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Accueil du site → Doctorat → Royaume-Uni → 1993 → A stream sediment investigation of the Collo area, NE Algeria.

University of Nottingham (1993)

A stream sediment investigation of the Collo area, NE Algeria.

Bounessah, Mustapha

Titre : A stream sediment investigation of the Collo area, NE Algeria.

Auteur : Bounessah, Mustapha.

Université de soutenance : University of Nottingham

Grade : Doctor of Philosophy (Ph.D.) : 1993

The Collo area, NE Algeria, is a mountainous area in which the drainage system is characterised by flowing rivers and ephemeral streams (torrents). Its geology consists of a basement, made up of gneiss and serpentinite, sedimentary nappes and a granitic intrusion which is subdivided into a fined-grained and a coarse-grained granite. As an alternative to the widely used `profile’ geochemical technique based on fresh and weathered bedrock sampling, the geochemistry of the stream sediments of the area is used to two purposes : to assess their effectiveness in delineating known mineralisation (As, Pb, Zn, Cu, Cr, and Fe) and the underlying geology, and its assistance for the mapping of the unexposed areas. This geochemical survey was carried out using multielement geochemical data obtained from samples analysed for their total contents (X-ray fluorescence spectrometry) and cold extractable contents (atomic absorption spectrometry). An orientation survey was first undertaken, showing that the minus 150 m is the optimum grain fraction and the effect of windblown material (quartz and carbonates is negligible). The sulphide mineralisation was relatively well delineated by both total and cold extraction analysis. However, the iron mineralisation was only reflected by the XRF abalyses. As regards the Cr mineralisation, this was poorly reflected. However, the serpentinite massif, where the Cr-pods are hosted was relatively well delineated by total MgO, Cr, Co and Ni and, cold extractable Co and Ni. In addition to the known mineralisation, new anomalies of possible potential have been discovered. These include anomalies similar to those of the sulphide mineralisation which are mainly towards the border of the granitic intrusion and also in the serpentinite massif. Other anomalies include Sn and U which are found to be concentrated in the coarse granite. These are both thought to be a reflection of pegmatitic intrusions. The underlying geology was relatively well reflected by single element distribution and multivariate analysis of the data set. R-mode factor analysis reduced the dimensionality of the data to a five-factor model : 3 lithological factors, 1 sulphide mineralisation factor, and 1 sterile mineralogical factor.

Annonce : EThOS (UK)

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