Debated topics of modern igneous petrology

Progress made thanks to the great amount of high-quality geochemical and isotopic data gathered over the last twenty years has allowed important insights into igneous petrology (e.g., Continental Flood Basalt petrogenesis, mantle source characterization, geophysical models of mantle plume systems, primary melt compositions, isotopic systematics of crustal and mantle domains, etc.). This large dataset has also been used to relate the compositional characteristics of igneous rocks with specific tectonic settings and to infer the geodynamic processes involved. However, inferring a tectonic setting mainly on the basis of geochemical constraints may fail, because partial melts with substantial compositional differences can originate from the same source, and the same melts may have been generated in different tectonic settings . Moreover, geochemical characterization of the main mantle components is still hotly debated, even in terms of concepts such as asthenosphere and lithosphere. Asthenospheric mantle is quite often believed to be a geochemically homogeneous convecting domain, whereas the lithospheric one is thought to be a variably enriched, heterogeneous, non-convecting reservoir, capable of retaining geochemical and isotopic gradients for periods of time exceeding 2 Ga. These assumptions are clearly over-simplifications, particularly when relationships between physical and geochemical mantle characteristics are not properly constrained. What emerges from recent literature is the «misuse» of petrological concepts tending towards the most convenient explanations and «effectively shutting out the entire creative thought process of the human mind» (Sheth, 1 999). More appropriate use of petrological data is necessary to stimulate true scientific growth, especially as regards our knowledge of mantle-crust dynamics.