Monte Cavaloro; piccolo affioramento a litologie differenziate (Fe-Ti-P dioriti) del complesso plutonico "ofiolitico" (Appennino Bolognese)  [Mount Cavaloro; small outcrop of a differentiated Fe-Ti-P diorite of an ophiolite complex (Northern Apennines of Bologna)]

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Alternate Title:Mount Cavaloro; small outcrop of a differentiated Fe-Ti-P diorite of an ophiolite complex (Northern Apennines of Bologna)
Authors:Simboli, Gianfranco; Gasparotto, Giorgio; Messino, Jan
Author Affiliations:Primary:
Universita di Bologna, Dipartimento di Scienze della Terra e Geologico-Ambientali, Bologna, Italy
Volume Title:Mineralogica et Petrographica Acta
Source:Mineralogica et Petrographica Acta, Vol.43, p.27-47. Publisher: Istituto di Mineralogia e Petrografia dell'Universita di Bologna, Bologna, Italy. ISSN: 0540-1437
Publication Date:2000
Note:In Italian with English summary. 26 refs.; illus., incl. 9 tables
Summary:At Monte Cavaloro near Bologna, outcrops a small olistolith of the ophiolite sequences of the Northern Apennines. This small outcrop is known in the geological literature as Bombicci (1868) find out a new type of rock which he named "oligoclasite". Cappellini (1878) studying the same outcrop, named the rock "Cavalorite". These two terms are still present (although obsolete) in the geological nomenclature. The same outcrop was studied by various authors which gave contrasting description of the mineralogy and recognized different rock types, from oligoclase bearing gabbro to quartzdiorite. The last study was by Gazzi (1961) who recognized the presence of stilpnomelane and classified the rock as stilpnomelane-oligoclase bearing gabbro. The present work lead us to the finding of several litothypes in the Monte Cavaloro olistolith: Fe-gabbros, Fe-gabbrodiorites, Fe-Ti-P diorites, Fe-Ti-P meladiorites, quartzdiorites and amphibole bearing albitite dikes. The Fe-Ti-P diorites are made up by oligoclase, ferroaugite, ferrohortonolite, ferrosilite, apatite, titanomagnetite and Fe-edenite and appear to be the product of cumulus processes from Fe-rich andesitic magmas which concentrate Fe-Ti oxides when apatite appeared as a liquidus phase. The other associated rocks are genetically linked through flow differentiation processes which generated the Fe-Ti-P meladiorites and the zircon rich quartzdiorites. The differentiation processes, took place in a closed system under low oxygen fugacity; during the late magmatic stages the high volatile content promoted the formation of hydrous minerals (mainly amphiboles) and the peculiar association biotite, cummingtonite-grunerite, stilpnomelane, chlorite. Stilpnomelane is variable in composition and in spite of its chemical features, it may correspond to that find in late stage granophyre of the Skaergaard pluton. This fact is a clear indication of the the highly evolved nature of our stilpnomelane bearing rock in keeping with the presence of stilpnomelane relics in the quartzdiorites. REE and trace elements abundances and composition of apatites and titanomagnetites agree with this genetic interpretation. Liquid immiscibility, as responsible of Fe-Ti-P rock, would seem to be not a viable genetic mechanism. The amphibole bearing albitite dikes represent a late injection of a slightly evolved gabbric magma.
Subjects:Chemical composition; Diorites; Ferrodiorite; Geochemistry; Igneous rocks; Magmas; Magmatic differentiation; Magmatism; Major elements; Metals; Mineral composition; Olistoliths; Ophiolite; Ophiolite complexes; Outcrops; Petrography; Plutonic rocks; Rare earths; Sedimentary structures; SEM data; Soft sediment deformation; Spectra; Textures; Trace elements; X-ray fluorescence spectra; Apennines; Bologna Italy; Emilia-Romagna Italy; Europe; Italy; Northern Apennines; Southern Europe; Mount Cavaloro
Coordinates:N434500 N451000 E0125000 E0091000
Abstract Numbers:05M/4325
Record ID:2006051220
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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