Distribution of Microfossils Within Polymetallic Nodules: Biogenic Clusters Within Manganese Layers

Abstract

Biomineralization is the process by which living organisms or organic matrices produced by them initiate and structure deposition of inorganic polymers/minerals. Deep-sea polymetallic nodules and crusts have recently been recognized as biominerals that are formed around bio-seeds; these deposits are of economic value. A detailed understanding of their formation will contribute to their sustainable exploitation in the future. Polymetallic nodules grow concentrically around discrete nuclei that have recently been described as bio-seeds formed from microorganisms, diatoms, or coccoliths. In the present study, polymetallic nodules from the Clarion-Clipperton Zone have been analyzed. It is described that the approximately 5-cm large polymetallic nodules are composed of micronodules (size of 100-450 μm) that aggregated to nests (2-3 mm). High-resolution scanning electron microscopy (HR-SEM) and high-resolution energy dispersive X-ray (HR-EDX) spectroscopic analyses revealed that the micronodules are composed of discrete layers of Mn and Fe. Imprints of microorganisms/microbe-like assemblies are found in the Mn-rich regions of the micronodules. HR-SEM/EDX analyses confirmed that these microorganisms are surrounded by a Mn-rich environment. These findings strongly suggest that those organisms acted as bio-seeds that allowed the deposition of Mn(IV) minerals which in turn helped Fe minerals to associate. Hence, these data support the concept that the growth of the polymetallic nodules starts as a biomineral and is completed by genuine mineralic depositions. It is expected that these data will contribute to the development of strategies for a sustainable exploitation of the polymetallic nodules.

Manganese: A New Emerging Contaminant in the Environment

“…Manganese oxides are present on the ocean floor as concretions, crusts and fine disseminations in sediments. It is well known, for example, that the soft bottom sediments of the oceans are particularly rich in manganese aggregates in the form of nodules (Bonatti & Nayudu, 1965;Wang et al, 2011).…”

Smectitization as a Trigger of Bacterially Mediated Mn-Fe Micronodule Generation in Felsic Glass (Livno-Tomislavgrad Paleolake, Bosnia and Herzegovina)

“…Chemical data were used as oxide percentages and were normalized to 100%. The NIST DTSA-II software package (NIST, Gaithersburg, MD, USA) [49] was used to quantify EDS spectra from literature when no chemical data was provided [50,51]. Table 1.…”

“…Another set of evidences of microbially generated Mn-Fe mineralization is their MnO/FeO ratio (Table 1). Wang et al (2012) [51] have shown that the portion of Mn-Fe micronodules consistent with bacterial morphologies (i.e., fossilized cocci) is marked by a strong increase in MnO/FeO relative to the rest of micronodules devoid of typical bacterial forms (i.e., banding). Furthermore, the microbial encrustations described here display a 3-fold decrease in FeO relative to the banding (~15 to 5 wt.%, Table 1.)…”

“…Considering the comparable shapes and sizes, as well as the proximity to the hollow cocci spheres, Thorseth et al (2003) [50] hypothesized that the observed spheres originated from fossilized cocci whose subsequent burial and infilling by inorganic precipitation obliterated their original organic content. The aggregations of 1 to 3 µm sized cocci spheres have become increasingly important in the identification of Mn-Fe mineralization present across the vastly different depositional environments, such as Mn nodules from the Clarion-Clipperton Fracture Zone (CCFZ) of the Eastern Pacific, as well as desert varnishes from the Gangdese region in Tibet, PRC [51,68,102]. In the former, the micronodules are characterized by the surfaces accommodating numerous cocci whose relatively high C content is taken as a proof of their biogenicity.…”

Jurassic Non-Carbonate Microbialites from the Betic-Rifian Cordillera (Tethys Western End): Textures, Mineralogy, and Environmental Reconstruction

“…However, other types of non-carbonate rocks are also organo-sedimentary deposits, resulting from different processes of BMC. There are examples related to iron oxides and oxyhydroxides [6,7], manganese oxides [8][9][10], phosphates [11][12][13], sulfates [14][15][16][17], and silicates [18]. Some of these examples are related to extremophile microbes [16,19,20], and they hold great interest for the study of the origin of life [21][22][23] and for astrobiology [24][25][26].…”