Mineral and chemical provenance indicators in some early Miocene sandstones of the Southern Apennines (Italy)
Fornelli, Annamaria; Piccarreta, Giuseppe
European Journal of Mineralogy Volume 9 Number 2 (1997), p. 433 - 448
published: Jun 26, 1997
manuscript accepted: Nov 18, 1996
manuscript received: Mar 18, 1996
ArtNo. ESP147050902019, Price: 29.00 €
Abstract The present study integrates the chemical composition of heavy minerals and whole rock with the conventional petrographic analyses, in the determination of sandstone provenance. Early Miocene sandstones of the "Sicilide" Complex show different petrofacies and reflect provenance from granitic, metamorphic, sedimentary rocks and subordinate ophiolites. The sandstone deposits might be referred to two groups: the first group includes feldspatholithic and volcanolithic petrofacies; the second group includes feldspatholithic and quartzose sandstones having variable quartz contents and subordinate intercalations of quartzarenites from the so-called "Flysch Numidico". As concerns the sandstones of the first group, it emerges that: i) they contain high-pressure metamorphic components, some serpentine-schist grains and andesitic detritus; ii) the composition of high-pressure minerals and the paragenesis of the pertinent lithics indicate provenance from areas having overall similarities with the Pennine Units of the Alps; iii) the mineral assemblages and mineral chemistry of the volcanic component indicate provenance from the Sardinian volcanic arc; iv) the feldspatholithic petrofacies has signatures of maficultramafic components expressed by high contents of MgO, Cr and Ni, coherently with the presence of the ophiolitic constituents. Probably, the crystalline detritus was derived from a nappe-structured orogenic belt located south of Corsica and presently flooring the Tyrrhenian sea. As regards the second group of sandstones, it emerges that: i) the feldspatholithic sandstones are indistinguishable from the analogous rock types of the first group on the basis of conventional QFL diagram though they have different plagioclase contents; ii) they are decidedly poorer in total Fe2O3, MgO, Ni and Cr, evidencing more pronounced "granitic" signatures in the source region; iii) the lithic grains consist of very low-grade metamorphic rocks, granitic to tonalitic fragments and of contact metamorphic rocks, whereas high-pressure metamorphic component and serpentine-schist grains are absent. The basement terranes of the eastern front of the Calabrian Arc are likely candidates for the source rocks of these sandstones.