Lunchtime Seminar Schedule

Dr. Soumya Ray, University of Maryland

A combined investigation of iron and silicon isotopic compositions of achondrites: Insights into differentiation processes

August 31, 2022 at 12:00 pm (CHEM 0215)

Abstract: Meteorites provide an opportunity to reconstruct the history of our Solar System. Differentiated meteorites, also called achondrites, are the products of melting and differentiation processes on their parent body. Stable isotopic compositions of bulk differentiated meteorites and their components can add to our understanding of physical parameters such as temperature, pressure, and redox conditions relevant to differentiation on planetesimals and planets in the early Solar System. In this talk, I will discuss my work on using iron and silicon isotopic compositions of a variety of achondrites that record different degrees of differentiation and redox conditions and what they tell us about the differentiation processes that occurred on their parent bodies.
About the speaker: Dr. Soumya Ray received her Ph.D. from the School of Earth and Space Exploration at Arizona State University (ASU). At ASU, Soumya was a NASA Earth and Space Science Fellow and her research involved utilizing stable isotope compositions of meteorites as proxies for planetary differentiation processes including core formation and partial melting. She has also worked on the mechanical properties of iron meteorites and their implications for asteroid (16) Psyche. At UMD, Soumya works on the CRATER (Characterization of Regolith and Trace Economic Resources) and CORALS (Characterization of Ocean Realms And Life Signatures) orbitrap mass spectrometers.

Dr. Laura Sammon, MathWorks

MATLAB for Geosciences

September 7, 2022 at 12:00 pm (CHEM 0215)

Abstract: Accessing and visualizing data is a critical requirement for researchers trying to gain information about, and insight into, natural phenomena. However, just connecting to and processing scientific datasets can sometimes result in large hurdles and time sinks. MATLAB® has many capabilities for working with and visualizing geospatial data and other popular scientific data formats. New features make data handling and viewing much easier and require less coding. In this seminar, we will use MATAB to demonstrate how to automate your data retrieval, plotting, and analysis techniques. Along the way, we’ll show you some new (and old) tips and tricks for working with geoscience data in MATLAB, useful functions, and where to access further resources. We will wrap up by discussing how you can ensure your results are Open Access, because sharing your data is crucial to adding value to your science.
After the demonstration, MathWorkers (Laura Sammon and Evan Cosgrove) will answer questions about MATLAB and other MathWorks products, and also about their graduate school/post graduate experiences, career paths, and opportunities.
About the speaker: Dr. Laura Sammon earned her Ph.D. at the University of Maryland in the spring of 2022, and shortly after became a Customer Success Engineer for MathWorks. Her graduate research focused on Earth’s composition, especially the composition of the deep continental crust, and on neutrino geoscience. Now, as a MathWorks CSE she drives the adoption of MATLAB for Earth and ocean sciences, teaching researchers how to use MATLAB efficiently while advocating for the geoscience community’s technical needs at the company.

Dr. Emilie Dunham, University of California, Los Angeles

Using Meteorite Inclusions to Learn About the Architecture of our Solar System

September 14, 2022 at 12:00 pm (Virtual)

Abstract: Ca-Al-rich inclusions (CAIs) are the first-formed solids in the Solar System, forming 4.56 billion years ago, and act as tracers of movement in the disk. CAI populations in different chondrites are all unique with respect to CAI size, abundance, and type; my goal is to figure out why this is to constrain the dynamics in the disk at this early stage. I will present about how I doubled the number of CAIs found in inner Solar System meteorites (ordinary and enstatite chondrites) and then statistically compared their size, abundance, mineralogy, and isotope systematics, to outer Solar System meteorite CAIs. I will also talk about my 2019-2020 trip to Antarctica with the ANSMET team to search for meteorites.
About the speaker: Dr. Emilie Dunham is currently a 51 Pegasi b postdoctoral fellow jointly at UCLA and UCSC studying ancient meteorite inclusions to constrain the Jupiter gap model. She obtained her PhD from ASU in 2020 where she measured short-lived radionuclides in meteorite inclusions. She is passionate about mentoring and DEI activities to foster a welcoming scientific environment.

