailed in West Junggar in the Late Carboniferous. The opening of related slab windows and upwelling asthenosphere have possibly triggered the formation of Late Carboniferous-Early Permian magmatic associations in West Junggar.

KW - Central Asian Orogenic Belt

KW - Nb-enriched and magnesian dikes

KW - Ridge subduction

KW - Slab window

KW - West Junggar

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U2 - 10.1016/j.lithos.2013.04.005

DO - 10.1016/j.lithos.2013.04.005

M3 - Journal Article (refereed)

VL - 175-176

SP - 146

EP - 162

JO - Lithos

JF - Lithos

SN - 0024-4937

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