Longevity of the Permian Emeishan mantle plume (SW China): 1 Ma, 8 Ma or 18 Ma?

J. Gregory Shellnutt, Mei Fu Zhou, Dan Ping Yan, Yanbin Wang

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

After the formation of the ∼ 260 Ma Emeishan large igneous province, there were two volumetrically minor magmatic pulses at ∼ 252 Ma and ∼ 242 Ma, respectively. Alkaline mafic dykes intruding both 260 Ma and 252 Ma felsic plutons in the Panxi region, southwestern China, have compositions similar to the Emeishan flood basalts. One dyke is dated using the SHRIMP zircon U-Pb technique at 242 ± 2 Ma, ∼ 18 Ma younger than the start of Emeishan magmatism. The dykes have enriched light rare earth element patterns (La/YbN = 4.4-18.8) and trace element patterns similar to the Emeishan flood basalts and average ocean-island basalts. Some trace element ratios of the dykes (Zr/Nb = 3.8-8.2, La/Nb = 0.4-1.7, Ba/La = 7.5-25.6) are somewhat similar to EM1 source material, however, there are differences. Their εNd values (εNd = +2.6 and +2.7) and ISr(ISr = 0.704542 and 0.704554) ratios are indicative of a mantle source. Thus Emeishan magmatism may have lasted for almost 20 Ma after the initial eruption. However, geological evidence precludes the possibility that the post-260 Ma magmatic events were directly related to Emeishan magmatism, which began at and ended shortly after 260 Ma. The 252 Ma plutons and 242 Ma dykes represent volumetrically minor melting of the fossil Emeishan plume-head beneath the Yangtze crust. The 252 Ma magmatic event was likely caused by post-flood basalt extension of the Yangtze crust, whereas the 242 Ma event was caused by decompressional melting associated with the collision between the South China and North China blocks during the Middle Triassic.

Original languageEnglish
Pages (from-to)373-388
Number of pages16
JournalGeological Magazine
Volume145
Issue number3
DOIs
Publication statusPublished - 2008 May 1

Fingerprint

flood basalt
mantle plume
magmatism
Permian
pluton
melting
trace element
crust
large igneous province
ocean island basalt
mantle source
dike
zircon
rare earth element
Triassic
volcanic eruption
plume
collision
fossil

Keywords

  • Emeishan large igneous province
  • Late Permian
  • Mafic dykes
  • Middle Permian
  • Middle Triassic

ASJC Scopus subject areas

  • Geology

Cite this

Longevity of the Permian Emeishan mantle plume (SW China) : 1 Ma, 8 Ma or 18 Ma? / Shellnutt, J. Gregory; Zhou, Mei Fu; Yan, Dan Ping; Wang, Yanbin.

In: Geological Magazine, Vol. 145, No. 3, 01.05.2008, p. 373-388.

Research output: Contribution to journalArticle

Shellnutt, J. Gregory ; Zhou, Mei Fu ; Yan, Dan Ping ; Wang, Yanbin. / Longevity of the Permian Emeishan mantle plume (SW China) : 1 Ma, 8 Ma or 18 Ma?. In: Geological Magazine. 2008 ; Vol. 145, No. 3. pp. 373-388.
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AB - After the formation of the ∼ 260 Ma Emeishan large igneous province, there were two volumetrically minor magmatic pulses at ∼ 252 Ma and ∼ 242 Ma, respectively. Alkaline mafic dykes intruding both 260 Ma and 252 Ma felsic plutons in the Panxi region, southwestern China, have compositions similar to the Emeishan flood basalts. One dyke is dated using the SHRIMP zircon U-Pb technique at 242 ± 2 Ma, ∼ 18 Ma younger than the start of Emeishan magmatism. The dykes have enriched light rare earth element patterns (La/YbN = 4.4-18.8) and trace element patterns similar to the Emeishan flood basalts and average ocean-island basalts. Some trace element ratios of the dykes (Zr/Nb = 3.8-8.2, La/Nb = 0.4-1.7, Ba/La = 7.5-25.6) are somewhat similar to EM1 source material, however, there are differences. Their εNd values (εNd = +2.6 and +2.7) and ISr(ISr = 0.704542 and 0.704554) ratios are indicative of a mantle source. Thus Emeishan magmatism may have lasted for almost 20 Ma after the initial eruption. However, geological evidence precludes the possibility that the post-260 Ma magmatic events were directly related to Emeishan magmatism, which began at and ended shortly after 260 Ma. The 252 Ma plutons and 242 Ma dykes represent volumetrically minor melting of the fossil Emeishan plume-head beneath the Yangtze crust. The 252 Ma magmatic event was likely caused by post-flood basalt extension of the Yangtze crust, whereas the 242 Ma event was caused by decompressional melting associated with the collision between the South China and North China blocks during the Middle Triassic.

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