FMF - Friends of Minerals Forum, discussion and message board

[prcantos]

Hi. Recently in the Spanish-side FMF-Forum we have been discussing about a pyrope-bearing serpentinite whose serpentine-mineral could have been originated by the serpentinization of the pyroxenes of a previous eclogite. (You can see this serpentine rock in the picture below).

I was really surprised or annoyed because of these presumed serpentinized pyroxenes, which led me to further readings. I would like to know your opinions about this topic: processes of (non-metasomatic) serpentinization. If you prefer, you can use these questions to arrange the information:

[1] Is it possible that Mg-pyroxenes, Mg-amphiboles (or even Mg-silicates in general) become serpentine minerals? If so, what conditions do these processes require?

[2] Do basic igneous rocks (not ultramafic) or eclogites become serpentinites? If so, what conditions are required?

Thank you.

[Roger Warin]

Hello Pablo, list,
This transformation of Mg- (also Fe-) pyroxene in serpentine is observed in meteorites. The presence of water is essential. Are concerned some meteorites from Mars and also those who have always been "cold", that is to say at a temperature below 100 ° C, as the CI and CM carbonaceous chondrites. Water-bearing, clay-rich silicates like smectite (montmorillonite) and serpentine-like minerals do occur under aqueous alteration.
Martian meteorites (as Nakhla) show significant impact heating and pressures. Water was once present on Mars. Hydrothermal processes occurred. Scientists say serpentine mineralization is associated with a production of methane.
Roger.

[prcantos]

Thank you, Roger. Really interesting information.