Metamorphic clues

I’ve been identifying minerals and structures within the thin sections I received last month and using them to draw conclusions on the kinds of deformation the area has undergone. The mineral assemblages in the rocks can help identify different kinds of metamorphic environments and therefore give us an idea of the scale and extent of deformation that occurred.

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Sample of quartzite, field of view is 1 mm. Muscovite mica and quartz grains labeled.

Quartzite is a metamorphic rock formed by its protolith, a sandstone, undergoing high temperatures and pressures typical of orogenic belts. It is common throughout mountain ranges and tectonic contacts. We collected many quartzite samples during our field work and have found that multiple samples display foliation in hand sample and now in thin section. Many of the thin sections show a general trend in the mineral fabric, meaning that deformation occurred in a plane. This is good news for us because once all the orientations of deformation are mapped out, we can create a schematic of how the plates shifted and how the area around Taww was affected. My next post will conclude with what we think occurred 80 million years ago and a schematic of that process.


  1. Hi Cece! It’s great to see your research and I have never thought about that the ocean plate can go above the land plate before reading your blog. I was wondering what device or method you use to identify the minerals in the rock samples. It might be easy to differentiate between quartz and other minerals, but I was wondering how to further identify the categories of the minerals.