Biogreigites (Fe3S4) in sea water sediments and their paleohydrological applications

Abstract

Biogreigites are formed inside sulfate reducing bacteria through crystallization of a 3D nanocrys tal of Fe 3 S 4 surrounded by a liposome. Two different types of clusters of twinned ferrimagnetic structures can be found, magnetotactic and framboidal biogreigites. Biogreigites are only stable under anoxic conditions. Under oxic conditions, ferrimagnetic biogreigites (Fe 3 S 4 ) react to non magnetic pyrite (FeS 2 ) and FeOOH. We investigated gravity cores of the Black and the Marmara Sea as well as sediments of the Cretaceous/Paleo gene (K/T) fallout from the meteorite impact (~66 million years ago) at Chicxulub (Yucatan, Mexico) regarding their greigite content. The samples were analyzed by X ray diffractometry, ore microscopy, trans mission, and scanning electron microscopy. Four applications of cluster analyses of twinned nanocrystalline greigites in sediments are presented: Proof of the evidence of sulfuric acid rain, investigation of climatic cycles in the Black Sea, analysis of the evolution of water and sediment flow in a sublacustrine river valley, and deter mination of the velocity and the amount of the water transport through the Bosporus.

Ripening Kinetics of Iron Sulfides in the Presence/Absence of a Carbonyl Group

“…Due to its magnetic behavior, greigite has received a great deal of attention as a paleomagnetic proxy Thompson, 1988, 1990;Roberts, 1995;Roberts et al, 2006;Ron et al, 2007). Greigite also forms clusters or framboids of cuboctahedra (Preisinger et al, 2012); similar to the arrangement in pyrite framboids.…”