HR: 1340h
AN: T33A-0518    [Abstracts]
TI: Low-Temperature Weathering of Hydrothermal Sulfide Minerals at Juan de Fuca Ridge
AU: * Toner, B M
EM: brandy.toner@gmail.com
AF: Woods Hole Oceanographic Institution, Room 203 McLean Lab, MS#8, Woods Hole, MA 02543
AU: Santelli, C M
EM: csantelli@whoi.edu
AF: Woods Hole Oceanographic Institution, Room 203 McLean Lab, MS#8, Woods Hole, MA 02543
AU: Rogers, D R
EM: drogers@whoi.edu
AF: Woods Hole Oceanographic Institution, Room 203 McLean Lab, MS#8, Woods Hole, MA 02543
AU: Edwards, K J
EM: katrina@whoi.edu
AF: Woods Hole Oceanographic Institution, Room 203 McLean Lab, MS#8, Woods Hole, MA 02543
AB: Phylogenetically and metabolically diverse microbial communities have been identified in several deep ocean settings, including the seafloor at mid-ocean ridge flanks. The microorganisms present in these environments appear to participate in geochemical processes, such as mineral dissolution and mineral precipitation, over geological time scales. The purpose of our study was to characterize the initial alteration products and geochemical signatures of hydrothermal sulfide minerals exposed at the seafloor near hydrothermal venting at the Juan de Fuca Ridge, and to identify those weathering products specific to microbial metabolism. Biominerals are notoriously difficult to characterize, often possessing structural defects and small particle size, and are commonly only one of many constituents within natural particles and biofilms. Given these challenges, focused beam X-ray absorption spectroscopic (XAS) techniques provide important capabilities for identifying microbial weathering products by (1) effectively simplifying the chemistry of the sample through examination of chemically discrete areas, (2) identifying co-occurring elements of interest, (3) providing complementary structural information from co-occurring elements, and (4) examining samples at the natural micro- to millimeter spatial scale of mineralogical heterogeneity. We collected 2-dimensional X-ray fluorescence (XRF) elemental maps of experimentally weathered sulfide minerals in cross section. For these experiments, fresh, unweathered sulfide minerals were incubated at low temperatures for a two month period and then collected for mineralogical and microbiological analysis. Previous work on these samples showed that abundant Fe oxide minerals (principally 2-line ferrihydrite) accumulated during weathering, and correlated with dense cell aggregates at the mineral surface. Additionally, a diverse collection of Fe oxidizing bacteria were cultured from these and other similar samples incubated or collected in the vicinity of these experiments. In this work, a variety of elements, Fe, S, Ca, Zn, Cu, As, and Se, were examined and their elemental maps were used to identify regions of chemical and biological interest. At chemically discrete regions of the samples, Fe, Cu, and Zn K-edge extended X-ray absorption fine structure (EXAFS) and S K-edge X-ray absorption near edge structure (XANES) spectroscopic data was collected.
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0419 Biomineralization
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0463 Microbe/mineral interactions
SC: Tectonophysics [T]
MN: Fall Meeting 2005