Silicified serpentinite in the Semail nappe of Oman
Abstract
The nature and origin of silicified serpentinite in the Semail nappe of Oman is described and discussed. Its formation was caused by fracturing of the basal serpentinite by late tectonic events followed by dissolution of serpentine and precipitation of silica under slightly acidic, high-pCO 2 groundwater conditions. The source of CO 2 was transient and atypical of present-day groundwater in the Oman environment. Silicification was restricted to groundwater pathways in wholly serpentinised ultramafic rock. Elsewhere the process was inhibited by restricted groundwater flow, inadequate CO 2 concentration, and strongly alkaline conditions caused by continuing low-temperature serpentinisation. A hitherto unexamined paragenesis of associated niccolite mineralisation results from low-temperature aqueous precipitation; the Ni being released by serpentine dissolution whilst the As is leached from the Fe oxide/hydroxide products of initial serpentinisation.
- Publication:
-
Lithos
- Pub Date:
- 1985
- DOI:
- 10.1016/0024-4937(85)90003-9
- Bibcode:
- 1985Litho..18...13S