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This study presents the chemical and isotopic compositions of hydrothermal gases from fumaroles discharging around Copahue volcano (Argentina). Gas samples, including those from two fumaroles at the active summit crater, were collected during 13 surveys carried out by different research teams from 1976 to February 2016. The time-series of H, CO and light hydrocarbons showed episodic increases related to the main events of the last eruptive cycle that started on 19 July 2012. Concentration peaks were likely caused by enhanced input of hot magmatic fluids affecting the hydrothermal reservoir. These data contrast with the temporal variations shown by Rc/ Ra and δC-CO values in 2012-2014, which indicated an increasing input from a crustal fluid source. In 2015-2016, however, these isotopic parameters showed opposite trends; their composition became closer to that of the two summit fumaroles, which possibly corresponds to that of the deep magmatic-related end-member. The delayed and reduced compositional changes in the peripheral hydrothermal fluid discharge in response to the 2012-2016 eruptive events suggest that geochemical surveys of these emissions are unlikely to provide premonitory signals of volcanic unrest if the volcanic activity remains centered in the main crater. Instead, an instrument which is able to provide measurements of volcanic gases in the air (e.g. MultiGAS) may be used to detect changes at the summit crater. Otherwise, monitoring of seismic activity and ground deformation, as well as the periodic measurement of the chemistry of the water in the Rio Agrio, which is fed by thermal discharge from the summit crater, seem to represent the most reliable means of monitoring at Copahue. However, the relative compositional stability of the hydrothermal reservoir is a great advantage in terms of geothermal resource exploitation and could encourage new investments in the Copahue geothermal project which was abandoned in the 1990s. [ABSTRACT FROM AUTHOR]

The Red Sea is part of the Afro-Arabian rift system, the world's largest active continental rift system. The early opening phases of the Red Sea Rift were accompanied by continental flood magmatism. Large volumes of flood basalts emplaced in the Oligocene through to the present time at discrete eruptive centres along the western margin of the Arabian plate. Some of these rocks, in Southern Yemen, were investigated by geochemistry and K/Ar whole rock (WR) geochronology. In addition, the Jabal At-Tair (JAT) volcano, in the Red Sea trough, was investigated by geochemistry, with particular concern to the lavas of the last eruption of September 2007. The magmatism of Yemen is divided in: Oligocene-Early Miocene trap series (YOM), Tertiary intrusive rocks, and Late Miocene-recent volcanic series (YMR). YOM and Tertiary intrusions yielded K/Ar WR ages mostly in the range 31.6-16.6 Ma. Three older ages of 34.6, 35.4 and 49.0 Ma, if confirmed by further investigation, could suggest an Eocenic pre-trap phase of magmatic activity. YMR samples yielded K/Ar WR ages between 2.52 and 8.14 Ma. Both YOM and YMR basalts are alkaline, but YMR tend to be richer in alkalis than YOM. JAT basalts have subalkaline tholeiitic character, are geochemically homogeneous, and in the hygromagmaphile element spidergrams display increasing normalised concentrations from Cs to Ta, then decreasing up to Lu, with negative spikes of Nb, K and Pb. YOM have patterns almost identical to those of JAT, whereas YMR have higher normalized concentrations of all trace elements, but REE. The geochemical characteristics of JAT, YOM and YMR, framed in the broader context of the Red Sea Rift, are mostly consistent with a model of continental uplift and magmatism occurring across a linear, north-south axis of mantle upwelling, which intersects the Red Sea axis at the initiation site of axial seafloor spreading. The symmetrical propagation of the rift system to opposite sides of the N-S lineament, along the Red Sea axis, resulted in the observed symmetrical distribution of geochemical signatures of the Red Sea basalts and Yemen continental magmas. [ABSTRACT FROM AUTHOR]

A geochemical survey of fumarolic and submerged gases from fluid discharges located in the Nea Kameni and Palea Kameni islets (Santorini Island, Greece) was carried out before, during, and after the unrest related to the anomalously high seismic and ground deformation activity that affected this volcanic system since January 2011. Our data show that from May 2011 to February 2012, the Nea Kameni fumaroles showed a significant increase of H concentrations. After this period, an abrupt decrease in the H contents, accompanied by decreasing seismic events, was recorded. A similar temporal pattern was shown by the F, Cl, SO, and NH concentrations in the fumarolic condensates. During the sharp increase of H concentrations, when values up to 158 mmol/mol were measured, the δC-CO values, which prior to January 2011 were consistent with a dominant CO thermometamorphic source, have shown a significant decrease, suggesting an increase of mantle CO contribution. Light hydrocarbons, including CH, which are controlled by chemical reactions kinetically slower than H production from HO dissociation, displayed a sharp increase in March 2012, under enhanced reducing conditions caused by the high H concentrations of May 2011-February 2012. The general increase in light hydrocarbons continued up to July 2012, notwithstanding the contemporaneous H decrease. The temporal patterns of CO concentrations and N/Ar ratios increased similarly to that of H, possibly due to sealing processes in the fumarolic conduits that diminished the contamination related to the entrance of atmospheric gases in the fumarolic conduits. The compositional evolution of the Nea Kameni fumaroles can be explained by a convective heat pulse from depth associated with the seismic activation of the NE-SW-oriented Kameni tectonic lineament, possibly triggered by either injection of new magma below Nea Kameni island, as apparently suggested by the evolution of the seismic and ground deformation activity, or increased permeability of the volcanic plumbing system resulting from the tectonic movements affecting the area. The results of the present study demonstrate that the geophysical and geochemical signals at Santorini are interrelated and may be precursory signals of renewed volcanic activity and encourage the development of interdisciplinary monitoring program to mitigate the volcanic risk in the most tourist-visited island of the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

The present work reports the results of 15 studies of diffuse CO degassing performed at Teide Volcano crater (Canary Island, Spain) and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010. A higher contribution of magmatic gases accompanied by enhanced total diffuse CO emissions were observed in relation with a seismic crisis that occurred in Tenerife Island between 2001 and 2005, with the main peak of seismic activity between April and June 2004. A significant pulse in total diffuse CO emission was observed at the crater of Teide (up to 26.3 t day) in 2001. In December 2003, the chemical composition of the Teide fumarole changed significantly, including the appearance of SO, an increase in the HCl and CO concentrations and in the CH/CH and CH/CH ratios, and a decrease in the HS, CH, and CH concentrations and in the gas/steam ratio. A few months after a drastic decrease in seismic activity, the SO, HCl, and CO concentrations and the CH/CH and CH/CH ratios strongly decreased, whereas the CH and CH concentrations and the gas/steam ratios increased. According to the trends shown by both the geochemical parameters and the seismic signals late in the observation period, the risk of a rejuvenation of volcanic activity at Teide is considered to be low. The associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related. Future monitoring programs aimed at mitigating volcanic hazard on Tenerife Island should involve coupled geophysical and geochemical studies. [ABSTRACT FROM AUTHOR]

Lake Albano (Alban Hills volcanic complex, Central Italy) is located in a densely populated area near Rome. The deep lake waters have significant dissolved CO concentrations, probably related to sub-lacustrine fluid discharges fed by a pressurized CO-rich reservoir. The analytical results of geochemical surveys carried out in 1989-2010 highlight the episodes of CO removal from the lake. The total mass of dissolved CO decreased from ∼5.8 × 10 kg in 1989 to ∼0.5 × 10 kg in 2010, following an exponential decreasing trend. Calculated values of both dissolved inorganic carbon and CO concentrations along the vertical profile of the lake indicate that this decrease is caused by CO release from the epilimnion, at depth <9 m, combined with (1) water circulation at depth <95 m and (2) CO diffusion from the deeper lake layers. According to this model, Lake Albano was affected by a large CO input that coincided with the last important seismic swarm at Alban Hills in 1989, suggesting an intimate relationship between the addition of deep-originated CO to the lake and seismic activity. In the case of a CO degassing event of an order of magnitude larger than the one that occurred in 1989, the deepest part of Lake Albano would become CO-saturated, resulting in conditions compatible with the occurrence of a gas outburst. These results reinforce the idea that a sudden CO input into the lake may cause the release of a dense gas cloud, presently representing the major volcanic threat for this densely populated area. [ABSTRACT FROM AUTHOR]

Lastarria volcano (25°10′ S, 68°31′ W; 5,697 m above sea level), located in the Central Andes Volcanic Zone (northern Chile), is characterized by four distinct fumarolic fields with outlet temperatures ranging between 80°C and 408°C as measured between May 2006-March 2008 and April-June 2009. Fumarolic gasses contain significant concentrations of high temperature gas compounds (i.e., SO, HCl, HF, H, and CO), and isotopic ratios (He/He, δC-CO, δO-HO, and δD-HO) diagnostic of magmatic gas sources. Gas equilibria systematics, in both the HO-H-CO-CO-CH and alkane-alkene C system, suggest that Lastarria fumarolic gasses emanate from a superheated vapor that is later cooled and condensed at relatively shallow depths. This two-stage process inhibits the formation of a continuous aquifer (e.g., horizontal liquid layer) at relatively shallow depth. Recent developments in the magmatic gas system may have enhanced the transfer and release of heat causing shallow aquifer vaporization. The consequent pressure increase and aquifer vaporization likely triggered the inflation events beginning in 2003 at the Lastarria volcano. [ABSTRACT FROM AUTHOR]

The present work aims to assess the hazard for human health related to CO2 anomalous concentrations in air emitted from dry gas vents located in the NE area of Mt. Amiata volcano (Tuscany, central Italy). A geochemical multi-methodological approach is adopted to determine the composition and the flux rate of the gas discharges in order to establish (1) the origin of the gas vents and (2) the behaviour of the discharged gases in the areas surrounding the emission sites. The gas vents are hosted within sub-circular morphological depressions (∅ ∼ 10–30 m), which likely originated by the collapse of cavities formed at shallow depth in the ground by dissolution of Triassic anhydrite formations and recent travertine deposits. CaCO3 and CaSO4 dissolution is mainly related to the underground circulation of CO2-rich fluids whose hydrological pattern is regulated by local and regional tectonics. The CO2-rich (up to 996,070 μmol/mol) gases tend to accumulate within the topographic lows, thus creating a sort of CO2 ponds, and the knowledge of their evolution in time and space is important to evaluate the related hazard. Consequently, a conceptual model of CO2 diffusion in air is developed to understand the dynamic of the CO2 accumulation/dispersion process based on (1) a 24-h continuous measurement of the CO2 flux from one of the main emission sites and (2) the recording of the main meteoric parameters, i.e. air temperature, wind direction and speed to check their influence. The results indicate that the threshold of CO2 concentrations considered dangerous for the human health is frequently overcome. Moreover, when meteoric conditions, i.e. low wind and cloudy weather, did not allow a rapid dispersion of the gas phase emitted from the dry vents, CO2-rich clouds periodically overflowed the morphological depressions for several tens of meters without any significant mixing with air. On the basis of these considerations, the monitoring of the output rate from the main gas emissions, combined with the continuous control of the local meteorological parameters, may be considered an efficient procedure to mitigate the CO2 hazard deriving from dry gas vents. An improvement of the protocol can be achieved in case of installations of CO2 sensors located in the most sensitive areas and connected to a telemetry system able to transmit the data in real time to the closest Civil Defence centre. The CO2 degassing sites can also represent a tourist attraction after the installation of suitable metallic fences and a proper campaign of information about these natural phenomena. [ABSTRACT FROM AUTHOR]

Knowledge of the chemical composition of volcanic exhalation is important in providing information on volcanic feeding systems and on the characteristics of the gaseous compounds emitted into the atmosphere. This paper reports a novel analytical method that makes use of capillary gas chromatography coupled to mass spectrometry, preceded by solid-phase micro extraction for sample enrichment. Such an approach enables considerable expansion of the number of neutral organic compounds that can be positively identified in volcanic exhalation. Data obtained from analysis of real samples are also reported. [ABSTRACT FROM AUTHOR]

A preliminary genetic map of the dioecious species Asparagus officinalis L. (2n = 20) has been constructed on the basis of restriction fragment length polymorphism (RFLP) and isozyme marker data. With DNA samples digested with either EcoRI or HindIII 61 out of 148 probes (41%) identified RFLPs in six families of doubled haploid lines obtained through anther culture. A higher level of polymorphism (65%) was observed when a single family was screened for RFLPs using six distinct restriction enzymes. Segregation analysis of the BC progenies (40-80 individuals) resulted in a 418-cM extended map comprising 43 markers: 39 RFLPs, three isozymes and one morphological (sex). These markers are clustered in 12 linkage groups and four of them exhibited significant deviations from the expected 1∶1 ratio. One isozyme and three RFLP markers were assigned to the sex chromosome. [ABSTRACT FROM AUTHOR]

Extracts from phylloclads of Asparagus officinails were electrophoretically analyzed for isozyme polymorphism. Fourteen enzyme systems were examined using four buffer systems: seven enzymes (acid phosphatase, catalase, glutamate-oxaloacetate transaminase, isocitrate dehydrogenase, malate dehydrogenase, peroxidase, and 6-phosphogluconate dehydrogenase) exhibited clear and consistent banding patterns. Isozyme polymorphism was studied in seven pairs of male and female doubled haploids and in their male Fs. Segregation of polymorphic loci was examined in the backcross progenies and was found to be consistent with a simple Mendelian inheritance in all cases, except for three anodical peroxidases, where two factors have been hypothesized. No linkage could be found between isozyme markers that were segregating in the same cross, but association was demonstrated between one malate dehydrogenase locus and the sex determining genes. The availability of isozyme markers may be useful in breeding and, in particular, the localization of one malate dehydrogenase locus on the sex chromosomes may be helpful in mapping the sex genes. [ABSTRACT FROM AUTHOR]

An integrated genetic map of the dioecious species Asparagus officinalis L. has been constructed on the basis of RFLP, RAPD, AFLP and isoenzyme markers. The segregation analysis of the polymorphic markers was carried out on the progeny of five different crosses between male and female doubled-haploid clones generated by anther culture. A total of 274 markers have been organized to ten linkage groups spanning 721.4 cM. Since the haploid chromosome number of asparagus is ten, the established linkage groups probably represent the different chromosomes; however, the only group associated with a specific chromosome is the one which includes sex, whose determinant genes have been located on chromosome 5. A total of 33 molecular markers (13 RFLPs, 18 AFLPs, 2 RAPDs and 1 isoenzyme) have been located on this chromosome. The closest marker to the sex determinant is the AFLP SV marker at 3.2 cM. [ABSTRACT FROM AUTHOR]