- End of an era – Part 2
Boy, is there a lot of room in the mass spec lab…. Today, the Micromass IsoProbe left the building, purchased by a scientific company for parts. A bit shocking how much space that instrument took. But, now there is plenty of room for a new quad mass spec, to be delivered later this year.
Posted 5 February 2019
- End of an era
Today, Brian threw the power switch to “off” on the Micromass IsoProbe, our first MC-ICP-MS, installed in 1999. This instrument has produced about a quarter-of-a-million isotope analyses and was responsible for pushing our Fe isotope program in the early 2000’s, and, most recently, was used to develop the K isotope system. But, with changes in technology, this instrument is now obsolete, so we decided it was time to de-commission it. A new instrument will be installed in its placed in the coming year (more on that later).
Posted 30 October 2018
- Astrobiology research in South Africa highlighted by University
As part of the “Origins” project, astrobiology research by the ICP-TIMS lab is highlighted in the current issue of the College of Letters & Science newsletter. Link here.
Posted 12 October 2018
- Randy Williams’ new paper pushes lab to #200
Former Ph.D. student Randy Williams continued his work on using radiogenic isotopes to trace fluid flow in the modern Rio Grande Rift fault system, this time adding Pb isotopes to the mix, with a new accepted paper in Journal of Structural Geology. Combining Pb, Sr, and U-series work allowed Randy to correlate fluid flow with earthquake patterns, as well a tease out possible contributions from the Socorro magma body. And, this paper marks paper #200 for the lab (see publication list).
Posted 29 July 2018
- Former student Ron Schott passed away
Last week we learned the sad news that Ron Schott, who obtained his M.S. and Ph.D. from the group in the 1990’s, passed away. Ron did isotopic (O, Sr, Nd, and Pb) and U-Pb zircon studies of the Late Cretaceous to Paleocene Gualala Basin, California. After leaving UW-Madison, Ron went on to have a very large impact in online geo education. A nice memorial was posted on the AGU blog site.
Posted 5 June 2018
- Several new papers posted
Former Ph.D. student Erik Haroldson published a paper in GSA Bulletin on Pb isotope studies of gold mineralization in NE Wisconsin, showing that fluid flow was very young, MVT age (see paper #196 in publication list). Current Ph.D. student Nick Levitt published a large experimental paper calibrating the clumped isotope geothermometer, which involved using Ca-spike seed crystals (see paper #197 in publication list). Former post-doc Andy Czaja published a paper on the Neoarchean Weld Range BIF that was done in the lab (paper #198 in publication list).
Posted 1 June 2018
- New faculty member to lead the ICP-TIMS lab
Prof. Clark Johnson will step down sometime in the next few years, and Dr. Annie Bauer will join the department as an Assistant Professor, officially starting in August 2019. Dr. Bauer has interests in geochronology of early Archean rocks, crust-mantle evolution, and redox evolution of surface environments of the Precambrian. She will join Dr. Brian Beard in leading the ICP-TIMS lab into new research directions, as well as continuing on-going lines of research. As part of Dr. Bauer’s arrival, the lab will expand a bit and add new instrumentation.
Posted 14 May 2018
- UW-Madison highlights lab research thru its “Origins” Project
University Communications and University Marketing divisions of UW-Madison have assembled a web site and documentary film that explores our origins from a variety of perspectives. The ICP-TIMS research on the early Earth geologic record is highlighted. Link can be found here.
Posted 23 April 2018
- Farewell to Aaron Satkoski
Post-doc/Assistant Scientist Aaron Satoski has moved to UT-Austin, where he will take up a Research Scientist position in the isotope geochemistry group. Aaron works on a number of projects in Archean geology, meteorites, and even Au mineralization in Wisconsin. We wish him well in his new endeavors!
Posted 5 January 2018
- New paper on laser ablation
Post-doc/Assistant Scientist published a paper in the Journal of Analytical and Atomic Spectroscopy that shows a head-to-head comparison between femtosecond and nanosecond laser ablation. JAAS chose this article for its cover. See paper #195 in publication list.
