Publication Date:
2020-02-19
Description:
We constrained the origin and genetic environment of modern iron ooids (sand-sized grains with a
core and external cortex of concentric laminae) providing new tools for the interpretation of their fossil
counterparts as well as the analogous particles discovered on Mars. Here, we report an exceptional,
unique finding of a still active deposit of submillimetric iron ooids, under formation at the seabed at a
depth of 80 m over an area characterized by intense hydrothermal activity off Panarea, a volcanic island
north of Sicily (Italy). An integrated analysis, carried out by X-ray Powder Diffraction, Environmental
Scanning Electron Microscopy, X-ray Fluorescence and Raman spectroscopy reveals that Panarea ooids
are deposited at the seafloor as concentric laminae of primary goethite around existing nuclei. The
process is rapid, and driven by hydrothermal fluids as iron source. A sub-spherical, laminated structure
resulted from constant agitation and by degassing of CO2-dominated fluids through seafloor sediments.
Our investigations point the hydrothermal processes as responsible for the generation of the Panarea
ooids, which are neither diagenetic nor reworked. The presence of ooids at the seawater-sediments
interface, in fact, highlights how their development and growth is still ongoing. The proposed results
show a new process responsible for ooids formation and gain a new insight into the genesis of iron ooids
deposits that are distributed at global scale in both modern and past sediments.
Description:
Published
Description:
id 7107
Description:
6A. Geochimica per l'ambiente e geologia medica
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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