Isotope Geochemistry
The Center for Isotope Geochemistry is a world-class facility for high-precision analysis of both radiogenic and stable isotopes on a wide range of materials. The Center is spread over two laboratories in Devlin Hall and 245 Beacon St. The Devlin lab comprises a 750 sq ft class 1000 trace-metal clean room with ten class 100 work spaces, four laminar flow exhausting fume hoods, and three analytical balances. This space is also home to two IsotopX Phoenix Thermal Ionisation Mass Spectrometers. These TIMS’ were installed in 2016 and 2022 and are primarily used for high-precision analysis of small sample size neodymium and strontium isotopes on materials spanning the earth and environmental sciences. We also have a mineral preparation laboratory for preparation of geologic materials.
The lab in 245 Beacon St comprises a Thermo Delta V Isotope Ratio Mass Spectrometer equipped with two Gas Bench II systems: one modified for high-precision N2O analysis using the denitrifier method, and another for the CO2 isotope analysis of carbonates. The IRMS is also equipped with an Elemental Analyser for Carbon-Nitrogen-Sulfur isotope analysis of solid samples. This lab is also home to an Agilent 8900 Inductively Coupled Plasma Mass Spectrometer (ICPMS) that can be used in solution mode or connected to our Applied Spectra RESOlution 193 nm ArF excimer Laser Ablation System for high-resolution in situ analysis of solid materials.
Principally, the Center takes a collaborative approach to research and in most cases the users are trained to prepare, separate, purify, and analyse samples under the direction of Center management. We value the educational experience of all users and highly encourage motivated undergraduates to get involved in the research activities of the Center. Interested parties and external users should contact Center management to discuss details of prospective collaborations.
Facility Director: Stephanie Walker
Facility Assistant Director: Andrew Lonero
Faculty Advisory Committee:
Ethan Baxter (TIMS)
Xingchen (Tony) Wang (IRMS)
Seth Kruckenberg (SEM)
Center Facility Description
Two trace-metal clean rooms comprising 750 sq ft are at the heart of the laboratories in Devlin Hall. The metal-free HEPA filtered labs are designed for processing small amounts of material (sub nanogram) with minimal environmental contamination. The space features 14 Class 100 ULPA filtered laminar flow benches and hoods, Savillex Teflon distillation devices, Analab metal-free hotplaces, and three analytical balances. The labs are designed to hold a steady temperature, and positive pressure is monitored by a Setra Multisense monitor at the interface of each lab door.
Our first TIMS was installed in 2016, and is equipped with nine moveable Faraday cups and an ion counting Daly detector, and has a full suite of both 1011 and 1012 Ohm resistors. In 2022 we installed a second Phoenix with new ATONA amplifiers, this TIMS is also equipped with nine moveable Faraday cups and an ion counting Daly detectors. The sensitivity of these instruments permit acquisition of high-precision (15ppm 2SE long-term external) isotope data for the smallest samples down to the sub-nanogram level for high-mass elements (e.g. 143Nd/144Nd, 87Sr/86Sr).
All filaments are prepared in-house using an Amada Miyachi spot welder and degassed in a DG60 outgasser. Samples are loaded under ULPA-filtered laminar flow conditions using a custom designed filament loading bench.
The IRMS is equipped with universal triple collectors and D/H collectors for a variety of stable isotope measurements. The IRMS currently has three front-end peripherals, a modified Gas Bench used for N2O isotope analysis, a Gas Bench for the analysis of carbon and oxygen isotope analysis of carbonates, and an Elemental Analyser for the measurement of Carbon-Nitrogen-Sulfur elemental and isotopic composition in solid samples. The CO2 Gas Bench is equipped with a 96 port heating block and autosampler for preparation and sample introduction for carbonates, water samples, and atmospheric gases. The setup allows for high-throughput automated continuous flow isotope analysis of CO2, O2, N2, and H2 gases. Drilling devices and a Sartorius microgram level analytical balance are available for the drilling and weighing of sample powders.
