Pages: 261 - 272
Abstract: The Oligocene-Miocene deposits of the Internal Domains and of the innermost sectors of the flysch basin, recognized along the Betic-Rifian Chain (Spain and Morocco; i.e. Malaguide/Ghomaride Units and mauretanien flysch, respectively), are characterized by the occurrence of crystalline pebbles within several conglomerate horizons. Their provenance is difficult to explain because of the absence of similar rocks in the pre-Alpine Paleozoic basement nappes of this chain. Geochemical characters of seven granitoid pebbles (two-mica, cordierite-bearing monzogranite up to leuco-monzogranite), sampled from conglomerate lithofacies occurring within the above mentioned sandstone suites (Internal Rif and mauretanien sector of the flysch basin), have been determined and compared with other plutonic rocks of the Western Mediterranean and Iberian areas in order to detect their provenance. This comparison has been realized with the syn- to late-Hercynian plutonic bodies widespread in the Iberian, Moroccan (109 analyses from north-eastern Morocco, western High Atlas and from western-central Anti-Atlas), Kabylian and Calabria-Peloritani massifs (14 and 282 analyses, respectively) and with the pre-Hercynian Pan-African plutonites of Algeria (55 analyses). The obtained results show very strong geochemical affinities only with the Hercynian granitoids of the Iberian Massif (115 analyses from central Spain and from northern and central Portugal), thus emphasizing a new hypothesis for the provenance of the analysed pebbles with important paleogeographical consequences. Such a hypothesis of provenance, in fact, shows evidence that the AlKaPeCa block (i.e. Alboran–Spain + Kabylides–Algeria + Calabria + Peloritani massifs — southern Italy), at least during Oligocene times, must have been still in crustal continuity with the Iberian Massif, supposed to be the source area of the studied plutonic pebbles.
Keywords: Morocco, Rif Chain, Oligocene-Miocene deposits, granitoid pebbles, petrography, geochemistryDownload PDF document