CRG - High intensity two-axis powder diffractometer

Texture of subduction rocks

The history of strain and stresses in the Earth’s crust are stored, memorised in rocks. Reading it through neutron texture analysis can tell us much about geological mechanisms, for example subduction, which are involved in volcanoes and earthquakes.

Why is rock study so important and why use neutrons ? 
Geology is the study of the birth and evolution of the Earth. The planet consists primarily of aggregates of minerals (rocks) and they remain the best records of preceding geological processes. The appearance of the rock is the consequence of all these events which have occurred over different time and distance scales.

As example: 

  • an earthquake is a sudden process related to lithospheric scale displacements.
  • rock-folding on a kilometere scale corresponds to very slow processes involving rock deformation at the atomic scale.

Neutrons are especially useful for studying rocks at the atomic scale. Being highly penetrating they can be used to investigate large samples of geological material, even where this is coarse-grained.

This movie shows measurements of the texture, the distribution of orientations of these coarse granules in samples of subduction rock (amphiboles), performed on D1B in 2002 by Michele Zucali.

Ref.: Zucali M. , Chateigner D. , Dugnani M. , Lutterotti L. , Ouladdiaf B., "Deformation Mechanisms, Rheology and Tectonics: Current Status and Future Perspectives", The Geological Society, 2002, pp.239-253.