Was the lethal eruption of Lake Nyos related to a double CO2/H2O density inversion?

Touret, Jacques; Grégoire, Marilaure; Teitchou, Merlin Isidore

doi:10.1016/j.crte.2009.10.005

Cited by 12 publications

(10 citation statements)

References 15 publications

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“…Seismic, gravity and petrological studies on the Adamawa Massif (Browne and Fairhead 1983;Girod et al 1984;Dautria and Girod 1986;Fairhead and Okereke 1988;Poudjom Djomani et al 1992 suggest the existence of the following features: (i) a crust uplifted by the upward migration of the lithosphere-asthenosphere boundary, (ii) an abnormally hot upwelling upper mantle located at the depth of 70-90 km (Dorbath et al 1986), and (iii), two broad negative gravity anomalies (-80 to -100 and -120 mGal/cm), attributable to lithospheric (40 km) and crustal (20 km) thinning respectively (Poudjom Djomani et al 1997). Upper-mantle xenoliths were found in basaltic lavas from several localities along the Cameroon Volcanic Line: São Tomé (Caldeira and Munhá 2002), Bioko and Palagu (Matsukage and Oya 2010), Biu Plateau, Lake Enep and Lake Mbarombi (Lee et al 1996), Lake Nyos area (Temdjim et al 2004a;Touret et al 2010), and Mount Cameroon (Ngounouno and Déruelle 2007;Wandji et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Petrology of spinel lherzolite xenoliths and host basaltic lava from Ngao Voglar volcano, Adamawa Massif (Cameroon Volcanic Line, West Africa): equilibrium conditions and mantle characteristics

Nkouandou¹,

Temdjim²

2012

J. Geosci.

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Thermobarometric calculations show equilibrium temperatures ranging between 850 and 950 °C and pressures of 8 to 17 kbar consistent with the spinel lherzolite stability field. These data suggest that the xenoliths come from a depth of 28-31km in the uppermost mantle situated just below a thinned crust; they are in agreement with the geophysical data previously determined in the Adamawa Massif. On the basis of these features, and considering the evidence for textural, mineralogical, and chemical equilibrium in the studied xenoliths prior to their entrainment in the host magma, we conclude that the source of these xenoliths was a chemically and petrographically homogeneous, spinel lherzolite lithospheric mantle. But the occurrence of mantle-derived xenoliths of various types (dunite, lherzolite, wehrlite, harzburgite, websterite, clinopyroxenite, and orthopyroxenite) in alkali basalts from many other localities of Cameroon (Oku Massif, Lake Nyos area and Mount Cameroon) is consistent with upper-mantle heterogeneities on a regional scale and implies that the nature of the upper mantle beneath the continental sector of the Cameroon Volcanic Line varies under its different volcanic centres.

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Section: Introductionmentioning

confidence: 99%

Petrology of spinel lherzolite xenoliths and host basaltic lava from Ngao Voglar volcano, Adamawa Massif (Cameroon Volcanic Line, West Africa): equilibrium conditions and mantle characteristics

Nkouandou¹,

Temdjim²

2012

J. Geosci.

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“…Fig. 2c) mantle and also upper crustal xenoliths (Aka et al 2004;Temdjim et al 2004;Touret et al 2010). Field evidence does not show any reaction rims between these xenoliths and their host lavas.…”

Section: Primary Melt Compositionmentioning

confidence: 89%

Depth of Melt Segregation Below the Nyos Maar-Diatreme Volcano (Cameroon, West Africa): Major-Trace Element Evidence and Their Bearing on the Origin of CO2 in Lake Nyos