Installed in 2022, the Agilent 8900 QQQ-ICPMS is a tandem mass spectrometer (MS/MS) used for (trace-)elemental analysis. The instrument uses a collision/reaction cell sandwiched between two quadrupole mass filters and can resolve isobaric interferences using reaction chemistry. This has applications in Earth and environmental sciences, but also in materials science, chemistry, forensic science, life sciences and many other fields. The ICP-MS can be used in solution mode, taking advantage of an auto-sampler, or in Laser Ablation mode for in-situ, spatially-resolved analysis of solid materials.
This 193 nm ArF excimer Laser Ablation system is used primarily in combination with the Agilent 8900 ICP-MS, providing the advantage of high spatial resolution trace-element data in a wide range of solid materials.
A facility for the processing of solid geological samples and the isolation of specific mineral phases. This Laboratory features a Spex ball mill for producing powders from rock fragments, petrographic and binocular microscopes, an exhausting fume hood for heavy liquid density separation, a new Frantz isodynamic separator for magnetic separation, and a New Wave MicroMill for high precision sampling.
The Scanning Electron Microscope (SEM) facility, housed within the Department of Earth and Environmental Sciences in Devlin Hall, is the other facility that serves the Center for Isotope Geochemistry. This facility hosts a Tescan Mira 3 Schottky Field Emission SEM that can be operated in either high-vacuum or variable pressure modes, allowing for the characterization of coated or non-conductive specimens. This FEG-SEM is equipped with a range of analytical detectors for materials imaging and characterization (e.g., secondary, backscatter, cathodoluminescence detectors). This system is also equipped with an integrated Oxford Instruments HKL Symmetry2 electron backscatter diffraction (EBSD) detector and an X-Max 50 Silicon Drift Detector, allowing for the rapid determination of crystallographic fabrics (i.e. lattice preferred orientations), patterns of rock microstructure (textural mapping), and semi-quantitative mineralogical and compositional maps. Supporting instrumentation for the SEM lab includes: (1) an EMS 150TE turbomolecular pumped Carbon Coater for producing very thin conductive coatings used in imaging, EDS, and EBSD analyses; (2) a Struers LabPol-5 sample polishing system; (3) Buehler MiniMet and Vibromet2 polishers used for EBSD sample surface preparation; (4) a digital camera-equipped petrographic microscope (Zeiss Axioskop 40) and macroscope (Leica Z6 APO) for transmitted and reflected light observation and imaging of polished thin sections; and (5) a variety of computer workstations for post-processing and data analysis.
Stephanie Walker, Ph.D.
Director, Center for Isotope Geochemistry
Dr. Stephanie Walker is an isotope geochemist specializing in geochronology of the solid Earth. She joined BC in 2017 as a postdoctoral fellow in the Department of Earth and Environmental Sciences after completing her PhD at Royal Holloway University of London. Steph has extensive expertise in the extraction and isolation of elements (particularly Sm, Nd, Lu, Hf, Rb, Sr) using clean-lab chemistry and column chromatography, and analysis of their isotopes using TIMS and MC-ICPMS. She also has experience of determining trace- and major-element concentrations using LA-ICPMS and XRF. Her research focuses on using isotope geochemistry and geochronology to understand the timing and rates of metamorphic processes, particularly in orogenic systems.
Center for Isotope Geochemistry
Stephanie Walker, Ph.D.
Director
walkerfj@bc.edu
617-552-2785
Devlin Hall 314
Andrew Lonero, M.S.
Assistant Director, Center for Isotope Geochemistry
Andrew Lonero received his B.S. from the University of Hawaii, Hilo and his M.S. from Washington State University. During his graduate research, he worked on the stable isotopes of hydrothermal alterations in volcanic rocks from Yellowstone National Park. His expertise spans stable isotope (CHONS) geochemistry, major and trace-element chemistry (ICP-OES, ICP-MS, XRF) on solid materials and solutions, and method development in mass spectrometry. Before arriving at Boston College as the Assistant Director of the Center for Isotope Geochemistry in 2022, he was the geochemistry lab manager at Utah State University.
Center for Isotope Geochemistry
Andrew Lonero, M.S.
Assistant Director
loneroa@bc.edu
617-552-3711
245 Beacon 004