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

研究成果: 雜誌貢獻文章

9 引文 斯高帕斯(Scopus)

摘要

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.

原文英語
頁(從 - 到)329-344
頁數16
期刊Journal of Asian Earth Sciences
79
DOIs
出版狀態已發佈 - 2014 一月 5

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

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