Microbial biomineralization of iron seepage water: Implication for the iron ores formation in intertidal zone of Zhoushan Archipelago, East China Sea

Abstract

The biogeochemcical reactions responsible for fossilized minerals preservation in ancient geological conditions are very often debatable, because little is known about the in situ processes at geo-historical period. In the present study, we describe the formation of iron ores collected in the intertidal zone of the Zhujiajian Island, Zhoushan Archipelago in the East China Sea. Morphological, mineralogical and geochemical analyses were performed on the iron ores and the surrounding geological materials. The results show that the iron ores, composed of spherical ferrihydrite and fibrous aggregates of goethite, presented morphological characteristics reminiscent of bacterial activity. The biominerization process in the seepage system is believed to represent an analogue mechanism for the biogenic formation of iron ores. The degradation of the ancient wood layer provided humic substances which accelerated the leaching process of iron from the surrounding bedrock and soils. The abundant leaching iron not only provided the sufficient iron material source, but also created the ideal conditions for the survival of the iron-oxidizing bacteria. The presence of Leptothrix-like sheaths and Gallionella-like stalks in the present-day seepage environment promoted the oxidization of Fe 2+ to Fe 3+ and the rapid precipitation of bacteriogenic iron oxides (BIOS) on bacterial sheaths and stalks, allowing the preservation of the morphological characteristics of the bacteria. As time went by, the amorphous biomineralization product (ferrihydrite) can further transfer to more crystalline goethite and therefore be preserved in the ores permanently, representing as the imprints of bacterial activity during the formation of iron ores. The present findings should help elucidate the role of bacteria in the formation of biogenic iron ores in different environments during geo-historical context.

Formation and release behavior of iron corrosion products under the influence of bacterial communities in a simulated water distribution system

“…Freshly formed amorphous biomineralization products can further transfer to more crystalline a-FeOOH. 40 Moreover, IOB can induce ferric hydroxide precipitation as a secondary by-product, and the ferric hydroxide may then serve as a precursor for more stable iron oxides, such as aFeOOH. 11 Some species belonging to the genus Acidovorax (such as Acidovorax sp.…”

Cool water geyser travertine: Crystal Geyser, Utah, USA

“…Sheaths that have been shed will flocculate and settle. Iron precipitates attached to the sheath can then act as nucleation sites on which other precipitates can be deposited (Wu et al, 2009), either with more iron or with a carbonate crust in the case of Crystal Geyser. Heavily mineralized filaments may merge together in a mucilaginous mat upon flocculation, similar to the goethiteencrusted mats described by Hofmann & Farmer (2000).…”

Microscale Characterization and Trace Element Distribution in Bacteriogenic Ferromanganese Coatings on Sand Grains from an Intertidal Zone of the East China Sea

“…Previous studies conducted by our group revealed that because of the fermentation of ancient woods, acidic pH (pH = 2.60), low oxygen content (DO = 2.19 mg/L), and reducing (Eh = -148.8 mV) seepage water significantly accelerated the release of Fe and Mn from bedrocks into the intertidal zone [ 33 ]. Fresh bacteriogenic oxides (BIOS) were present near the ancient wood layer characterized by very high contents of Fe (41.54%) and Mn (0.51%), which were 7–25 and 17–25.5 times higher than those of weathering bedrocks [ 33 – 35 ]. Iron-oxidizing bacteria, such as Leptothrix -like sheaths and Gallionella -like stalks, were abundant in BIOS, and played important roles in Fe biomineralization in the present study site [ 35 ].…”