Ask GeoMan...

What is serpentinization? I'm a senior Chemical Engineering student at Clemson University and I can't seem to find a decent definition.

Serpentinization is a processes whereby rock (usually ultramafic) is changed, with the addition of water into the crystal structure of the minerals found within the rock. A common example is the serpentinization of peridotite (or dunite) into serpentinite (the metamorphic equivalent).

Here's where it gets a bit fuzzy:

Metamorphic processes usually involve the addition of heat and pressure: a rock is buried, heats up and is squeezed, and the minerals change in an attempt to regain equilibrium with the new environment (like shale to slate, or limestone to marble).

In the case of peridotite to serpentinite, the process actually involves a reduction in heat and pressure. Peridotite starts out as a sub-crustal, upper mantle rock. If tectonic forces move it nearer to the surface, the reduction in T&P cause the minerals (usually olivine and pyroxene) to destabilize and change into the mineral serpentine. No, I'm not mixing up rocks and minerals. Serpentinite is a rock which is composed of the mineral serpentine and formed by a process called serpentinization (which results in far too much confusion for most of us normal mortals).

Click here for some additional information from my GeoTour to the serpentinites of the Josephine Ophiolite.

Hope this helps, and good luck with your studies. If you need any additional information, you know how to reach me.


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