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Geology; September 2002; v. 30; no. 9; p. 839-842; DOI: 10.1130/0091-7613(2002)030<0839:MIBTWA>2.0.CO;2
© 2002 Geological Society of America
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Mantle insulation beneath the West African craton during the Precambrian-Cambrian transition

Miguel Doblas1, José López-Ruiz1, José-María Cebriá1, Nasrrddine Youbi2 and Eugenio Degroote3

1 Departamento de Geología, Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas, 28006 Madrid, Spain
2 Université Cadi Ayyad, Faculté des Sciences Semlalia, 2390 Marrakech, Morocco
3 Escuela Universitaria de Ingeniería Técnica Agrícola, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid, Spain

At the time of the Precambrian-Cambrian transition, the West African craton underwent widespread magmatism, hydrothermal activity, and thermal rejuvenation. This tectonothermal event gave rise to an anorogenic "ring of fire" along the rim of this craton, following the Pan-African–Brasiliano belt that was reactivated by extension and transtension. The thermal phenomena were due to the progressive peripheral release of mantle heat that had built up beneath this craton because of strong insulating conditions. The West African craton at the Precambrian-Cambrian transition can thus be envisioned in terms of a gigantic pressure-cooker with a thick blanketing lithospheric lid. These insulation processes triggered an unusually hot mantle that was channeled by edge-driven convection toward the peri–West African craton extensional corridors and released through magmatic pressure-relief valves. Massive ice melting and outgassing of volcanic CO2 gave rise to a planet-scale sea-level rise, a greenhouse effect, and the end of the icehouse snowball Earth. These processes played an important role in the Phanerozoic explosion of life on Earth.

Key Words: mantle insulation • thermal activity • ice sheets • extension • explosion of life • West African craton




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