For mapping sessions, the following mass channels were recorded: m/z = 7 (Li), m/z = 27 (Al), m/z = 60 (~ ~ 28 Si), m/z = 57 (Fe), m/z = 85 (Rb), m/z = 103 (~ 87 Sr), m/z = 104 (~ 88 Sr). Dwell times, repetition rate and scan speed (Table ) were optimized on test line scans on target grains to suppress aliasing and carry-over effects and to obtain a signal/noise ratio > 10 for each mass channel. Grains were mapped with a 3-4 µm round spot at a fluence of 5.0 J/cm 2 by using a raster of unidirectional scans with no overlap between lines and a 2 s pause after each line. The total penetration depth of the laser is estimated to between 1-2 µm based on the 10-fold degree of spot overlap (dosage in Table ) and assuming 100-200 nm ablation per laser shot. At regular intervals (~ every 120 minutes), a set of reference materials (RM) was ablated in 30-40 s long line scans (total of 6-15 scans per RM and session). Reference materials were NIST610 as the primary calibration standard and the in-house secondary RM, which are single crystal mica, namely SagaB biotite, Phalaborwa biotite and Harvard 98987 muscovite. In run GAD08, the pressed mica nanopowder MicaMg has been measured in addition. A comprehensive overview of the essential ICP and laser settings used in each session is presented in Table and.