The University of Wisconsin SIMS lab (WiscSIMS) was installed in 2005 and became a National Facility for Stable Isotope Geochemistry in 2008 with support from NSF, Division of Earth Sciences, Instrumentation and Facilities Program (link).
As of 2014, the lab has experience with analysis of Li, C, O, Mg, Si, and S isotope ratios. Best results come from well-prepared samples that are vacuum stable, have a smooth, flat, low-relief surface, are 25 mm in diameter and <6 mm thick (see our sample preparation page). Surface relief is minimized by careful polishing and is measured at sub-μm-scale by white light profilometer. Other materials can be analyzed, as can isotope ratios for trace elements. Accurate analysis requires well characterized, homogeneous standards with similar chemistry and crystal structure to samples. For oxygen isotope ratios, WiscSIMS has many silicate, carbonate, and oxide standards (Valley & Kita 2009; Page et al., 2010). Other standards exist or are being developed. Potential users should inquire about standard availability.
Use of associated instrumentation at nominal cost can be arranged in support of projects at WiscSIMS including: an Hitachi S3400N Variable Pressure Scanning Electron Microscope with capability for imaging uncoated samples, Electron Back Scatter Diffraction (EBSD), color-filtered CL, EDS, and BSE detectors; a CAMECA SXFiveFE electron microprobe with 5 crystal spectrometers, Field Emission Gun, EDS, CL, and BSE; conventional and laser fluorination stable isotope lab; and a white light optical profilometer.
Analytical Capabilities for WiscSIMS Facility Users
Currently, the following stable isotope analyses are well-established and routinely available to external users. The beam sizes are typically 10µm and analyses take 3-10min/spot (depending on isotope system). Mineral analysis is limited by availability of standards. Potential users should inquire about creation of other standards.
- Oxygen isotopes (δ18O) with ~10 µm spots:
Zircon, quartz, olivine*, pyroxene*, garnets*, titanite*, calcite*, aragonite, dolomite-ankerite*, magnesite-siderite*, plagioclase*, K-feldspar, spinel*, chromite*, epidote*, opal, coesite, silicate glass*: precision typically ~0.3‰ (2SD)
- Carbon isotopes (δ13C) with ~8 µm spots:
Diamond, graphite: precision typically ~0.4‰ (2SD)
Calcite, aragonite, dolomite, ankerite, magnesite-siderite*,: precision typically ~0.7‰ (2SD)
- Sulfur isotopes (δ34S) with ~10 µm spots:
Pyrite, anhydrite, pyrrhotite, chalcopyrite: precision typically ~0.4‰ (2SD)
- Si isotope (δ30Si) with ~10 µm spots:
Quartz: precision typically ~0.2‰ (2SD)
(*: We request that users obtain EPMA data of individual spots prior to SIMS analyses for correction of matrix effect.)
An analysis with smaller beam sizes down to 2 µm is available for some systems, but analysis is slower (15-30 min/spot) and with degraded precision (~1‰). Other applications with more difficult samples, requiring new standards, or with Li isotopes (δ7Li), Mg three isotopes (δ25Mg, δ26Mg, and excess δ26Mg), oxygen three isotopes (δ18O, δ17O, and Δ17O), and sulfur three and four isotopes (δ33S, δ34S, δ36S, Δ33S, and Δ36S) may also be available. Please contact us for more detailed information.
Note that some samples show an orientation effect and can only be analyzed for isotope ratio by SIMS at reduced precision (Kita et al., 2011). WiscSIMS has detected orientation effects in magnetite, hematite, baddeleyite, rutile, galena, and sphalerite.
Applications for Instrument Time
Applications should be sent to WiscSIMS Contact with a brief description of the project and samples. The WiscSIMS Oversight Board allocates instrument time according to the scientific merits and feasibility of the project. Applications should be made by grant PIs.
- John Valley (Chair, WiscSIMS Oversight Board)
- Chloe Bonamici (WiscSIMS Oversight Board)
- Noriko Kita (Director, WiscSIMS Laborratory)
WiscSIMS receives a subsidy from NSF/EAR Instrumentation and Facilities Program (link), and external NSF-funded investigators receive priority in allocation of instrument time and are eligible to perform analyses at a subsidized rate. The current subsidized rate is $1,800/day (12 hours), applied to US federally-funded research. The unsubsidized academic rate is $3,600/day (12 hours). Commercial or confidential analysis is also available at a rate of $10,000/day (12 hours).
Analysis of extraterrestrial samples is outside the scope of the NSF/EAR Facility Program. The rate for US federally-funded meteorite research is $2400/day (12 hours) and the unsubsidized academic rate is $3,600/day (12 hours).
PUBLICATION AND ACKNOWLEDGEMENT:
We request that any data produced from WiscSIMS lab explicitly recognize NSF support in the acknowledgements of the journal articles with the following sentence: “WiscSIMS is partly supported by NSF (EAR03-19230, EAR10-53466, EAR13-55590).”
WiscSIMS subscribes to the UCLA Protocol for collaborative research.
“While all the personnel of the ion probe group take an active interest in assisting visitors, we have always sought flexible arrangements in defining our specific roles in the projects of external facility users. Specifically, this means that we have no requirement (explicit or implicit) that WiscSIMS scientists become actively involved in scientific interpretations, and certainly no expectation for co-authorship on routine data acquisition work. It has been our experience, however, that many visitors seek our expertise in the interpretative aspects of their work and many projects have tangibly benefited from collaborative efforts. We believe that it is not only useful, but necessary, that the facility be staffed by expert scientists who are not merely technologists but are also actively engaged in geochemical research.” (link)