Dr. Brendan Anzures, Lunar and Planetary Institute/NASA Johnson Space Center

Sulfur speciation and Solubility at Very Reducing Conditions Applied to Mercury and Enstatite Chondrites

September 21, 2022 at 12:00 pm (Virtual)

Abstract: MESSENGER revealed that lavas on Mercury are enriched in sulfur (1.5-4 wt.%) compared with other terrestrial planets (<0.1 wt.%) due to high S solubility under its very low oxygen fugacity (ƒO2). To understand S solubility and speciation in reduced magmas, S K-edge XANES spectra were collected in 60 experiments that span a range of P (177 bar to 5 GPa), T (1225 to 1850 °C), and ƒO2 (IW-0.8 to IW-8.6) using new XANES standards [1] and XANES unmixing technique [2]. We find that as ƒO2 decreases from IW-2 to IW-7, S speciation in silicate melt goes through two major changes. At IW-2, FeS and FeCr2S4 species are destabilized, and CaS becomes the dominant S species with minor Na2S and MnS. At IW-4, MgS is the dominant S species with minor CaS. The S speciation changes have substantial impacts on physicochemical properties such as viscosity, melting temperature, and mineral stability, which led to Mercury’s distinct evolution.
[1] Anzures et al. (2020) Am. Min.
[2] Anzures et al. (2020) GCA.
About the speaker: Dr. Brendan Anzures (LPI/ARES postdoctoral researcher) is a planetary petrologist and geochemist with a spectroscopist twist interested in the chemical, thermal, and redox evolution of airless rocky bodies in the early solar system (Mercury, meteorites, and asteroids). He uses high-pressure, high-temperature experiments and meteorites to understand the chemical behavior of planetary materials at depth and at the surface, with a special focus on the behavior of volatiles (S, C, F, Cl, H).

Dr. Julianne Fernandez, University of Maryland

A Methane Tail of two European Cities

September 28, 2022 at 12:00 pm (CHEM 0215)

Abstract: Recent research has shown that urban methane (CH4) emissions are influenced by local utilities, especially a city’s natural gas distribution network (NGDN). National inventories, e.g. UK National Atmospheric Emission Inventory (NAEI), do not accurately represent the spatial distribution of natural gas leaks throughout a city, as estimates of emissions are averaged over an area using population density as an emission factor. Therefore, there is a need for more precise information to allow local governments and utilities to effectively prioritize activities to take on the task of mitigating CH4 emissions.
Presented here are measurements and emission quantifications of urban CH4 emissions from a western European city (London, U.K) and an eastern European city (Bucharest, Romania), which differ culturally, governmentally, and economically. Extensive mobile surveys were conducted from 2018 to 2019, measuring street-level CH4 mole fractions, ethane (C2H6), and analyzing δ13CCH4 and δ2HCH4 for additional source type determination.
Compared to other recently measured cities, both Bucharest (1832 tons CH4 yr-1) and London (~2220 tons CH4 yr-1) had greater city-wide emission rates than Paris, France, and Hamburg, Germany. Isotopes (δ13CCH4 & δ2HCH4) and ethane-methane ratios (C2:C1) were used extensively in an attempt to identify the main sources of CH4 in both cities. In Bucharest, both tracers showed the greatest emission dominance from wastewater (58%-63%), where less than half (32%– 42%) were fossil fuel, and 0-5% were pyrogenic. Source tracers for London indicated a dominance of fossil fuel emissions (86% to 91%) and the remaining emissions attributed to biogenic (7%-14%) and pyrogenic (2%) sources. These data will help local governments with emission compliance and prioritize greenhouse gas mitigation strategies.
About the speaker: Dr. Julianne M. Fernandez recently finished her Ph.D. at Royal Holloway University of London, with the Greenhouse Gas Research Laboratory in the Department of Earth Sciences. Where her research focused on source identification of methane emissions from urban cities using high-precision stable isotopic measurements coupled with mobile measurement techniques. Previously, Fernandez completed her Master's in Geology at the University of Cincinnati, where her research was centered on methane and nitrous oxide surface water emissions from Lake Erie, a eutrophic freshwater body of the North American Great Lakes. Fernandez recently joined the UMD PanoLab with James Farquhar and is continuing research in urban methane and source apportionment.

