Institute: Ibaraki University, Japan
Title: Visiting Professor
Country/Region: Cameroon
Period: 2024/4/1 - 2024/8/31 and 2025/3/1 - 2025/3/31
Theme: Inverting Cameroon Line geochemical data for primary magmas and mantle potential temperatures: Toward the elucidation of plume-lithosphere interaction and global geodynamics
Host: Shuhei SAKATA
Introduction: I worked for many years as a Research Professor in the Cameroon Ministry of Scientific Research and Innovation. I also taught and supervised graduate and postgraduate students in Universities and Colleges in Cameroon, Japan, and the USA. My volcanology research is mainly focused on the intracontinental Cameroon Line (CL) in west Africa. Geochronology (Ar-Ar, K-Ar, U-Th-Ra, & cosmogenic nuclides), and geochemistry (major/trace elements & Sr-Nd-Pb isotopes) are applied to basalts, mantle xenoliths, surface fluids (springs), and deep fluid-inclusion-hosted volatiles (CO2, He, Ne, Ar), in order to prob the spacio-temporal variability of sources, magma plumbing, and mantle dynamics.
The origin of the CL is still debated because its 12 polygenetic volcanic centers are aligned (1600 km-long) but lack a space-time relationship. It has one of the currently most active volcanoes in Africa (Mt. Cameroon), and contains the most dangerous volcanic (maar) lakes in the world, like Lakes Nyos and Monoun which exploded in the 1980s releasing gas that asphyxiated 2000 people, 3000 cattle, and displaced 15000 people. Lead and helium isotopes suggest deep plume material in the genesis of CL magmas. Vp/Vs ratios are relatively low (≈1.74) and support a formation by shear zone reactivation or small-scale (<1000 km) mantle convection, meanwhile tomographic imagining reveals anomalous absolute P-wave residuals and slow wave speeds in the CL upper mantle (<410 km) and at ≈660 km depths, suggesting the involvement of shallow (convection) and deep mantle (plume) material.
Convection and plume geodynamic models of the Earth can be tested by calculating mantle potential temperatures (TPs) for unfractionated magmas. They show ambient mantle-like TPs if generated from mantle convection, and higher TPs if generated from mantle plumes. During my stay at ERI, I will collaborate with Prof. Sakata to collate CL geochemical data which will be filtered, inverted for primary magma compositions, used to calculate TPs, and then analyzed statistically to isolate trends with their geodynamic significance.



Fiscal Year: 2024