Redistribution of magnetite during multi-stage serpentinization: Evidence from the Taishir Massif, Khantaishir ophiolite, western Mongolia

Research output: Contribution to journalArticlepeer-review

Abstract

Magnetite veins are commonly observed in serpentinized peridotite, but the mobility of iron during serpentinization is poorly understood. The completely serpentinized ultramafic rocks (originally dunite) in the Taishir Massif in the Khantaishir ophiolite, western Mongolia, contain abundant antigorite + magnetite (Atg + Mag) veins, which show an unusual distribution of Mag. The serpentinite records multi-stage serpentinization in the order: (1) Atg + lizardite (Lz) with a hourglass texture (Atg-Lz); (2) thin vein networks and thick veins of Atg; (3) chrysotile (Ctl) that cuts all earlier textures. Mg# values of the Atg-Lz (0.94-0.96) are lower than those of the Atg (~ 0.99) and chrysotile (~ 0.98). In the Atg-Lz regions, magnetite occurs as arrays of fine grains (<50 µm) around the hourglass texture, and magnetite is absent in the thin Atg vein networks replacing Atg-Lz. Magnetite occurs as coarse grains (100-250 µm) in the center of some thick Atg veins. As the volume ratio ofthin Atg veins to Atg-Lz increases, both the modal abundance of Mag and the bulk iron content decrease. These features indicate that hydrogen generation occurred mainly during Atg-Lz formation, and that the Mag distribution was largely modified by dissolution and precipitation in response to the infiltration of the higher temperature fluids associated with the Atg veins. The transport of iron during redistribution of Mag in the late-stage of serpentinization is potentially important for ore deposit formation and modifying the magnetic properties of ultramafic bodies.

Original languageEnglish
Pages (from-to)176-181
Number of pages6
JournalJournal of Mineralogical and Petrological Sciences
Volume116
Issue number3
DOIs
Publication statusPublished - 2021

Keywords

  • Antigorite
  • Iron mobility
  • Khantaishir ophiolite
  • Magnetite
  • Serpentinization
  • Taishir Massif

ASJC Scopus subject areas

  • Geophysics
  • Geology

Fingerprint

Dive into the research topics of 'Redistribution of magnetite during multi-stage serpentinization: Evidence from the Taishir Massif, Khantaishir ophiolite, western Mongolia'. Together they form a unique fingerprint.

Cite this