Peculiarities of some mafic-ultramafic- and ultramafic-hosted massive sulfide deposits from the Main Uralian Fault Zone, southern Urals

P. Nimis*, V. V. Zaykov, P. Omenetto, I. Yu Melekestseva, S. G. Tesalina, J. J. Orgeval

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Some Cu-rich, mafic-ultramafic- and ultramafic-hosted massive sulfide deposits from the southern segment of the Main Uralian Fault Zone (Ivanovka and Ishkinino deposits, southern Urals) show unusual characteristics. Their major features include: (i) relatively high Co (Ni, Au), very low Zn and negligible Pb grades; (ii) a pyrrhotite-dominated mineralization, locally characterized by the presence of open-latticework aggregates of lamellar pyrrhotite with Mg-saponite ± Mg-chlorite and carbonate matrix; (iii) hydrothermal alteration of ultramafic host rocks into talc ± carbonate ± quartz ± chlorite and of mafic host rocks into chloritites; (iv) the presence of clastic facies with reworked sulfide and ultramafic or mafic components; (v) the widespread occurrence of sulfide-associated chromite; (vi) the specific mineralogy of Co, Ni, Fe and As, including sulfoarsenides, mono- and diarsenides, and Co-rich pentlandite and pyrite; (vii) the supra-subduction-zone geochemical signature of the host serpentinites and volcanic rocks. Although some of these features have been separately reported in certain modern ocean-seafloor and ophiolite-hosted fossil deposits, a true equivalent has yet to be found. Based on recognized partial analogies with a few modern seafloor examples, the arc tholeiitic-boninitic geochemical signature of sulfide-associated volcanic rocks and the highly refractory compositions of sulfide-hosted chromite relicts, the studied deposits are believed to have formed by seafloor-subseafloor hydrothermal processes in an oceanic island arc setting. Possible tectonostratigraphic correlation of sulfide-associated units with infant, non-accretionary arc volcanic units of the adjacent Magnitogorsk oceanic island-arc system suggests formation of the studied deposits during the earliest stages of Devonian subduction-related volcanism.

Original languageEnglish
Pages (from-to)49-69
Number of pages21
JournalOre Geology Reviews
Volume33
Issue number1
DOIs
Publication statusPublished - Jan 2008
Externally publishedYes

Keywords

  • Mafic-ultramafic-hosted
  • Main Uralian Fault Zone
  • Oceanic island arc
  • South Urals
  • Volcanogenic massive sulfides

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