The mechanism of pyrite formation: Implications for metal mobility during iron-sulfide transformations
EMSL Project ID
50248
Abstract
Sulfidic sediments are a key sink for many potentially toxic trace elements in marine settings, with much of these elements ultimately being concentrated into the mineral pyrite. Pyrite can be an effective store for these elements because it is relatively stable and does not readily oxidize unless redox conditions change significantly. However, less stable pyrite precursor minerals may be more susceptible to re-dissolution and thus may be more at risk than pyrite for potential release of toxic trace elements when sediments are disturbed. The presence of pyrite precursors has long been argued to be an important part of pyrite formation. However, mineralogical analyses are rarely done to identify these species so their importance in marine pyrite formation is still unclear. We seek Mossbauer and XRD analyses at EMSL to determine the mineralogy of these species, if present. We will take samples from 4 different sediment cores from different redox environments: euxinically deposited sediments from Effingham Inlet, BC; oxically deposited sediments from the FOAM site in Long Island Sound, seasonally euxinically deposited sediments from Saanich Inlet, and contaminated oxically deposited sediments from the Derwent Estuary, Tasmania. In addition to the detailed mineralogical analyses that will be completed at EMSL we will also complete complementary analyses in our lab at UCR. Pore waters and bulk sediments will be analyzed for major and trace elements, total organic C, total inorganic C, and total S, Fe speciation (sequential extractions that yield total Fe, Fe oxides, magnetite Fe, pyrite Fe, and carbonate Fe), acid volatile sulfur (AVS) and chromium reducible sulfur (CRS; pyrite sulfur) will extracted and analyzed for S isotope ratios, and pyrite framboids will also be removed from the samples, mounted in epoxy, and examined using SEM. These data, coupled with the detailed Fe mineralogy obtained at EMSL will give unprecedented understanding of the role of meta-stable Fe species in marine sediments and how the effect the S cycle and ultimate fate of potentially toxic trace elements in marine sediments.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2018-10-01
End Date
2021-03-31
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members