Mafic inclusions in the silica-rich rocks of the Tolfa-Ceriti-Manziana volcanic district (Tuscan Province, Central Italy): Chemistry and mineralogy

Abstract

A chemical and mineralogical study of magmatic inclusions in the silica-rich rocks of the Tolfa-Ceriti-Manziana sector (Tuscan Province, Central Italy) shows that they can be grouped according to their degree of alkalinity. We distinguish: TCM latites (TCML) with an alkaline-potassic affinity; Ceriti latites (CL) with calc-alkaline affinity; and Manziana shoshonites and latites (MS-ML) with an affinity intermediate between alkaline and subalkaline. The latter are hybrid rocks originating from the mixing of two magmas with slightly different geochemical affinities. These magmas may represent liquids derived by partial melting of a heterogeneous mantle, metasomatized by a crustal source. The most alkaline magmas (TCML) are associated with the largest degree of metasomatism which, if more pronounced, could lead to the production of the potassic magmas of the Roman Province.