title: Surface chemistry allows for abiotic precipitation of dolomite at low temperature.
abstract: Although the mineral dolomite is abundant in ancient low-temperature sedimentary systems, it is scarce in modern systems below 50 °C. Chemical mechanism(s) enhancing its formation remain an enigma because abiotic dolomite has been challenging to synthesize at low temperature in laboratory settings. Microbial enhancement of dolomite precipitation at low temperature has been reported; however, it is still unclear exactly how microorganisms influence reaction kinetics. Here we document the abiotic synthesis of low-temperature dolomite in laboratory experiments and constrain possible mechanisms for dolomite formation. Ancient and modern seawater solution compositions, with identical pH and pCO2, were used to precipitate an ordered, stoichiometric dolomite phase at 30 °C in as few as 20 d. Mg-rich phases nucleate exclusively on carboxylated polystyrene spheres along with calcite, whereas aragonite forms in solution via homogeneous nucleation. We infer that Mg ions are complexed and dewatered by surface-bound carboxyl groups, thus decreasing the energy required for carbonation. These results indicate that natural surfaces, including organic matter and microbial biomass, possessing a high density of carboxyl groups may be a mechanism by which ordered dolomite nuclei form. Although environments rich in organic matter may be of interest, our data suggest that sharp biogeochemical interfaces that promote microbial death, as well as those with high salinity may, in part, control carboxyl-group density on organic carbon surfaces, consistent with origin of dolomites from microbial biofilms, as well as hypersaline and mixing zone environments.
authors: Department of Geology, University of Kansas, Lawrence, KS 66045, USA. jenrob@ku.edu
authors: Jennifer A
authors: JA
authors: Roberts
authors: Paul A
authors: PA
authors: Kenward
authors: David A
authors: DA
authors: Fowle
authors: Robert H
authors: RH
authors: Goldstein
authors: Luis A
authors: LA
authors: González
authors: David S
authors: DS
authors: Moore
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology; D002119:Calcium Carbonate / Q000737:chemistry* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D011232:Chemical Precipitation; D004783:Environmental Microbiology; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D054712:Salinity; D012623:Seawater / Q000382:microbiology; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D002245:Carbon Dioxide; D002119:Calcium Carbonate; D008274:Magnesium; C028042:calcium magnesium carbonate
keywords: biomineralization; carbonates
references: Biochemistry. 2005 Mar 29;44(12):4877-85
references: 15779914
references: Science. 1981 Jul 10;213(4504):214-6
references: 17782787
references: Science. 2004 Mar 12;303(5664):1656-8
references: 15016997
references: Science. 2010 Feb 26;327(5969):1114-7
references: 20133522
references: Geobiology. 2009 Dec;7(5):556-65
references: 19663931
references: Adv Colloid Interface Sci. 2006 Dec 21;128-130:135-58
references: 17254533
references: Water Res. 2004 Oct;38(17):3685-92
references: 15350419
references: Proc Natl Acad Sci U S A. 2009 Dec 22;106(51):21511-6
references: 19955417
references: Science. 2001 Nov 2;294(5544):1086-8
references: 11691988