Snaky Words like Serpentinite and Ophiocalcite
Tuesday, August 3, 2010 3:46:52 PM
Serpentine has allegedly not only got its name because of its banded or streaked texture, but also because it was used against snakebites. The ancient Greek word for serpent or snake is ὄφις (ophis). A term that has crept into a few geological words. Known by most is maybe "ophiolite” (literally meaning snake stone). The term ophiolite was originally used for an assemblage of green rocks (serpentine, diabase) in the Alps. It was later modified in use to include serpentine, pillow lava, and chert. Here I shall avoid to discuss what ophiolites today are supposed to be, just mention that they document the existence of former ocean basins that have been consumed by subduction, and that they have always played a central role in plate tectonic theory.
On a field trip to the Alps some years ago I got the chance to see ophiocalcite (also spelled ophicalcite).
Ophiocalcite is a breccia with clasts of serpentinite set in a calcitic matrix. Replacement of serpentinite by calcite is visible. (The most common color of ophiocalcite is white (due to its high calcium content), although a green version of ophiocalcite is also known to exist.) Sediments (or basalts) must have been deposited directly on the serpentinised mantle crust (on ocean floor). This sort of tectonic breccia forms along faults and in particular transform faults. The photo is taken to the north of Davos in Switzerland in the Totalp, and the ophiocalcites are part of an ophiolite complex.
This ophiocalcite (or ophiocalcite breccia) in the Alps is part of the evidence for uplifting, rifting and opening of an ocean in the Jurassic (203 — 135 million years ago). Likewise it has often been pointed out in the many blog posts lately on the Californian serpentinite, that it is not only connected to the history of the Californian people, but that it through its significance for the plate tectonic history of the area, tells a tale of millions of years rather than a few hundreds.
Ophiocalcite is used in traditional Chinese medicine (stops heavy bleeding), and I wonder if this has anything to do with the staff of Aesculapius, which consists of a serpent entwined around a staff. The name of the symbol derives from its early and widespread association with Asclepius, the son of Apollo, who was a practitioner of medicine in ancient Greek mythology. - Probably it hasn’t - what’s in a name?
Although California is extremely far from my bed, I find that California - so far - has a fantastic state rock, which I hope they may keep. Best luck to California! History matters!