Search

BACKGROUND Apatite is a common U-bearing accessory mineral with a U-Pb closure temperature of ~500℃, making U-Pb dating of apatite a potentially valuable thermochronometer. However, its low U concentration, high common lead concentration and lack of reference material has limited widespread application to LA-ICP-MS dating. OBJECTIVES To develop a technique for U-Pb dating of apatite using laser ablation sector field inductively coupled plasma-mass spectrometry (LA-HR-ICP-MS). METHODS The U-Pb isotope ratio in apatite samples was determined by LA-HR-ICP-MS, with apatite MAD2 as the external standard to correct U-Pb and Pb-Pb elemental fractionation directly without a common Pb correction. RESULTS Long-term U-Pb analysis of Madagascar apatite sample (MAD2) showed homogeneous distribution of U, Pb and U-Pb isotope ratios, with average contents of U and Pb ~23.8×10-6 and ~13.5×10-6, respectively and weighted average 207Pb/206Pb and 206Pb/238U ratios of 0.0941±0.0006 and 0.0794±0.0004, respectively. Taking MAD2 apatite as a reference mineral, combined with 207Pb-correction method, the ages of apatite samples, McClure Mountain (521±5Ma), Tory-Hill-apt (1021±16Ma), a Durango (30.7±1.5Ma) and Fagnshan diorite apatite (~131Ma) can be determined accurately. CONCLUSIONS The Madagascar apatite sample (MAD2) can be used to calibrate apatite U-Pb isotope ratio measured by LA-ICP-MS directly, without common-Pb correction, similar to the calibration strategy in zircon U-Pb dating. The method greatly reduces the difficulty of data processing during apatite U-Pb dating by LA-ICP-MS, which is conducive to the wide application of the method.

[Introduction] To fill the shortcomings of traditional on-line power quality monitoring system, such as high deployment cost, large maintenance workload, low coverage and single function, which are highlighted under the higher requirement of information and intellectualization for the rapid development of UHV grid and new energy grid-connected technology. [Method] A method of identifying, extracting and calculating power quality characteristic parameters based on fault recorder data mining was proposed, and a system architecture of non-intrusive power quality monitoring, evaluation and decision support for wide area power grid using existing recorders and dispatching data network was designed. [Result] The results of pilot application show that the power quality indicators monitored by the system are comprehensive, the acquisition accuracy is better than the standard requirements, and the accuracy of event recognition and diagnosis is high. It has obvious advantages in station coverage, capacity of monitoring points, file upload, early warning and information delivery. [Conclusion] The design of the system is feasible and can extend and supplement the existing power quality online monitoring system in wide area power grid with a small input.