Author name: Bernard W. Evans

Rock-forming serpentine minerals form flat, cylindrical, and corrugated crystal microstructures, which reflect energetically efficient layering of alternate tetrahedral and octahedral sheets. Serpentinization of peridotite involves internal buffering of the pore fluid, reduction of oxygen fugacity, and partial oxidation of Fe2+ to Fe3+. Sluggish MgFe diffusion in olivine causes precipitation of magnetite and release of H2. The tectonic environment of the serpentinization process dictates the abundance of fluidmobile elements in serpentinites. Similar enrichment patterns of fluid-mobile elements in mantle-wedge serpentinites and arc magmas suggest a linkage between the dehydration of serpentinite and arc magmatism.

Serpentinites are rocks consisting mostly of the serpentine-group minerals chrysotile, lizardite and antigorite. They are formed by the hydration of olivine-rich ultramafi c rocks and they contain up to ~13 wt% H2O. They have long been used by many cultures as building and carving stones. Serpentinites play essential roles in numerous geological settings. They act as a lubricant along plate boundaries during aseismic creep and contribute to the geochemical cycle of subduction zones. In the mantle, they are a reservoir of water and fluid-mobile elements. Serpentinites can produce nickel ore where weathered, and they can sequester CO2 where carbonated. They may have provided an environment for the abiotic generation of amino acids on the early Earth and other planets, potentially leading to the development of life.