Prof. Sarah Mazza, Smith College

Solving the mystery of Bermuda: A unique volcanic history

October 5, 2022 at 12:00 pm (Virtual)

Abstract: Bermuda is an intraplate volcano found off the coast of the Carolinas in the Atlantic Ocean. New geochemical data suggest that Bermuda sampled a previously unknown mantle domain, characterized by silica undersaturated melts that have significant enrichments in incompatible elements and volatiles, and a unique, extreme isotopic signature (Mazza et al., 2019). Bermuda records the most radiogenic 206Pb/204Pb isotopes ever documented in an ocean basin (19.9-21.7), coupled with low 207Pb/204Pb (15.5-15.6) and relatively invariant Sr, Nd, and Hf isotopes, suggesting that this source must be <650 Ma.  These silica undersaturated melts are interpreted to be sourced in the transition zone, tapping a young mantle reservoir that resulted from recycling and storage of incompatible element and volatile rich material. Ongoing work explores the nature of the carbonate source for Bermuda with thin section analysis of ocelli and stable zinc isotopes.
About the speaker: Dr. Sarah Mazza did her undergrad at UNC-Chapel Hill and moved to Virginia Tech for her masters in Structural Geology. She stayed at Virginia Tech for her PhD but switched over to the 'dark-side' to study mantle geochemistry. Her research focused on understanding non-mantle plume derived intraplate volcanoes, by studying both magmatism in Virginia and Bermuda. After VT, Sarah moved to Muenster, Germany for a post-doc at the Institute for Planetology exploring stable W isotopes in arcs. She is now an Assistant Professor at Smith College in Massachusetts.

Dr. Amaury Bouyon, University of Maryland

Multiple Sulfur isotope record of Brazilian Archean sediments, challenging the homogeneity of the Archean record

October 12, 2022 at 12:00 pm (CHEM 0215)

Abstract: Multiple sulfur isotope compositions are one of the main evidence of an anoxic atmosphere prior to the Great Oxygenation Event, about 2.3 Gy ago. Most of the samples analyzed so far show a similar pattern that can be explained by the photolysis of SO2 generating sulfates with a negative D33S and elemental sulfur with a positive D33S. However no experimental or theoretical work is able to reproduce the isotopic patterns measured in the rock record. This record is also biased with around 80% of the data coming from the Kaapvaal and Pilbara cratons, making our understanding of this period quite limited.

Here we report multiples sulfur isotope measurements from an overlooked brazilian craton: the Amazonian craton. In 5 different pristine drill cores we observe various isotopic signatures ranging from classical Archean behavior to unusual isotopic data. We interpret this previously unreported signatures as an expression of photochemical processes, which could be linked with a latitudinal effect.
About the speaker: Dr. Amaury Bouyon did his masters and his PhD at IPG Paris, France. He investigated various systems including carbonatites and Archean sedimentary rocks using multiple sulfur isotopes. This aimed to understand how the mass-independent fractionations of sulfur were recorded in the Archean sediments and may have been recycled in the Earth mantle. During his PhD Amaury came to UMD on a Fulbright fellowship to work with James Farquhar. He is now an Agouron post-doc at UMD to work on coupling multiple sulfur and multiple mercury isotopes to better understand past sedimentary environments.

