The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

Abstract

Kimberlites are igneous rocks whose formation remains enigmatic due to their severely altered nature, highly variable compositions and rapid ascent through the lithosphere. The spatiotemporal distribution of kimberlites suggests that mantle metasomatism may play an essential role in their emplacement. Since the magnetotelluric (MT) method is sensitive to metasomatic mantle modification in the forms of interconnected minerals and water, we compiled MT models from Australia, Brazil, Botswana, Canada, Namibia, South Africa and the USA, calculated water content variations and compared them to the distribution of kimberlites. Results indicate that kimberlites mostly ascend through hydrated/metasomatized lithosphere and avoid both dry and heavily metasomatized lithosphere. Diamondiferous kimberlites preferentially occur on moderately metasomatized lithosphere, with the diamondiferous rate increasing with the degree of metasomatism in Archean terranes and decreasing in Proterozoic terranes. These results link geophysical observations of mantle metasomatism to kimberlite magmatism and will improve mineral systems models for diamond exploration.

Magnetotelluric Imaging of the Lithospheric Structure of the Southern Oklahoma Aulacogen: Evidence for Long‐Term Weakening Caused by Rifting

“…As with the SOAC, metasomatic enrichment of the lithosphere in water likely occurred during rifting while also escaping late‐stage partial melt depletion. Additionally, this type of lithosphere keel enrichment would be in line with similar SCLM keel enrichment observed in other plume impacted regions (e.g., Aulbach et al., 2017; Bedrosian, 2016; S. F. Foley, 2008; S. F. Foley & Fischer, 2017; Özaydın & Selway, 2022). Further, the compositional changes associated with keel enrichment can produce the small reductions in shear wave velocity observed in the region (Deen et al., 2006; Evanzia et al., 2014; Griffin et al., 2009).…”

“…Ti and water enrichment accompany each other, and both follow the enrichment state of the mantle, and Ti values are often high in rock impacted by plumes (Berry et al., 2005, 2007; De Hoog et al., 2010; Padrón‐Navarta & Hermann, 2017; Rehfeldt et al., 2008). Given the sensitivity of MT data to water content (e.g., Özaydın & Selway, 2022) resistivity anomalies can be used as a proxy for determining the location of associated rheological weakening.…”

Role of Metasomatism in the Development of the East African Rift at the Northern Tanzanian Divergence: Insights From 3D Magnetotelluric Modeling

“…(2017) was utilized with a fluorine content of 0.52 w.t. % (average fluorine content value in mantle rocks, Özaydın et al., 2022). All electrical conductivity models are corrected for the water measurement calibrations of Withers et al.…”

“…A lherzolitic composition was used to calculate the water contents in the region (Table S1 in Supporting Information ). The use of different mantle peridotitic modal compositions has been shown to have a negligible effect on understanding the variations of metasomatism (Özaydın & Selway, 2022). The Generalized Archie's Law (Glover, 2010) was used for phase mixing to calculate bulk electrical conductivity.…”

“…It has been demonstrated that MT can be useful in understanding the relationship between mantle composition and magmatic processes. For instance, (Özaydın & Selway, 2022) used MT models to show that kimberlites might exploit the “lithospheric fuel” frozen in metasomatized mantle in order to ascend. However, the effects of large‐volume magmatism (e.g., basalts) on the composition of the lithosphere need to be better understood (Özaydın et al., 2022), since they could possibly exhaust these metasomes and dehydrate the mantle as well.…”