Geochemistry/Cosmochemistry Group

Steven B Shirey

Geochemistry/Cosmochemistry Group


Our current TIMS instrument is a 2004, nine moveable Faraday cup collector, single ion multiplier Thermo-Fisher Triton.  The Triton has state of the art sensitivity and accuracy and is used in positive ion mode (P-TIMS) for isotopic analyses of Sr, Nd, Ba, Sm, Pb and Cr. In negative mode (N-TIMS) it is used primarily for Os.


Thermal ionization mass spectrometry (TIMS): Thermo-Fisher Triton

Facilities for Research in the Geochemistry/Cosmochemistry Group

TIMS:   Thermo-Fisher Triton

ICP-MS:   Nu Plasma HR, Nu Plasma II, Thermo iCap Qc, Photon Machines Analyte-193 Laser

SIMS:   NanoSIMS 50L, Cameca IMS 6f

SEM:   JOEL SX-6500

with GL:   JOEL Field Emission EPMA, Zeiss Auriga FIB-SEM, WiTec confocal Raman spectrometer

Chemistry LABS:   Multiple clean-room facility equipped for all aspects of sample preparation

SUPPORTING LABS:   Optical microscopy lab, microsampling, rock room, machine shop, electronics lab

     The Geochemistry/Cosmochemistry Group has five staff members: Conel Alexander, Rick Carlson, Erik Hauri, Larry Nittler, and Steve Shirey.  With the support of chemistry lab manager, Mary Horan, mass spec lab manager, Tim Mock, and ion probe specialist, Jianhua Wang, research projects involving the staff can range from a short, informal nature to those that are long term. Research collaborations are welcome on almost any professional level: as an intern, a pre-doctoral fellow, a post-doctoral fellow, a visiting scientist, or a Tuve fellow. Most projects are NSF or NASA funded, but with the Carnegie Institution’s high level of ongoing lab support, important scientific questions can be attacked without the proposal lead time that NSF or NASA funding requires. The most fruitful collaborations are those that align with the interests of the staff and the type of analyses suited to our facilities (see below).

       The scientific environment at DTM is stimulating and the Washington area is the best in the world for science as it hosts a unique collection of institutions and laboratories (see below) with ongoing programs in Earth and Planetary Science with which joint research projects can be carried out: Geophysical Lab, Goddard Space Flight Center, National Institute of Standards and Technology, Naval Research Laboratory, Smithsonian Institution, US Geological Survey, and University of Maryland.  Interested? Please contact any one of the staff directly and see the announcement below.

Inductively coupled plasma mass spectrometry (ICP-MS):

Nu Plasma HR, Nu Plasma II, iCap Q

The newest ICP-MS in the Geochemistry/Cosmochemistry Group is the multi-collector (12 faradays, 4 multipliers) Nu Plasma HR that was just installed in June, 2009 as a replacement for our aging VG P-54.  It is used for isotopic measurements of B, Si, Fe, Ag, Sr, Nd, Hf, Pb as well as isotope dilution concentration measurements of Rb, Sr, Pd, Sm, Nd, Lu, Hf, PGE, Re, U, Pb, and Th. The second ICP-MS is a VG Axiom single collector instrument (2000 year vintage, refurbished in 2009) which was a swap from Ionflight Inc. for our aging multi-collector VG Axiom. This instrument is used for simple elemental concentration work on unknowns, diagnostic work supporting the chemistry lab and tests for sensitivity for laser ablation analysis. Laser ablation for ICP-MS instruments is accomplished using a newly-installed 193 nm Excimer laser (Analyte 193.H) made by Photon Machines Inc. In January, 2011 we will take delivery of a Nu Plasma II, an instrument belonging to GL staff member Anat Shahar but installed in our main mass spec lab for shared use.

A top down view of the collector of the Triton showing the moveable Faraday cup array.

