Abstract
The 1986 lethal eruption of Lake Nyos (Cameroon) was caused by a sudden inversion between deep, CO2-loaded bottom lake waters and denser, gas-free surface waters. A deep CO2 source has been found in fluid inclusions which occur predominantly in clinopyroxenes from lherzolitic mantle xenoliths, brought to the surface by the last erupted alkali basalts. P-T conditions of CO2 trapping correspond to a gas density equal (or higher) than that of liquid water. It is suggested that this dense CO2, found in many ultrabasic mantle xenoliths worldwide, has accumulated at km depth, below a column of descending lake water. It may remain in a stable state for a long period, as long as the temperature is above the density inversion temperature for pure H2O/CO2 systems. At an estimated depth of about 3 km, cooling by descending waters (to about 30 °C) induces a density inversion for the upper part of the CO2 reservoir. This causes a constant, regular upstream of low-density CO2 which, in its turn, feeds the shallower lake density inversion.
Original language | English |
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Pages (from-to) | 19-26 |
Number of pages | 8 |
Journal | Comptes Rendus - Geoscience |
Volume | 342 |
Issue number | 1 |
DOIs | |
Publication status | Published - Jan 2010 |
Externally published | Yes |
Keywords
- Density inversion
- Fluid inclusions
- Gaseous eruption
- Lake Nyos (Cameroon)
- Mantle xenoliths