Young Earth: An Introduction to Archean Geology

ISBN-13: 9780045500499 / Angielski / Miękka / 1987 / 402 str.

E. G. Nisbet; Euan G. Nisbet

Opis

'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.

Spis treści

I Background: Concepts and field evidence.- 1 Introduction.- 1.1 Purpose and scope.- 1.2 Concepts.- 1.3 Catastrophes vs. uniformity.- 1.4 Archaean stratigraphy and mapping.- 2 Geochronology and other uses of isotopic analysis.- 2.1 Introduction.- 2.2 K-Ar and 40Ar/39Ar methods.- 2.3 Application of K-Ar data.- 2.4 Rb-Sr dating.- 2.5 Sm-Nd, Lu-Hf and Re-Os methods.- 2.6 U, Th-Pb dating methods.- 2.7 Choosing a dating technique.- 2.8 The isotopiC record of planetary evolution.- 3 Archaean terrains: the available geological evidence.- 3.1 Introduction.- 3.2 Transects through the Archaean crust.- 3.3 Archaean ‘cover’ successions.- 3.4 Granite-greenstone terrains.- 3.5 Construction of the craton.- 3.6 Other Archaean low-grade terrains.- 3.7 Gneiss terrains.- 3.8 Archaean high-grade terrains.- 3.9 The information available in Archaean terrains.- 3.10 An example of an Archaean field area: the Belingwe Belt, Zimbabwe.- 3.11 The Archaean record: a basis for interpretation.- II Reconstructing the Archaean Earth.- 4 The beginnings of life.- 4.1 Geological evidence for life.- 4.2 Molecular palaeontology and the History of Life in the Archaean.- 5 Archaean continents.- 5.1 Continents and oceans.- 5.2 Archaean sediments.- 5.3 The sedimentological record: stratigraphic examples.- 5.4 Archaean sedimentary facies: some deductions from evaporites, stromatolites, cherts and ironstones.- 5.5 The composition of the sedimentary mass.- 5.6 The crustal residence times of the sedimentary mass.- 5.7 The thermal regime of the continental crust: metamorphosis and intrusion.- 5.8 Archaean granitoids: the substance of the continents.- 5.9 Metamorphism: the problem of ‘equilibrium’ gradients.- 5.10 Archaean continental geotherms: how thick was the subcontinental lithosphere?.- 5.11 Plate tectonics: an Archaean necessity.- 6 Archaean volcanism.- 6.1 Andesitic suites.- 6.2 Alkaline rocks.- 6.3 Kimberlites: the case of the missing diamonds again.- 6.4 Komatiites.- 6.5 Basalts.- 6.6 Ultramafic complexes.- 6.7 The composition of Archaean mafic and ultramafic lavas.- 6.8 Possible relationships between komatiites and komatiitic basalts.- 6.9 Implications of the major element compositions of komatiites: the source region.- 6.10 Through a glass darkly: the trace element and isotopic window to the Archaean mantle.- 6.11 The evolution and stratification of the mantle.- 6.12 The rates of growth of the continents and depletion of the mantle.- 7 Mineral deposits in Archaean rocks.- 7.1 Gold deposits.- 7.2 Base metal deposits.- 7.3 Archaean nickel deposits.- 7.4 Platinum group elements.- 7.5 Chrome.- 7.6 Asbestos.- 7.7 Iron ore.- 7.8 Other minerals.- 8 Models of the early Earth.- 8.1 The bowels of the Earth.- 8.2 Plate tectonics.- 8.3 Continents and water.- 8.4 The degassing of the planet.- 8.5 Gaia.- 8.6 Life.- 8.7 The origin of life.- 8.8 The home of life.- Glossary of geological terms for non-geologists.- References.- Author Index.