Carbonatiti dell'area romana poco note: Forcinella e Ficoreto

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Marco E. Ciriotti
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Carbonatiti dell'area romana poco note: Forcinella e Ficoreto

Messaggio da Marco E. Ciriotti » dom 16 set, 2018 12:12

© Società Geologica Italiana, Roma 2018 CONGRESSO SGI-SIMP 2018

Carbonatites of Roman Region, genetic relationship with Italian alkaline Rocks

Ambrosio F.A.*1, Stoppa F.1, Rosatelli G.1, Schiazza M.1, Vicentini N.1 & Sharygin V.V.2

1 Department of Psychology, Health and Territory Sciences, Università “G. D’Annunzio” Chieti-Pescara
2 V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk State University, Institute of Physics and
Technology, Ural Federal University

* Corresponding email:

Keywords: Carbonatites, RHA method, alkaline rocks.

Carbonatites associated with kamafugites rocks type characterize the central Italy magmatism. These rocks
occur in several volcanic center localized about 50 Km east of the volcanic complex of the Roman Region (RR)
in the Intra-mountain Ultra-Alkaline Province (IUP). Most of IUP occurrences are monogenic, extrusive and
of small volume 106 to 1006 m3 (Lavecchia et al., 2006). The origin of carbonate is essential to define a unique
petrogenetic model for Italian rocks. In fact, if is correct the Daly (1910) theory of limestone assimilation
(syntexis) and further variants, then it is possible to hypothesize a subduction related model (e.g. Gvirtzman &
Nur, 1999). If the carbonate have a primary origin, then it is correct hypothesize a plume model and thinning
of the lithosphere (e.g. Bell et al., 2013). We have found two new outcrops of subvolcanic carbonatites at
Forcinella (Vulsini district) and at Ficoreto (Sabatini District). The carbonatitic rocks are associated to leucititic
rocks and to foid syenites (ejecta). Forcinella and Ficoreto outcrops have similar geological, mineralogical and
geochemical characteristics to IUP carbonatites. In particular, they are monogenic vent, with tuffisitic texture
(intrusive lapilli tuff). To provide a geochemical representative model of this complex rock association we
used Rank Analyses (RHA), this is an information language (Petrov, 2001). The software used to calculate
main statistical discriminating factors that resulted as F-C-Ca, Si-Al-Alk, Mg-Fe-P in terms of their atomic%
of elements. These factors draft a ternary diagram were the bisector clearly separates analytic data of carbonate
and silicate rocks are. The diagram also defines a possible petrogenetic model. Our hypothesis is that silicate
rocks and carbonate becomes immiscible starting from a mantle primitive melt. They can erupt along a diatremic
path as a mechanical mixture of two magmatic rocks or as physically separate convoys of the two components.
If the liquid has a silicate composition it evolves by orthomagmatic differentiation to foid syenites. On the
other hands CO2-F-rich fluids have a complex crystallisation history which may range from near magmatic
temperature to hydrothermal condition.

Bell, K., Lavecchia, G. & Rosatelli, G. (2013): Cenozoic Italian magmatism e Isotope constraints for possible plumerelated
Activity. Journal of South American Earth Sciences 41, 22-40.
Daly R.A. 1910. Origin of alkaline rocks. Bull. Geol. Soc. Am. 21, 87-118.
Gvirtzman, Z. & Nur, A. (1999): The formation of Mount Etna as the consequence of slab rollback. Nature, 401, 782-785.
Lavecchia, G., Stoppa, F. & Creati, N. (2006): Carbonatites and kamafugites in Italy: mantle-derived rocks that challenge
subduction. Annals of Geophysics, Supplement to vol. 49, N. 1, 389-402.
Petrov, T.G. (2001): Informative language for description of poly-component object’s composition. Scientific-Technical
information, 3, 8-1.
Marco E. Ciriotti

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