Yimiao Liu

To characterize the trace-element characteristics of chrysoberyl, we studied twenty-six chrysoberyl samples from various localities by using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), photoluminescence (PL), and ultraviolet–visible–near-infrared (UV–Vis–NIR) spectroscopy. Chemical analysis has confirmed the existence of trace elements, including Fe, Ti, Ga, Sn, B, Cr, and V. The phenomenon of ionic isomorphic substitution frequently occurs at lattice sites within chrysoberyl. Notably, the isomorphic substitution of Al³⁺ in octahedral sites is significant, with the primary substituting elements being Fe, Ti, Cr, V, Ga, and Sn. The PL spectra of chrysoberyl samples exhibit sharp peaks at 678 and 680 nm, which are attributed to Cr³⁺, even in samples in which the Cr concentration is below the detection limit of LA-ICP-MS. This demonstrates the high-sensitivity feature of PL spectroscopy. The UV–Vis–NIR spectra of chrysoberyl samples consistently exhibit a band at 440 nm, and strong double narrow bands near 367 nm and 375 nm are observed. These spectral features are associated with Fe³⁺ chromophores—specifically, Fe³⁺-Fe³⁺ pairs or clusters and Fe³⁺ ions, respectively. By combining LA–ICP–MS analysis and PL mapping on a sample exhibiting color zoning, it has been found that the darker sections contain a higher concentration of Cr compared to the lighter sections, while the concentrations of other elements remain largely consistent. In other words, subtle variations in Cr concentration may be the underlying cause of color zoning in chrysoberyl.

Megacrystic zircons have recently been found in alluvial deposits in the Huadian area of northeastern China. However, studies have rarely been conducted on these zircons. In this article, we present systematic in situ trace element, U-Pb age and Hf isotope data regarding these Huadian zircons, with the aim of investigating their source characteristics and provenance. The studied zircons, with a diameter of 0.7–1.2 cm, are dominantly irregular in shape and have a rounded termination, with a color ranging from near-colorless to reddish brown to maroon. The zircons show oscillatory zoning in CL images, with a Th/U value of 0.18–1.27, which is consistent with the typical features of magmatic zircons. The positive ε_Hf(t) value of Huadian zircons (4.8–9.2) further indicates the presence of precipitation from the mantle-derived melt, with limited contamination of the crustal components. The obtained weighted mean ²⁰⁶Pb/²³⁸U age for these zircons is 17.9 ± 0.12 Ma, which is slightly older than the eruptional ages of the associated alkali basalts (from 17.6 ± 1.09 Ma to 17.8 ± 0.69 Ma), implying a short residence time in the mantle before entrainment. Huadian zircons incorporate a wide range of trace elements, including ΣREE (117–2790 ppm), Hf (4902–11856 ppm) and Y (145–3645 ppm) contents, generating mixed-source protolith assignments. As is suggested by the moderate variations seen in the Hf isotopes, we propose that the source melts of Huadian zircons are complex in nature, which is likely the result of the chemical heterogeneity of the upper mantle.

A comprehensive look at the gemological features and advanced analysis of blue and fancy-color sapphire from the agricultural area of Muling, China.