Elemental and isotope ratio mapping on mica from mylonite and metapegmatites were performed at the MAGMA Lab of the TU Berlin during three sessions (GÄD08, WIL1A and GER2B, corresponding to the sample names) using an Agilent 8900 ICP-MS/MS coupled to an Analyte Excite 193 nm excimer laser (Teledyne Photon Machines). Prior to analysis, the reaction cell is flushed for at least 12 hours with N 2 O (25 %) to reduce instrumental drift. For introduction of N 2 O into the Agilent 8900 CRC, the 4 th cell gas mass flow controller is used, where a flow rate of 100% corresponds to ~1.07 ml/min. The aerosol rapid introduction system ARIS (Teledyne Photon Machines) was used in combination with a low-volume adapter from Glass Expansion. Helium (99.999 %) was used as a carrier gas with a total flow rate of 0.95 l/min (0.5 l/min cell flow, 0.45 l/min cup flow) and small amounts (3 ml/min) of high-purity N 2 (99.999%) were admixed to increase sensitivity. After plasma ignition and initialization of He flow, m/z = 42 (e.g., N 14 N 14 N + ) and m/z = 31 (e.g., N 16 O + ) were recorded to monitor the amount of air entrained in the interface tubing and ablation cell. After count rates were stable and below 30000 cps for m/z = 31 and 42, the Ar nebulizer gas and He carrier gas flows were tuned to achieve m/z = 248/232 ratios of < 0.1 % (ThO/Th) and m/z = 232/238 ratios of 100 ± 1 % (Th/U), while ablating NIST 610 in line scans and in single quadrupole mode. An automatic lens tune was performed on NIST 610 to maximize sensitivity in the mid-mass range with m/z = 88 (Sr) as the sensitivity monitor. Laser parameters for the sensitivity and gas flow tuning were 50 Hz repetition rate, 5 μm circular spot size, and 4 J/cm 2 fluence.