1. Carbon-Isotope Characteristics of CO2 and CH4 in Geothermal Springs from the Central Andes
- Author
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Carolyn Chenery, Baruch Spiro, and Leonore Hoke
- Subjects
geography ,geography.geographical_feature_category ,Volcanic arc ,Geothermal Springs ,Continental crust ,Earth science ,Geochemistry ,Geology ,Methane ,Mantle (geology) ,chemistry.chemical_compound ,chemistry ,Isotopes of carbon ,Carbon dioxide - Abstract
Carbon stable-isotope compositions of coexisting carbon dioxide and methane from geothermal springs across the Central Andes of northern Chile and Bolivia are reported. A total of 60 samples were analyzed for δ13CCO2 and, of these, 10 were selected for δ13CCH4 analyses. The Central Andes are characterized by an active volcanic arc and an unusually thick (up to 75 km) continental crust behind the arc, beneath the high plateau region of the Altiplano. Furthermore, helium-isotope evidence suggests active mantle degassing in a 350-km-wide zone beneath the thick continental crust in the Central Andes (Hoke et al., 1994). The present results show a wide range of δ13CCO2 (-14.9 to -0.6‰) and a surprisingly heavy δ13CCH4 (−20.9 to −12.3‰). The difference between δ13CCO2 and δ13CCH4 (δ13CCO2-CH4 ) for individual samples varies between 1.5‰ and 13.5‰. The δ13CCO2 results show wide and overlapping ranges in the samples collected from the Precordillera, the Volcanic Arc (or Western Cordillera), the Altiplano, and the...
- Published
- 1997