Tiny crinkly folds form the main basis of today’s Imaggeo on Mondays. Folding can occur on a number of scales; studying folds at all scales can reveal critical information about how rocks behave when they are squeeze and pinched, as described by Sina Martin, from the University of Basel.
Although many geoscientists have seen such fold structures many times before, if you noticed the scale bar in the lower left of the image, you might be surprised of the small scale of these folds!
The presented image is a high-magnification image taken on an electron microscope, showing sub-micrometer scale folds developed within a deformed pyroxene grain – a chain silicate mineral, for example common in the oceanic crust of the earth. The folded layers are primary exsolution lamellae of more calcium rich and calcium poor chemical composition. These lamellae formed during the early, magmatic history of the pyroxene grain, where it crystallized and cooled down in a shallow intrusion. The folding subsequently took place during deformation and the following text will try to give a short overview on why and how these folds have formed.
To find out more, head over to the #EGUBlogs: egu.eu/01PJ90
#folds #structuralgeology #electronmicroscopy #pyroxene #layers