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Project Progress

Field work in 2006-2007 included trips to the high Arctic and to the Precambrian Canadian Shield. Study sites were selected on the basis of temperature and contrasting levels of hydrogen. Study sites included environments impacted by permafrost and environments at latitudes south of persistent permafrost. The level of free hydrogen gas is temperature-dependent and appears to be an important controlling factor on microbial processes.

Permafrost sites: Lupin Gold Mine is hosted by 2.8 billion year old metasediments. It possesses methane bearing brine beneath a permafrost layer that persists to approximately 500m below land surface. Gases were sampled from approximately a dozen boreholes from depths between 890 and 1130 m. The gases were predominantly methane with a substantial component of C2+ (ethane, propane and butane). Concentrations of helium were high (typically between 2-5 % by volume) but unlike the gases sampled at Kidd Creek Mine and the Sudbury Basin, H2 concentrations were below detection. Compositional and isotopic characterization was carried out for eleven boreholes in detail.

Permafrost sites: High Lake mine in the Nunavut Territory is a new mine. A dedicated borehole reserved for scientific investigations was drilled during the summer of 2006 on the High Lake property. Instrumentation of the High Lake borehole is anticipated in fall of 2007 and if successful, this site will provide long-term monitoring of microbial communities in sub-permafrost brines. During this past year cores and fluids (including sorbed and dissolved gases) were collected and are currently under analysis in laboratories at University of Toronto, Princeton University, University of Waterloo, Geological Survey of Finland, Indiana University, and University of Tennessee. Concentrations of gases are being determined for oxygen, nitrogen, helium, methane, hydrogen, and higher molecular-weight hydrocarbons. Once the compositional analyses are complete, isotopic characterization will be carried out for all components above detection limit. Cation and anion compositions of water samples are being determined by ion chromatography. This data set will provide an excellent basis of comparison between permafrost environments such as High Lake, and the Thompson site which is located at mid-latitudes but in a similar Archean greenstone belt setting.

Permafrost sites: An expedition was made by the Toronto field team to Axel Heiberg island for the purpose of sampling water and gases from springs and methane seeps in the high Arctic. Microbiological, geochemical, and isotopic analyses of these samples are currently underway.

Non-permafrost sites: Kidd Creek Mine and Thompson Mine are the focus of a study to integrate geochemical and theoretical databases with microbiological information (including PCR and MPN or most probable number enumeration) and microbiological counts. Boreholes samples within the mines ranged from saline waters to fresh-brackish water. These end-member compositions are interpreted to result from mixing of saline indigenous fracture waters with more recent waters infiltrating downwards due to mining activities. Stable isotopic analysis of the waters for oxygen and hydrogen were able to pinpoint waters that were influenced by mixing. Waters with isotopic compositions lying along the paleometeoric water line can be differentiated from waters with isotopic compositions lying well above the global meteoric water line and bearing the signature of extensive water-rock alteration reactions and long geological residence times. Methane, higher hydrocarbons and hydrogen (up to several % by volume) were exclusively associated with the fracture water end-member. High concentrations of hydrogen are associated with 13C-enriched methane waters, while low concentrations of hydrogen are associated with 13C-depleted methane waters. This relationship suggests the possibility that abiogenic gases may support hydrogen autotrophy linked to microbial methanogenesis in the deep subsurface.

A key objective of our continuing research on serpentinization is testing the hypothesis of fracture feeding by a detailed integration of geochemical and isotopic characterization of groundwaters and gases with both culture-based and molecular microbiological data on microbial community structure and function. During the past year, we have sampled and studied multiple ultramafic-hosted sites in Precambrian Shield Archean greenstone belts such as the Thompson, Kidd Creek and High Lake sites. A major result of this year’s research was the publication of a paper that explored the feasibility of fracture formation as a major geological and hydrogeological process influencing serpentinization in the deep-subsurface. We have a paper in press with Astrobiology entitled “Hydrogeologic controls on episodic H2 release from Precambrian fractured rocks – Energy for deep subsurface life on Earth and Mars.” The Astrobiology paper integrates results from current study sites with prior work on the Fennoscandian Shield in ultramafic rocks and on the Witwatersrand Basin in South Africa. Our serpentinization research has been presented at several international venues during the past year including Stanford University, the United States Geological Survey, Tokyo Institute of Technology, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), the University of Southern California and the Gordon Conference on Organic Geochemistry. The Astrobiology paper provides a mechanistic model to account for the development of energy-rich, but low biomass and slow metabolic communities, similar to the microbial community discovered by the IPTAI team in South Africa and reported in a 2006 paper in Science.

The study of deep subsurface ecosystems in ancient groundwater is directly relevant to the exploration for extant life in the subsurface of Mars. Results from successful field campaigns in the subsurface of the Canadian Shield are working towards the characterization of the microbial diversity and longterm subsurface sustainability of trends in deep Shield groundwaters, and indicate that deep subsurface microbial ecosystems do exist on Earth that are completely separate from surface photosynthesis.

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