Pelagic barite precipitation at micromolar ambient sulfate

Abstract

Geochemical analyses of sedimentary barites (barium sulfates) in the geological record have yielded fundamental insights into the chemistry of the Archean environment and evolutionary origin of microbial metabolisms. However, the question of how barites were able to precipitate from a contemporary ocean that contained only trace amounts of sulfate remains controversial. Here we report dissolved and particulate multi-element and barium-isotopic data from Lake Superior that evidence pelagic barite precipitation at micromolar ambient sulfate. These pelagic barites likely precipitate within particle-associated microenvironments supplied with additional barium and sulfate ions derived from heterotrophic remineralization of organic matter. If active during the Archean, pelagic precipitation and subsequent sedimentation may account for the genesis of enigmatic barite deposits. Indeed, barium-isotopic analyses of barites from the Paleoarchean Dresser Formation are consistent with a pelagic mechanism of precipitation, which altogether offers a new paradigm for interpreting the temporal occurrence of barites in the geological record.

The Middle to Late Miocene “Carbonate Crash” in the Equatorial Indian Ocean

“…Goldberg and Arrhenius () originally suggested that the accumulation rate of barium in deep‐sea sediments is a function of the rate of organic production in the euphotic zone and used BaO/TiO 2 to trace the zone of upwelling‐related enhanced productivity in the equatorial Pacific Ocean. Total Ba, as measured by the XRF core scanner, closely matches biogenic Ba in deep marine sedimentary environments, which do not contain Ba from terrigenous sources and where no significant barite remobilization occurs (Dymond et al, ; Hendy, ; Horner et al, ; Piela et al, ; Torres et al, ; Von Breymann et al, ). The dissolution resistance of biogenic barium and its strong correlation with the organic carbon (C org ) export flux additionally make Ba/Al a robust indicator of C org export flux in sediments with low clay content (Dymond et al, ; Eagle et al, ; Piela et al, ).…”

High‐Precision Barium Isotope Measurements of Carbonates by MC‐ICP‐MS

“…(), Horner et al . () and Hsieh and Henderson (). [Colour figure can be viewed at wileyonlinelibrary.com]…”

Organic–mineral interfacial chemistry drives heterogeneous nucleation of Sr-rich (Ba x , Sr 1− x )SO 4 from undersaturated solution

“…Second, Sr-rich marine barite (>50 mol% strontium) formation (7, 9) is not thermodynamically favorable (7, 10), as the solubility of SrSO 4 (K sp,SrSO4 = 10 −6.63 ) is three orders of magnitude higher than BaSO 4 (K sp,BaSO4 = 10 −9.98 ) (3, 10). Field and laboratory studies provide evidence for the association of organics with both paradoxes (7, 11); however, the specific roles of organics in these thermodynamically unfavorable mineralization processes are not clear (7,11,12).Organic-mineral interactions play essential roles in biomineralization processes (13,14), which produce minerals with well-controlled morphologies, structures, and compositions not readily explained by traditional inorganic mineral nucleation and growth processes (13,15). Therefore, understanding how organic-mineral interactions direct mineral nucleation and growth could advance the use of biominerals as chemical archives of paleoenvironments (7,16,17).…”

“…Field and laboratory studies provide evidence for the association of organics with both paradoxes (7, 11); however, the specific roles of organics in these thermodynamically unfavorable mineralization processes are not clear (7,11,12).Organic-mineral interactions play essential roles in biomineralization processes (13,14), which produce minerals with well-controlled morphologies, structures, and compositions not readily explained by traditional inorganic mineral nucleation and growth processes (13,15). Therefore, understanding how organic-mineral interactions direct mineral nucleation and growth could advance the use of biominerals as chemical archives of paleoenvironments (7,16,17). In addition, manipulating organic-mineral interactions offers strategies for the synthesis of crystals with tunable properties for a variety of applications (13).Despite the importance of organic-mineral interactions, the impact of the organic interface on the thermodynamics and kinetics of mineralization is poorly understood (14).…”

“…Sr-rich marine barite | organic-mineral interactions | solid solution | nucleation and growth | paleoenvironments S r-bearing barite [(Ba x , Sr 1−x )SO 4 ] is an important marine authigenic mineral present in the seawater column and marine sediments (1)(2)(3)(4)(5). Marine barite formation, essential to the global cycles of organic carbon, sulfate, and oxygen, can be used to reconstruct the changes in geochemical cycles and paleoproductivity, and Sr incorporation may reflect the oceanographic conditions (2,(5)(6)(7). Despite the geochemical importance of marine (Ba x , Sr 1−x )SO 4 formation, two paradoxes still exist.…”