DCO Project Summary

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Project Title
Proposal to Apply Pyro-Tag 16S rRNA Gene Sequence Analyses to the Deep Microbial Communities in the Witwatersrand Basin, South Africa
Start DateEnd Date
2011-01-01 2013-12-31
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The Witwatersrand Basin is ~300 km long x 150 km wide and comprised  of 2.9 Ga terrigenous, siliclastic detrital sediments of the Witwatersrand Supergroup, overlain uncomformably by the 2.7 Ga Ventersdorp Supergroup continental volcanic units, which in turn are overlain by the 2.5 Ga Transvaal Supergroup marine dolomite and banded iron formation. The entire sequence was metamorphosed to 250-300°C during circulation of hydrothermal fluids, first from the intrusion of outliers of the 2.06 Ga Bushveld Igneous Complex (BIC) and then from the 2.02 Ga Vredefort Impact  at the center of the basin. The Au and Pt mines offer access to fracture fluid over a range of depths (approaching 4 km), temperatures (geothermal gradients vary from 9-15°C/km), geochemical conditions, and subsurface residence times. The fracture water represents a mixture of low salinity, hypoxic, paleometeoric water, some as young as 5 to 40 kyr old, and anoxic, saline water, ~2.0 byr old, with bulk ages of ~1 to 100 million years old. The younger fresh and typically shallower fracture water originates from the Karroo and Transvaal Supergroups’ aquifers and contains a diverse bacterial and archaeal planktonic community with potential eukaryotic components. The typically deeper, older, saline fracture water contains abiogenic hydrocarbons and radiolytically produced H2 and sulfate that fuels a planktonic microbial community comprised of sulfate-reducers and autotrophic methanogens. Our objectives for this CoDL project include exploring the “rare” biosphere in the fracture systems, differentiating the sessile from planktonic communities, and identify the distribution of the Desulforudis audaxviator in the mine subsurface.

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Reporting Year 2014 Click to expand

  • RY2014-1 - submitted on Aug 31, 2014

    Update Details:

    Two papers are in review:

    Lau, M.C.Y., C. Cameron, F., Schilkey, S. Grim, C. Magnabosco, C.T. Brown, S. Hendrickson, M. Pullin, G. Lacrampe-Couloume, B. Sherwood Lollar, R. Purtschert, Z.-T. Lu, Esta van Heerden, T.L. Kieft and T.C. Onstott. Phylogeny and phylogeography of functional genes shared among seven terrestrial subsurface metagenomes reveal N-cycling and microbial evolutionary relationships. Front. Microbiol.

    Magnabosco, C., C.Y.M. Lau, , T.L. Kieft, Memory Tekere, Jana Olivier, B. Linage, O. Kuloyo, M. Erasmus, E. Cason, E. van Heerden, G. Borgonie, and T.C. Onstott. Comparisons of the composition and biogeographic distribution of the bacterial communities occupying South African thermal springs with those inhabiting deep subsurface fracture water. Front. Microbiol.

    One paper is in preparation:

    Magnabosco, C., D. Simkus, M. Lau, E. van Heerden, T. Kieft, B. Sherwood Lollar, G. Slater, and T.C. Onstott. A metagenomic window into the prokaryotic carbon metabolism at 3 km depth in the continental crust.

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