Carl Martin, University of Cambridge

Adventures in ULVZland: a global quest for hidden signals and taming unwieldy non-linear inversions

October 19, 2022 at 12:00 pm (CHEM 0215)

Abstract: The deep mantle hosts two antipodal Large Low Shear Velocity Provinces (LLSVPs), which sit on the core-mantle boundary (CMB) beneath Africa and the Pacific. These structures appear to extend up to 1000km height, and have a velocity reduction of up to ~4% compared to the radially averaged velocity. Ultra Low Velocity Zones (ULVZs) are even more extremal features, with Vs reduction 10--50% and Vp 5--25%, but are much smaller on the order of 10s km tall and 100s km in lateral extent. In this study, we use the S core-diffracted phase, Sdiff, which can be recorded in teleseimic events between ~100--140°. We have compiled a global dataset of over 7 million source-receiver waveforms to manually interrogate the CMB. We then develop a 2D wavefront forward model (adapted from Hauser et al, 2008) in order to perform a Bayesian inversion for the lateral velocity structure of the Hawaiian ULVZ. In this talk, we will explore the inversion methodology, the dataset (including some very-in-progress analysis), and touch upon the geochemical interpretation of a recent student on the Galapagos ULVZ (Cottaar et al, 2022).
About the speaker: Carl Martin did his undergraduate at the University of Cambridge, reading Physics at the Cavendish Laboratory via Natural Sciences. He remained in Cambridge to do his graduate studies due to Stockholm syndrome, but defected to the Earth Sciences Department. He can usually be found organising a BBQ, shouting at a computer, or having a nap on the sofa in his office. Carl is interested in gathering and mining datasets related to the core-mantle boundary, and applying them to Bayesian methods.

Dr. Nico Küter, ETH Zürich

The role of stishovite in the deep Earth water cycle

October 26, 2022 at 12:00 pm (Virtual)

Abstract: Hydrous mineral inclusions in deep diamonds as well as geophysical constraints indicate the presence of water-bearing fluids or melts in Earth’s transition zone. The sequestration of surface water by the subduction of oceanic lithosphere is considered the primary mechanism of introducing water into the transition zone. However, metamorphic breakdown reactions of water-bearing minerals along the subduction trajectory reduce the capacity of an oceanic slab to carry its hydrous load towards the lower mantle. The high-pressure SiO2 polymorph stishovite has recently been recognized as a potential water carrier with the ability to incorporate up to 3.5 wt% water. Crystallizing at >9 GPa and 450 °C, stishovite becomes a major mineral phase in metamorphosed oceanic crust and, thus, a potential sink for water released by concomitant devolatilization reactions. Stishovite stays stable over a wide range of pressures and temperatures, reaching into the transition zone and the lower mantle, thus providing a way for the deep sequestration of slab water.
The mechanism of water storage in stishovite is debated and includes the formation of hydrogarnet defects and interstitial water molecules in the mineral lattice. This talk presents an overview of previous research and discusses our recent experimental results on water speciation in hydrous stishovite. By combining X-ray diffraction, Raman, and NMR methods on partially deuterated stishovite, we find evidence for the incorporation of molecular water in the stishovite structure. Hydrogen isotope systematics further indicate that deuterium preferentially partitions into stishovite during precipitation from a coexisting silicate-saturated fluid.
About the speaker: Dr. Nico Küter is a senior researcher at the Geological Institute at ETH Zurich, Switzerland. He previously was a Postdoctoral Fellow at the Carnegie Earth and Planets Laboratory in Washington DC. In 2019, he graduated from the Institute of Geochemistry and Petrology at ETH Zurich with a PhD focusing on high-temperature carbon isotope fractionation processes.
Nico’s research focus lies on the experimental investigation of the mechanisms of light stable isotope exchange processes, ranging from high-pressure, high-temperature environments of the deep Earth to the more ambient conditions of the Earth’s surface. His current research at ETH investigates the systematics of heavy isotope clumping in natural and synthetic methane.

