Rock art and archaeoastronomy in Morocco: preliminary observations

The purpose of this paper is to make public the exceptional discovery in the province of Essaouira (Morocco) of three petroglyphs engraved with an original subject in Moroccan rock art. By incision, astronomical, anthropomorphic, zoomorphic figures with Tifinagh inscriptions are engraved. The distribution and the nature of the engraved subjects evoke, most probably, a testimony with a material document on a natural disaster caused most likely by the fall of a great meteorite contributing, thus; to the understanding of the Ancient History of natural disasters in Morocco

Découverte d'une association d'enclaves carbonatite-lherzolite dans le volcanisme plio-quaternaire de Foum El Kouss (Jbel Saghro) : mise en évidence d'un manteau carbonaté à l'aplomb de l'Anti-Atlas oriental marocain

The Plio-quaternary Foum El Kouss volcano (Moroccan Anti-Atlas) is composed of pyroclastic rocks and two volcanic phases of Pleistocene to Recent age. Massive lava flows : olivine nephelinites first and pyroxene nephelinites toward the top. Carbonatite inclusions have been found in the pyroxene nephelinites. Major mineral phases are SrO-rich calcite, SrO-rich fluorapatite, ZrO-rich pyrochlore, barian titanian biotite, magnetite (with ilme-nite exsolution) and salite. Reaction rims around these enclaves, made of fluorine rich glass, confirm their xenolitic origine. Spinel lherzolitic xenoliths also found in these nephelinites, display mineralogical evidence of interaction (of carbonated fluids) with the lithospheric mantle. Such an association of carbonatite inclusion and spinel Iherzolitite with Foum El Kouss nephelinites is favour of the presence of an underlying carbonatite complex and carbonated mantle in the Anti-Atlas region.Le volcanisme alcalin plio-quaternaire de Foum El Kouss (Anti-Atlas oriental marocain) est formé de dépôts pyroclastiques et de deux coulées de laves massives : une première coulée néphélinitique à olivine et une deuxième représentée par des néphélinites à pyroxène. Cette dernière contient deux types d'enclaves : -des enclaves millimétriques à centimétriques de carbonatite formées de calcite riche en strontium, de fluorapatite, de pyrochlore riche en zirconium et en niobium, de phlogopite riche en baryum et en titane, de magnétite (à exsolution d'ilménite) et de salite verte. La bordure réactionnelle de ces enclaves, faite de verre riche en fluor, témoigne de leur origine xénolithique. -des enclaves de Iherzolite à spinelle, présentant des structures réac-tionnelles et une paragenèse secondaire, révélatrices d'une interaction du manteau lithosphérique avec des fluides riches en carbonates. L'association de ces deux types d'enclaves témoigne de l'existence, d'une part, d'un magmatisme carbonatitique sous-jacent et d'autre part, d'un manteau carbonaté à l'aplomb de l'Anti-Atlas oriental.Ibhi A., Nachit Hassane. Découverte d'une association d'enclaves carbonatite-lherzolite dans le volcanisme plio-quaternaire de Foum El Kouss (Jbel Saghro) : mise en évidence d'un manteau carbonaté à l'aplomb de l'Anti-Atlas oriental marocain. In: Géologie Méditerranéenne. Tome 26, numéro 1-2, 1999. pp. 19-28

The application of Fick's law to evaluate the period of stay of mega-olivines in alkaline lavas

The integration of the differential equation of the second law of Fick applied to the diffusion of chemical elements in a semi-infinite solid made it easier to estimate the time of stay of olivine mega-cristals in contact with the host lava The results of this research show the existence of two groups of olivine. The first remained in contact with the magmatic liquid during 19 to 22 days, while the second remained so during only 5 to 9 days. This distinction is correlative to that based on the qualitative observation

The Imilchil meteorite strewn field and Isli-Agoudal craters

New meteorite prospections at different places in the region of Imilchil showed that (1) besides the Ataxite of Tasraft all the other collected specimens belong to the same and only IIAB iron mother meteorite (2) the strewn field of the meteorite has a length of about 38 km into north-south direction (3) the small crater of Agoudal as well as the impact crater of Isli are situated on a parallel north-south axis, if not put together with the strewn field of the Imilchil meteorite (4) these two structures might be the result of the fall of the same and only mother meteorite of the IIAB type

Titanium and barium incorporation into the phyllosilicate phases: The example of phlogopite-kinoshitalite solid solution

Extremely high abundances of BaO (up to 21.46 wt. % ) and TiO$_{2}$ (up to 13.85 wt. % ) are reported from brown phlogopite in calcite carbonatite inclusions from Jbel Saghro, Anti-Atlas Morocco. The substitution of Ba into the phlogopite structure can be explained by the scheme $^{[12]}$Ba + $^{[4]}$Al $\Leftrightarrow$ $^{[12]}$K + $^{[4]}$Si. At least 50 % of the K on the interlayer sites of phlogopites from Saghro is replaced by Ba. The incorporation of Ba into phlogopite allow the occurence of kinochitalite phases. Al compensates for tetrahedral Si deficiencies, and Ti is probably limited to octahedral substitution for Mg and Fe. A substitution scheme of the type Ba$^{2+}$ + 2Ti$^{4+}$ + 3Al$^{3+} \, \Leftrightarrow$ K$^{+}$ + 3(Mg, Fe)$^{2+}$ + 3Si$^{4+}$ is proposed