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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 172-7
Presentation Time: 3:15 PM

BIOLOGICAL IMPACTS ON SERPENTINITE WEATHERING


OLSEN, Amanda Albright1, HAUSRATH, Elisabeth M.2, TAYLOR, Agnes R.3, OLSEN, Brian J.4, CARDACE, Dawn5, BAUMEISTER, Julie L.6 and NEGRICH, Kimberly3, (1)School of Earth and Climate Sciences, University of Maine, 5790 Bryand Global Sciences Center, Orono, ME 04469, (2)Geoscience, University of Nevada Las Vegas, 4505 S Maryland Parkway, Las Vegas, NV 89154, (3)School of Earth and Climate Sciences, University of Maine, Bryand Global Sciences Center, Orono, ME 04469, (4)Climate Change Institute, School of Biology & Ecology, University of Maine, Orono, ME 04469, (5)Department of Geosciences, University of Rhode Island, 9 East Alumni Avenue, Woodward Hall, Kingston, RI 02881, (6)Department of Geoscience, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154, amanda.a.olsen@maine.edu

Serpentinites, perhaps more than any other rock type, control the composition and evolution of the biota that develop on them. The bulk chemistry of serpentinite rocks, high in Mg and trace elements, and low in nutrients such as Ca, K, P, and N, causes an extreme and stressful environment for biota. For this reason, serpentinites have been used as a model system to study endemism and speciation for decades. However, the role that serpentine biota play in development of serpentine soils has not been well examined.

We completed lizardite and whole serpentinite rock dissolution experiments to test several hypotheses regarding dissolution behavior in the presence of bacteria and organic acids. Our experiments suggest that Fe-oxidizing bacteria accelerate lizardite dissolution rates for the first eight hours of our experiments; however rates are similar after two weeks. Similar experiments show that oxalic acid accelerates lizardite dissolution by less than one order of magnitude. Whole rock serpentinite dissolution experiments examining the effect of 14 different organic acids (acetic, formic, lactic, glycolic, glutamic, oxalic, fumaric, gluconic, citric, malic, methanesulfonic, nonanoic, 2-aminoisobutyric, and valeric acids) on rock dissolution suggest that oxalic, citric, and malic acids are the most effective acids at enhancing weathering at earth surface temperatures.

Field studies of serpentinite weathering in the Klamath Mountains of California and on Little Deer Isle in Maine show that early weathering is driven by the dissolution of Fe-rich pyroxenes. In particular, the presence of ferrous Fe appears to contribute to greater dissolution, whereas the presence of Al within the parent rock appears to contribute to greater stability. Both soils and rock cores at the Klamath sites were tested for the presence of iron oxidizing bacteria which were found to be present in some samples, suggesting that the early alteration of these Fe-rich minerals may be mediated by iron-oxidizing bacteria.

Session No. 172

T204. The Reactive Soil: Processes at the Bio-Geo Interface in the Rhizosphere
Monday, 2 November 2015: 1:30 PM-5:30 PM
Room 343 (Baltimore Convention Center)
Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.442
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