Understanding Granites

In Granite and Grace Michael Cohen reflects on a lifetime of climbing, walking, and pondering the granite in Yosemite National Park at Tuolumne Meadows. This high-country region of Yosemite is dominated by a young, beautifully glaciated geological formation known as the Tuolumne Intrusive Suite. It does not include familiar Yosemite icons like Half Dome, yet geologists describe this granitic realm at over 8,000 feet as “an iconic American landscape.” Drawing together the humanistic and scientific significance of the wild landscapes he traverses, Michael uncovers relationships between people and places and meaning and substance, rendering this text part memoir—but also considerably more. On-the-rock encounters by hand and foot open up a dialogue between the heart of a philosopher and the mind of a geologist. Michael adds a literary softness to this hard landscape, blending excursions with exposition and literature with science. It is through his graceful representations that the geological becomes metaphorical, while the science turns mythological. This high country, where in 1889 John Muir and Robert Underwood Johnson planned what would become Yosemite National Park, is significant for cultural as well as natural reasons. Discoursing on everything from Camus’s “Myths of Sisyphus” to the poems of Gary Snyder, Michael adds depth to an already splendorous landscape. Premier early geologists, such as François Matthes, shaped the language of Yosemite’s landscape. Even though Yosemite has changed over half a century, the rock has not. As Michael explores the beauty and grace of his familiar towering vistas, he demonstrates why, of the many aspects of the world to which one might get attached, the most secure is granite.

The origin of granite has for long fascinated geologists though serious debate on the topic may be said to date from a famous meeting of the Geological Society of France in 1847. My own introduction to the subject began exactly one hundred years later when, in an interview with Profes sor H. H. Read, I entered his study as an amateur fossil collector and left it as a committed granite petrologist - after just ten minutes! I can hardly aspire to convert my reader in so dramatic a way, yet this book is an attempt, however inadequate, to pass on the enthusiasm that I inherited, and which has been reinforced by innumerable discussions on the outcrop with granitologists of many nationalities and of many shades of opinion. Since the 1960s, interest in granites has been greatly stimulated by the thesis that granites image their source rocks in the inaccessible deep crust, and that their diversity is the result of varying global tectonic context. So great a body of new data and new ideas has accumulated that my attempt to review the whole field of granite studies must carry with it a possible charge of arrogance, especially as I have adopted the teaching device of presenting the material from a personal point of view with its thinly disguised prejudices.

This book is mainly about the field geology of granites at all scales from that of a single outcrop to plutons and batholiths. All field geologists work initially at the scale of the outcrop, consequently most of the phenomena treated herein are those which are visible at outcrop scale. However, granites typically occur as plutons and batholiths, some of which are so large as to apparently defy any effort at systematic treatment. Having had the opportunity of mapping two very large and very different batholiths, namely the Coastal Batholith of Peru and the tin granites of Southeast Asia, I have found that it is possible to map large batholiths within a relatively short time, so that the geology of the batholith as a whole can be appreciated. Moreover batholiths are one of the most common modes of granite occurrence, so it makes sense to study them at their natural scale. During my working life I have worked with many geologists from underdevel oped countries and this book is mainly to help them in unravelling the geology of their native batholiths. I have been lucky with my friends and colleagues of many nationalities, and I particularly thank Wallace Pitcher, who took me on as an untried apprentice in Peru, and who, by his kindness and example, showed me how to look at granites properly.

This volume brings together a collection of papers that summarize current ideas and recent progress in the study of granite-related mineralization systems. They provide a combination of field, experimental and theoretical studies. Papers are grouped according to the main granite-related ore systems: granite-pegmatite, skarn and greisen-veins, porphyry, orogenic gold, intrusion-related, epithermal and porphyry-related gold and base metal, iron oxide-copper-gold (IOCG), and special case studies. The studies provide a broad spread in terms of both space and time, highlighting granite-related ore deposits from Europe (Russia, Sweden, Croatia and Turkey), the Middle East (Iran), Asia (Japan and China) and South America (Brazil and Argentina) and spanning rocks from Palaeoproterozoic to Miocene in age.

Granite is exposed over more than 15% of the continents, implying that its significance to the Earth’s surface is comparable to that of the carbonates. Landforms and Geology of Granite Terrains is devoted to this phenomenon and provides a comprehensive explanation of the landforms and landscapes developed on granitic rocks and forms. Whereas existing literature in the field predominantly deals with karst landscapes, this book is specifically focussed on granitic terrains. Landforms and Geology of Granite Terrains provides detailed considerations of the forms, major and minor, well-known and not so familiar granitic terrains, developed over large areas of the continents. It comprises interpretations which are of general significance in the analysis and understanding of the landscape and includes many theories in the context of granite landforms. The importance of structure, including crystal stresses, and the value of etching of subsurface initiation, multi-stages or two-stages development, neotectonic forms, solution forms is emphasized as well as the antiquity of some forms and surfaces (inherited forms). Morphogenetic forms are placed in perspective and comparison is made with similar forms in other rock types. This work is intended for geologists, geomorphologists, geographers and mining engineers and can serve both as a practical guide for professionals and as a textbook for university courses. Author, location and subject indices are included.