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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 15, 1817, doi:10.1029/2003GL017731, 2003

Self-potential, soil CO₂ flux, and temperature on Masaya volcano, Nicaragua

J. L. Lewicki

Department of Geology, University of South Florida, Tampa, Florida, USA

C. Connor

Department of Geology, University of South Florida, Tampa, Florida, USA

K. St-Amand

J. Stix

Department of Earth and Planetary Sciences, McGill University, Montréal, Canada

W. Spinner

Department of Geology, University of South Florida, Tampa, Florida, USA

Abstract

We investigate the spatial relationship between self-potential (SP), soil CO₂ flux, and temperature and the mechanisms that produce SP anomalies on the flanks of Masaya volcano, Nicaragua. We measured SP, soil CO₂ fluxes (<1 to 5.0 × 10⁴ g m⁻² d⁻¹), and temperatures (26 to 80°C) within an area surrounding a normal fault, adjacent to Comalito cinder cone (2002–2003). These variables are well spatially correlated. Wavelengths of SP anomalies are ≤100 m, and high horizontal SP gradients flank the region of elevated flux and temperature. Carbon isotopic compositions of soil CO₂ (δ¹³C = −3.3 to −1.1‰) indicate a deep gas origin. Given the presence of a deep water table (100 to 150 m), high gas flow rates, and subsurface temperatures above liquid boiling points, we suggest that rapid fluid disruption is primarily responsible for positive SP anomalies here. Concurrent measurement of SP, soil CO₂ flux, and temperature may be a useful tool to monitor intrusive activity.

Received 13 May 2003; accepted 9 July 2003; published 13 August 2003.

Index Terms: 0925 Exploration Geophysics: Magnetic and electrical methods; 8424 Volcanology: Hydrothermal systems (8135); 1040 Geochemistry: Isotopic composition/chemistry; 8419 Volcanology: Eruption monitoring (7280); 5104 Physical Properties of Rocks: Fracture and flow.

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Citation: Lewicki, J. L., C. Connor, K. St-Amand, J. Stix, and W. Spinner (2003), Self-potential, soil CO₂ flux, and temperature on Masaya volcano, Nicaragua, Geophys. Res. Lett., 30(15), 1817, doi:10.1029/2003GL017731.

Copyright 2003 by the American Geophysical Union.