Exploring the CAM18 Crystal as a Potential Reference Material for U-Pb Analysis of Zircon

In the process of in situ zircon U-Pb dating, it is an effective means to overcome the matrix effect by using a matrix-matched external reference material. However, the limited number of available zircon reference materials still makes it difficult to meet the research needs. In this paper, we performed a preliminary analysis of the gemological characteristics, trace elements and U-Pb ages of natural zircon CAM18 to assess its suitability as a reference material for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating. This tawny, gem-quality zircon has no visible inclusions and weighs approximately 0.55 g. Its density, full width at half maximum (FWHM) of the Raman peak and alpha flux (D & alpha;) indicate that the sample has suffered mild-to-moderate radiation damage without any thermal treatment. The LA-ICP-MS U-Pb dating results reveal that the trace elements content and U-Pb ages of the sample are fairly homogeneous at the 50 & mu;m scale, and there is no obvious loss of radiogenic Pb. The 206Pb/238U age (571.0 & PLUSMN; 3.0 Ma, 2s) and 207Pb/235U age (573.4 & PLUSMN; 6.0 Ma, 2s) are consistent within the analytical uncertainty, and the calculated concordia age is 571.4 & PLUSMN; 1.4 Ma (2s, n = 20). The variation in the 206Pb/238U ages is small, with a measurement repeatability of 0.46% (RSD), which is within the uncertainty of the age accuracy obtained by LA-ICP-MS. The oscillatory zoning, Th/U ratio (0.2) and chondrite-normalized rare-earth element (REE) pattern imply a magmatic origin of zircon CAM18. The Ti-in-zircon temperature ranges from 714 to 742 & DEG;C, and the oxygen fugacity ranges from & UDelta;FMQ-2.87 to & UDelta;FMQ-3.17, suggesting that it is crystallized in a reducing environment. All the results show that zircon CAM18 may has great potential in LA-ICP-MS U-Pb dating.