Posted 31 December 2017
- New paper on potassium stable isotopes
Former post-doc Weiqiang Li published a paper with Brian Beard on stable K isotopes. Development of this new isotope system is aimed at tracing weathering processes. Published in Geochimica. See paper #194 in publication list.
Posted 14 August 2017
- Mini-review on iron formations
Clark Johnson published a mini-review of iron formations aa part of the new Encyclopedia of Geochemistry published by Springer. See paper #193 in publication list.
Posted 30 July 2017
- New large review paper on iron formations
Clark Johnson anchors the authorship list of a new large review of iron formations (Konhauser et al., paper #192 in publication list). Clark’s contributions focused on the isotopic story of iron formations, from the sources of Fe (benthic Fe shuttle, hydrothermal) to Fe(II)aq oxidation to microbial diagenetic transformations (dissimilatory iron reduction). The author list includes those who have fallen on different sides of the story on iron formations, and where we could not agree, the alternative views on IFs are noted. Published in Earth Science Reviews.
Posted 14 July 2017
- New paper on the role of microbial processes in 2.9 Ga granular iron formations (GIFs)
Former post-doc Andy Czaja, along with long-standing colleagues in South Africa, have published a paper in Geobiology on the oncoidal GIFs from the Mesoarchean Pongola Supergroup, southern Africa. The work documents the oldest known GIF, whose domical structures and related iron oxides are interpreted to record microbial iron oxidation in shallow marine conditions. The Fe isotope results indicate partial oxidation under oxygen-limited conditions. See paper #191 in publication list.
Posted 14 July 2017
- New paper on lacustrine deposits of the Green River Formation
Former Ph.D. student M’bark Baddouh published a paper in the Journal of Sedimentary Research on chronostratigraphic correlations using 87Sr/86Sr ratios in lacustrine deposits of the Green River Formation. He finds clear correlations between Sr isotope compositions, lake levels, and deposition of organic matter, highlighting this approach as a useful correlation tool. See paper #190 in publication list.
Posted 14 July 2017
- New paper on the the timescales of Crater Lake magma chamber
Former Ph.D. student Meagan Ankney published a new paper in Geochimica that uses U-Th isotopes and SIMS oxygen isotope measurements on partially melted granitoid blocks from the climactic eruption at Crater Lake. She finds that assimilation and melting occurred over very short timescales immediately before the caldera-forming eruption. See paper #189 in publication list.
Posted 14 July 2017
- New paper on the start of plate tectonics and evolution of seawater
Post-doc Aaron Satkoski published a new paper in Geochimica that builds on his earlier study of the Sr isotope evolution of Archean seawater, this time with a focus on 2.8-3.0 Ga carbonate sequences in Canada. This work provides clear evidence for emergent and evolved continental crust throughout the Archean. See paper #188 in publication list.
Posted 11 May 2017
- New paper on Laguna del Maule
Ph.D. student Nathan Andersen published a new paper in Journal of Petrology that includes U-Th and Sr and Pb isotopes obtained in the lab on Laguna del Maule, an “active” volcanic center that has undergone dramatic recent uplift. See paper #187 in publication list.
Posted 7 April 2017
- New paper comparing femtosecond and nanosecond lasers for in situ isotopic analysis
A common question we get is: “Are femtosecond lasers worth it relative to much less expensive nanosecond lasers?”. A new paper from the group answers this question. See paper #186 in publication list.
Posted 11 February 2017
- New paper on Mars meteorites
Brian Beard, along with post-doc Aaron Satkoski, published a paper on Mars meteorites, in collaboration with former Ph.D. student Tom Lapen at the University of Houston. See press release here. See paper #185 in publication list.
Posted 1 February 2017
- Fall AGU meeting
Post-doc Xinyuan Zheng presents an abstract entitled “Silicon isotope fractionations in pure Si and Fe-Si systems and their geological implications”.
