cover

Werner Zeil:

The Andes - a geological review

1979. VIII, 260 pages, 143 figures, 17x25cm, 840 g
Language: English

(Beiträge zur regionalen Geologie der Erde, Band 13)

ISBN 978-3-443-11013-0, bound, price: 65.00 €

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Keywords

geology the Andes igneous rock geodynamic plate tectonic mineral deposit

Contents

Content Description top ↑

Extending as they do over about 7,500 km, the Andes form the Pacific boundary of South America and represent, as it were, the backbone of this southern continent. They are part of the circumpacific mountain system, some features of which differ from those of the W-E trending orogenic zones of the earth: There are more igneous rocks present than in many parts of the Tethyan geosynclines.

The tectonic structure is characterized in particular by significant normal faulting while there are fewer overthrusts or deformations caused by folding, especially in the overlying rock. The majority of the deep-focus earthquakes and megaseisms, and also most of the recent volcanic activity, are connected with this region. Prominent deep-sea trendies run parallel to the continents and to the island arcs which encircle the Pacific.

The actual Andean orogen is distinguished by further dominant geological aspects: From the morphology one would think that the orogenic events were contemporaneous whereas in fact the mountain range has been formed, since the Precambrian, by temporally and spatially superimposed crustal sections. There is no such thing as a uniform Andean geosyncline, but instead there are several separate fully developed sections which were welded together during different geodynamic phases.

Any attempt to give a concise general account of the problems encountered and the progress made in studying the geology of the Andes is a questionable venture. In the last twenty years so many data have been gathered in all the geoscientific disciplines in the Andean region that it has become next to impossible for a single individual to follow every aspect of the subject, let alone to write about them. It was therefore necessary right from the start to limit the subject matter and to make a selection of the new knowledge to be dealt with. For example, merely to have attempted to describe all the new stratigraphie details would have gone far beyond the scope of this book. Here, and in many other instances, it is necessary to refer the reader to the literature on the subject. In addition, the state of researdi still varies considerably from section to section of the orogen. The accuracy and the scale of the geological maps - on which the geoscientific facts are mainly based - flucuate within wide limits and in many countries the preparation of large-scale maps has only recently got under way.

Contents top ↑

Introduction 1
Present and future status of geological research 7
Crust and mantle in the Andes 8
General 8
Northern section 13
Central and southern sections 19
Deep-sea trenches and continental margin 26
Igneous rocks 32
The plutonic rocks of the Andes 32
Introduction 32
Northern section (Colombia, Venezuela, Ecuador) 34
Central and southern Andes (Peru, Bolivia, Chile, Argentina) 38
Summary 49
Mesozoic volcanism 50
The region between Tierra del Fuego and the Peru/Ecuador border 50
The region of Ecuador and Colombia 54
Cainozoic volcanism 56
Introduction 56
Regional distribution and activity 57
Petrology and Metrogenesis 67
Correlations with the tectonics 72
Sedimentary and metamorphic structural material 77
The basement of the Andes 77
Introduction 77
Northern section (Colombia, Venezuela, Ecuador) 78
Central and southern sections (Peru, Chile, Argentina) 82
Paleozoic sedimentation basins in the Andes 88
General 88
Northern section (Colombia, Venezuela, Ecuador) 91
Central and southern sections (Peru, Bolivia, Argentina, Chile) 98
The sedimentary cover of the Andes 104
Introduction 104
Northern section (Colombia, Venezuela, Ecuador) 106
Southern section (Peru, Bolivia, Chile, Argentina) 113
The Andes as a geodynamic body 125
Introduction 125
Tectonic events up to the end of the Paleozoic 126
Northern section (Venezuela, Colombia, Ecuador) 127
Central and southern sections (Peru, Bolivia, Chile, Argentina) 133
Summary 146
The geodynamic development since the start of the Triassic 147
Introduction and themes 147
Northern section (Venezuela, Colombia, Ecuador) 149
Southern section (Peru, Bolivia, Argentina, Chile) 156
The Andes as a plate tectonics model 185
Preliminary remarks 185
Facts and arguments in favour of the Andean model 186
Critical objections to the model 190
The mineral deposits of the Andes - a brief review 196
Economic importance 196
Status of research 198
Ore deposits 200
Non-metallic deposits 204
Bibliography 208
Author Index 241
Locality Index 249
Subject Index 253