A Gigapan image of #omphacite from Jenner, California.
The glorious green omphacite is surrounded by assorted other minerals.
https://www.gigapan.com/galleries/7874/gigapans/17328
Ron Schott
Eclogite: the Christmas Rock
Eclogite is an absolutely fascinating and beautiful rock that has earned the nickname “Christmas rock” due to its colorful mineral garnet (red) and omphacite (green). What’s so fascinating about eclogite is the way it forms
Eclogite is a high pressure and temperature metamorphic rock formed from protolithic basalt or grabbro (oceanic crust) that has been dragged down a subduction zone to (or nearly to) the upper mantle. It is brought up by a process now known as “eduction.” More here: https://c.im/@vickyveritas/109668814063843473
The process of bringing eclogite back up from a subduction zone was first proposed by W. G. Ernst in 1965, and was an immediate controversy. Ernst’s early ideas have been accepted, expanded upon, tested, and extended. As an undergrad in the 90s, I had the great pleasure to have gone on a geology field trip, led by Gary Ernst, to Pacheco Pass, California, where eclogite is found in the Franciscan Complex. He is a lovely guy, very approachable, enthusiastic and willing to share.
Here is Ernst’s famous paper/abstract: https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/76/8/879/5938/Mineral-Parageneses-in-Franciscan-Metamorphic?redirectedFrom=fulltext
Here is Evelyn Mervine’s great AGU blog on eclogites: https://blogs.agu.org/georneys/2011/07/02/geology-word-of-the-week-e-is-for-eclogite/
#eclogite #gabbro #basalt #garnet #omphacite #ChristmasRock #geology #ScienceMastodon @geology
