Noble gas and carbon isotope systematics at the seemingly inactive Ciomadul volcano (Eastern‐Central Europe, Romania): evidence for volcanic degassing

Ciomadul is the youngest volcano in the Carpathian-Pannonian Region, Eastern-Central Europe, which last erupted 30 ka. This volcano is considered to be inactive, however, combined evidence from petrologic and magnetotelluric data, as well as seismic tomography studies suggest the existence of a subvolcanic crystal mush with variable melt content. The volcanic area is characterized by high CO2 gas output rate, with a minimum of 8.7 × 103 t yr-1. We investigated 31 gas emissions at Ciomadul to constrain the origin of the volatiles. The δ13C-CO2 and 3He/4He compositions suggest the outgassing of a significant component of mantle-derived fluids. The He isotope signature in the outgassing fluids (up to 3.10 Ra) is lower than the values in the peridotite xenoliths of the nearby alkaline basalt volcanic field (R/Ra 5.95Ra±0.01) which are representative of a continental lithospheric mantle and significantly lower than MORB values. Considering the chemical characteristics of the Ciomadul dacite, including trace element and Sr- Nd and O isotope compositions, an upper crustal contamination is less probable, whereas the primary magmas could have been derived from an enriched mantle source. The low He isotopic ratios could indicate a strongly metasomatized mantle lithosphere. This could be due to infiltration of subduction-related fluids and postmetasomatic ingrowth of radiogenic He. The metasomatic fluids are inferred to have contained subducted carbonate material resulting in a heavier carbon isotope composition (13C is in the range of -1.4 to -4.6 ‰) and an increase of CO2/3He ratio. Our study shows the magmatic contribution to the emitted gases

Geogenic emission of methane and carbon dioxide at beciu mud volcano, (berca-arbănaşi hydrocarbon-bearing structure, eastern carpathians, Romania)

As shown by previously performed flux measurements, the mud volcanoes of Berca-Arbănaşi hydrocarbon-bearing structure in Eastern Carpathians Foredeep, including Pâclele Mari, Pâclele Mici, and Fierbători, represent a main gas seepage system in Romania, with considerable emissions of methane. The present work completes these gas emission studies by reporting the flux of methane and carbon dioxide at Beciu mud volcano, belonging to the same structure, not measured previously. In total, 78 measurements were carried out in June 2011 (40 on the vents, 34 on the area covered by mud and 4 in the external area, covered by vegetation). Diffuse fluxes from mud were found ranging from 102 to 105 mg CH4 m-2 day-1, and 102-104 mg CO2 m-2 day-1; the emission from individual vents was in the range of 0.014 to 32 t CH4 year-1 and 0.003 to 2.9 t CO2 year-1. These values are comparable with those typically documented for mud volcanoes worldwide. Gas seepage occurs pervasively throughout the muddy cover, even if it appears to be saturated with water. The total emission of CH4 and CO2 from Beciu mud volcano is conservatively estimated to be at least 190 t year-1 and 35 t year-1, respectively. The Beciu output leads the total CH4 emission from the four Berca mud volcanoes to at least 1350 t year-1, a value comparable with that reported for a similar number of giant mud volcanoes in Azerbaijan. This work contributed to update the geogenic gas flux data-set of Romania and to extend the global data-set of methane and carbon dioxide emissions from mud volcanoes.Published159 - 1664.5. Studi sul degassamento naturale e sui gas petroliferiJCR Journalrestricte

Geogenic emission of methane and carbon dioxide at beciu mud volcano, (berca-arbănaşi hydrocarbon-bearing structure, eastern carpathians, Romania)

As shown by previously performed flux measurements, the mud volcanoes of Berca-Arbănaşi hydrocarbon-bearing structure in Eastern Carpathians Foredeep, including Pâclele Mari, Pâclele Mici, and Fierbători, represent a main gas seepage system in Romania, with considerable emissions of methane. The present work completes these gas emission studies by reporting the flux of methane and carbon dioxide at Beciu mud volcano, belonging to the same structure, not measured previously. In total, 78 measurements were carried out in June 2011 (40 on the vents, 34 on the area covered by mud and 4 in the external area, covered by vegetation). Diffuse fluxes from mud were found ranging from 102 to 105 mg CH4 m-2 day-1, and 102-104 mg CO2 m-2 day-1; the emission from individual vents was in the range of 0.014 to 32 t CH4 year-1 and 0.003 to 2.9 t CO2 year-1. These values are comparable with those typically documented for mud volcanoes worldwide. Gas seepage occurs pervasively throughout the muddy cover, even if it appears to be saturated with water. The total emission of CH4 and CO2 from Beciu mud volcano is conservatively estimated to be at least 190 t year-1 and 35 t year-1, respectively. The Beciu output leads the total CH4 emission from the four Berca mud volcanoes to at least 1350 t year-1, a value comparable with that reported for a similar number of giant mud volcanoes in Azerbaijan. This work contributed to update the geogenic gas flux data-set of Romania and to extend the global data-set of methane and carbon dioxide emissions from mud volcanoes