Archaean Geochemistry

Archaean Geochemistry

Archaean Geochemistry 1972 - 1984 The realisation that the continental crust contains well-preserved relics which date as far back as 4/5 of the Earth's age has given a great impetus to the study of early Precambrian terrains. As late as the mid-sixties the Archaean still constituted the 'terra-in cognita' of earth science. High metamorphic grades, poor out crop, and not least a widely assumed obliteration of early crustal records by convective recycling and thermal reworking had com bined to discourage research in this field. Many excellent local studies existed, notably around gold mining centres, but remained unrelated to a broader regional and theoretical understanding. This situation has changed as the consequence of two inter-related factors: (1) advances in isotopic methods and their application to Precambrian rocks, and (2) the recognition that some of the oldest terrains have retained a wealth of primary igneous and sedi mentary textures and even geochemical characteristics.

This book provides a comprehensive overview of the evolution of one of the oldest and best-exposed Archaean cratons on this planet. There is currently a renewed interest in the early Earth, and the Kaapvaal craton has long served as a model for early crustal evolution. This unique multidisciplinary resource features information on geology, tectonics, geochemistry, and geochronology. It offers a wealth of new data on various aspects of the craton as well as contributions on the various crustal units by international specialists.

Archaean terrains contain a wealth of structural, stratigraphic, textural, mineralogical, geochemical and isotopic features allowing insights into the nature of the early Earth. This book is based on studies during 1964-2007 of Archaean terrains in Australia and to a lesser extent in South Africa and India, as well as on visits to Archaean terrains in Canada, the US and China, as well as petrological and geochemical studies of igneous and sedimentary rock suites from a range of terrains. The book will include a range of photographic and microscopic images, geological sketch maps and diagrams illustrating the lessons derived from field and the laboratory. Also other Archaean terrains are being reviewed. The book is intended for Earth scientists as well as broader intelligent readership.

Archaean terrains contain a wealth of structural, stratigraphic, textural, mineralogical, geochemical and isotopic features allowing insights into the nature of the early Earth. This book is based on studies during 1964-2007 of Archaean terrains in Australia and to a lesser extent in South Africa and India, as well as on visits to Archaean terrains in Canada, the US and China, as well as petrological and geochemical studies of igneous and sedimentary rock suites from a range of terrains. The book will include a range of photographic and microscopic images, geological sketch maps and diagrams illustrating the lessons derived from field and the laboratory. Also other Archaean terrains are being reviewed. The book is intended for Earth scientists as well as broader intelligent readership.

Early Earth Systems provides a complete history of the Earth from its beginnings to the end of the Archaean. This journey through the Earth's early history begins with the Earth's origin, then examines the evolution of the mantle, the origin of the continental crust, the origin and evolution of the Earth's atmosphere and oceans, and ends with the origin of life. Looks at the evidence for the Earth's very early differentiation into core, mantle, crust, atmosphere and oceans and how this differentiation saw extreme interactions within the Earth system. Discusses Archaean Earth processes within the framework of the Earth System Science paradigm, providing a qualitative assessment of the principal reservoirs and fluxes in the early Earth. “The book would be perfect for a graduate-level or upper level undergraduate course on the early Earth. It will also serve as a great starting point for researchers in solid-Earth geochemistry who want to know more about the Earth’s early atmosphere and biosphere, and vice versa for low temperature geochemists who want to get a modern overview of the Earth’s interior.” Geological Magazine, 2008

'What are we going to do with a parcel of old stones?' wrote the director of an African museum a century and a half ago, when one of my ancestors presented him with a splendid collection of fossils of mammal-like reptiles. Old stones, however intriguing, are difficult to interpret, dusty, and do not fit well in the neatly ordered contents of a house of learning. Archaean geology, which is the study of the Earth's history in the period from after 9 the end of planetary accretion (4.5-4.4 x 10 years ago) up to the beginning 9 of the Proterozoic (2.5 x 10 years ago) is much the same - a parcel of old stones seemingly impossible to understand. Yet these stones contain the history of our origins: they can tell us a story that is interesting not just to the geologist (for whom this book is primarily written) but instead addresses the human condition in general.

This Special Publication sheds light on crust formation and tectonic processes in early Earth by focusing on Archaean granitoids and related rocks from West Greenland in the North Atlantic Craton, Karelia Province of the Fennoscandian Shield, Eastern Dharwar and Bundelkhand cratons in the Indian Shield and Bug Complex of the Ukrainian Shield. Resulting from the IGCP-SIDA 599 project `The Changing Early Earth’, this compilation of papers provides explanations on the nomenclature of Archaean granitoids and explores the petrology, element and isotope geochemistry, geochronology and metamorphism of granitoids and supracrustal rocks of variable metamorphic grade. This volume provides information on the increase and timing of crust-mantle interactions and granitoid diversification from early Archaean protoliths of island arc origin to the emergence of multi-source high-K calc-alkaline granitoid batholiths at convergent continental margins. The formation of abundant granitoid batholiths suggests a significant change in mantle dynamics and plate tectonics towards the end of the Archaean.