DCO Project Summary

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Project Title
Generation and Flux of Hydrocarbons from Continental Cratons
Start DateEnd Date
2011-04-01
NameRoleInstitutionDCO ID
Related GrantsDCO ID
11121/3515-2688-3796-9573-CC
Description
Saline fracture waters in Precambian shields are some of the most H2-rich waters on the planet and thus an important setting in which to study the role of H2 in methanogenesis. We are analyzing C, H, N, and S isostopes and noble gas compositions of fluids from deep subsurface sites in South Africa, Canada, and Fennoscandia in order to determine the source of H2 production, the net production of H2, and mechanisms of hydrocarbon production in these settings.
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Reporting Year 2012 Click to expand


  • RY2012-1 - submitted on Aug 31, 2012

    Update Details:

    [2012-01-01] Sample collection and initial geochemical analyses are under way.

    10-1-2013 (First DE project)

     

    Univ. Toronto/Manchester Univ. (Barb Sherwood Lollar & Chris Ballentine, Leads) Two major discoveries were made in the first phase of this work from the Toronto/Manchester. First, building on a network of underground observatories (NISO) including active mines, boreholes and underground research laboratories, data was compiled from > 200 boreholes/samples, at 32 continental sites worldwide. This was used as the basis for the first global estimate of H2 source potential from both radiolysis and serpentinization from the Precambrian continental lithosphere. In a paper in prep. for Nature, we were able to estimate that the flux of H2 from the Precambrian continental lithosphere is on the same order of magnitude as estimates from marine hydrothermal systems reported elsewhere (Sleep et al. 2004) – a major source, yet until now largely neglected in global estimates of H2 potential and related potential for CH4 production.

     

    Simply put, more than 70% of the Earth’s continental crust is Precambrian in age, yet H2 production potential from this major component of the planet is missing to date in all the major models. Given the continental crust (on average 30-50km thick) is also much thicker than typical oceanic crust, our work suggests that a significant volume of this planet has been almost completely neglected in our understanding of H2 contributions. While marine systems record processes on a less than 200 Ma timescale, the Precambrian crust encompasses most of the Earth’s history and contains a record of the planet on a billion year timescale, recording processes that contributed to the origin of life and the evolution of the modern atmosphere.

     

    The second major discovery was that indeed saline fracture fluids in the deeper (2-3 km) rocks of the Precambrian Shields may contain noble gas components of immense age. In results in press at Nature (Holland et al.) we discovered in fracture waters from the Canadian Shield at Timmins mine, at 2.7 km depth, the most radiogenic He, Ne, Ar signatures ever identified. These correspond to the oldest bulk residence times (on order of Ga) ever measured for groundwater and attest to the extreme hydrogeologic isolation of these deep fracture networks.

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