Aka

2015

Advances in Volcanology

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The Nyos maar-diatreme volcano on the Oku Volcanic Group (OVG) in NW Cameroon carries yet the most infamous maar lake in the world because the lake exploded in 1986 releasing CO 2 that killed *1,750 people and over 3,000 livestock. A process of safely getting rid of accumulated gas from the lake started in 2001. Even though *33 % of it has been removed, gas continues to seep into the lake from the mantle, so the lake still poses a thread. Available data on basaltic lava from the maar-diatreme volcano and other volcanoes of the OVG are used here to determine the depth and location where the magmas are produced, and to make inferences on the generation of CO 2 in the Nyos mantle. Fractionation-corrected major element data agree well with experimental data on mantle peridotite and suggest that Lake Nyos magmas formed at pressures of 2-3 GPa in the garnet stability field. This inference is corroborated by trace element models that indicate small degree (1-2 %) partial melting in the presence of residual garnet (2-3 %). The basalts have elevated High Field Strength Element (HFSE) ratios (Zr/Hf = 48.5 ± 1.2 and Ti/Eu = 5,606 ± 224) which cannot be explained by any reasonable fractional crystallization model. A viable mechanism would be melting of a mantle that was previously spiked by percolating carbonatitic melts. It is suggested that small degree partial melting of this metasomatised mantle produces the lavas with super chondritic HFSE ratios, and is generating the CO 2 that seeps into and accumulates in the lake, and which asphyxiated people and animals during the 1986 gas disaster. This finding requires that current efforts to degas Lake

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“…Increased CO 2 content lowers a H2O at depth, which triggers the destabilization of biotite and amphibole (Janardhan et al, 1982). Possible evidence for a metamorphic CO 2 flux is found in the charnockised granites (Frost & Frost, 1987), which often contain fluid inclusions saturated in carbon dioxide (i.e., 70 -100%) (Hansen et al, 1987;Touret et al, 2010). In the Dharwar craton, the source of CO 2 -rich fluid in the lower crust is generally attributed to the underplating of mafic to ultramafic melt (Condie et al, 1982).…”

Section: Limit Of the Modellingmentioning

confidence: 99%

Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India

Nicoli

2019

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The fluid budget of a composite crustal column is a critical parameter that influences many lithospheric processes. The amount of water introduced in the middle and lower crust can be quantified using phase equilibrium modelling. The Dharwar craton, India, displays a now-exposed continuous crustal section from near surface conditions to ~30 km depth. This section records the different steps of a ~15 Ma long high-temperature metamorphic event (60 °C.kbar -1 ), responsible for the formation of syn-to post-tectonic anatectic intrusions. The global water budget is assessed using thermodynamic modelling on bulk-rock compositions of an average early Proterozoic supracrustal unit (SU) and ca. 3.0 Ga felsic basement, the Peninsular Gneisses (B). Results show the fast burial of a water-saturated supracrustal package (1.6 wt.%) will release ~ 50 % of its mineral-bound water, triggering water-fluxed partial melting of the basement. Modelled anatectic magma compositions match the observed granitoid chemistries and distinction can be made between water-fluxed melting and water-absent melting in the origin of syn-to post-tectonic anatectic granites. Findings from this study show the importance of crustal pile heterogeneity in controlling the nature of partial melting reactions, the composition of the magmas and the rheology of the crust. The amount of fluid circulating in the lithosphere (e.g. H 2 O, CO 2 ) exerts a direct control on a large range of processes such as the nature of partial melting mechanisms (Stevens &

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Was the lethal eruption of Lake Nyos related to a double CO2/H2O density inversion?

Cited by 12 publications

References 15 publications

Petrology of spinel lherzolite xenoliths and host basaltic lava from Ngao Voglar volcano, Adamawa Massif (Cameroon Volcanic Line, West Africa): equilibrium conditions and mantle characteristics

Petrology of spinel lherzolite xenoliths and host basaltic lava from Ngao Voglar volcano, Adamawa Massif (Cameroon Volcanic Line, West Africa): equilibrium conditions and mantle characteristics

Depth of Melt Segregation Below the Nyos Maar-Diatreme Volcano (Cameroon, West Africa): Major-Trace Element Evidence and Their Bearing on the Origin of CO2 in Lake Nyos

Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India

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