A102
Goldschmidt Conference Abstract 2006
New geochemical data of hydrothermal system of Baransky Volcano (Kuril Islands) O.V. CHUDAEV1, V.A. CHUDAEVA2, K. SUGIMORI3, A. KUNO4, M. MATSUO4, D.K. NORDSTROM5
Distribution of REE in thermal springs and surrounded surface waters of some active volcanic zones in Russia and Japan V.A. CHUDAEVA1, O.V. CHUDAEV2, K. SUGIMORI3, M. MATSUO4, A. KUNO4
1
Far East Geological Institute, Vladivostok, Russia (chudaev@ fegi.ru) 2 Pacific Institute of Geography, Vladivostok, Russia (valchud@ hotmail.com) 3 Toho University, School of Medicine, Tokyo, Japan (kensan@ med.toho-u.ac.jp) 4 Tokyo University, Tokyo, Japan (
[email protected]) 5 US Geological Survey, Boulder, USA (
[email protected]) Intensive volcanic and hydrothermal activity in the Kuril Islands started in the Late Cretaceous and continue today. The Kuril Islands are isolated and unevenly studied. Using data collected between 2002 and 2005, we present results of trace elements and H, O, S, and He isotopes ratios for the hydrothermal system of Baransky Volcano. The data show that three main groups of thermal waters can be distinguished: acid sulfate waters (pH < 3.7), weak alkaline sodium-chloride (pH > 7.3) and neutral, sodium-chloride-bicarbonate thermal waters. Acid sulfate waters have rather high contents of siderophile, chalcophile, and lithophile elements. Sodium chloride waters have high contents of main ions and very low rare earth elements. Sodium-chloride–bicarbonate waters occupied an intermediate position in contents of chemical elements. The index of mineral saturation indicates that the sodium-chloride waters are oversaturated relative to adularia, epidote, chlorite, and wairakite. Sodium-chloride–bicarbonate waters are oversaturated relative to albite, smectite, and low temperature zeolite assemblages. For Baransky Volcano, the classical geochemical zoning of thermal waters is observed. In the volcano crater acid sulfate waters occur; hypsometrically below in the volcano basement—sodium chloride water is typical. Neutral sodium-chloride–bicarbonate waters occur on the periphery of Baransky Volcano. On the basis of hydrogen and oxygen isotopic data thermal waters have an atmospheric origin. Sulfur isotopic data indicate magmatic origin of the sulfur in acid waters. The high values of the 3He/4He ratio (7.74) indicate a high percentage of mantle helium in waters. Thus, the chemical composition of the thermal waters is formed under influence of the country rocks and abyssal fluids. The flows of magmatic fluid which combine with infiltration waters change the solution influencing significantly the reaction run in the water– rock system.
Acknowledgments This work was supported by RFBR (Grant # 04-05-65245), and by FEB RAS (Grant # 06-1-OH3-117).
1
Pacific Institute of Geography, Vladivostok, Russia (valchud@ hotmail.com) 2 Far East Geological Institute, Vladivostok, Russia 3 Toho University, School of Medicine, Tokyo, Japan (kensan@ med.toho-u.ac.jp) 4 Tokyo University, Tokyo, Japan (
[email protected]. ac.jp) Distribution of chemical elements, especially REE in the areas with hydrothermal activities was investigated on Kunashir and Paramushir Islands of Kuril ridge (Far East of Russia) and in the Hakone area of Japan. The waters studied are mostly acidic (pH up to 1 in the springs and up to 2.5–1.8 in the surface waters). The low pH of thermal waters was accompanied by a low oxygen concentration (up to 0 mg/l) with high mineralization and concentrations of trace elements. Concentrations of REE are very different in different groups of springs and pots of studied areas and good connection of REE concentrations and water pH was found: the highest REE contents were found in the water with lowest pH. At the time of study, the highest REE contents for acid waters were found in group of hot springs on the Ebeco’s north-eastern fumarole fields (Paramushir island) where total dissolved REE reach more then 100 ppb. Concurrently, the pots of Mendeleev Volcano on Kunashir Island had REE concentrations ranging between 30 and 40 ppb. For Hakone area of Japan, REE concentrations were lower then those measured during the Kuril study. In total the composition of the surrounded surface waters reflects the composition of the thermal springs, discharge on the areas and has essentially different concentrations of REE as well. Maximum concentrations are typical in the stream draining north-eastern fumarole field of Ebeko Volcano where contents of La reach >20 ppb and Ce up to 48 ppb. The lowest concentrations were found in the stream of Hakone area. Normalized with NASC concentrations of REE in studied waters show more often enrichment in heavy REE with positive Eu anomaly.
Acknowledgments This work was financially supported by RFBR (Grants 06-0596003 and 04-05-65245) and FEB RAS (Grant 06-1-IH3-117). doi:10.1016/j.gca.2006.06.118
doi:10.1016/j.gca.2006.06.117
