caa a22 4500 47582606X CHVBK 20180406123829.0 cr unu---uuuuu 170329e20000501xx s 000 0 eng 10.1007/s004450050289 doi (NATIONALLICENCE)springer-10.1007/s004450050289 Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador [Elektronische Daten] [Fraser Goff, Gary M. McMurtry, Dale Counce, James A. Simac, Alfredo R. Roldán-Manzo, David R. Hilton] 2: and approximately 85% SO2 of the total sulfur gas. Relative amounts of He, Ar, and N2 show a distinct hot-spot signature ( ). The δ13C-CO2 is approximately −3.6‰ and δ34ST is approximately +3.3‰. The δD/δ18O of fumarole H2O indicates steam separation from local meteoric waters whose estimated minimum mean residence time from 3H analyses is ≤40 years. Fumarolic activity at Alcedo is controlled by a caldera-margin fault containing at least seven hydrothermal explosion craters, and by an intracaldera rhyolite vent. Two explosion craters which formed in 1993-1994 produce approximately 15 m3/s of steam, yet discharge temperatures are ≤97°C. Water content of the total gas is 95-97 mol.%, noncondensible gas is 92-98 mol.% CO2, and sulfur gas is dominated by H2S. Relative amounts of He, Ar, and N2 show extensive mixing between hot spot and air or air-saturated meteoric water components but the average . The δ13C-CO2 is approximately −3.5‰ and δ34ST is approximately −0.8‰. The δD/δ18O of fumarole steam indicates separation from a homogeneous reservoir that is enriched 3-5‰ in 18O compared with local meteoric water. 3H indicates that this reservoir water has a maximum mean residence time of approximately 400 years and empirical gas geothermometry indicates a reservoir temperature of 260-320°C. The intracaldera hydrothermal reservoir in Alcedo is probably capable of producing up to 150 MW; however, environmental concerns as well as lack of infrastructure and power users will limit the development of this resource. Springer-Verlag Berlin Heidelberg, 2000 Galapagos nationallicence Volcanic gases nationallicence Gas geochemistry nationallicence Isotope geochemistry nationallicence Geothermal systems nationallicence Sierra Negra nationallicence Alcedo nationallicence Goff Fraser Los Alamos National Laboratory, Los Alamos, NM 87545, USA, US aut McMurtry Gary M. SOEST University of Hawaii, Honolulu, HI 96822, USA, US aut Counce Dale Los Alamos National Laboratory, Los Alamos, NM 87545, USA, US aut Simac James A. Unocal Corporation, Philippines, 14141 Southwest Freeway, Sugar Land, TX 77478, USA, US aut Roldán-Manzo Alfredo R. INDE, Guatemala City, Guatemala, GT aut Hilton David R. Department of Earth Sciences, Vrije Universiteit, HV1081 Amsterdam, The Netherlands, NL aut https://doi.org/10.1007/s004450050289 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s004450050289 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Goff Fraser Los Alamos National Laboratory, Los Alamos, NM 87545, USA, US aut NATIONALLICENCE 700 1- McMurtry Gary M. SOEST University of Hawaii, Honolulu, HI 96822, USA, US aut NATIONALLICENCE 700 1- Counce Dale Los Alamos National Laboratory, Los Alamos, NM 87545, USA, US aut NATIONALLICENCE 700 1- Simac James A. Unocal Corporation, Philippines, 14141 Southwest Freeway, Sugar Land, TX 77478, USA, US aut NATIONALLICENCE 700 1- Roldán-Manzo Alfredo R. INDE, Guatemala City, Guatemala, GT aut NATIONALLICENCE 700 1- Hilton David R. Department of Earth Sciences, Vrije Universiteit, HV1081 Amsterdam, The Netherlands, NL aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer