TY - JOUR
T1 - Secular variations of helium and carbon isotopes at Galeras volcano, Colombia
AU - Sano, Yuji
AU - Gamo, Toshitaka
AU - Williams, Stanley
N1 - Funding Information:
We thank T.P. Fischer and M.L. Calvache V. t’o~ collecting some samples.W e are grateful to N. Taka-hata, H. Hiyagon and M. Tsutsumi for help in helium and carbon isotope measurementsT. his work is dedicatedt o the memory of Jose A. Zapata G.. who lost his life in the 14 January 1993 eruption of Galeras. Jose collected important samples for this study and made major contributions of our understanding of gas geochemistrya t Galeras through his efforts in the field and laboratory. SNW also ac- knowledges the US NSF for support of the research and Galeras Workshop. Comments and suggestions by editor, John Stix, and two anonymous reviewers were useful to revision of the original manuscript.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1997/5
Y1 - 1997/5
N2 - We have measured 3He/4He, 4He/20Ne and CO2/4He ratios, and δ13C values of CO2 in eighteen samples from crater fumaroles of Galeras volcano, Colombia, and seven samples of bubbling gases of the Pandiaco mineral spring located about 8 km east of the volcano from April 1988 to July 1995. The 3He/4He ratios of crater fumaroles, corrected for atmospheric contamination, increased significantly from 5.47 Ratm in December 1989 to 7.93 Ratm in August 1990 and reached a maximum of 8.84 Ratm in May 1992. The ratio then decreased gradually until July 1995. Overall variation of helium isotopes appears to be related to the current activity of the volcano. The 3He/4He ratios of Pandiaco mineral spring were constant between April 1988 and November 1991 and increased in April 1993, although experimental error is large. The δ13C values of CO2 of crater fumaroles show negative correlation to the helium isotopes, while those of Pandiaco are relatively constant. Based on the δ13C values and CO2/3He ratios, it is possible to estimate fractions of upper mantle carbon in these samples. Calculated mantle fractions are 3-10% in crater fumaroles, while those in Pandiaco spring are negligibly small.
AB - We have measured 3He/4He, 4He/20Ne and CO2/4He ratios, and δ13C values of CO2 in eighteen samples from crater fumaroles of Galeras volcano, Colombia, and seven samples of bubbling gases of the Pandiaco mineral spring located about 8 km east of the volcano from April 1988 to July 1995. The 3He/4He ratios of crater fumaroles, corrected for atmospheric contamination, increased significantly from 5.47 Ratm in December 1989 to 7.93 Ratm in August 1990 and reached a maximum of 8.84 Ratm in May 1992. The ratio then decreased gradually until July 1995. Overall variation of helium isotopes appears to be related to the current activity of the volcano. The 3He/4He ratios of Pandiaco mineral spring were constant between April 1988 and November 1991 and increased in April 1993, although experimental error is large. The δ13C values of CO2 of crater fumaroles show negative correlation to the helium isotopes, while those of Pandiaco are relatively constant. Based on the δ13C values and CO2/3He ratios, it is possible to estimate fractions of upper mantle carbon in these samples. Calculated mantle fractions are 3-10% in crater fumaroles, while those in Pandiaco spring are negligibly small.
KW - Carbon isotopes
KW - Galeras volcano
KW - Helium isotopes
KW - Volcanic gas
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U2 - 10.1016/S0377-0273(96)00098-4
DO - 10.1016/S0377-0273(96)00098-4
M3 - Article
AN - SCOPUS:0030807333
SN - 0377-0273
VL - 77
SP - 255
EP - 265
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-4
ER -