Wed 14th November @ noon, Rm 312.222

Abstract:

Large igneous provinces (LIP) are the manifestations of mantle plume activities, i.e. the rise of hot deep mantle materials. Mantle plumes play crucial roles in Earth’s tectonic and geodynamic evolution, climatic changes, and mass extinction events.  Two competing theories exist about the origin and operation of mantle plumes: (1) the fixed model where plumes (or superplumes) are anchored to the core deep in the mantle, and (2) the dynamic model where the formation and evolution of plumes and superplumes are link to large scale mantle convection and supercontinent cycles. The current global LIP record appears to show a cyclic nature following that of the supercontinent cycle. However, this LIP record is predominantly a continental record due to the destruction of oceanic LIPs (O-LIP) as part of the oceanic crust for much of Earth’s earlier history. Establishing the O-LIP record will enable us to evaluate if LIP intensity in the oceanic realm has remained semi-constant over geological time as some have suggested or followed similar cycles to the continental LIP record. Here we show that O-LIP basalts possess distinct elemental and isotopic compositional distributions that allow us to statistically discriminate O-LIP volcanic rocks from MORB, arc basalts, and continental-LIP basalts. We applied such a filter system to identify O-LIP from the global ophiolite records. Together with the geotectonic and age variations for each such record, we have started to establish a GIS-based global O-LIP record.

Short bio:

 Luc Doucet comes from Bourg-en-Bresse, a small town in France famously known for its blue-white-red tricoloured chickens. After a Ph.D. in St Etienne, France on mantle petrology, he moved to Brussels, Belgium to apply the “non-traditional” stable-isotope systematics on mantle and crustal rocks to study the formation of both oceanic and continental lithosphere (Kerguelen LIP and Siberia and Kaapvaal). March 2018, he moved to Perth to join the Earth Dynamics Research Group, in which he tries to figure out about oceanic large igneous provinces in the geologic record.