Chemical variability in volcanic gas plumes and fumaroles along the East African Rift System: New insights from the Western Branch

The origin of magmatic fluids along the East African Rift System (EARS) is a long-lived field of debate in the scientific community. Here, we investigate the chemical composition of the volcanic gas plume and fumaroles at Nyiragongo and Nyamulagira (Democratic Republic of Congo), the only two currently erupting volcanoes set on the Western Branch of the rift. Our results are in line with earlier conceptual models proposing that volcanic gas emissions along the EARS mainly reflect variable contributions of either a Sub-Continental Lithospheric Mantle (SCLM) component or a Depleted Morb Mantle (DMM) component, and deeper fluid. At Nyiragongo and Nyamulagira, our study discards a major contrib…