Nanoparticulate Apatite and Greenalite In The Oldest, Well-preserved Hydrothermal Vent Precipitates
Paleoarchean jaspilites are used to track ancient ocean chemistry and photoautotrophy because they contain hematite interpreted to have formed following biological oxidation of vent-derived Fe(II) and seawater P-scavenging.
However, recent studies have triggered debate about ancient seawater Fe and P deposition. Here, we report greenalite and fluorapatite (FAP) nanoparticles in the oldest, well-preserved jaspilites from the ~3.5-billion-year Dresser Formation, Pilbara Craton, Australia.
We argue that both phases are vent plume particles, whereas coexisting hematite is linked to secondary oxidation. Geochemical modeling predicts that hydrothermal alteration of seafloor basalts by anoxic, sulfate-free seawater releases Fe(II) and P that simultaneously precipitate as greenalite and FAP upon venting.
The formation, transport, and preservation of FAP nanoparticles indicate that seawater P concentrations were ≥1 to 2 orders of magnitude higher than in modern deepwater.
We speculate that Archean seafloor vents were nanoparticle “factories” that, on prebiotic Earth, produced countless Fe(II)- and P-rich templates available for catalysis and biosynthesis.
Locality map and stratigraphic column, North Pole Dome. (A) Simplified geological map of the North Pole Dome area. PDP, Pilbara Drilling Project. (B) Map of the eastern flank of the dome showing the location of stratigraphic sections and samples. (C) Simplified stratigraphic column. Fm, formation. (D) Stratigraphic columns for sections H and J of Buick (20) showing location of jaspilitic cherts (UWA100624 and UWA100625) and thinly laminated chert (UWA100641). — Science Advances
Optical and electron microscope images of jaspilite from Dresser Formation (UWA100625). (A) Hand specimen of jaspilite from section J. (B) Polished thin section of jaspilite showing hematite-rich chert and hematite-poor chert. (C) PPL image of jaspilitic chert with polygonal pattern. (D) PPL image showing location of focused ion beam (FIB) pit from jaspilitic chert. (E) Backscattered electron image of jaspilitic chert showing abundant minute particles, including platy laths (circled). HV, high voltage. (F) High-angle annular dark-field (HAADF) scanning TEM (STEM) image of FIB foil (D) showing abundant greenalite laths (gre) and equant hematite (white) in chert cement. (G) STEM-EDS iron element map. Mag, magnification. (H) Bright-field TEM image of greenalite (gre) nanoparticles in chert from foil cut by FIB. (I) High-resolution TEM image of greenalite particle with characteristic structural modulations. (J) TEM–EDS spectra from greenalite nanoparticle in FIB foil of greenalite-rich chert. — Science Advances
Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates, PubMed
Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates, Science Advances
Astrobiology, paleontology,