Dr. Quinn Shollenberger, Lawrence Livermore National Laboratory

Applications of Samarium Isotopes to Pre- and Post-detonation Nuclear Forensics

November 2, 2022 at 12:00 pm (Virtual)

Abstract: Nuclear materials found outside regulatory control are subject to forensic analyses to determine their origin and intended use. Uranium ore concentrate (UOC) is an early material in the nuclear fuel cycle and is commonly traded on the worldwide market, so diversion of this material from regulatory control is a concern to law enforcement agencies worldwide. Consequently, a major research focus of pre-detonation nuclear forensic efforts involves characterizing the chemical and isotopic signatures of UOCs in order to identify the original source of the material and to determine where it diverted from regularly control. On the other hand, post-detonation nuclear forensics research uses a range of tools to characterize the device and who was potentially responsible in the event of a nuclear blast. To this end, isotopic analyses of nuclear fallout and melt glass can reveal important details about the device and neutron energies. In this presentation, I will cover how samarium isotopes can be used as both a pre-detonation and post-detonation nuclear forensics signature.
Finally, the long-lived isotope, 147Sm decays to 143Nd with a well-known half-life of 106 Ga. In contrast, 146Sm is a short-lived isotope that decays to 142Nd with a much more poorly defined half-life. In the last section of my talk, I’ll describe our methods for measuring the half-life of 146Sm via alpha-decay counting and discuss ongoing work.
About the speaker: Dr. Quinn Shollenberger is a cosmochemist at Lawrence Livermore National Lab who uses chemical and isotopic signatures to investigate samples of meteorites and nuclear materials. Her past and current cosmochemistry research has focused on examining meteorites and their components to reconstruct the birth environment of the solar system and how the solar system evolved to its current configuration. In addition to cosmochemistry research, Quinn is making high-precision measurements of various isotopic systems in nuclear materials with applications in nuclear safeguards and deterrence efforts. In her free time, Quinn enjoys spending time outdoors and drinking a hot cup of tea.

Dr. Christian Renggli, University of Münster

Sulfur on the Moon and Mercury

November 9, 2022 at 12:00 pm (Virtual)

Abstract: The terrestrial Moon and the innermost planet Mercury share remarkable similarities. They are both very reduced planets and they lack atmospheres. At the reducing conditions the behavior of sulfur differs considerably from that on Earth, Mars, or Venus, and S occurs entirely in its reduced form. In this talk I will provide an overview of what is known about S on the Moon and Mercury, from more than 50 years of lunar sample research and observations from the recent NASA MESSENGER mission to Mercury. I will present results from experimental approaches that allow us to constrain the behavior of S at the surfaces of these two planets, in fumarolic and volcanic processes.
About the speaker: Dr. Christian Renggli is originally from Bern in Switzerland, where he obtained a Bachelor degree in Earth Sciences. He continued his studies in Munich, Germany, where he obtained a Master of Science in Geomaterials and Geochemistry with a focus on volcanology. In his PhD research at the Research School of Earth Sciences, Australian National University, he investigated the reactive behavior of SO2 in volcanic processes experimentally.
Since 2018 he is a postdoctoral researcher at the Institute for Mineralogy, University of Münster in Germany. His main research interest lies in applying experimental methods to understand high-temperature gas-solid reactions on Earth and other planetary bodies. He investigates the reaction of S-bearing gases with melts, glasses and rocks. This experimental work addresses fundamental questions of how chemical elements are mobilized and deposited in ore forming magmatic systems and in explosive volcanic eruptions, and also how surfaces of other S-rich planetary bodies, such as Mercury, are modified. Furthermore, he conducts experiments to investigate the transport of metals in volcanic gas, and how volatile elements (H, S, Cl, F and C) control the volatility, degassing behavior from silicate melts and deposition of trace metals.

Dr. Samantha Jacob, Arizona State University

Spectra and mineralogy of Mt. Sharp units explored by the Curiosity rover

November 16, 2022 at 12:00 pm (Virtual)

