First Identification of Periodic Degassing Rhythms in Three Mineral Springs of the East Eifel Volcanic Field (EEVF, Germany)

Abstract

We present a geochemical dataset acquired during continual sampling over 7 months (biweekly) and 4 weeks (every 8 hours) in the Neuwied Basin, a part of the East Eifel Volcanic Field (EEVF). We used a combination of geochemical, geophysical, and statistical methods to identify potential causal processes underlying the correlations of degassing patterns of four gases (He, Rn, CO 2 , O 2 ), earth tides, and tectonic processes in three mineral springs (Nette, Kärlich and Kobern). We explored whether temporal relations in gas concentrations in the three mineral springs could be indicators of hidden faults through which the gases migrate to the surface from deeper underground. Our results do not confirm CO 2 as a primary carrier gas for trace gases in all springs. Temporal analyses of the CO 2 -He couple indicate that Nette and Kärlich are directly linked via a continuous tectonic fault in an ENE-WSW trending direction.There is also evidence that Kärlich and Kobern (NNE-SSW fault system) and Nette and Kobern (NW-SE fault system) are tectonically linked. These fault linkages are unknown previously but could be related to the rising numbers of earthquake events occurring in this area since 2010.We did not find any evidence that weather processes (e.g., barometric pressure), earth tides, or low local earthquake magnitudes actively modulate degassing. The volcanic activity in the EEVF is dormant but not extinct and to understand and monitor its magmatic and degassing systems, we recommend bi-weekly samplings at minimum.

Periodicity in Volcanic Gas Plumes: A Review and Analysis

“…Although beyond the scope of this review, we highlight that periodicity in volcanic gas emissions can also be manifest in timeseries of regional diffuse degassing. Berberich et al [123] identified periodic fluctuations in degassing from mineral springs in the East Eifel Volcanic Field, Germany, on timescales of 1 day (solar diurnal cycle), 4-6 days and 10-15 days, which they suggested reflected either variations in the deep gas source, changes in the transport pathway for gases to reach the surface, or the influence of volcano-tectonic earthquakes. Soil degassing (predominantly CO 2 ) can also provide good indications of the onset of volcanic unrest and magma movement at depth [124], although such datasets can also be sensitive to environmental and climatic influences [125,126]; for example, 47% of the soil CO 2 flux variations at Fogo, Azores, could be explained by the effect of the soil and air temperature, wind speed, and soil water content [127].…”

Degassing Rhythms and Fluctuations of Geogenic Gases in A Red Wood-Ant Nest and in Soil in The Neuwied Basin (East Eifel Volcanic Field, Germany)

“…Berberich et al [28] provide a more complete geological, tectonic, and volcanological description of the Goloring study site. Our Goloring study site is situated in the center of a triangle-shaped study area formed by the three previously-investigated mineral springs (Flöcksmühle in the Nette river near Ochtendung [hereafter: ‘Nette’], Waldmühle in Mülheim-Kärlich [hereafter: ‘Kärlich’] and ‘Kobern’ in Kobern-Gondorf (Figure 2a; [35]). No fault zones had been reported and identified previously from the Goloring study site; local earthquakes magnitude never exceeded M L = 2, and focal depths of earthquakes near it never exceeded 28 km during our sampling campaign [37].…”

“…We measured gases in ambient air (AA), soil (SG; Figure 2d), and the RWA nest (NG) at the Iron age henge sanctuary at the Goloring site (Figure 2b) biweekly from 1 March–30 September 2016 (7-M; 16 times) and every eight hours between 12 July and 11 August 2016 (4-W; 83 times), yielding a total of 2673 gas samples. Gas sampling followed procedures described by Berberich [24] using analytical equipment and sampling methods described by Berberich et al [28,35]. Briefly, AA was sampled at 1 m height, 1 m away from the RWA nest.…”

“…We used these associations to test whether: (a) associations between NG and SG concentrations indicated actively in situ degassing faults trapping migrating geogases from deep underground (Figure 1); (b) NG and SG fluctuations in soil and nest were affected by external agents (earth tides, earthquakes, or meteorology); and (c) SG and NG concentrations were associated with those of three nearby degassing mineral springs [35].…”

“…This study is part III of the research project “GeoBio-Interactions” in which we also monitored geochemistry of three mineral waters ≈6 km from the Goloring site [35] and the association of RWA nests and fault-related CH 4 degassing at Goloring [28].…”