TARIM calcite: a potential reference material for laser ICPMS in situ calcite U-Pb dating

Assisted with laser ablation (LA) inductively coupled plasma mass spectrometry (ICPMS) analytical techniques, calcite is now accepted as an important U-Pb dating mineral applying to various issues in geology. However, appropriate calcite reference materials with homogeneous composition and structure remain lacking due to limited work on such reference material research. This study successfully identifies a new natural megacryst calcite reference material TARIM for in situ U-Pb isotope measurement by LA-ICPMS analysis. Electronic probe microanalysis (EPMA) shows TARIM as a homogenous low-Mg calcite. LA-ICPMS trace elemental analyses and mapping results suggest that TARIM is relatively homogenous with U contents (mean value = 0.48 mu g center dot g(-1)) appropriate for U-Pb isotopic dating. The isotope dilution-thermal ionization mass spectrometry methods (ID-TIMS) U-Pb analysis yielded a lower intercept age of 208.5 +/- 0.6 Ma (2S, mean squared weighted deviation (MSWD) = 1.04). A total of 515 LA-ICPMS U-Pb isotope analyses on random calcite pieces show consistent ages with a lower intercept age of 208.0 +/- 0.4/3.2 Ma (2S, MSWD = 3.0), overlapping with the ID-TIMS age. We propose that the TARIM calcite can be applied as a reference material for the matrix-matched calibration or monitoring standard for calcite LA-ICPMS U-Pb dating.

Automated summary

This study successfully identifies a new natural megacryst calcite reference material TARIM for in situ U-Pb isotope measurement by LA-ICPMS analysis. TARIM calcite can be applied as a reference material for calcite LA-ICPMS U-Pb dating.