Our dependence on the minerals that underpin modern life has grown enormously over the last few decades. Figure 1.1 shows the price, the average grade and production of copper ore has changed dramatically from 1900 to the present. At the start of last century the price was 7000 US$ per ton (expressed in 1998 currency) to negate the effects of inflation; by 2002 it had decreased three-fold to about 1800 US $ per ton, then, in the three years to 2010 it rose sharply to about 9000 US$ per ton before declining again in the latest recession. Over the same period, the total amount of copper mined gradually increased, except in the early 20s and 30s when both price and production dropped. How do we explain these changes, and what do they tell us about how the metal is found and mined, and about how it is used by society? Understanding these concepts is the basis of economic geology <...>

This book is about metamorphic rocks: the processes involved in their formation and the reasons why they occur at particular places on the continents. It has been written to serve as an elementary text on the subjects of metamorphism and mountain building for non-specialist students of geology. It will be equally useful where geology is either the main or subsidiary subject and could be used by students intending to advance further in geology (the list of advanced texts in the further reading section would be more appropriate to such students). My intention in writing this book has been to try to dispel the notion that metamorphism comprises the 'haunted wing' of geology. Admittedly, there are rather a large number of technical terms in the book, but I hope that after working through it you will not find metamorphism an unduly difficult or obscure aspect of geology. Throughout, I have emphasised the strong links between mountain building, plate tectonics and metamorphic processes

METAMORPHISM is the mineralogical and structural (textural) adjustment of (dominantly) solid rocks to physical and chemical conditions which differ from those under which the rocks originated. Weathering and similar processes are conventionally excluded. The type of metamorphism depends on the relative values of temperature ( T ) , confining pressure (/*con)> pressure or chemical activity or fugacity of water (expressed generally as PHJO)* deformation or directed pressures (P^ir) and their variation with time {t). There is only a limited degree of interdependence of these controls and the metamorphic history of a rock is an expression of their mutual interaction with time (Fyfe, Turner and Verhoogen, 1958; Pitcher and Flinn, 1965). <...>

In the foreword of the volume Mantle Metasomatism by Menzies & Hawkesworth (1987), Boettcher stated that the concept of mantle metasomatism has been of immense heuristic value for Earth scientists. At that time, metasomatism was still strongly related to allochemical metamorphism, where chemical composition of the rock is changed by the additional or removal of material.