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  • Cumbal Volcano Hydrothermal system Gases Fumaroles Springs Geochemistry Isotopes  (1)
  • Key words El Chichón Volcano  (1)
  • Schlüsselwörter Melatonin (N-Acetyl-5-Methoxytryptamin)  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Geochemistry of the volcano-hydrothermal system of El Chichón Volcano, Chiapas, Mexico (1998)
    Springer
    Bulletin of volcanology 59 (1998), S. 436-449 
    Details
    ISSN: 1432-0819
    Keywords: Key words El Chichón Volcano ; Crater Lake ; Hydrothermal system ; Volcanic gases ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The 1982 eruption of El Chichón volcano ejected more than 1 km3 of anhydrite-bearing trachyandesite pyroclastic material to form a new 1-km-wide and 300-m-deep crater and uncovered the upper 500 m of an active volcano-hydrothermal system. Instead of the weak boiling-point temperature fumaroles of the former lava dome, a vigorously boiling crater spring now discharges  / 20 kg/s of Cl-rich (∼15 000 mg/kg) and sulphur-poor ( / 200 mg/kg of SO4), almost neutral (pH up to 6.7) water with an isotopic composition close to that of subduction-type magmatic water (δD=–15‰, δ18O=+6.5‰). This spring, as well as numerous Cl-free boiling springs discharging a mixture of meteoric water with fumarolic condensates, feed the crater lake, which, compared with values in 1983, is now much more diluted (∼3000 mg/kg of Cl vs 24 030 mg/kg), less acidic (pH=2.6 vs 0.56) and contains much lower amounts of S ( / 200 mg/kg of SO4, vs 3550 mg/kg) with δ34S=0.5–4.2‰ (+17‰ in 1983). Agua Caliente thermal waters, on the southeast slope of the volcano, have an outflow rate of approximately 100 kg/s of 71  °C Na–Ca–Cl water and are five times more concentrated than before the eruption (B. R. Molina, unpublished data). Relative N2, Ar and He gas concentrations suggest extensional tectonics for the El Chichón volcanic centre. The 3He/4He and 4He/20Ne ratios in gases from the crater fumaroles (7.3Ra, 2560) and Agua Caliente hot springs (5.3Ra, 44) indicate a strong magmatic contribution. However, relative concentrations of reactive species are typical of equilibrium in a two-phase boiling aquifer. Sulphur and C isotopic data indicate highly reducing conditions within the system, probably associated with the presence of buried vegetation resulting from the 1982 eruption. All Cl-rich waters at El Chichón have a common source. This water has the appearence of a "partially matured" magmatic fluid: condensed magmatic vapour neutralized by interaction with fresh volcaniclastic deposits and depleted in S due to anhydrite precipitation. Shallow ground waters emerging around the volcano from the thick cover of fresh pumice deposits (Red waters) are Ca–SO4–rich and have a negative oxygen isotopic shift, probably due to ongoing formation of clay at low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050202
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical and isotopic compositions of fluids at Cumbal Volcano, Colombia: evidence for magmatic contribution (2000)
    Springer
    Bulletin of volcanology 62 (2000), S. 347-361 
    Details
    ISSN: 1432-0819
    Keywords: Cumbal Volcano Hydrothermal system Gases Fumaroles Springs Geochemistry Isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. We present chemical and isotopic data for fumarolic vapor and thermal spring discharges from Cumbal Volcano, SW Colombia. In 1988 Cumbal showed signs of apparent reactivation. Gases and steam condensates were sampled from summit fumaroles (83–375°C) of Cumbal in 1988–1996 and discharges from thermal springs (15–37°C) on its flanks in 1995–1996. Based on relative CO2, total S (H2S+SO2), and HCl contents, fumarolic discharges are principally magmatic in composition. Fumarolic steam condensates (1993–1996) have δ18O values of –11.4 to +2.5‰ and δD values of –91 to –43‰. δ18O and δD compositions indicate mixing between local meteoric and magmatic waters. 