HR: 16:00h
AN: B44C-01 INVITED    [Abstracts]
TI: New Insights to Interplay of Factors that Influence Biomineral Signatures: Intrigue of the Solvation Environment
AU: * Dove, P M
EM: dove@vt.edu
AF: Virginia Tech, Department of Geosciences, Blacksburg, VA 24061,
AU: Stephenson, A E
EM: aestephe@vt.edu
AF: Virginia Tech, Department of Geosciences, Blacksburg, VA 24061,
AU: De Yoreo, J J
EM: deyoreo1@llnl.gov
AF: Lawrence Livermore National Laboratory, Dept. Chemistry and Materials Sciences, Livermore, CA 94550,
AB: For many years, studies of compositional signatures contained in the skeletons of certain calcifying species have suggested that Mg levels correlate with temperature of formation. With the growing urgency to decipher how earth environments have changed over geologic time, this long-standing proxy for estimating temperature has developed and also encouraged a frenzy of new measurements that claim additional composition and isotope- based proxy relations. Because organisms employ mineralization strategies that create highly controlled chemical and spatial microenvironments for the nucleation and growth of biominerals, it would seem probable that local chemical/biochemical factors could enforce controls on impurity contents that are equal to or greater than the relatively small thermal differences found in earth surface conditions. Over the last seven years, our group has conducted molecular scale studies using in situ atomic force microscopy and computational modeling to understand the physical basis for shape and signature controls on biomineral formation. By linking direct measurements of growth modification with the underlying chemical interactions, our findings have provided new insights into relative importance of factors that produce observed compositional signatures. Several principles are emerging to give a mechanism-based understanding of growth processes and are also allowing us to establish the interplay of factors that produce mineral shapes and measured compositional signatures: 1) Changes in dominant growth processes as determined by chemical driving force; 2) Roles of growth dynamics and corresponding kink site density at step edges; 3) First-order influence of minor changes in local solvation environment induced by simple biomolecules and salinity; 4) Comparatively small influence of temperature; 5) Realization that classical models of crystal growth, developed for kink-rich highly soluble salts, need to be extended to explain most earth materials which are only sparingly soluble (kink limited). By developing these insights, the possibilities for a new mechanism-based understanding are significant. New findings showing the importance of solvation environment give reason to suspect that signatures also have a significant sensitivity to local alkalinity, salinity, and the types of electrolytes present in solution but this remains to be tested.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
DE: 1030 Geochemical cycles (0330)
DE: 4855 Phytoplankton
SC: Biogeosciences [B]
MN: 2007 Fall Meeting