• journal_title：American Mineralogist
• Contributor：Leone Melluso ; Sandro Conticelli ; Massimo D’Antonio ; Nicoletta P. Mirco ; Emilio Saccani
• Publisher：Mineralogical Society of America
• Date：2004-
• Format：text/html
• Language：en
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：88
• issue：8-9
• firstpage：1287
• section：Articles

Small outcrops of wollastonite- and melilite-bearing pyrometamorphic rocks (paralavas) are found along the Apennine chain in Central Italy at the localities of Colle Fabbri and Ricetto. These rocks have coarse- to fine-grained crystalline, spotted, and glassy textures. The Colle Fabbri rocks have abundant and ubiquitous wollastonite, with plagioclase ± clinopyroxene. Melilite is found only in the most Ca-rich and silica-poor samples. Garnet, perovskite, quartz, leucite, silica-rich glassy mesostasis, and ocelli filled by calcite are present locally. The Ricetto rock is made up of wollastonite and melilite with minor clinopyroxene set in a glassy matrix with a few crystals of restitic quartz. These rocks have variable contents of SiO₂ (43 to 64 wt%) and CaO (37 to 3.7 wt%). The latter decreases with increasing MgO, Al₂O₃, Fe₂O_{3 tot}, TiO₂, K₂O, SiO₂, and most trace elements, excluding Sr. Peculiar parageneses (e.g., coexisting melilite and anorthite in the most silica-poor samples, abundance of wollastonite), mineral compositions (gehlenite-rich melilite; Al-, Ti-, and Fe³⁺-rich clinopyroxene; Al-, Ti-rich, but Fe-poor garnet), and major- and trace-element geochemistry suggest that the Colle Fabbri and Ricetto rocks are not ultimately mantle-derived, but are the result of melting, devolatilization, and recrystallization of marly sediments (50–60 to 5–10% calcite, with clay minerals ± quartz), likely due to coal fires. The ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd range from 0.70772 to 0.71190 and from 0.51223 to 0.51219, respectively, again suggesting sedimentary protoliths of a mixed nature. Substantial chemical and isotopic differences between these samples and those from the Roman Magmatic Province are highlighted.