Plio-Quaternary volcanism in Italy. Petrology, Geochemistry, Geodynamics

Italian Plio-Quaternary magmatism exhibits a very wide petrological, geochemical and radiogenic-isotope variability, which makes magma genesis and geodynamic significance difficult issues. A large number of papers have been published on these rocks trying to explain the petrogenesis and evolution of single volcanoes or magmatic provinces. However, papers presenting a comprehensive review of the data and hypotheses on the magmatism of the region as a whole are few, if any. Synthesis of data at the local scale has definitely increased our degree of understanding of volcanism at that scale, but it has not resolved ambiguous issues such as the relationship among various magmatic provinces, the significance of regional compositional variations, and the geodynamic setting for this complex magmatism. The objective of this book is to fill this gap by providing an overview of the most prominent petrological and geochemical data and discussing currently held ideas on the petrogenesis and geodynamic significance of Italian Plio-Quaternary volcanic rocks. In summarising the intense debate on Italian magmatism, I have tried to report on, as objectively as possible, all the most significant ideas. The different weight given to the discussion of various points of view depends only marginally on the au-thor’s choice but is mostly an effect of the very different amounts of factual constraints which have been brought to supporting various hy-potheses. The book is subdivided into ten chapters. The first one provides an introduction to the main petrological and geochemical characteristics and gives the rationale for subdivision of the Italian Plio-Quaternary magmatism into several distinct magmatic provinces. The last chapter is a summary of the petrological, volcanological and structural characteristics of the volcanic provinces and of the most popular hypotheses that have been proposed to explain the relationship between geodynamics and volcanism. The other chapters are devoted to the volcanology, petrology and geochemistry of single magmatic provinces into which Recent Italian magmatism has been subdivided. The number of these provinces is slightly higher than recognised by most authors. However, the present subdivision is based on the bulk of compositional data, included a large number of trace elements and radiogenic isotopes, which have provided the tools for setting new boundaries that were not obvious during early studies. The data discussed in the text have been generally taken from the most recent literature; old analyses have not been considered in order to avoid analytical bias. In most diagrams, especially those showing major elements and the most commonly determined trace elements, a limited number of representative data have been plotted. Such a choice has been dictated by the need to avoid excessive crowding, which would have made diagrams difficult to read. In goes without saying that, in the choice of data points, care has been taken to select representative compositions, in order to preserve all necessary information. A few representative data for the single magmatic provinces have been reported in the tables attached to the end of each chapter. More data can be found in the CD attached to this book and at the Author’s web-site (http://www.unipg.it/~pecceang). For classification and nomenclature of volcanic rocks, the IUGS scheme of Le Maitre (1989) has been consistently adopted through the book. For rocks related to volcanic arcs, the classification scheme of Peccerillo and Taylor (1976) has been used. These classification schemes, together with a few notes on the petrogenesis of potassium-rich rocks, have been explained in the Appendix. Rocks names not reported in these schemes and eventually used through the book have been defined in footnotes. Explanations and comments reported in the Appendix, in footnotes and, sometimes, through the text are trivial for petrologists and geochemists, but may be useful for other potential readers who are not familiar with petrological-geochemical issues and jargon. The bibliography on Italian volcanism and geodynamics is enormous and would deserve a book by itself. Therefore, the attached reference list is far from being comprehensive of the large quantity of the published papers and many important contributions, especially in the field of mineralogy, geophysics and geodynamics, have been omitted because of space constraints. Again, a more complete list of papers is reported in the attached CD and at the Author’s web-site.