We can use olivine as a “crystal clock” to determine the timing of magmatic events leading up to eruption which was discussed in detail in a previous Volcano Watch here. Two other minerals that we ...

Seawater seeps down into the mantle and heats up. As the seawater hits the minerals, the olivine and pyroxene within the periodite turn into serpentine minerals and produce hydrocarbons.

In this case the olivine crystals formed early in the crystallization history but also at elevated temperatures. Pyroxene oikocrysts show distinct zoning from pigeonite to augite, i.e. from Ca-rich ...