Posted 19 December 2016
- New paper published on the Greenland ice sheet
Former faculty member Anders Carlson, and former post-doc Alberto Reyes, along with Brian Beard and other scientists, published, in Earth and Planetary Science Letters, the results of a Sr, Nd, and Pb isotope study that documents interglacial responses of the southern Greenland ice sheet over the last 430,000 years. See Publications page (paper #183).
Posted 15 November 2016
- Life in ancient oceans enabled by erosion from land
Posted 7 November 2016
- Terrestrial rocks enable ancient life in oceans
Post-doc Aaron Satkoski provides a radio interview to WORT FM on his work on the Sr isotope compositon of the Archean oceans, which indicates a large continental weathering flux.
Posted 3 October 2016
- Group presents at Annual GSA Meeting
Haroldson, E, Beard, B, Satkoski, A, Johnson, C, and Brown, P (2016) Phanerozoic Au in Paleoproterozoic Cu vein deposit of central Wisconsin: Evidence from Pb isotopes using LA-ICP-MS.
Baddouh, M, Carroll, AR, Beard, BL, and Johnson, CM (2016) Lake-Margin Carbonate δ18O, δ13C, and 87Sr/86Sr, Northern Bridger Basin Eocene Green River Formation, Wyoming.
Jagniecki, E, Lowenstein, TK, Demico, RV, Baddouh, M, Carroll, AR, Beard, BL, and Johnson, CM (2016) Paleohydrology of Spring Deposits in the Wilkins Peak Member of the Eocene Green River Formation, Bridger Basin, WY.
Posted 27 September 2016
- New post-doc Piyali Chanda joins group
Fresh from her Ph.D. at Penn State, new post-doc Piyali Chanda joins the group, where she will work on Mg, Fe, and Si isotopes in experimental systems on carbonates and Fe-bearing cherts, as well as applications to the Archean rock record.
Posted 1 September 2016
- New paper published on Sr isotopes in 3.26 Ga marine sediments
Current post-doc Aaron Satkoski published a new paper in Earth and Planetary Science Letters that documents a much more radiogenic Sr isotope composition for early Archean seawater than previously thought, which indicates that significantly greater continental crust existed, and was emergent, in the early Archean than previous studies indicated. See Publications page (paper #182).
Posted 1 September 2016
- Breana Hashman finishes M.S. degree
M.S. student Breana Hashman completed her degree, entitled “A Mesoarchean microbial iron shuttle, Witwatersrand Basin, South Africa”.
Posted 30 August 2016
- New paper published on biological fractionation of Si isotopes
Former M.S. student Thiru Reddy’s paper on biological fractionation of Si isotopes was published in Geochimica et Cosmochimica Acta, where she documents the largest yet determined Si isotope fractionation during biological reduction of Fe(III)-Si gels. See Publications page (paper #181).
Posted 15 Aug 2016
- Group collects Archean samples in Australia and South Africa
Post-doc Aaron Satkoski and Clark Johnson worked in the Pilbara craton of South Africa, in collaboration with Martin Van Kranendonk, in July. In August, they traveled to South Africa where Ph.D. student Kick Levitt joined for field work and core sampling of the Campbellrand sequence (in collaboration with Nic Beukes) and the Barberton Greenstone Belt (in collaboration with Christoph Huebeck).
Posted 10 Aug 2016
- New paper published on Si isotopes in abiologic experiments
Post-doc Xinuan Zheng a new paper in Geochimica et Cosmochimica Acta that outlines the result of a large experimental program on Si isotope fractionations in Fe-Si gel systems, which document very large Si isotope variations as compared to pure silica systems. See Publications page (paper #180).
Posted 15 July 2016
- European workshop on laser ablation, Slovenia
Post-doc Xinuan Zheng presents a talk at the European workshop on laser ablation, Slovenia entitled “Contrasting sizes and Fe isotope compositions of particles produced by ns- and fs-laser ablation of natural Fe minerals”.
Posted 15 July 2016
- Australasia Astrobiology Conference, Perth
Post-doc Aaron Satkoski presented a talked entitled “The link between continental evolution and biological evolution”.
