36 research outputs found
Trachytes employed for funerary artefacts in the Roman colonies Regium Lepidi (Reggio Emilia) and Mutina (Modena) (Italy): provenance inferred by petrographic and chemical parameters and by magnetic susceptibility
No full textSubduction-related(?) ophiolitic metabasalts from Northern Apennines (Modena province, Italy)
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New chemical and petrographic data of some undersature lavas from Nyiragongo and Mikeno (Virunga Western African-Rift-Zaire)
No full textThe lavas investigated from Nyiragongo and Mikeno volcanoes (Virunga volcanic field) are leucite - melilite - nephelinites, melilite - nephelinites (Nyiragongo) and leucitites (Mikeno): melilite characterizes the Nyiragongo lavas whereas clino-pyroxene is the prevalent mafic phase at Mikeno. The mineralogy is consistent with the highly alkaline (Ealk = 7.6-15.3 wt.%), potash-rich (K.20/Na20 > 1) and strongly silica undersaturated nature of the lavas. The samples analyzed are more or less fractionated. At Nyiragongo, addition of nepheline and leucite (in a very constant ratio) possibly to a bergalite-type magma may explain the “dilution” of both “incompatible” and “compatible” elements with increasing fractionation. On the contrary, at Mikeno, crystal fractionation processes seem to be dominated by the separation of mafic phases. Geochemical features indicate that the analyzed lavas from Baruta, and those from Nyiragongo and Mikeno were generated from different sources
Trachytes used for paving Roman roads in the Po plain: characterization by petrographic and chemical parameters and provenance of flagstones
No full textNew chemical and petrographic data of some undersaturated lavas from Nyiragongo and Mikeno (Virunga-Western African Rift - Zaire).
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Euganean trachytes: identification of quarried sites by petrographic and chemical parameters and by magnetic susceptibility and its bearing on the provenace of stones of ancient artefacts
No full text“Boninitic” clasts from the Mesozoic olistostrome and turbidites of Angelokastron (Argolis, Greece).
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