^1,4M. D. Hopkins,^1,2,3S. J. Mojzsis
¹Department of Geological Sciences, NASA Lunar Science Institute Center for Lunar Origin and Evolution (CLOE), University of Colorado, UCB 399, 2200 Colorado Avenue, Boulder, CO, 80309-0399, USA
²Laboratoire de Géologie de Lyon, École Normale Supérieure de Lyon, CNRS UMR 5276, Université Claude Bernard Lyon 1, 46 Allée d’Italie, 69007, Lyon, France
³Research Center for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Hungarian Academy of Sciences, 45 Budaörsi Street, Budapest, 1112, Hungary
⁴Department of Earth Science, Santa Monica College, 1900 Pico Boulevard, Santa Monica, CA, 90405, USA

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Reference
Hopkins MD, Mojzsis SJ (2015) A protracted timeline for lunar bombardment from mineral chemistry, Ti thermometry and U–Pb geochronology of Apollo 14 melt breccia zircons. Contributions to Mineralogy and Petrology 169:30
Link to Article [DOI 10.1007/s00410-015-1123-x]

¹Donald S. Burnett et al. (>10)*
¹California Institute of Technology, Pasadena, CA, USA
*Find the extensive, full author and affiliation list on the publishers Website

Ion microprobe elemental and isotopic determinations can be precise but difficult to quantify. Error is introduced when the reference material and the sample to be analysed have different compositions. Mitigation of such ‘matrix effects’ is possible using ion implants. If a compositionally homogeneous reference material is available which is ‘matrix-appropriate’ (i.e., close in major element composition to the sample to be analysed, but having an unknown concentration of the element, E, to be determined) then ion implantation can be used to introduce a known amount of an E isotope, calibrating the E concentration and producing a matrix-appropriate calibrator. Nominal implant fluences (ions cm−2) are inaccurate by amounts up to approximately 30%. However, ion implantation gives uniform fluences over large areas; thus, it is possible to ‘co-implant’ an additional reference material of any bulk composition having known amounts of E, independently calibrating the implant fluence. Isotope ratio measurement standards can be produced by implanting two different isotopes, but permil level precision requires postimplant calibration of the implant isotopic ratio. Examples discussed include (a) standardising Li in melilite; (b) calibrating a 25Mg implant fluence using NIST SRM 617 glass and (c) using Si co-implanted with 25Mg alongside NIST SRM 617 to produce a calibrated measurement of Mg in Si.

Reference
Burnett DS et al. (2015) Ion Implants as Matrix-Appropriate Calibrators for Geochemical Ion Probe Analyses. Geostandards and Geoanalytical Research (in Press)
Link to Article [DOI: 10.1111/j.1751-908X.2014.00318.x]

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