Secondary ion mass spectrometry (SIMS):

NanoSIMS 50L, Cameca IMS 6F with 1 meter magnetic sector

The Geochemistry/Cosmochemistry group has two ion microprobes: a Cameca IMS 6F (single-collector,  installed in 1995) and a Cameca nanoSIMS 50L (7-collector, installed in 2006). Each instrument is equipped with oxygen and cesium primary ion sources and an electron flood gun for charge compensation.  They are used for a wide variety of applications where spatial resolution is critical, from measurements of volatiles and trace elements on individual minerals and fluid/melt inclusions to isotopic measurements of C, O, Mg, Si, S, Ca, Ti and Fe in both terrestrial, meteoritic, and extra-solar materials. In addition, a high-transmission, large radius, multi-collector secondary beamline for the 6f is being developed that will have capabilities (high transmission at high resolution) similar to or better than the Cameca 1270 ion microprobe when completed.

Two views of the Thermo-Fisher Triton with the source on the left and the collector on the right in both pictures.

Mass spectrometer lab chief Tim Mock and staff scientist Richard Carlson discuss Nd isotope data.

Postdoc MattJackson, Nu engineer Scott Brereton and Tim Mock unwrap the frame of the Nu Plasma upon delivery.

A view of the Nu Plasma HR from the collector end.  The plasma source is in the background

Within high vacuum, a complicated set of ion optical lenses takes the circular ion beam and shapes it for the magnetic sector of the Nu.

At the collector end of the Nu, four, large, discrete-dynode electron multipliers are placed behind an array of 12 Faraday cups (see arrangement below).

Postdoc Christian Miller analyzing a multi-element standard of Mg, Al, Zn, Si, Fe, Ni, Ca, and Ba on the iCap Q to improve chemical separation procedures before analyzing samples.

The business end of the Photon Machines Analyte-193 excimer laser system. It can be used with any of the ICP-MS.

The custom designed collector block of the DTM Nu Plasma allows for the analysis of an extensive suite of isotope systems by simultaneous multicollection both on Faraday cups (light blue) and discrete-dynode electron multipliers (pink).

The Cameca IMS 6F viewed from the source end. Samples are inserted with the long tube at the left. Beyond the ims 6F label is the 1-meter extended geometry sector, part of which is shown in the figure at right

The 1-meter extended geometry sector under development at DTM. This will allow for high-resolution, high-transmission simultaneous analyses of stable isotopes of H, C, N, O, and S.

The Cameca NanoSIMS 50L (left) with staff member Erik Hauri adjusting an aperature on the primary beam column (right). The collector of the instrument is in the foreground in the picture at right. In the NanoSIMS, the ion source starts vertical and turns coaxial to the secondary ion beam path. The magnet is of high dispersion Mattauch-Herzog design allowing simultaneous collection of up to 7 isotopes.

The collector trolley of the NanoSIMS with 3 collectors in view. Each collector has an ESA and can use either a Faraday cup or an electron multiplier.

A comparison of the spot size between the IMS 6F and the NanoSIMS 50L displayed within a olivine-hosted melt inclusion showing the superior spot size resolution of the NanoSIMS.

Tim Mock, Rick Carlson and ion probe specialist Jianhua Wang look over the Faraday amplifier board housing on the NanoSIMS.

The Intellectual Environment for Science at DTM

Astronomy and planetary science1

The DTM astronomy group — a strongly interacting mix of observers and theorists — is expert in the theory of formation of gas-giant, ice-giant, and rocky planets; in the detection and characterization of planets and planetary systems around other stars; in the study of the circumstellar disks from which planets form; in the nature of small bodies that carry a signature of early solar system processes; and in the evolution of rocky planets.”

Geochemistry and cosmochemistry

“The DTM geochemistry and cosmochemistry group — united by their ability to exploit sophisticated analytical instruments — is expert in the discovery and characterization of presolar grains; the chemistry and chronology of early solar system material, including meteorites, interplanetary dusk particles (IDPs), and samples from cometary and planetary bodies; chemical processing on Earth associated with early global differentiation, continent formation, and subduction; and dynamical mixing in the Earth's mantle revealed by products of mantle melting.”

