C3He in volatile fluxes from the solid Earth: implications for carbon geodynamics

The search for extraterrestrial life may be facilitated if ecosystems can be found on Earth that exist under conditions analogous to those present on other planets or moons. It has been proposed, on the basis of geochemical and thermodynamic considerations, that geologically derived hydrogen might support subsurface microbial communities on Mars and Europa in which methanogens form the base of the ecosystem1,2,3,4,5. Here we describe a unique subsurface microbial community in which hydrogen-consuming, methane-producing Archaea far outnumber the Bacteria. More than 90% of the 16S ribosomal DNA sequences recovered from hydrothermal waters circulating through deeply buried igneous rocks in Idaho are related to hydrogen-using methanogenic microorganisms. Geochemical characterization indicates that geothermal hydrogen, not organic carbon, is the primary energy source for this methanogen-dominated microbial community. These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets.

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A hydrogen-based subsurface microbial community dominated by methanogens

Gas geochemistry and seismotectonics: a review

Hydrogen generation from mantle source rocks in Oman

Terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas, especially in USSR, China, Japan, and United States, in search of premonitory changes that might be useful for earthquake prediction. Concentrations of radon, helium, hydrogen, mercury, carbon dioxide, and several other volatiles have been found generally to be anomalously high along active faults, suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere. Temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers. These “sensitive” stations are generally located along active faults, especially at intersections or bends of faults, or some other structurally weak zones, possibly because of tectonic strain concentration at such places. However, gas concentrations, especially those measured at or near the ground surface, may also be significantly affected by meteorological, hydrological, and other nontectonic changes in the environment. The nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake-related anomalies.

Gas geochemistry applied to earthquake prediction: An overview

The hydrogen concentration in soil gas has been measured in the area around the Yamasaki Fault, one of the active faults in southwestern Japan. Degassing of a significant amount of hydrogen (up to more than 3 percent by volume) has been observed for sites along the fault zone. The hydrogen concentration in soil gas at sites away from the fault zone was about 0.5 part per million, almost the same as that found in the atmosphere. The spatial distribution of sites with high hydrogen concentrations is quite systematic. A hypothesis on the production of hydrogen by fault movements is postulated.

http://science.sciencemag.org/content/sci/210/4466/188.full.pdf

Hydrogen release: new indicator of fault activity.

Granite and quartz were crushed under moist conditions in the temperature range of 25–270°C, in order to obtain the information on the mechanism operative for H2 degassing along active faults. It was found that the amounts of H2 gas released by crushing granite and quartz increased with temperature up to around 200°C and then decreased suddenly. The results indicate that H2 gas is generated by a chemical reaction between water and such radicals as Si · and Si—O · formed on the fresh surfaces when the Si—O—Si bonds are destroyed by crushing and that the existence of a maximum for amount of H2 gas is due to the decrease of the lifetime of Si—O · radical at the temperature higher than about 200°C. The results lend credence to the possibility that H2 gas is generated in the temperature range of 25–270°C along the active fault through the reaction between groundwater and the fresh surfaces of underground rocks formed by the fault movements.

H2 generation by reaction between H2O and crushed rock: An experimental study on H2 degassing from the active fault zone

The δD values of molecular hydrogen in soil gases obtained from sites along the Yamasaki fault, one of active faults in Southwest Japan were measured. The δD values were in the range between -770 and -470‰, which suggests that molecular hydrogen is formed by chemical reactions between groundwater and the fresh surface of basement rocks formed by the fault movement.

D/H ratios of H2 in soil gases as an indicator of fault movements.

A ball mill made of pyrex glass with an alumina ball was devised. The features are as follows, 1) quartz and rocks can be powdered manually in a short period of time, 2) pulverization is possible in the pressure range from 10-3torr to about 3 atm and the temperature up to about 300°C, 3) interior of the mill is visible, and 4) the mill is handy to manipulate and easy to repair. The mill may be useful for varieties of crushing experiments.

https://www.jstage.jst.go.jp/article/geochemj1966/15/5/15_5_289/_pdf

Itsuro Kita

Papers

Hydrogen release: new indicator of fault activity.

H2 generation by reaction between H2O and crushed rock: An experimental study on H2 degassing from the active fault zone

D/H ratios of H2 in soil gases as an indicator of fault movements.

A new type ball mill made of pyrex glass.