My posts on metamorphism form a sequence. I start with what anyone ought to know, the core concepts of metamorphic facies and how we estimate conditions of metamorphism. Next I cover the concepts of grade, zones, index minerals and Barrovian metamorphism. What useful things can metamorphic rocks tell us? Well Pressure-Temperature-time paths are useful things to know, and can be related to tectonic conditions such as mountain-building or subduction. What about the business of quantifying the conditions of metamorphism, thermobarometry, is it really witchcraft? Looking at complications to thermobarometry, how easy is it to achieve chemical equlibrium and is metamorphism really closed? Looking at work on the cutting edge, how can we use geospeedometry to put the t in P-T-t?
Originally these posts started out as a short note in a blog post about the Vredefort impact structure. I was talking about the amazing things metamorphic petrologists had discovered and wanted to quickly summarise how they got their results. My quick summary soon turned into a post of its own, and then split off into multiple posts.
I’ve been encouraged to write these post by an off-the-cuff remark from Dana Hunter (and her inspiring post “Adorers of the Good Science of Rock-breaking“). I learnt my metamorphic petrology 15+ years ago and I wanted to write about what is left in my memory. Not the chemical formula of staurolite, but the interesting stuff - understanding, not just knowledge. An excellent post by MK (part of the education themed Accretionary Wedge #38) gave me a name for this, the scaffolding.