Nova Terra 52

Spot sizes = 25 and 35 μ m; crater depth ~15 μ m. 206 Pb/ 238 U error is the quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the primary reference material. 207 Pb/ 206 Pb error propagation (207Pb signal dependent) following Gerdes & Zeh (2009). 207 Pb/ 235 U error is the quadratic addition of 207 Pb/ 206 Pb and 206 Pb/ 238 U uncertainies. a Within run background-corrected mean 207 Pb signal in cps (counts per second). b U and Pb content and Th/U ratio were calculated relative to the primary reference material. c Percentage of common Pb on the 206 Pb. b.d. = below dectection limit. d Corrected for background, within-run Pb/U fractionation (in case of 206 Pb/ 238 U) and common Pb using Stacy and Kramers (1975) model Pb composition and subsequently normalised to the primary reference material (ID-TIMS value/measured value); 207 Pb/ 235 U calculated using 207 Pb/ 206 Pb / ( 238 U/ 206 Pb * 1/137.84). e Rho is the 206 Pb/ 238 U / 207 Pb/ 235 U error correlation coefficient. f Degree of concordance = 206 Pb/ 238 U age / 207 Pb/ 206 Pb age x 100 g RM1: Primary reference material g Accuracy and reproducibilty was checked by repeated analyses of secondary reference materials; data given as mean with 2 standard deviation uncertainties. Appendix I