A Geological Itinerary Through the Southern Apennine Thrust-Belt (Basilicata—Southern Italy)

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Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy)

In this paper, fluid source(s) and processes controlling the chemical composition of volatile organic compounds (VOCs) in gas discharges from Mt. Etna and Vulcano Island(Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of magmatic and hydrothermal components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic-matterbearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alkene and aromatic compounds via catalytic reactions (dehydrogenation and dehydroaromatization, respectively). Nevertheless, an abiogenic origin for the light hydrocarbons cannot be ruled out. Oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions, typical of these volcanic-hydrothermal fluids, may explain the production of alcohols, esters, aldehydes, as well as O- and S-bearing heterocycles. By comparing the concentrations of hydrochlorofluorocarbons (HCFCs) in the fumarolic discharges with respect to those of background air, it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes. Finally, chlorofluorocarbon (CFC) abundances appear to be consistent with background air, although the strong air contamination that affects the Mt. Etna fumaroles may mask a possible geogenic contribution for these compounds. On the other hand, no CFCs were detected in the Vulcano gases, which are characterized by low air contribution. Nevertheless, a geogenic source for these compounds cannot be excluded on the basis of the present data

Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary

18.5: Le "argille brecciate" siciliane. Con i rilievi di dettaglio di Grottacalda (Valguarnera, Enna), Passarello (Licata, Agrigento), Zubbi (S. Cataldo, Caltanissetta)

92 p., 5 carte di tav. Memorie degli Istituti di geologia e mineralogia dell'Università di Padova, vol. 18, fasc. 5 (1954)

18.5: Le "argille brecciate" siciliane. Con i rilievi di dettaglio di Grottacalda (Valguarnera, Enna), Passarello (Licata, Agrigento), Zubbi (S. Cataldo, Caltanissetta)

92 p., 5 carte di tav. Memorie degli Istituti di geologia e mineralogia dell'Università di Padova, vol. 18, fasc. 5 (1954)

18.5: Le "argille brecciate" siciliane. Con i rilievi di dettaglio di Grottacalda (Valguarnera, Enna), Passarello (Licata, Agrigento), Zubbi (S. Cataldo, Caltanissetta)

92 p., 5 carte di tav. Memorie degli Istituti di geologia e mineralogia dell'Università di Padova, vol. 18, fasc. 5 (1954)

18.5: Le "argille brecciate" siciliane. Con i rilievi di dettaglio di Grottacalda (Valguarnera, Enna), Passarello (Licata, Agrigento), Zubbi (S. Cataldo, Caltanissetta)

92 p., 5 carte di tav. Memorie degli Istituti di geologia e mineralogia dell'Università di Padova, vol. 18, fasc. 5 (1954)

18.5: Le "argille brecciate" siciliane. Con i rilievi di dettaglio di Grottacalda (Valguarnera, Enna), Passarello (Licata, Agrigento), Zubbi (S. Cataldo, Caltanissetta)

92 p., 5 carte di tav. Memorie degli Istituti di geologia e mineralogia dell'Università di Padova, vol. 18, fasc. 5 (1954)