A model for Nb–Zr–REE–Ga enrichment in Lopingian altered alkaline volcanic ashes: Key evidence of H-O isotopes

Shifeng Dai, Victor P. Nechaev, Igor Yu Chekryzhov, Lixin Zhao, Sergei V. Vysotskiy, Ian Graham, Colin R. Ward, Alexander V. Ignatiev, Tatyana A. Velivetskaya, Lei Zhao, David French, James C. Hower

Research output: Contribution to journalArticlepeer-review

76 Scopus citations

Abstract

Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions.

Original languageEnglish
Pages (from-to)359-369
Number of pages11
JournalLithos
Volume302-303
DOIs
StatePublished - Mar 2018

Bibliographical note

Publisher Copyright:
© 2018

Keywords

  • Critical metals
  • Hydrothermal activity
  • Mineralization
  • O-H isotopes
  • Volcanic ash

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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