Posted 10 July 2016
- Visit to Monash University
Clark Johnson visited former post-doc Andrew Frierdich at Monash University, Melbourne, and presented a talk entitled “Evolution of the Archean Biosphere as Seen through Isotope Geochemistry”
Posted 8 July 2016
- New paper published on Fe isotopes in clays
Graduate student Bin Shi, from Waterloo University (advised by formed post-doc Lingling Wu) published a new paper in Environmental Science and Technology that documents large stable Fe isotope variations in clays that are determined by a finite bioavailable Fe pool during structural Fe(III) reduction. See Publications page (paper #179).
Posted 3 July 2016
- Australian Earth Sciences Conference, Adelaid
Former post-doc Andrew Frierdich, along with Madison and Iowa researchers, presented a paper “New Pathways for Isotopic Fractionation during Iron Redox Cycling” at the Australian Earth Sciences Conference in Adelaid.
Posted 30 June 2016
- New paper published on Sr isotopes in the Green River Basin
Former Ph.D. student M’Bark Baddough published a new paper in Earth and Planetary Science Letters that uses 87Sr/86Sr ratios in the lacustrine sediments of the Green River Basin as a tracer to reconstruct Milankovitch forcing of the Eocene hydrologic cycle. See Publications page (paper #178).
Posted 15 June 2016
- Thiru Reddy finishes M.S. degree
M.S. student Thiru Reddy completed her degree, entitled “Si isotope variations in the Precambrian rock record explained through experimental studies and development of new methods on femtosecond laser ablation for in situ Si analysis”.
May 30, 2016
- New paper published on Fe cycling in Yellowstone
Ph.D. student Nathan Fortney, along with colleagues at UW-Madison and MSU, published a new paper in Geobiology that investigates the role of microbial Fe(III) reduction in Chocolate Pots hot spring, Yellowstone National Park. See Publications page (paper #177).
Posted 1 May 2016
- Clark Johnson presents lecture on Astrobiology at Nanjing University
Clark Johnson presented an overview of the field of astrobiology, with a specific application to evolution of the biosphere in the Archean.
Posted April 1, 2016
- Clark Johnson presents short course at Nanjing University
As part of his sabbatical visit to the Nanjing University, hosted by former post-doc Weiqiang Li, Clark Johnson presented five-day short course on stable isotope geochemistry (ten hours).
Posted March 30, 2016
- Clark Johnson presents short course at University of Auckland
As part of his sabbatical visit to the University of Auckland, Clark Johnson presented a one day short course on stable isotope geochemistry (five hours).
Posted 15 March 2016
- New paper published on potassium isotope analysis
Former post-doc Weiqiang Li, along with Brian Beard, published a new paper in the Journal of Analytical Atomic Spectroscopy that outlines the development work the lab has done in establishing stable potassium isotope analysis. See Publications page (paper #176).
Posted 16 February 2016
- New paper published combining Os and Th isotopes at Crater Lake
Former Ph.D. student Meagan Ankney published a new paper in Earth and Planetary Science Letters based on work in the lab and at Carnegie-DTM, combining Os and Th isotopes to investigate the role of young lower crust during the magmatic evolution of Mt. Mama (Crater Lake) in the Cascade arc. See Publications page (paper #175).
Posted 15 January 2016
- Lab group presents research results at Fall AGU meeting
Liu, K, Wu, L, Shi, B, Smeaton, C, Li, W, Beard, BL, Johnson, CM, Roden, EE, and Van Cappellen, P (2015) Iron Isotope Fractionation Reveals Structural Change upon Microbial and Chemical Reduction of Nontronite NAu-1.
Shi, B, Wu, L, Liu, K, Smeaton, C, Li, W, Beard, BL, Johnson, CM, Roden, EE, and Van Cappellen, P (2015) Importance of Tetrahedral Iron during Microbial Reduction of Clay Mineral NAu-2.
