Metamorphic and plutonic basement complexes
Francisco Hervé (coordinator), Victor Faundez, Mauricio Calderón, Hans-Joachim Massonne, Arne P. Willner, 2007. "Metamorphic and plutonic basement complexes", The Geology of Chile, Teresa Moreno, Wes Gibbons
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The present-day Andes have formed in response to subduction-related processes operating continuously along the western margin of South America since the Jurassic period. When these processes started, the continental margin was mainly formed of metamorphic complexes and associated magmatic rocks which evolved during Proterozoic (?), Palaeozoic and Triassic times, and which now constitute the basement to the Mesozoic and Cenozoic Andean sequences. These older units are commonly referred to in the Chilean geological literature as the ‘basement’ or the ‘crystalline basement’.
The basement rocks crop out discontinuously (Fig. 2.1) in northern Chile, both in the coastal areas and in the main cordillera. In contrast, from latitude 34°S southwards, they form an almost continuous belt within the Coastal Cordillera extending to the Strait of Magellan. In addition, sparse outcrops occur both in the main Andean cordillera as well as further east in the Aysen and Magallanes regions. In the first maps and syntheses of the geology of Chile (e.g. Ruiz 1965) these rocks were generally considered to be of Precambrian age, forming a western continuation of the Brasilian craton. Later work has demonstrated that rocks first described as metamorphic basement units show a wide range of metamorphic grades and ages extending from possible Late Proterozoic through Palaeozoic and even, in some cases, to Jurassic–Cretaceous.
With regard to previous works that have attempted to synthesize data on Chilean basement geology, the reader is referred to those by González-Bonorino (1970, 1971), González-Bonorino & Aguirre (1970), Aguirre et al.
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This book is the first comprehensive account in English of the geology of Chile, providing a key reference work that brings together many years of research, and written mostly by Chilean authors from various universities and other centres of research excellence. The 13 chapters begin with a general overview, followed by detailed accounts of Andean tectonostratigraphy and magmatism, the amazingly active volcanism, the world class ore deposits that have proven to be so critical to the welfare of the country, and Chilean water resources. The subject then turns to geophysics with an examination of neotectonics and earthquakes, the hazardous frequency of which is a daily fact of life for the Chilean population. There are chapters on the offshore geology and oceanography of the SE Pacific Ocean, subjects that continue to attract much research not least from those seeking to understand world climatic variations, and on late Quaternary land environments, concluding with an account examining human colonization of southernmost America.
During his voyage on H.M.S. Beagle, an extended visit to Chile (1834-35) had a profound impact on Charles Darwin, especially on his understanding of volcanoes, earthquakes and tsunamis. Over more recent decades scientists have come to recognize the Chilean Andes as providing the classic example of a mountain belt produced by oceanic subduction beneath a continent, as well as some of the most dramatic scenic and climatic variations on Earth. In the final chapter, the editors offer a description of a drive from the Mediterranean landscapes of central Chile to the hyperarid Atacama Desert, a contribution designed to give visitors a chance to experience for themselves the geology and scenery of this extraordinary country.