Abstract: The Mars Science Laboratory Curiosity rover has spent the last five years exploring layers of Mt. Sharp, a 5 km sedimentary mound near the center of Gale crater. Mt Sharp layers showcase an exciting and pivotal sequence of mineralogical transitions from phyllosilicates to Mg-sulfates and ultimately to anhydrous ferric oxides. To understand how the mineralogy of Mt. Sharp has changed, I analyzed visible to near-infrared spectra from the Mastcam instrument from Vera Rubin Ridge to the recently explored clay sulfate transition. Comparisons between Mastcam spectral parameters to quantitative mineralogy from the CheMin instrument highlighted compositional trends that are controlling variations seen in Mastcam absorption features. I also collected laboratory spectra of powered mineral mixtures to understand how common minerals such as plagioclase, pyroxene, and hematite might obscure the spectral features of phyllosilicates and Mg-sulfates. Some of the mixtures with Mg-sulfates were analyzed in a nitrogen filled glovebox to better understand the spectral characteristics of hydrated minerals under conditions more similar to present day Martian environmental conditions. These in situ rover analyses of recent Mt. Sharp units could help scientists better understand the mineralogical transitions that occurred as Mars began shifting from a planet hospitable to liquid water to the cold/dry planet it is today.
About the speaker: Dr. Samantha Jacob was born and raised in Colorado where she fell in love with space from stargazing in her backyard. She went to the University of Hawaii at Manoa for her bachelor's and masters in geology. It was during her masters that Samantha started working with the Curiosity rover team, which continues during her PhD at Arizona State University. Samantha hopes to keep working in space exploration and eventually go to space herself.

Dr. Tian Gan, University of Maryland

Lithium Isotope Evidence for a Plumeworld Ocean in the Aftermath of the Marianoan Snowball Earth

November 30, 2022 at 12:00 pm (Virtual)

Abstract: The termination of the Cryogenian Marinoan snowball Earth at ~635 Ma was followed by the global deposition of basal Ediacaran cap dolostone. It has been hypothesized that the cap dolostone was deposited from a plume of glacial meltwater that overlaid hypersaline seawater and persisted for ≥ thousand years. Here we test this hypothesis using lithium isotopes from the Ediacaran cap dolostone of the Doushantuo Formation in South China, taking advantage of the expected difference in δ7Li between meltwater and hypersaline seawater. Disparate from the homogeneity of modern seawater δ7Li, an overall decreasing δ7Li trend from inner shelf to outer shelf and slope facies is observed in the aftermath of the Marianoan Snowball event, and is best explained by mixing between two endmembers: a glacial meltwater plume with a high δ7Li value and hypersaline seawater with a low δ7Li value. Therefore, the δ7Li data support the plumeworld hypothesis that a persistent lens of glacial meltwater sat above hypersaline seawater that aged during millions of years of global glaciation.
About the speaker: Dr. Tian Gan achieved her Ph.D. at the Institute of Geochemistry Chinese Academy of Sciences. Her dissertation focused on the paleoenvironment of Cryogenian Marinoan deglaciation. Now as a post-doc with Alan Jay Kaufman, she studies the life-environment co-evolution at the start and end of the Neoproterozoic Era (c.a. 1,000 and 538 Ma, respectively) using lithium and uranium isotopes.

Dr. Natasha Almeida, The Natural History Museum, London

The Natural History Museum Meteorite Collection - past, present & future

December 7, 2022 at 12:00 pm (Virtual)

Abstract: Since the first meteorite was acquired in 1776, the Natural History Museum has developed and researched a collection of meteorites, which now stands at 5000 specimens representing 2000 individual meteorites, including 700 observed falls. I will give a whistle-stop tour through the history of meteoritics, focusing on the museum, including key players and notable acquisitions as well as some of the stories of British meteorites. I will speak to the importance of curation and present how curatorial practices have developed, focusing on the case of the most recent British fall, Winchcombe – one of the best observed and most pristine chondrites yet.
About the speaker: As the Curator of Meteorites at the Natural History Museum, Dr. Almeida is responsible for conserving, developing and providing access to the national collection of meteorites and impactites. Her background is in Planetary Science and Museum Studies, and she has spent 13 years at the NHM in a variety of roles across science and public engagement. Her research has focused on the use of X-ray computed tomography as a tool for exploring extraterrestrial material, which has enabled her to work with a diverse set of specimens, including most meteorite groups, micrometeorites, Apollo and Ryugu samples.

The coordinator for the Colloquium Series is Dr. Jan Hellmann. You can contact him at hellmann [at] umd [dot] edu.