Technical note: "u-Th Analysis" - Open-source software dedicated to MC-ICP-MS U-series data treatment and evaluation

Abstract

We present our stand-alone data analysis application for 230Th/U dating with multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The Python-based algorithm is equipped with a graphical user interface (GUI) and comprises raw data treatment, corrections, age calculation, and error estimation. Our underlying measurement protocol employs a combination of Faraday cups (FCs) and secondary electron multipliers (SEMs), and the software allows for different detector layouts for the measurement of the least abundant isotopes 234U, 230Th, and 229Th. We especially focus on features that ensure reproducibility and enable user-friendly reanalysis of measurements such as customized calculation constants with templates. Result files are saved automatically and contain all relevant settings used. We demonstrate the relevance of adequate data outlier treatment and generally recommend using the median instead of the mean of calculated ratios. The performance of our evaluation software is demonstrated by a case study from a Puerto Rican stalagmite with growth phases from the modern era to 40 kyr old. The majority of the obtained ages reach uncertainties in the range of 0.3 %-0.6 %, underlining the capability of our measurement protocol.