Abstract:

1) Federico Casetta - The interaction between Kimberlite melts and the Siberian sub-cratonic lithosphere

Kimberlites and the entrained mantle xenoliths and diamonds open a window on the processes occurring in the deepest realms of the Earth’s lithosphere. However, modelling the structure and composition of the lithospheric mantle and the physico-chemical properties of the ascending kimberlite melts is not straightforward, because kimberlites appear as mixtures of mantle- and magmatic-derived phases, often pervaded by intense hydrothermal alteration. So, what information can we extract from kimberlites and their crystal cargo?
In this presentation, I will show how routine and high-precision electron microprobe analyses of the main mineral phases in fresh samples of the Udachnaya-East kimberlite (Siberia, Russia) can be used to:
- discriminate the mantle-derived cargo from the “magmatic” phases;
- reconstruct the P-T-X-fO2 path of kimberlite melts;
- model the interactions between kimberlite-related fluid/melts and the sub-cratonic lithosphere.

2) Tom Griffiths - Cristallographic orientation mapping in magmatic petrology: new insights into crystal clustering

Formation of crystal clusters has important impacts on the rheology and differentiation of crystal-bearing magmas. Determining the origin of crystal clusters is key to extracting petrological information from them, and improved understanding of clustering processes is needed in order to predict clustering behaviour and its effects on magmatic plumbing systems. Crystallographic orientation mapping, using the electron backscatter diffraction (EBSD) technique, is routine in metamorphic petrology but seldom applied to magmatic rocks and their experimental analogues. In this presentation I will demonstrate how EBSD can reveal the crystallographic orientation relationships between clustered crystals and how these orientation relationships may record information about both the mechanism and conditions of cluster formation as well as the modification of clusters after their formation.