Satkoski, A, Fralick, P, Beard, B, and Johnson, C (2015) 87Sr/86Sr Ratios in Carbonate From the Red Lake and Steep Rock Groups in Canada Suggest Rb-enriched Continental Crust was Influencing Seawater Chemistry Prior to 3.0 Ga.
Li, W, Beard, B, and Johnson, C (2015) Identification of biologically recycled continental materials in banded iron formations.
Posted 16 December 2015
- Clark Johnson gives NASA Director’s Seminar
A joint seminar was given by Clark Johnson and Loren Williams (Georgia Tech) entitled “Ironing out the Universe and Life”. Information on this virtual seminar can be found here. The archived video can be found here (Adobe Connect).
Posted 13 Novermber 2015
- Randy Williams presents his isotope research at the GSA Annual Meeting
Williams, RT, Goodwin, LB, Mozley, PS, Beard, BL, Johnson, CM, and Huntington, KW (2015) Tectonic controls of fault-zone flow pathways in the Rio Grande Rift: Insights from C, O, Sr, and clumped isotope analyses of syntectonic calcite cement.
Posted 4 November 2015
- Clark Johnson’s talk at University Colorado blogged on STEPPE Newsletter
“Using Geology to Put Time Stamps on the Tree of Life” article on Clark’s talk by STEPPE blogger Zoe Gentes, can be found here.
Posted 16 October 2015
- New EPSL paper on origin of oxygenic photosynthesis highlighted in press release
Further coverage of Aaron Satkoski’s paper that suggests oxygenic photosynthesis arose prior to 3.2 b.y. ago can be found in this press release from UW-Madison News.
Posted 7 October 2015
- An ancient iron world
Clark Johnson talks about an ancient iron world for Wednesday Nite at the Lab at UW-Madison. Link to video can be found here.
Posted 7 October 2015
- Nick Levitt awarded research grant from the Geological Society of America
Nick Levitt was selected to receive a 2015 GSA Student Research Award as well as a GSA Division of Mineralogy, Geochemistry, Petrology, and Volcanology (MGPV) Supplemental Research Award for his proposal to investigate the “Temperature and Geochemical Composition of the Archean Ocean by Clumped Isotope Analysis of Stromatolitic Carbonates”. More information can be found here.
Posted 15 September 2015
- Aaron Satkoski’s research highlighted in Science News
Post-doc Aaron Satkoski is interviewed by Science News on his discovery of the oldest redox gradient known in the ancient Earth at 3.2 b.y. ago. Article can be found here.
Posted 8 September 2015
- Astrobiology interview with UW-Madison Daily Cardinal
Clark Johnson is interviewed about recent research in astrobiology on the origin of banded iron formations by the UW-Madison student newspaper, The Daily Cardinal. Story can be found here.
Posted 2 September 2015
- New paper published that shows ocean redox stratification at 3.2 Ga
A new paper, published in Earth and Planetary Science Letters, combines stable Fe isotopes and U-Th-Pb geochronology on jaspers from the Barberton Greenstone Belt, South Africa, to demonstrate that a significant redox gradient existed in the oceans at this time. Shallow water samples formed in the presence of low levels of dissolved oxygen in the photic zone of the oceans, whereas deeper water samples formed in anoxic conditions. This is the oldest known redox gradient in the ancient oceans, demonstrating that oxygenic photosynthesis evolved prior to 3.2 Ga. Lead author is post-doc Aaron Satkoski. See Publications page (paper #174).
Posted 25 August 2015
- Allison Wende starts new position at Los Alamos
Former grad student Allison Wende began a new position with the mass spectrometry group at Los Alamos National Laboratory. We are sure she will thrive in her new position.
Posted 1 August 2015
- New NSF grant awarded for work on the Antarctic ice sheet
Brian Beard, in collaboration with former UW-Madison faculty member Anders Carlson, was awarded an NSF grant entitled “Collaborative Research: Development of a Suite of Proxies to Detect Past Collapse of the West Antarctic Ice Sheet”. The work will use Sr, Nd, and Pb isotopes to determine the sources of sediments discharged by the West Antarctic ice sheet to better understand the history of the ice sheet and to develop predictive models for ice sheet response to rising temperatures.
