Geochemical and mineralogical evidence for a coal-hosted uranium deposit in the Yili Basin, Xinjiang, northwestern China

Shifeng Dai, Jianye Yang, Colin R. Ward, James C. Hower, Huidong Liu, Trent M. Garrison, David French, Jennifer M.K. O'Keefe

Research output: Contribution to journalArticlepeer-review

187 Scopus citations

Abstract

The petrological, geochemical, and mineralogical compositions of the coal-hosted Jurassic uranium ore deposit in the Yili Basin of Xinjiang province, northwestern China, were investigated using optical microscopy and field emission-scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer, as well as X-ray powder diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The Yili coal is of high volatile C/B bituminous rank (0.51-0.59% vitrinite reflectance) and has a medium sulfur content (1.32% on average). Fusinite and semifusinite generally dominate the maceral assemblage, which exhibits forms suggesting fire-driven formation of those macerals together with forms suggesting degradation of wood followed by burning. The Yili coals are characterized by high concentrations of U (up to 7207. μg/g), Se (up to 253. μg/g), Mo (1248. μg/g), and Re (up to 34. μg/g), as well as As (up to 234. μg/g) and Hg (up to 3858. ng/g). Relative to the upper continental crust, the rare earth elements (REEs) in the coals are characterized by heavy or/and medium REE enrichment. The minerals in the Yili coals are mainly quartz, kaolinite, illite and illite/smectite, as well as, to a lesser extent, K-feldspar, chlorite, pyrite, and trace amounts of calcite, dolomite, amphibole, millerite, chalcopyrite, cattierite, siegenite, ferroselite, krutaite, eskebornite, pitchblende, coffinite, silicorhabdophane, and zircon. The enrichment and modes of occurrence of the trace elements, and also of the minerals in the coal, are attributed to derivation from a sediment source region of felsic and intermediate petrological composition, and to two different later-stage solutions (a U-Se-Mo-Re rich infiltrational and a Hg-As-rich exfiltrational volcanogenic solution). The main elements with high enrichment factors, U, Se, As, and Hg, overall exhibit a mixed organic-inorganic affinity. The uranium minerals, pitchblende and coffinite, occur as cavity-fillings in structured inertinite macerals. Selenium, As, and Hg in high-pyrite samples mainly show a sulfide affinity.

Original languageEnglish
Pages (from-to)1-30
Number of pages30
JournalOre Geology Reviews
Volume70
DOIs
StatePublished - Oct 1 2015

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 41172143 ), and the Program for Changjiang Scholars and Innovative Research Team in University ( IRT13099 ). Many thanks are given to Shande Liu, Xibo Wang, and Lei Zhao for their help during sample preparation. We are very grateful to two anonymous reviewers for comments which greatly improved the quality of the paper.

Publisher Copyright:
© 2015 Elsevier B.V.

Keywords

  • Coal-hosted uranium deposit
  • Hydrothermal solutions
  • Jurassic coal
  • Minerals in coal
  • Trace-element geochemistry
  • Yili coal basin

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology
  • Economic Geology

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