Olivine is the first mineral to crystallize when magma is cooling.
It is the reason why Olivine is often present in the gabbros, but also in the basalts.
Olivine can crystallize at a temperature of about 1000 ° C. This is the first mineral of the Bowen reaction sequence (see enigma 7: Minerals!)
Being formed at high temperature and in the absence of water, the olivines are very sensitive to hydrothermal alteration.
Surprises on the seabed !.
Whether you are very close to the ocean ridge or in the middle of the ocean, hydrothermal vents are always a great moment for scientists.
But also a source of questions. (No pun intended!)
Enigma attached !