VUME Upper Mantle of the Earth




Geophysical and Petrological Modeling of the Structure and Composition of the Mantle. Pyrolite.


The structure and composition of the crust and upper mantle depend on the geological history.
Understanding the structure of the lithosphere–asthenosphere system is fundamental for gaining a better insight into several processes, including volcanism and seismicity. Information on the properties of the upper mantle and lower crust can be gained by geophysical investigations. Seismicwave velocities and gravimetric data are extensively used to investigate crustal and mantle structure.
Equally important information can be obtained from petrological and geochemical studies of magmas and of high-pressure xenoliths entrained in volcanic rocks. Magmas are generated at various depths, from middle–upper crust to the asthenosphere, and are important potential carrier of information on the composition of the entire LAS.
Combined petrological, geochemical and geophysical studies are particularly useful in complex areas where young and compositionally variable magmatism occurs.

Pyrolite is a theoretical rock considered to be the best approximation of the composition of Earth's upper mantle. The definition varies, but it is generally considered as being about one part tholeiitic basalt and three parts peridotite. The relative abundances of the principal metallic element components (except iron) are similar to those in chondritic meteorites and in the solar photosphere. Accordingly, it is reasonable to assume that to a first approximation these abundances are applicable to the entire mantle. If fused experimentally, this mix yields high pressure tholeiitic basaltic melts, and intermediate pressure alkaline basalts. The hypothetical pyrolite compositions are not compatible with trace element, isotopic and chondritic abundances data as well as evidence for mantle heterogeneity

Upper Mantle and Lithosphere Dynamics


The lithosphere features many of Earth's active processes such as the formation of mountain belts, subduction of oceanic lithosphere into the mantle underneath, rifting of continents, the formation of passive margins and the evolution of sedimentary basins.
An understanding of the dynamic evolution of these processes is of prime importance for understanding the hazards related to them (volcanism, land slides and earthquakes) and for research into petroleum occurrences.
Plate reconstructions document the movement of continents and the creation and destruction of oceanic plates. On a large scale, lithosphere movements provide a driving force for mantle flow through subduction and gravitational spreading at mid-ocean ridges. In turn, dynamic flow of the mantle drives lithosphere deformation. On a more regional scale, feedback processes also exist between erosion and sedimentation at the surface and tectonic deformation.