May 11, 2009
Scientists find source of carbon lava
U.S. and French scientists say they have discovered the origin of carbon-based lavas erupting from a Tanzanian volcano.
The researchers, led by the University of New Mexico, analyzed gas samples collected from inside the active crater of Tanzania's Oldoinyo Lengai volcano -- the only volcano that is actively producing carbon-based lavas. The geochemical analyses revealed a very small degree of partial melting of minerals in the Earth's upper mantle is the source of the rare carbon-derived lava.
Although carbon-based lavas, known as carbonatites, are common, the Oldoinyo Lengai volcano, located in the East African Rift in northern Tanzania, is the only place on Earth where they are actively erupting. The researchers said the lava expelled from the volcano is highly unusual in that it contains nearly no silica and greater than 50 percent carbonate minerals. Typically lavas contain high levels of silica, which increases their melting point to above 1,652 degrees Fahrenheit. The lavas of the Oldoinyo Lengai volcano erupt as a liquid at approximately 1,004 degrees Fahrenheit.
The research by the scientists from the University of New Mexico, the Scripps Institution of Oceanography at the University of California-San Diego and the Research Center for Petrographics and Geochemicals in Nancy, France, appears in the journal Nature.