Plume-induced dynamic instabilities near cratonic blocks: implications for P-T-t paths and metallogeny

Laurent Guillou-Frottier (1) , Evgenii E.B. Burov (2) , Sierd Cloetingh (3) , Elisabeth Le Goff (1) , Yves Deschamps (1) , Benjamin Huet (2) , Vincent Bouchot (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 iSTeP - Institut des Sciences de la Terre de Paris
3 Faculty of Earth and Life Sciences

Plume head - lithosphere interactions around cratonic blocks result in thermo-mechanical disturbances that lead to heating and burial phases of crustal rocks. We present results from numerical models of plume head - cratonic blocks interactions where a free upper surface condition and realistic rheologies are accounted for. These models include distinct cratonic blocks embedded within a continental lithosphere and separated by several hundreds of kilometres. Surface topography, thermal field and effective viscosity values are tracked for 20 Myr of interactions. The modelled dynamic interaction of a plume head around cratonic blocks results in two main types of instabilities, each of them resulting in a distinct P-T-t path. The "slab-like" instability, focused on cratonic edges when plume head is away from the craton centre, shows a near-isothermal burial phase, while the "drip-like" instability occurring above plume head material results in a near-isobaric heating phase. Consequently, both clockwise and counterclockwise P-T-t paths can be expected around cratons, as actually observed around the Tanzanian craton and other cratonic areas. Metallogenic data from gemstone-bearing rocks in south-east Africa and data from ultrahigh temperature and ultrahigh pressure metamorphism are compatible with our model. It appears that vertical mantle dynamics around cratons may also explain thermobarometric signatures that are often attributed to horizontal tectonics

Mots clés: Cratons; mantle plumes; numerical modelling; ore deposits

Domaines: Planète et Univers [physics]; Sciences de la Terre

Laurent Guillou-Frottier, Evgenii E.B. Burov, Sierd Cloetingh, Elisabeth Le Goff, Yves Deschamps, et al.. Plume-induced dynamic instabilities near cratonic blocks: implications for P-T-t paths and metallogeny. Global and Planetary Change, 2012, 90-91, pp.37-50. ⟨10.1016/j.gloplacha.2011.10.007⟩. ⟨hal-00634433⟩