Posted 29 July 2015
- Searching for alien life – a YouTube interview
Posted 28 July 2015
- New paper published on evolution of Mt. Shasta
A new paper, published in Earth and Planetary Sciences, studies the magmatic evolution of Mt. Shasta, the largest volcano in the Cascades, using U-series and Sr isotopes. The Th excesses identified using U-series isotopes are interpreted to record garnet production during deep crustal melting, and Sr isotope compositions, which correlate with geography, are used to infer lateral crustal heterogeneity. The largest of the four cone-building stages at Shasta correlate with the greatest deep crustal interaction. Lead author is former grad student Allison Wende. See Publications page (paper #173).
Posted 24 July 2015
- Meagan Ankney starts faculty position at University of Akron
One of our recent Ph.D. students, Meagan Ankney, left to start a new faculty position at Akron. She will be in the Department of Geosciences. We wish Meagan the best of luck – lots of lectures to prepare!
Posted 15 July 2015
- Clark Johnson steps down as Associate Editor of GCA
After over a decade of service as AE for Geochimica et Cosmochimica Acta, Clark Johnson put the last manuscript he has handled, out of hundreds, to bed.
Posted 20 July 2015
- New paper published on fluid sources in the Rio Grande Rift
A new paper, published in Geology, uses Sr isotopes to trace fluid flow patterns in the Rio Grande Rift. By combining Sr isotopes with other geochemical data, fluid flow along the large master faults of the rift margin was documented to come from deep Precambrian and Paleozoic basement, whereas smaller fault systems in the central part of the basin only involved fluid flow through younger syn-rift lithologies. Lead author is current structural geology grad student Randy Williams. See Publications page (paper #172).
Posted 1 July 2015
- New NSF grant awarded for studying Archean seawater evolution
A new grant, entitled “Archean continental weathering: Revisiting the Sr isotope seawatercurve”, was funded. Post-doc Aaron Satkoski is a co-I and will be spear-heading the research. The goals of the work are to re-evaluate the Sr isotope seawater curve for the Archean oceans, which is very poorly constrained, and likely to reflect significant exposure of continental crust, given recent O-Hf isotope data on detrital zircons that indicate significant crustal recycling ~3.2 b.y. ago.
Posted 1 July 2015
- New study on Banded Iron Formations (BIFs) published
A new paper was published in the Proceedings of the National Academy of Sciences that combines Fe and Nd isotopes to document a major biologic component in 2.5 b.y. old BIFs. The sources of iron in BIFs has been previously thought to by hydrothermal, but this new approach documents that about half the iron comes from iron released from shallow marine continental margins through microbial reduction of iron oxides, followed by transport to the deep basin. Lead author is former lab post-doc Weiqiang Li. See Publications page (paper #170). Press release here.
Posted 25 June 2015
- New paper published on metamorphic history of the Alps
A new paper that brings together a decade of geochronological research by the lab on the Western Alps, was published in the Journal of Metamorphic Geology. Lead author is long-term collaborator Susanne Skora (ETH Zurich). By combining Rb-Sr, Sm-Nd, and Lu-Hf geochronology of eclogite-facies rocks of the Zermatt-Saas ophiolite (Western Swiss and Italian Alps), the work showed that subduction of the ophiolite to HP and UHP conditions was diachronos and correlated to structural position above underlying granitic units. Despite this, all units were rapidly uplifted from HP/UHP conditions. See Publications page (paper #171).
Posted 25 June 2015
- Weiqiang Li returns to explore stable potassium isotope fractionation
Former post-doc Weiqiang Li, who is now a faculty member at Nanjing University, returned this summer to explore stable K isotope variations.
