Magnetic fabrics of the Miocene ignimbrites from West-Cameroon: Implications for pyroclastic flow source and sedimentation

Dedzo, Merlin Gountié; Nédélec, Anne; Nono, Alexandre; Njanko, Théophile; Font, Eric; Kamgang, Pierre; Njonfang, Emmanuel; Launeau, Patrick

doi:10.1016/j.jvolgeores.2011.04.012

Cited by 42 publications

(13 citation statements)

References 70 publications

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“…Gas emissions were also observed to have increased in September (Werner et al, 2013;Schaefer, 2012). In January 2009, volcanic activity appeared to increase as volcanic tremor began occurring (Fig.…”

Section: Eruption Chronologymentioning

confidence: 98%

“…Spectral analysis by Power et al (2013) and Ketner and Power (2013) show that peak frequencies in these periods were between 1 and 6 Hz, although frequencies up to 15 Hz were observed. The seismic activity corresponded with high SO 2 levels (Werner et al, 2013;Schaefer, 2012), and occurred alongside noticeable volcanic-related activity such as mudflows, collapse holes and increased gas emissions (Schaefer, 2012;Bleick et al, 2013). In early February, lower amplitude tremor began occurring and continued throughout February.…”

Section: Eruption Chronologymentioning

confidence: 99%

See 1 more Smart Citation

Duration–amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of Redoubt Volcano, Alaska

DeRoin

McNutt

Thompson

2015

Journal of Volcanology and Geothermal Research

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Section: Eruption Chronologymentioning

confidence: 98%

Section: Eruption Chronologymentioning

confidence: 99%

Duration–amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of Redoubt Volcano, Alaska

DeRoin

McNutt

Thompson

2015

Journal of Volcanology and Geothermal Research

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“…Archanjo et al, 2002;Archanjo et al, 2009Archanjo et al, , 2012Diot et al, 2003) and to infer flow characteristics of ignimbrites and basaltic lava flows (e.g. Boiron, 2011;Gountié Dedzo et al, 2011). These studies found that petrofabric and magnetic AMS fabric are generally spatially coincident, i.e.…”

Section: Relation Between the Spo Of Silicates And Magnetitementioning

confidence: 99%

The relation between magnetite and silicate fabric in granitoids of the Adamello Batholith

et al. 2015

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Keywords:Rock fabrics in granites; X-ray micro-tomography; Anisotropy of magnetic susceptibility (AMS); 3D shape fabrics (SPO); Magnetic interactions AbstractThe link between the macroscopic silicate fabric and the magnetite-controlled AMS (anisotropy of magnetic susceptibility) fabric in ferromagnetic rocks was investigated through a comprehensive comparison between different fabric measurement techniques. Sample lithologies include tonalites and granodiorites from the Lago della Vacca Complex, Adamello Batholith, Italy. The datasets used to assess the link between subfabrics and the coherence between methods include: 1) macroscopic silicate fabric measured directly in the field; 2) macroscopic silicate fabric derived from image analysis (IA) of outcrop pictures and sample pictures; 3) shape-preferred orientations (SPO) of mafic silicates, 4) SPO of magnetite, and 5) calculated distribution of magnetite grains from computer-assisted highresolution X-ray tomography (X-ray CT) images; 6) fabrics derived from the AMS. Macroscopic mineral fabrics measured in the field agree with the IA results and with the SPO of mafic silicates obtained from the X-ray CT imaging. The X-ray CT results show that the SPO of the magnetite grains are consistent with the AMS data whereas the spatial distribution of the magnetite grains is less compatible with the AMS fabric. This implies that the AMS signal is mainly controlled by the shape of the magnetic carrier mineral rather than by the spatial arrangement of the magnetite grains. An exception is the presence of magnetite clusters. Furthermore, the SPO of mafic silicates and the SPO of the magnetite grains are consistent with the AMS data. Another finding of this study is that the magnetic susceptibility correlates linearly with the amount of magnetite in the samples. The coherent results obtained from a variety of methods reinforce the application of both AMS measurements and IA as robust tools to analyse fabrics in granitic intrusions.

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“…The color of rock and the proportions of lithic fragments and minerals are variable depending of the type of the facies identified at Bamenda, Mbu, Mbengwi, Bambili, Sabga and Big Babanki (Gountié Dedzo et al, 2011).…”

Section: The Welded Ignimbritesmentioning

confidence: 99%

Hazards from Pyroclastic Density Currents at Mount Bamenda (West-Cameroon, Cameroon Volcanic Line): Mapping and Assessment by AMS Method

Dedzo¹,

Kamgang²,

Njonfang³

et al. 2015

American Journal of Geoscience

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Hazards related to pyroclastic density current continue to raise victims on many volcanoes in our planet. The Cameroon is not spared to this type of hazard because deposits of pyroclastic flows and surges are found on Mount Bamenda; products of this volcano are relatively young (27-0 Ma). Besides Mount Bamenda, Mounts Bambouto and Oku are the only volcanoes located in the central part of the Cameroon Volcanic Line where these ignimbritic deposits are found. Several factors highlight dangerousness and damage that can cause ignimbritic flows on the flanks of this volcano. This is essentially the high aspect ratio of these ignimbrites, the important population (about 750,000 people) that lives on the slopes and around the volcano. In order to have an idea of a nowadays ignimbritic eruption scenario on Bamenda volcano, the Anisotropy of Magnetic Susceptibility (ASM) method is used in this study to highlight the palaeoflow in ancient deposits of ignimbrites which are mostly discontinuous and isotropic. Results of AMS study are used to produce map of hazards and assess risks that may be related with such eruptions in Bamenda volcano.

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Magnetic fabrics of the Miocene ignimbrites from West-Cameroon: Implications for pyroclastic flow source and sedimentation

Cited by 42 publications

References 70 publications

Duration–amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of Redoubt Volcano, Alaska

Duration–amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of Redoubt Volcano, Alaska

The relation between magnetite and silicate fabric in granitoids of the Adamello Batholith

Hazards from Pyroclastic Density Currents at Mount Bamenda (West-Cameroon, Cameroon Volcanic Line): Mapping and Assessment by AMS Method

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