3He/4He ratios in 1993–1996 samples (5.3–7.9 Rcor) are consistent with addition of mantle-derived helium. δ13CCO2 values for 1996 samples (–6.7 to –5.0‰) likely indicate contribution of marine-carbonate, organic sediment, and mantle-derived CO2. δ34SStotal compositions (–4.6 to +5.6‰) of 1988–1996 fumarolic discharges have magmatic signatures and may reflect cycles of deposition and remobilization of native sulfur. Thermal waters are acid-sulfate or bicarbonate in composition. Relative concentrations of chemical constituents of thermal waters imply that the composition of waters is controlled by absorption of magmatic volatiles into shallow ground- and surface waters, dilution with meteoric waters along flow paths, and dissolution of host rocks. δ18O and δD compositions are consistent with a meteoric origin of waters. δ34SStotal values for thermal spring gas discharges (9.6–10.5‰) suggest deposition of δ34S-depleted sulfur minerals along flow paths. Chemical and isotopic compositions of 1988–1995 fumarolic discharges provide evidence for input of magmatic volatiles into the Cumbal hydrothermal system. From 1995 to 1996, geochemical data show increasing hydrothermal signatures, suggesting a decline in magmatic volatile input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450000100
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  • 3
    Electronic Resource
    Electronic Resource
    Melatonin in der Dermatologie Experimentelle und klinische Aspekte (1999)
    Springer
    Der Hautarzt 50 (1999), S. 5-11 
    Details
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Melatonin (N-Acetyl-5-Methoxytryptamin) ; Zirkadianer Rhythmus ; Schlaf-Wach-Rhythmus ; Radikalfänger ; Key words Melatonin (N-acethyl-5-methoxytryptamin) ; Circadian rhythm ; Daily sleep induction ; ageing ; Free radical scavenger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Melatonin (N-acetyl-5-methoxytryptamine) is a hormone with multiple functions in humans, produced by the pineal gland and stimulated by β-adrenergic receptors. Serum melatonin levels exhibit a circadian rhythm with low levels during the day, rise in the evening and maximum levels at night between 2 and 4 a.m.. Melatonin participates in the regulation of several physiological processes such as seasonal biological rhythm, daily sleep induction, aging and modulation of immunobiological defence reactions. Furthermore, melatonin has a highly lipophilic molecular structure facilitating penetration of cell membranes and serving as an extra- and intracellular free radical scavenger. Melatonin seems to quench mainly hydroxyl radicals, the most damaging of all free radicals. Melatonin may play a role in the etiology and treatment of several dermatoses e.g. atopic eczema, psoriasis and malignant melanoma. The influence of melatonin on hair growth is another aspect. Topical application of melatonin inhibits the development of UV-erythema. Penetration through skin after topical application and oral bioavailability auxit further investigations on the pharmacokinetic and pharmacodynamic actions of melatonin.
    Notes: Zusammenfassung Melatonin (N-Acetyl-5-Methoxytryptamin) ist ein unter dem Einflußβ-adrenerger Rezeptoren von der Glandula pinealis produziertes und sezerniertes Hormon mit vielfältigem Wirkungsspektrum. Die Ausschüttung des Hormons folgt einem zirkadianen Rhythmus mit niedrigen, gleichmäßigen Spiegeln tagsüber und einem abendlichen Ansteigen und nächtlichen Peak zwischen 2.00 und 4.00 Uhr. Melatonin beeinflußt den saisonalen Biorhythmus, den Schlaf-Wach-Rhythmus, den Alterungsprozeß und moduliert immunbiologische Abwehrfunktionen. Zusätzlich besitzt Melatonin unabhängig von einem Rezeptorsystem durch seine starken lipophilen Eigenschaften die Fähigkeit, frei durch Zellmembranen zu diffundieren und im extra- wie intrazellulären Raum als Radikalfänger zu wirken. Die Affinität zu dem stark schädigenden Hydroxylradikal ist besonders groß. In der Dermatologie ergeben sich für Melatonin Perspektiven bei einigen Hauterkrankungen wie zum Beispiel dem atopischen Ekzem, der Psoriasis und dem malignen Melanom. Der Einfluß von Melatonin auf das Haarwachstum ist ein weiterer Aspekt. In topischer Anwendung hat Melatonin eine suppressive Wirkung auf die Ausbildung eines UV-Erythems. Über die Penetrationseigenschaften durch die Haut und die orale Verfügbarkeit liegen einige Erkenntnisse vor, die durch weitere Untersuchungen der Pharmakokinetik und Pharmakodynamik ergänzt werden können.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001050050857
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