Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/9991
Authors: Voltattorni, N.* 
Lombardi, S.* 
Beaubien, S. E.* 
Title: Gas migration from two mine districts: The Tolfa (Lazio, Central Italy) and the Neves-Corvo (Baixo Alentejo, Portugal) case studies
Issue Date: 7-Feb-2015
Series/Report no.: /152 (2015)
DOI: 10.1016/j.gexplo.2015.01.011
URI: http://hdl.handle.net/2122/9991
Keywords: Soil gas migration
Subject Classification04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration 
Abstract: Detailed soil gas surveyswere conducted at twomine districts to understand gas migrationmechanisms fromdeposits buried at different depths. The Tolfa (Lazio, Central Italy) and Neves-Corvo (Baixo Alentejo, Portugal) mine districts have different characteristics: the former is relatively shallow (30–100 m) whereas the latter is at a depth of 400–500 m and covered by low-permeability metamorphic rocks. The studied gases included major (N2, O2, CO2) and trace (4He, 222Rn) gases, hydrocarbons (CH4, C2H6 and C3H8) and S compounds (H2S, COS, SO2). The measured concentrations (some examples of max values at Tolfa: Rn 233 Bq/L, CO2 9.5%, CH4 12.3 ppm, COS 3.7 ppm; and at Neves-Corvo: Rn 130 Bq/L, CO2 24.3%, CH4 0.1%) indicate that gases migrate preferentially through zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration needed to obtain anomalies of short-lived 222Rn in the soil pores. Considering the different depths of the two ore deposits, obtained results can be considered as features of near-field (Tolfa) and far-field (Neves- Corvo) gas migration.
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