Mixing between cold, oxygenated seawater and hot, anoxic hydrothermal vent fluids induce the formation and/or precipitation of (nano)mineral phases. Using the NanoEarth Facility at Virginia Tech, we demonstrate the occurrence and/or formation of a wide variety of chemical constituents as nano and submicron mineral phases in the mixing zone (first 1-2 meters from the vent orifice) between high-temperature hydrothermal fluids and ambient seawater and in diffuse flow waters at the 9° 50¢ N East Pacific Rise hydrothermal fields. Phases include pyrite, chalcopyrite, sphalerite, wurtzite, graphite, and silicates containing Mg and Fe (kaolinite, Fe-rich mica, and talc/lizardite). We find that silicate (nano)particles are ubiquitous in sampled fluids and are a previously undocumented source of Fe to the global ocean. Particle size and uniformity, in addition to the inclusion of Mg, suggests that these (nano)particles form from solution in rapid reverse weathering reactions rather than representing pieces of basement rock or chimneys entrained into the flow. The formation of hydrothermal silicates may be more widespread than previously documented and have an impact on the ocean’s Si, Fe, and other element budgets. Thus, both nanoparticulate pyrite and metal-bearing (alumino)silicate phases can transport away from vent sites, and act as a source of Fe and other metals to the global ocean. In addition to SEM/EDS and TEM/EDS data, selected area electron diffraction patterns confirm the identity of these (nano)mineral phases. We define nanoparticles in the size range from 20-200 nm based upon filtering with 200 nm filters. Filters also trap these nanoparticles as they co-occur and aggregate during filtration indicating that ICP-MS data underdetermine the concentration of these nanoparticles as “dissolved” species. Analytical methods commonly used for determining DOC and POC indicate that graphite is measureable as DOC and POC. ICP-MS data suggest that, for Fe, nano-silicate particles may be more prevalent than nano-sulfides. 

Myriad (nano)particulate phases emanating from hydrothermal vent and diffuse flow fluids fertilize the ocean

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.