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A Potential New Chalcopyrite Reference Material for LA‐MC‐ICP‐MS Copper Isotope Ratio Measurement

A new natural chalcopyrite reference material TC1725 is prepared for in situ Cu isotope measurement by femtosecond laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (fsLA‐MC‐ICP‐MS). Detailed textural examination and major element determination suggest the TC1725 chalcopyrite grains have no growth rim or zoning. The chalcopyrite grain is homogeneous with respect to Cu isotopes based on a large number of measurements performed by bulk solution nebuliser (SN)‐MC‐ICP‐MS, single‐grain SN‐MC‐ICP‐MS and fsLA‐MC‐ICP‐MS. The traditional bulk isotope analyses by SN‐MC‐ICP‐MS yielded a mean δ65Cu value of −0.06 ± 0.03‰ (2s, n = 132). Randomly selected single chalcopyrite grain of TC1725 determined by SN‐MC‐ICP‐MS without column chromatography gave a mean δ65Cu value of −0.06 ± 0.04‰ (2s, n = 188). The intermediate measurement precision for four measurement sessions was better than 0.04‰ (2s), suggesting TC1725 chalcopyrite is suitable as a microanalysis reference material for Cu isotope measurement. The mean δ65Cu value determined by fsLA‐MC‐ICP‐MS analyses on different individual chalcopyrite mounts and strips was −0.06 ± 0.03‰ (2s, n = 393), consistent with the bulk isotope composition within uncertainty. The recommended mean δ65Cu value for this chalcopyrite reference material is −0.06 ± 0.03‰ (2s, n = 132) as determined by bulk SN‐MC‐ICP‐MS.