Textures, Structures and Processes of Volcanic Successions: Examples from Southern Central Andes (Northwestern Argentina, 22º-28ºS)

Abstract

The Central Andes provides an excellent natural laboratory for studying the processes associated with subduction of oceanic crust beneath a continental margin constituting an example type of active continental margin particularly built on thick crust. The onset of the Andean Magmatic Cycle is considered took place in late Triassic-early Jurassic (Dalziel 1986) although subduction had already commenced in the late Carbonifeous after the passive margin configuration. The volcanic activity has been essentially continuous from that time to the present day (Coira et al., 1982; Jordan et al., 1983, 1997; Ramos, 1988; Mpodozis and Ramos, 1989; Kay et al., 1991, 1999; Kay and Abbruzzi, 1996) offering examples whose analysis open new perspectives in the understanding of the volcanic processes linked to active continental margins as the Central Andes.As a result of our research carried out over the last 40 years on volcanism (Cenozoic to Paleozoic) of the Southern Central Andes, especially of the northwestern Argentina we have collected illustrative material, on both modern and ancient volcanic successions, which shows a great diversity of types of rocks and processes, reflecting the particular conditions resulting from the conjunction of lithospheric structure, tectonic history and magmatism, reached along the evolution of the Andean continental margin. We believe that they gathered together in a book that contemplates: Textures and structures of volcanic rocks: examples from Southern Central Andes (Northwestern Argentina, 22º-28ºS) will allow to get through the Central Andean volcanism from the Lower Paleozoic to the Cenozoic times in the framework of its processes, eruptive mechanisms and geodynamic conditions. , awakening, given the particular characteristics of the Andean margin, the interest of volcanologists and specialists in the Earth Sciences. For the purposes of the treatment of the different types of volcanic successions to be considered in the book, have been selected the more representative volcanism records of the Southern Central Andes, which have taken place during the Cenozoic as: caldera complexes, composite volcanoes (stratovolcanoes) , silicic dome complexes, and in monogenetic mafic centers as well in the Paleozoic times as : submarine-subaerial volcanism. In each of the volcanic successions to be treated are presented illustrative examples accompanied by maps, stratigraphic sections, petrographic and geochemical data, photographs and microphotographs of structures and textures. These examples will allow the reader to know the different typologies that characterize the volcanism, environment of emplacement and tectonic setting. The analysis of the ancient volcanic successions, in which recognition of the original rock type can be difficult by the effects of deformation, metamorphism and alteration, is a subject of particular attention. Through the description of distinctive cases are provided different tools to be applied in the analysis and interpretation of them.