Geophysics and planetary physics

“The DTM geophysics group — who have traditionally emphasized the development of novel instruments and the design of field experiments — is expert in those aspects of Earth structure pertinent to the formation and evolution of continents, the dynamics of the Earth's mantle, and the relationship between mantle dynamics and the history of motions of the tectonic plates.  The group has parallel interests in the search for precursors to earthquakes and the understanding of magma movements at depth prior to major volcanic eruptions.”

1This distillation of DTM research groups was written by Director, Sean Solomon and presented to the CIW President and Board of Trustees, November, 2010.

The Department of Terrestrial Magnetism (DTM)

The Department of Terrestrial Magnetism is a diverse group of over 30 researchers (15 staff and 15 postdocs, visiting investigators and students) conducting research in the areas of astronomy and planetary science, geochemistry and cosmochemistry, and geophysics and planetary physics. Past and present research initiatives include the Kaapvaal Project, the High Lava Plains Experiment, the Messenger Mission to Mercury, the MELT Experiment and the PLUME Experiment.

The Geophysical Laboratory (GL) our sibling dept on the Broad Branch Rd Campus

The Washington, DC region -a unique science setting for DTM

The Geophysical Laboratory is a diverse department of over 45 researchers (15 staff and 30 postdocs, visiting investigators and students) conducting research in the areas of geobiology, experimental petrology, mineral physics, crystallography, and materials science. In many areas, their expertise and facilities dovetail with the research interests of researchers at the DTM. Major departmental initiatives include AMASE, CDAC, EFREE, DCO, HP-CAT (needs more and some active links).

The Washington area is unique in the world in hosting many institutions and laboratories with ongoing programs in Earth and Planetary Sciences with which joint research projects can be carried out: Geophysical Lab, Goddard Space Flight Center, National Institute of Standards and Technology, Naval Research Laboratory, Smithsonian Institution, US Geological Survey, and University of Maryland. All of these groups run seminar series to which scientists in the area are often invited. In addition, the area is host to the headquarters of many societies, publishers, and media outlets such as AAAS, AAS, AGI, AGU, NAS, Nature, Science, the National Geographic, the Discovery Channel, and National Public Radio. The city boasts local societies in such as the Washington Area Astronomers, the Potomac Geophysical Society, and the Geological Society of Washington which serve to bring members of these scientific groups together on a monthly basis. Through all these connections, many opportunities exist in straight research, society governance, science policy, and science journalism.

Mass spec lab manager, Tim Mock in front of the Thermo-Fisher Triton thermal ionization mass spectrometer.

Staff member Erik Hauri (right) with visiting investigator Steve Jacobsen (left), a former Geophysical Lab postdoctoral fellow who is now an assistant professor at Northwestern University. Jacobsen traveled to DTM to analyze the water content of high pressure mantle minerals produced in his experimental lab. The NanoSIMS 50L is in the background.


Our location at 5241 Broad Branch Road, NW, Washington, DC 20015



  Postdoctoral fellowships that provide support for creative independent research of the applicant’s choosing in one or more of the fields of geophysics, volcanology, geochemistry, cosmochemistry, astronomy, and planetary science are available beginning Fall 2016.  Details on DTM research staff, laboratory facilities, and ongoing research can be found at under “Research” and "People".  Fellowships are for 1 year and are normally renewable for a second year.

    Applications should include a curriculum vitae and bibliography, description of thesis research, and a short (2-3 page) statement of research plans for the fellowship period.  Creativity in the proposed research figures heavily in the evaluation of the application.  Three letters of recommendation should be sent directly to DTM by those familiar with your work.  Review of the applications will begin after December 1, 2015.  Please apply for a fellowship online here and direct any questions to one of the research staff of interest at their e-mail address or in general by e-mail to:  Women and minority candidates are encouraged to apply.  (AAE/EOE.).

Carnegie Postdoctoral Fellowships at DTM for 2016

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