Geology of Granite

The unifying theme for granite landscapes of the world is the granite itself, hence it is logical to start with a brief account of granite geology. For obvious reasons of space and relevance, this chapter cannot provide a comprehensive and extensive treatment of granite as a rock. Rather, its aim is to provide background information on those aspects of granite geology which are relevant to geomorphology and may help to explain the variety of landforms and landscapes supported by granite. The survey of literature about the geomorphology of granite areas reveals that in too many studies the lithology of granite and the structure of their intrusive bodies have not received adequate attention, especially if a ruling paradigm was one of climatic, or climato-genetic geomorphology. Granites were usually described in terms of their average grain size, but much less often of their geochemistry, fabric, or physical properties. Even the usage of the very term ‘granite’ may have lacked accuracy, and many landforms described as supported by granite may in fact have developed in granodiorite. On the other hand, it is true that granite may give way to granodiorites without an accompanying change in scenery. In the Yosemite National Park, Sierra Nevada, California, these two variants occur side by side and both support deeply incised valleys, precipitous slopes and the famous Sierran domes. Likewise, wider structural relationships within plutons and batholiths, and with respect to the country rock, have been considered in detail rather seldom. In analyses of discontinuities, long demonstrated to be highly significant for geomorphology, terms such as ‘joints’, ‘faults’, and ‘fractures’ have not been used with sufficient rigour. But it has to be noted in defence of many such geologically poorly based studies that adequate geological data were either hardly available or restricted to a few specific localities within extensive areas, therefore of limited use for any spatial analysis of granite landforms. Notwithstanding the above, there exist a number of studies in which landforms have been carefully analysed in their relationships to various aspects of the lithology, structure, and tectonics of granite intrusions.