Mantle evolution beneath Siberian and Archean cratons worldwide: evidence from thermobarometry of diamond inclusions

Thermobarometric calculations for diamond inclusions allowed systematically compare the pressure-temperature, fO₂ conditions in the mantle beneath different cratons worldwide. Beneath Siberia, Kaapvaal, and other cratons, the cold geotherm branch, reconstructed using sub-Ca garnets and eclogitic diamond inclusions relates to a major event of continental growth. Colder geotherms (32 mWm^-2) are related to early subduction. High-temperature plume-related geotherms are common for inclusions in Proterozoic kimberlites beneath Africa. In mobile belts such as Magondi, Ural and Limpopo belts, the amount of pyroxenitic and eclogitic garnets is greater than in the central cores of cratons where dunitic pyropes prevail. Beneath the Khapchan accretionary terrane in Siberia, eclogites are highly diamondiferous. In the mantle beneath Archean cratons, peridotite pyropes differ in CaO content. Depleted peridotitic and Fe-eclogitic diamond inclusions are abundant beneath the Zimbabwe craton, whereas beneath the Congo and West Africa, diamond inclusions yield higher temperatures. Beneath North American cratons, diamond-bearing eclogites are mainly Mg-type. In the Superior craton, Archean diamond inclusions from Wawa are Fe-, Ca-rich pyropes. The diamond inclusions of the Slave and Superior cratons give complex high-temperature plume-related geotherms. Beneath the Amazonian craton, peridotite garnets indicate complex layering at the base of the lithosphere and a pyroxene-rich layer in the middle. Fe-Mg eclogites from a high-temperature trend in which FeO increases with decreasing pressure. Diamond inclusions from the Kimberley craton of Australia show the greatest variations in temperature and composition. The  Eastern Europe craton and the Urals have greater amounts of eclogitic diamond inclusions and advective geotherms. Estimated pressure conditions lower than diamond stability field is due to exceeding pressures around magmatic system transferred by hydraulic forces from depth. 

Support: RFBR 19-05-00788, Russian Ministry of Education and Science