Posted 20 June 2015
- Lab group presents research at AbSciCon 2015
Seven abstracts were presented at the international astrobiology conference in Chicago:
- Fortney, N.W., B.J. Converse, B.L. Beard, C.M. Johnson, E.S. Boyd, and E.E. Roden. In vitro and in situ iron geochemistry and microbial activity at Chocolate Pots Hot Springs, Yellowstone National Park.
- Hashman, B. M., B. M. Guy, N. J. Beukes, B. L. Beard, and C. M. Johnson. A Mesoarchean Microbial Iron Shuttle.
- Levitt, L. P., C. M. Johnson, J. M. Eiler, B. L. Beard, H. Xu. Application of Clumped Isotopes in Carbonates as an Indicator of Life and Habitability.
- Li, Weiqiang, Brian L Beard, and Clark M Johnson. Isotopic records of thriving dissimilatory iron reduction microbes in the late Archean ocean.
- Reddy TR, Zheng XY, Roden EE, Beard BL, and Johnson, CM. Silicon isotope fractionation during reductive dissolution of Fe-Si gel in Artificial Archean Seawater (AAS) by Desulfuromonas acetoxidans.
- Satkoski, A. M., C. M. Johnson, B. L. Beard, N. J. Beukes. Identification of a discrete redoxcline in 3.2 Ga seawater.
- Zheng X-Y, Beard BL, Reddy TR, and Johnson Exploring Silicon isotope fractionation between Precambrian-like artificial seawater and Fe-Si gel.
Posted 18 June 2015
- Nanosecond laser installed (temporarily)
A loaner nanosecond laser was installed for a comparative study against our existing femtosecond laser system, a research project funded by NSF. After the comparative work is done, the ns laser will move down the hall to the Ar/Ar lab – hopefully we will not break it before they get it!
Posted 26 May 2015
- New NSF grant awarded for Fe isotope studies
A new grant, in collaboration with long-standing colleague Prof. Michelle Scherer (University of Iowa), was awarded. The grant is entitled “SusChEM: Collaborative Research: Influence of Fe2+- catalyzed recrystallization on Fe oxide reactivity and C stabilization”. Given the importance of biology in redox cycling of Fe, this new work will focus on Fe-C interactions, and the specific role organics may play in electron transfer reactions and associated isotopic fractionations; surprisingly, this has not yet been explored. The Fe isotope work will involve both enriched tracers (to determine rates of exchange and reactivity), as well as natural-abundance isotopic work to explore Fe isotope variations that might be preserved in natural systems.
Posted 18 May 2015
- New paper published on Fe and O isotope fractionations in goethite
A new study on studying the Fe and O isotope exchange kinetics and fractionation of goethite, which turned up some remarkable surprises, was published in Geochimica et Cosmochimica Acta. Using a unique “double-triple-isotope” approach that combined enriched 17O-57Fe tracers, along with “natural” isotope ratios (18O/16O and 56Fe/54Fe), we explored the isotopic exchange kinetics for O and Fe for goethite in equilibrium with aqueous Fe(II). We thought that Fe and O isotope exchange rates would be similar, following the stoichiometry of goethite, but O isotope exchange rates were far slower than Fe. This demonstrated the profound effect that electron exchange has on catalyzing Fe isotope exchange. We interpreted the sluggish O exchange to reflect the bond strengths of different surface O groups, some of which are resistant to isotopic exchange with an ambient fluid. Lead author is former post-doc Andrew Frierdich. See Publications page (paper #169).
Posted 29 April 2015
- UW-Madison hosting AbGradCon 2015
We are proud to announce that UW-Madison is hosting the annual astrobiology science conference that is aimed at early career astrobiologists – “AbGradCon” – which will be held in Madison, WI on July 19 thru 23, 2015. Graduate students Nick Levitt, Breana Hashman, Thiru Reddy, and Nathan Fortney in our lab spearheaded the organizational efforts. More information can be found here.
Posted 15 April 2015
- New paper published on stable Mg isotope fractionations in dolomite
Application of stable Mg isotopes to carbonates took a major leap forward with a new paper published in Geochimica et Cosmochimica Acta.