Micro-beam Lu-Hf dating on REE minerals: A preliminary study

<p indent="0mm">Rare earths are advantageous strategic mineral resources in China, playing an extremely important role in economic development and national security. Rare earth element (REE) minerals usually have relatively high Lu/Hf ratios and closure temperatures for the Lu-Hf isotopic system. Thus, they are ideal objects for the Lu-Hf isotopic dating. In this paper, we have briefly introduced the principles and data processing methods of the micro-beam Lu-Hf isotopic dating analysis by using laser-ablation inductively coupled plasma tandem mass spectrometry (LA-ICPMS/MS), and have systematically summarized and reviewed research progresses made in the micro-beam Lu-Hf isotopic dating of phosphate and silicate REE minerals. Meanwhile, we here have undertaken the micro-beam Lu-Hf isotopic dating analysis for oxide REE minerals (fergusonite and aeschynite) by using the LA-ICPMS/MS for the first time. The obtained Lu-Hf ages are broadly consistent with their geological occurrences. These results presented here show that the elemental fractionation between Lu and Hf during the LA-ICPMS/MS analysis is insignificant, which significantly reduces the difficulty of micro-beam Lu-Hf isotopic dating of REE minerals. In the future, the precision and accuracy of micro-beam Lu-Hf isotopic dating can be further improved by developing high-efficient reaction gases and adopting multi-collector inductively coupled plasma tandem mass spectrometry (MC-ICPMS/MS) and femtosecond lasers. This will provide a new means with high spatial resolution, high efficiency, and high precision for dating REE minerals.