Brama: a new freeware Python software for reduction and imaging of LA-ICP-MS data from U–Pb scans

Abstract

U–Pb dating of hydrothermal and hydrothermal accessory minerals is challenging because they often contain high concentrations of common Pb, low U concentrations, and they can be altered and fractured. Photomicrography, Bayesian regression, and trace element and isotope ratio maps have effectively been used to overcome these problems in dating such minerals. A new software, Brama (Bayesian regression and age mapping application) for LA-ICP-MS U–Pb data, performs outlier processing, baseline correction, isotope calculation and Bayesian regression by matching the laser ablation position of the line scan with the time-resolved signal of the plasma mass spectrometry data generated from quadrupole instruments, resulting in high resolution spatial maps of trace element and isotope ratios as well as age results. The software-derived data can also be used in the Tera–Wasserburg and Wetherill methods to calculate mineral ages. We demonstrate the key advantages and potential applications of Brama with two examples of LA-ICP-MS calcite and apatite U–Pb dating.