James W.
Dottin, IIIHe/His
James Dottin is a geochemist who focuses on measuring and evaluating the causes of sulfur isotope variations in Ocean Island Basalts (OIBs), Martian meteorites, pallasite meteorites, lunar basalts, and lunar soils. Dottin's overall goal of his research is to understand how sulfur is processed on various solar system bodies through constraints on the dynamic interplay between sulfur and other volatiles that are cycled through planetary atmospheres, crustal components, and planetary interiors.
At EPL, Dottin works with Staff Scientist Dr. Steve Shirey and EPL Director Dr. Mike Walter to trace the potential global distribution and interaction of recycled protoliths in HIMU mantle reservoirs through sulfur isotope measurements of key HIMU basalts and sulfide inclusions in superdeep diamonds.
CV
- Ph.D. in Geology, University of Maryland, 2020
- M.Sc. in Geology, University of Maryland, 2016
- B.A. in Earth and Environmental Science, Wesleyan University, 2013
- NSF-EAR Postdoctoral Fellowship (January 1, 2022 – December 31, 2023)
- Deans Fellowship, University of Maryland (2019)
- Carl Storm Underrepresented Minority Fellowship (2019)
- Geochemical Society Travel Grant (2018)
- NASA Travel Grant (2016)
- Ronald E. McNair Graduate Student Fellowship, University of Maryland (2013)
- Deans Fellowship, University of Maryland (2013)
- Ronald E. McNair Undergraduate Fellow, Wesleyan University (2012)
Research
Dottin's Ph.D. dissertation research was focused on determining the sulfur isotope composition of various mantle reservoirs that are sampled by mantle plumes. For his dissertation, he made bulk sulfur isotope measurements on sulfide inclusions in mineral separates from Mangaia (a type locality for HIMU) and whole rocks from the Samoan islands (the type locality for EM II).
With the high precision analyses, he was able to identify distinct sulfur sources that contributed to the respective plumes.
A portion of Dottin's research is grounded in studying the S-isotope composition of early formed meteorites to understand the nature of sulfur in the primitive solar system.
Questions of interest include: Where in the solar system did the sulfur form? How has it been processed before planetary accretion? How has it been processed post-planetary accretion? Can we use sulfur to link meteorite groups to specific parent bodies in the solar system?
His work published on the S-isotope composition of Main Group Pallasites (assumed representatives of the core-mantle boundary of differentiated meteorites) shows that Pallasites host sulfur that has been mass-independently fractionationed in the early solar nebula and incorporated into the interior of the parent body. Furthermore, he shows that the S-isotope signal is similar to that of IIIAB iron meteorites, further supporting a genetic link between the two meteorite groups.
Dottin's Mar's research focuses on the dynamic interplay between sulfur in the Martian atmosphere, surface, and subsurface.
His Master's thesis focused on the S-isotope composition of paired Nakhlites (MIL090030/32/136). These Nakhlites are highly oxidized, showing evidence of late-stage intercumulus, skeletal magnetite grains, and sulfides. The S-isotope compositions of the intercumulus sulfides collected via Secondary Ion Mass Spectrometry (SIMS) reveal a fractionated atmospheric signal from an assumed sulfate precursor.
Through modal analysis, he determined that the amount of Titano-magnetite and sulfide can account for the highly oxidized state of the meteorites through a process of assimilation of 10’s of centimeters of Martian sediment with sulfate by overriding lava and subsequent sulfate reduction that penetrates ~1 m into the flow from the surface.
James Dottin has also worked on Lunar materials returned by the Apollo missions with the goal of using S isotope measurements to determine the S cycling history on the moon throughout its evolution. In their recent publication, Dottin et al. (2022) demonstrate the first unambiguous evidence of mass-independent fractionation on the moon that occurred during lunar gardening events.
Dottin et al. (2022) hypothesize that when micrometeorites bombard the lunar surface, sulfur is released as a gas and undergoes photochemical reactions with UV from the sun. Subsequently, that sulfur condenses as sulfur-rich silicate vapor coatings on soil grain exteriors.