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Andosolization of Soils on a strombolian Cone at Mount Bambouto, Cameroon

Open Journal of Soil Science 2011年第3期1卷 97-105页

作者： Pierre S. Tsopjio Jiomeneck Paul Tematio Mike A. Wilson Martin Yemefack 不详

Morphology, mineral and geochemical investigations were carried out on two selected soil pedons (ZA and TO) developed on a late Quaternary-aged strombolian cone to better understand andosolization processes in Mount Bambouto, Cameroon. Both pedons have A-BC-C horizonation. They have thick surface (A) horizon with bulk density -3, Alo + 0.5Feo about 2% and P retention >90%. Mineral association consists predominantly of kaolinite, gibbsite, goe- thite, organometal complexes and trace amount of ferrihydrite and allophane. The Ki values between 1.1 and 1.6, the low TRB (45 to 67 mg kg-1), the important IMob (20% to 24%), the CIA between 60% and 70% and the EFs above 1.16 for Al and Fe, and below 0.6 for Si indicate sparingly hydrolysis process in subsoil during which released Al, Fe and Si form allophanic or ferrihydrite minerals undergo crystallization into kaolinite, gibbsite and goethite, respectively. At topsoil, part of released Al (and Fe) is organically bounded with organic acids to form organometal complexes.

关键词： Soil Morphology Mineralogy Geochemistry Andosolization strombolian Cone Cameroon Volcanic Line

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Ash Features from Ordinary Activity at Stromboli Volcano

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International Journal of Geosciences 2014年第11期5卷 1361-1382页

作者： Chiara Benedetta Cannata Rosanna De Rosa Paola Donato Jacopo Taddeucci University of Calabria Cosenza Italy

In this work we focus our attention on micro-scale textural observations and chemical analysis of the surface of ash particles erupted from ordinary activity at Stromboli volcano (Aeolian Islands, Italy). Ashes are related to three vent systems: NE1, NE2 and SW showing different eruptive styles. Samples were collected during three campaigns: 1-5 September 2008;20, 22 September 2008 and 18 June 2009, with two different methods: collection on a clean surface downwind and use of remotely controlled, electrically propelled aeromodels, which penetrate directly in the eruptive plume and collect ash samples that are less affected by transport-related sorting processes. A micro-textural approach has been conducted working at step: from preliminary observations under binocular microscope on a medium number of 700 particles, to thin sections and sub-micron investigations, using high resolution instruments. Micro-texture and morphology of ash particles were observed under FE-SEM, at high magnification (30,000/50,000×) measuring the main shape parameters (area, perimeter, max length, compactness, Feret’s diameter, Heywood’s diameter and elongation). Ashes are made up by a wide spectrum of fragments whose end-members are represented by two main textural types with different colour, shape, internal textures and vesicularity named “Type a” and “Type b”. “Type a” shows great similarities with fragments called “tachilite” while “Type b” fragments are very similar to the named “sideromelane” fragments. Fragments with intermediate textural features are present and named as “Type a1” and “Type b1”, respectively. The relative abundances of each type of fragments greatly vary in samples collected from different groups of vents. Chemical analysis of the external surfaces indicates that all the different grain types underwent alteration phenomena and precipitation of neo-formation minerals on their surfaces. The alteration is dependent from the atmospheric conditions around the vent and no

关键词： Ash Basaltic strombolian Tachylite Sideromelane Ordinary Persistent Activity

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