An ultramafic primary magma for a low Si, high Ti-Fe gabbro in the Panxi region of the Emeishan large igneous province, SW China

J. Gregory Shellnutt, Kuo Lung Wang

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The Kelang gabbro (256±3Ma) is in contact with the peralkaline syenite of the Late Permian (~260Ma) Fe-Ti oxide-bearing Baima igneous complex and contains high contents of TiO2 (~4.0wt.%) and Fe2O3t (~20wt.%) and low SiO2 (~42wt.%) and Al2O3 (~11wt.%) content. The gabbros are primarily composed of plagioclase, clinopyroxene, olivine (Mg# ~50), ilmenite, magnetite, orthopyroxene (Mg# ~60), biotite and apatite. The Sr-Nd whole rock isotope data (ISr=0.7046, εNd(T)=+2.5) and positive primitive mantle normalized anomalies of Ba, Sr and Ti and high Eu/Eu* (~1.1) of the Kelang gabbro suggest a possible connection to the Baima cumulate gabbro (ISr=0.7047-0.7052, εNd(T)=+1.6 to +4.2, Eu/Eu*=1.5-3.6) but the bulk Cr content (~4ppm) and mineralogy are very different. Mass-balance, least-squares modeling suggests that the low Cr content of the Kelang gabbro is likely a result of fractionation of Cr-spinel from a picritic primary magma. After early fractionation of Mg-rich mafic silicates and Cr-spinel, the residual liquid will be enriched in Ti and Fe, depleted in Cr, have low Si and Al and resemble the bulk composition of the Kelang gabbro. Consequently, the Kelang gabbro may be the uppermost portion of a large mafic-ultramafic intrusion unrelated to the Baima igneous complex.

Original languageEnglish
Pages (from-to)329-344
Number of pages16
JournalJournal of Asian Earth Sciences
Volume79
DOIs
Publication statusPublished - 2014 Jan 5

Fingerprint

large igneous province
gabbro
magma
spinel
fractionation
syenite
cumulate
ilmenite
orthopyroxene
clinopyroxene
apatite
magnetite
biotite
plagioclase
mass balance
olivine
Permian
mineralogy
silicate
oxide

Keywords

  • Emeishan large igneous province
  • Permian
  • Ti-rich gabbro
  • Ultramafic

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

Cite this

@article{4c9e1342638c45789cc5b075272acf9c,
title = "An ultramafic primary magma for a low Si, high Ti-Fe gabbro in the Panxi region of the Emeishan large igneous province, SW China",
abstract = "The Kelang gabbro (256±3Ma) is in contact with the peralkaline syenite of the Late Permian (~260Ma) Fe-Ti oxide-bearing Baima igneous complex and contains high contents of TiO2 (~4.0wt.{\%}) and Fe2O3t (~20wt.{\%}) and low SiO2 (~42wt.{\%}) and Al2O3 (~11wt.{\%}) content. The gabbros are primarily composed of plagioclase, clinopyroxene, olivine (Mg# ~50), ilmenite, magnetite, orthopyroxene (Mg# ~60), biotite and apatite. The Sr-Nd whole rock isotope data (ISr=0.7046, εNd(T)=+2.5) and positive primitive mantle normalized anomalies of Ba, Sr and Ti and high Eu/Eu* (~1.1) of the Kelang gabbro suggest a possible connection to the Baima cumulate gabbro (ISr=0.7047-0.7052, εNd(T)=+1.6 to +4.2, Eu/Eu*=1.5-3.6) but the bulk Cr content (~4ppm) and mineralogy are very different. Mass-balance, least-squares modeling suggests that the low Cr content of the Kelang gabbro is likely a result of fractionation of Cr-spinel from a picritic primary magma. After early fractionation of Mg-rich mafic silicates and Cr-spinel, the residual liquid will be enriched in Ti and Fe, depleted in Cr, have low Si and Al and resemble the bulk composition of the Kelang gabbro. Consequently, the Kelang gabbro may be the uppermost portion of a large mafic-ultramafic intrusion unrelated to the Baima igneous complex.",
keywords = "Emeishan large igneous province, Permian, Ti-rich gabbro, Ultramafic",
author = "{Gregory Shellnutt}, J. and Wang, {Kuo Lung}",
year = "2014",
month = "1",
day = "5",
doi = "10.1016/j.jseaes.2013.10.017",
language = "English",
volume = "79",
pages = "329--344",
journal = "Journal of Asian Earth Sciences",
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T1 - An ultramafic primary magma for a low Si, high Ti-Fe gabbro in the Panxi region of the Emeishan large igneous province, SW China

