Mineralogical and geochemical compositions of Late Permian coals and host rocks from the Guxu Coalfield, Sichuan Province, China, with emphasis on enrichment of rare metals

Shifeng Dai, Jingjing Liu, Colin R. Ward, James C. Hower, David French, Shaohui Jia, Madison M. Hood, Trent M. Garrison

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147 Scopus citations

Abstract

This paper reports the geochemical and mineralogical compositions of the Late Permian No. 25 Coal (semi-anthracite) and its host rocks (roof and floor strata) from the Guxu (Gulin–Xuyong) Coalfield, Sichuan Province, China. The coal is characterized by medium-sulfur content (average 2.73%) and has an average ash yield of 20.95%. In contrast to other Late Permian coals from southwestern China that are enriched in Sc, V, Cr, Co, Ni, and Cu, the No. 25 coal does not contain an abundance of these transition elements but is rich in lithophile elements Be, Y, Nb, Zr, Hf, and U. The elevated concentrations of trace elements in the No. 25 Coal were probably derived from the felsic–intermediate rocks at the top of the Emeishan basalt sequence, rather than from the Emeishan mafic basalts. The floor strata of the No. 25 Coal can be divided into two sub-sections. The upper sub-section of the sequence immediately below the No. 25 Coal consists of material with a felsic–intermediate composition probably derived from terrigenous sources and the lower sub-section is composed of mafic tuff. The terrigenous mineral matter in the No. 25 coal appears to have the same sediment-source region as the upper sub-section of the floor strata, based on their similar geochemical compositions. The roof strata of the No. 25 Coal are more quartzose, and were probably derived from a different sediment-source region. The mineral matter in the coal is dominated by kaolinite and, to a lesser extent, calcite and pyrite; the roof and floor strata each have quite different mineralogy, with kaolinite dominant in the latter and illite, kaolinite and quartz in the former; pyrite contents are variable both in the coal and in the host rocks. The floor strata and the coal have been affected by hydrothermal solutions, leading to the enrichment of rare earth elements and yttrium (REY), Nb, Ta, Zr, Hf, and U. The REY in the coal and floor strata, as well as the Nb, Ta, Zr, Hf, and U in the floor strata, represent potentially economic rare metal resources.

Original languageEnglish
Pages (from-to)71-95
Number of pages25
JournalInternational Journal of Coal Geology
Volume166
DOIs
StatePublished - Sep 1 2016

Bibliographical note

Funding Information:
This research was supported by the National Key Basic Research Program of China (no. 2014CB238902), the National Natural Science Foundation of China (nos. 41420104001 and 41272182), and the Program for Changjiang Scholars and Innovative Research Team in University (IRT13099).

Publisher Copyright:
© 2015 Elsevier B.V.

Keywords

  • Emeishan Large Igneous Province
  • Late Permian
  • Minerals in coal
  • Rare earth elements
  • Trace elements in coal

ASJC Scopus subject areas

  • Fuel Technology
  • Geology
  • Economic Geology
  • Stratigraphy

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