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Thus, the accurate U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration.Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device (SSD), using laser spot and frequency of 10 µm and 1 Hz, respectively.In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) analysis was studied in detail.The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value.When calibrated using GBW04420 as the external standard, two samples give weighted mean U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation.TY - JOURT1 - In situ LA-ICP-MS U–Pb dating of metavolcanics of Norrbotten, Sweden: records of extended geological histories in complex titanite grains AU - Storey, Craig AU - Smith, M. This study reports data chiefly from titanite, but also from rutile and apatite, obtained using the laser ablation (LA)-ICP-MS methodology on polished thick sections in order to retain as much petrologic information as possible, and allowing trace element analyses from adjacent areas to the U–Pb analyses.Apatite has a lower closure temperature than zircon, i.e., ~400 - 500°C, and so are more easily ‘reset’ by heating than zircons.
Standards of titanite (BLR-1 and OLT-1) and zircon (91500 and GJ-1) were dated using single spot and line raster scan analytical methods.
These ages are consistent with its reference age of about 1014 Ma.
However, using 91500 zircon as the external standard, the weighted mean =24) for OLT-1 titanite by single spot and line raster scan analyses, respectively.
Rare earth element (REE) analysis by LA-ICP-MS demonstrates that the core and rim zones are distinct and supports a model for two-stage evolution in two out of three samples, with the rims in these samples being enriched in total REE, and particularly in LREE in one sample, and displaying a positive Y-anomaly in contrast to the cores.
In situ U–Pb analysis reveals that core zones from all samples retain distinct older ages of c.2050 Ma, whereas the reworked rims have either distinct younger or strongly reset ages.