AU - Gregory Shellnutt, J.

AU - Wang, Kuo Lung

PY - 2014/1/5

Y1 - 2014/1/5

N2 - The Kelang gabbro (256±3Ma) is in contact with the peralkaline syenite of the Late Permian (~260Ma) Fe-Ti oxide-bearing Baima igneous complex and contains high contents of TiO2 (~4.0wt.%) and Fe2O3t (~20wt.%) and low SiO2 (~42wt.%) and Al2O3 (~11wt.%) content. The gabbros are primarily composed of plagioclase, clinopyroxene, olivine (Mg# ~50), ilmenite, magnetite, orthopyroxene (Mg# ~60), biotite and apatite. The Sr-Nd whole rock isotope data (ISr=0.7046, εNd(T)=+2.5) and positive primitive mantle normalized anomalies of Ba, Sr and Ti and high Eu/Eu* (~1.1) of the Kelang gabbro suggest a possible connection to the Baima cumulate gabbro (ISr=0.7047-0.7052, εNd(T)=+1.6 to +4.2, Eu/Eu*=1.5-3.6) but the bulk Cr content (~4ppm) and mineralogy are very different. Mass-balance, least-squares modeling suggests that the low Cr content of the Kelang gabbro is likely a result of fractionation of Cr-spinel from a picritic primary magma. After early fractionation of Mg-rich mafic silicates and Cr-spinel, the residual liquid will be enriched in Ti and Fe, depleted in Cr, have low Si and Al and resemble the bulk composition of the Kelang gabbro. Consequently, the Kelang gabbro may be the uppermost portion of a large mafic-ultramafic intrusion unrelated to the Baima igneous complex.

AB - The Kelang gabbro (256±3Ma) is in contact with the peralkaline syenite of the Late Permian (~260Ma) Fe-Ti oxide-bearing Baima igneous complex and contains high contents of TiO2 (~4.0wt.%) and Fe2O3t (~20wt.%) and low SiO2 (~42wt.%) and Al2O3 (~11wt.%) content. The gabbros are primarily composed of plagioclase, clinopyroxene, olivine (Mg# ~50), ilmenite, magnetite, orthopyroxene (Mg# ~60), biotite and apatite. The Sr-Nd whole rock isotope data (ISr=0.7046, εNd(T)=+2.5) and positive primitive mantle normalized anomalies of Ba, Sr and Ti and high Eu/Eu* (~1.1) of the Kelang gabbro suggest a possible connection to the Baima cumulate gabbro (ISr=0.7047-0.7052, εNd(T)=+1.6 to +4.2, Eu/Eu*=1.5-3.6) but the bulk Cr content (~4ppm) and mineralogy are very different. Mass-balance, least-squares modeling suggests that the low Cr content of the Kelang gabbro is likely a result of fractionation of Cr-spinel from a picritic primary magma. After early fractionation of Mg-rich mafic silicates and Cr-spinel, the residual liquid will be enriched in Ti and Fe, depleted in Cr, have low Si and Al and resemble the bulk composition of the Kelang gabbro. Consequently, the Kelang gabbro may be the uppermost portion of a large mafic-ultramafic intrusion unrelated to the Baima igneous complex.

KW - Emeishan large igneous province

KW - Permian

KW - Ti-rich gabbro

KW - Ultramafic

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