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Irina Artemieva, China University, Thermal and Density Structure of Cratonic Lithosphere Mantle

Thursday, Jan 21, 2021 12:00 PM
Where:  Passcode: 083990
General Public
Geophysics Department

Irina Artemieva

China University of Geosciences, Wuhan and GEOMAR, Kiel Germany

Thermal and Density Structure of Cratonic Lithosphere Mantle

Geochemical studies of mantle-derived xenoliths indicate that the cratonic lithospheric mantle has a unique depleted composition such that it has low bulk density at SPT (room pressure-temperature) conditions. However, the nature’s sampling is uneven, sparse, and possibly biased. Here I compare mantle density structure of the cratonic regions in Eurasia (Europe, Siberia, China) and southern Africa based on gravity and free-board modeling. In situ mantle density is then converted to SPT density by introducing a temperature correction based on my regional thermal models in order to compare the modelled mantle density with global and regional xenolith data. In all studied regions, the cratonic lithospheric mantle has a highly heterogeneous density structure with strong regional variations, that are not known from xenolith data. In Europe, a low density mantle beneath the Archean-early Proterozoic shields of Baltica and Greenland corresponds to the known kimberlite provinces with a strong correlation between mantle density and the occurrence of diamondiferous kimberlites. In Siberia and Kaapvaal, kimberlites sample exclusively those parts of the mantle where the isopycnic condition is satisfied. In contrast, the pristine lithospheric mantle which has not been affected by magmatism has a significantly lower SPT density. In the North China craton, only a part of the Trans-North China Orogen retains the density structure typical of the Archean undisturbed cratonic lithosphere, while most of the craton has density values typical of fertile lithospheric mantle. Deep intracratonic basins have a very dense mantle, which indicates that eclogitization may have played an important role in their formation. The results indicate that most of the Archean lithospheric mantle has been significantly reworked by tectono-magmatic processes and kimberlite-hosted xenoliths provide deceptive basis for density of the Archean lithosphere mantle.  Passcode: 083990

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