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Metamorphic Geology: Microscale to Mountain Belts

metamorphic geology coverWhen the first of the Geological Society’s special publications was published in 1964, a book containing a selection of scientific papers on a theme was the only practical way to get an overview of a subject. In today’s world of ‘online first’, preprint servers and more, do these volumes still have a role to play?

This, the 478th volume, ranges widely over the complicated topic of rocks that change, tracing the advances made in the last 30 years. The book is anchored in rocks and minerals and contains many attractive photomicrographs, some with laser pits from analysis. On the microscale, it shows how advances in analytical instruments and computer-aided calculations can give detailed maps of mineral composition and relate these to the pressure and temperature conditions under which they formed. This linkage has moved beyond simple assumptions of chemical equilibrium and now considers the role of factors such fluid flow, kinetics and nucleation in the growth and destruction of metamorphic minerals.

It’s long been known that tiny grains have big implications; for example, micro-diamonds or coesite inclusions in eclogites indicating very deep burial.  One paper describes how in high-grade rocks dusty-looking garnets may contain ‘nanogranitoids’. These tiny samples of now-crystallised magma can give useful information about how the rock itself melted. This paper sent me off on a successful hunt in some old thin sections.

Many of the latest hot topics in the subject are touched on, from how rapid metamorphism can be to evolving ideas that challenge the assumption that measured pressure is always a function of depth and show localised sources of stress may be important. 

The final section shows how regional metamorphic studies can trace the history of mountain belts from the summit of Mount Everest to a range of other places around the globe.

The choice of papers and excellent introductory chapter, stylishly ending with a quote from T. S. Eliot, is what makes this a book worth having. An online search could provide the papers, each with a microscopic focus on a particular area. But it’s the expert editing that joins them together, giving the reader a birds-eye view of the heights the subject has reached and glimpses of the undiscovered peaks beyond.

Reviewed by Simon Wellings

METAMORPHIC GEOLOGY: MICROSCALE TO MOUNTAIN BELTS Edited by S. Ferrero, P. Lanari, P. Goncalves and E. G. Grosch 2019. Published by: The Geological Society 482pp (hbk) ISBN: 9781786204004 List Price: £120.00 W: