409 research outputs found
HELIUM ISOTOPES AND TECTONICS IN SOUTHERN ITALY
Geodynamic evolution of southern Italy can
be understood within the framework of the Mediterranean-
Alpine System. Subduction of a plate along the Sicily-
Calabrian forearc under the Tyrrhenian Sea has been suggested
by many geophysicists, although it is not yet confirmed
and remains somewhat controversial. Helium isotope
ratios provide useful information on the geotectonic structure
of the region. We report here the 3He/4He ratios of
terrestrial gas samples from southern Italy. The observed
3He/4He ratios are relatively high in the Eolian volcanic arc
region and low in the other areas. Dichotomous explanations
are presented. Firstly volcanic arc-forearc hypothesis
suggests the subduction along the Sicily-Calabrian forearc.
Secondly horizontal transport hypothesis is described based
on the relationship between the ratios and radial distance
from the recent spreading basin in Southern Tyrrhenian Sea
Elemental and isotope covariation of noble gases in mineral phases from Etnean volcanics erupted during 2001–2005, and genetic relation with peripheral gas discharges
During 2001–2005, Mount Etna was characterized by intense eruptive activity involving the emission of
petrologically different products from several vents, which involved at least two types of magma with
different degrees of evolution. We investigated the ratios and abundances for noble-gas isotopes in fluid
inclusions trapped in olivines and pyroxenes in the erupted products. We confirm that olivine has the most
efficient crystalline structure for preserving the pristine composition of entrapped gases, while pyroxene can
suffer diffusive He loss. Both the minerals also experience noble gas air contamination after eruption. Helium
isotopes of the products genetically linked to the two different magmas fall in the isotopic range typical of
the Etnean volcanism. This result is compatible with the metasomatic process that the Etnean mantle is
undergoing by fluids from the Ionian slab during the last ten kyr, as previously inferred by isotope and trace
element geochemistry. Significant differences were also observed among olivines of the same parental
magma that erupted throughout 2001–2005, with 3He/4He ratios moving from about 7.0 Ra in 2001
volcanites, to 6.6 Ra in 2004–2005 products. Changes in He abundances and isotope ratios were attributed to
variations in protracted degassing of the same magma bodies from the 2001 to the 2004–2005 events, with
the latter lacking any contribution of undegassed magma. The decrease in 3He/4He is similar to that found
from measurements carried out every fifteen days during the same period in gases discharged at the
periphery of the volcano. To our knowledge this is the first time that such a comparison has been performed
so in detail, and provides strong evidence of the real-time feeding of peripheral emissions by magmatic
degassing
Constraints on mantle source and interactions from He-Sr isotope variation in Italian Plio-Quaternary volcanism
Helium isotope ratios of olivine and pyroxene phenocrysts from Plio-Quaternary volcanic rocks from Southern Italy (seven Eolian Islands, Mt. Vulture, Etna, Ustica, Pantelleria) range from 2.3 to 7.1 Ra. Importantly the phenocryst 3He/4He correlate well with whole rock Sr isotopic composition (0.70309-0.70711) reflecting the mixing of two sources. A significant contribution of He from crustal contamination is recorded only occasionally (e.g., pyroxenes from Vulcano). When merged with data from the Roman Comagmatic Province, a remarkably strong near-linear He-Sr isotope correlation is apparent. The general northward decrease in 3He/4He corresponds to an increase in 87Sr/86Sr (and decrease in 143Nd/144Nd and 206Pb/204Pb) that is due to increasing metasomatic enrichment of the mantle wedge via subduction of the Ionian-Adriatic plate. Calculations based on the ingrowth of 4He in the wedge and on the 4He content of the subducting crust show that mechanisms of enrichment in radiogenic He are effective only if the wedge is strongly depleted in He relative to best estimates of the depleted mantle. This can be accommodated if the process of metasomatism by the subduction fluids depletes the mantle wedge. The 3He/4He of Pantelleria, Etna, Iblei, Ustica, Alicudi and Filicudi basalts (7.0 ± 0.6 Ra) define the mantle composition least affected by subduction-related metasomatism. Although these volcanoes are from a variety of tectonic regimes (subduction-related, intraplate, rifting) their similarities suggest a common origin of geochemical features. Their characteristics are consistent with a HIMU-type mantle that is either younger than the Cook-Austral island end-member, or has a lower 238U/204Pb
Remote detection of fumarolic gas chemistry at Vulcano, Italy, using an FT-IR spectral radiometer
An infrared absorption spectroscopy remote sensing technique was used to determine the S02/HCl ratio in fumarolic
plumes at Vulcano, Italy. The measurements were made from the southern crater rim of Fossa Grande Crater, about 400 m
from the fumarolic area in the crater. Infrared absorption spectra of HCl and SO, were observed for four fumaroles a few
tens of metres apart using the hot fumarolic surface as an infrared light source. The measured S02/HCl ratios in the FA,
F47, FW and lower parti of the F21 fumaroles were 4.5-5.4, 3.5, 9.5-11.2 and 5.8 respectively. The S02/HCl ratio of the
FA fumarole was higher than that of the gas collected directly in the fumarolic vent (S02/HCl ratio = 2.9), and was closer
to the S~,,,,,,/HCl ratio (= 4.6) of the collected gas. Our results show that the SO,/HCl ratios of two fumaroles only a few
tens of metres apart exhibits differences of about twofold. This suggests that this remote monitoring technique is capable of
detecting spatial distribution in the S02/HCl ratios of volcanic plumes. Because temporal variations in S/Cl ratios can
provide precursory signals for volcanic eruptions [l-31, this remote sensing technique can used efficiently for evaluation of
volcanic activity
Using Small-Scale Studies to Prioritize Threats and Guide Recovery of a Rare Hemiparasitic Plant: Cordylanthus rigidus ssp. littoralis
BACKGROUND: Recovering endangered species would benefit from identifying and ranking of the factors that threaten them. Simply managing for multiple positive influences will often aid in recovery; however, the relative impacts of multiple threats and/or interactions among them are not always predictable. We used a series of experiments and quantitative observational studies to examine the importance of five potential limiting factors to the abundance of a state-listed endangered hemiparasitic annual forb, Cordylanthus rigidus ssp. littoralis (C.r.l., California, USA): host availability, mammalian herbivores, insect seed predators, fire suppression, and exotic species. While this initial assessment is certainly not a complete list, these factors stem from direct observation and can inform provisional recommendations for management and further research. METHODOLOGY AND PRINCIPAL FINDINGS: Studies were conducted at five sites and included assessments of the influence of host availability, exotic species, exclusion of mammalian herbivores and insect seed predators on C.r.l. productivity, and simulated effects of fire on seed germination. C.r.l. was limited by multiple threats: individuals with access to host species produced up to three times more inflorescences than those lacking hosts, mammalian herbivory reduced C.r.l. size and fecundity by more than 50% and moth larvae reduced seed production by up to 40%. Litter deposition and competition from exotic plant species also appears to work in conjunction with other factors to limit C.r.l. throughout its life cycle. CONCLUSIONS AND SIGNIFICANCE: The work reported here highlights the contribution that a series of small-scale studies can make to conservation and restoration. Taken as a whole, the results can be used immediately to inform current management and species recovery strategies. Recovery of C.r.l. will require management that addresses competition with exotic plant species, herbivore pressure, and availability of preferred host species
Inferences on physico-chemical conditions and gas-water interaction by new quantitative approaches: The case of Panarea (Italy)
We have developed two new quantitative approaches to
calculate temperatures in hydrothermal reservoirs by using the
CO2-CH4-CO-H2 gaseous system and to model selective
dissolution of CO2-H2S-N2-CH4-He-Ne mixtures in fresh
and/or air saturated seawater. The anomalous outgassing
starting November 2003 from the submarine exhalative
system offshore Panarea island (Italy), was the occasion to
apply such approaches to the extensive collection of volcanic
gases.
Gas geothermometry suggest the presence of a deep
geothermal system at temperature up to 350°C and about 12
mol% CO2 in the vapor, which feeds the submarine emissions.
Based on the fractional dissolution model, the rising
geothermal vapor interacts with air-saturated seawater at low
depths, dissolving 30-40% CO2 and even more H2S,
modifying the pH of the aqueous solution and stripping the
dissolved atmospheric volatiles (N2, Ne). Interaction of the
liquid phase of the thermal fluids with country rocks, as well
extensive mixing with seawater, have been also recognized
and quantified.
The measured output of hydrothermal fluids from Panarea
exhalative field [1] accounts for the involvement of volatiles
from an active degassing magma, nonetheless the climax of
the investigated phenomenon is probably overcome and the
system is new tending towards a steady-state. Our quantitative
approaches allow us to monitor the geochemical indicators of
the geothermal physico-chemical conditions and their
potential evolution towards phreatic events or massive gas
releases, which certainly are the main hazards to be expected
in the area. The event at Panarea has in fact highlighted how
hydrothermal systems can exhibit dramatic and sudden
changes of their physico-chemical conditions and rate of fluid
release, as a response to variable activity of feeding magmatic
systems
Constraints on mantle source and interactions from helium-strontium isotope variations in Italian volcanism
Helium isotope ratios of olivine and pyroxene from Plio-Quaternary volcanic rocks from Southern Italy (each of the seven Eolian Islands, Mt. Vulture, Etna, Ustica, Pantelleria), range from 2.3 to 7.1 Ra. A good correlation emerges with the 3He/4He of fumarolic fluids. Importantly the phenocryst 3He/4He correlate with whole rock Sr isotopes (0.70309-0.70711) reflecting the mixing of two sources. Crustal contamination of magmatic He isotopes is recorded only occasionally (e.g., pyroxenes from Vulcano). The He isotope values of Pantelleria, Etna, Iblei, Ustica, Alicudi and Filicudi (7.0 ± 0.6 Ra) define the mantle composition least affected by subduction. That these characterise volcanoes from a variety of tectonic regimes (subduction-related, intraplate, rifting) suggest a common origin of geochemical features and are consistent with a HIMU-type mantle that is either younger than the Cook-Austral island end-member, or one with lower 238U/204Pb. When merged with data from the Roman Comagmatic Province (Latium and Campania), a remarkably strong He-Sr isotope correlation is apparent. The general northward decrease in 3He/4He corresponds to an increase in 87Sr/86Sr and decrease in 143Nd/144Nd and 206Pb/204Pb that is due to increasing metasomatic enrichment of the mantle wedge via subduction of the Ionian Adriatic plate since 30 Ma. Calculations based on the ingrowth of 4He in the wedge and on the 4He content of the subducting crust show that mechanisms of enrichment in radiogenic He are effective only if the wedge is strongly depleted in He relative to best estimates of the depleted mantle
Selected In-Season Nutritional Strategies to Enhance Recovery for Team Sport Athletes: A Practical Overview
Team sport athletes face a variety of nutritional challenges related to recovery during the competitive season. The purpose of this article is to review nutrition strategies related to muscle regeneration, glycogen restoration, fatigue, physical and immune health, and preparation for subsequent training bouts and competitions. Given the limited opportunities to recover between training bouts and games throughout the competitive season, athletes must be deliberate in their recovery strategy. Foundational components of recovery related to protein, carbohydrates, and fluid have been extensively reviewed and accepted. Micronutrients and supplements that may be efficacious for promoting recovery include vitamin D, omega-3 polyunsaturated fatty acids, creatine, collagen/vitamin C, and antioxidants. Curcumin and bromelain may also provide a recovery benefit during the competitive season but future research is warranted prior to incorporating supplemental dosages into the athlete's diet. Air travel poses nutritional challenges related to nutrient timing and quality. Incorporating strategies to consume efficacious micronutrients and ingredients is necessary to support athlete recovery in season
Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy)
We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles
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