Zhi-Li Qiu

Investigating the provenance of carbonate-related nephrite (C-nephrite), a prestigious stone mainly found and used in East Asia and linked to various tectonic domains, has long been a challenge in Chinese jade archaeology. Examining the correlations between the geochemical compositions, formation mechanisms, and tectonic domains of C-nephrite mineralisation could provide important clues for tracing its origin. In this study, 352 C-nephrite samples from 15 key localities across East Asia were analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results show significant variations in lithium (Li) and beryllium (Be) concentrations, as well as cerium (Ce) anomalies, in the main mineral, fine-grained tremolite (Tr-II), of C-nephrites from different tectonic domains. C-nephrites from the North China Craton (NCC) have low Li and high Be (typically Li < 1.5 μg g⁻¹, Be > 6 μg g⁻¹) with no marked Ce anomalies. However, specimens from the Yangtze Craton (YC) show high Li and low Be (generally Li > 6 μg g⁻¹, Be < 1.5 μg g⁻¹) and pronounced negative Ce anomalies. C-nephrites from phanerozoic orogenic belts (POBs) typically exhibit variable Be contents (ranging from 6*Li + 6 to 1.5*Li − 7.5) and generally lack Ce anomalies. Further research indicates that the geochemical signatures are largely governed by sources of ore-forming fluids, depositional ages, and paleoenvironmental conditions of host carbonate rocks. Based on the correlational between the Li–Be–δCe features of Tr-II and the mineralisation mechanisms and tectonic domains, this study further categorises C-nephrite into the North China Craton type (NCC-nephrite), the Yangtze Craton type (YC-nephrite), and the Phanerozoic orogenic belt type (POB-nephrite). Thus, key information such as the formation mechanisms and tectonic domains of C-nephrite can be obtained through nearly non-destructive LA-ICP-MS trace element tests, thereby aiding in its source prediction and providing robust geological constraints for provenance determination. This study offers a new perspective on the provenance research of archaeological C-nephrites in East Asia and may also have broader applications extending to serpentine-related nephrite (S-nephrite) and other precious gemstones.

Chinese HPHT diamonds have improved dramatically in recent years. However, this brings a challenge in identifying type IIa colorless diamonds. In this study, eleven HPHT and three natural, colorless, gem-quality IIa diamonds were analyzed using magnified observation, Raman, PL and chemical element analysis. The results show that only HPHT samples possessed kite-like inclusions and lichenoid inclusions, as verified by their complex Raman spectra (100–750 cm⁻¹). Through PL mapping, HPHT and natural IIa diamonds were distinguished by their growth environments, which were reflected by PL peaks at 503, 505, 575, 637, 693, 694 and 737 nm. The chemical components of HPHT IIa diamond carbide inclusions are mainly Fe, Co, Ni and Mn, but those of Natural IIa are mainly Fe and Ni. As a result, the chemical components can be used to distinguish a natural colorless IIa diamond from a synthetic diamond.

The geographic locality determination of diamonds is of great significance in understanding the mantle evolution, restricting the illegal trade of conflict diamonds, etc. In the present article, the in-situ analysis of micro-FTIR surface scan technique was first applied to analyze 14 IaAB natural diamond specimens from China's three commercial localities. According to the FTIR spectra of diamonds, the nitrogen contents were calculated (1616 data points of FTIR) and used for mapping tracer. Th results showed that the nitrogen contents and its aggregation often varied in the process of diamond growth, and the nitrogen contents in initial nucleation stage could be higher or lower than in other stages. It is not an unidirectional variation for nitroge contents in different growth stages, indicating that the carbon and nitrogen had a complex exchange with mantle fluid during the diamond's crystallization course. It was regionally different between the diamonds from the three localities in the frequency distribution of nitrogen contents and NB%/N(T). Micro-FTIR mapping is more intuitive than the method of selecting discontinuous points, and it can trace the heterogeneous growth of nitrogen impurities in natural diamonds consecutively.

Xiuyan, Liaoning was an important locality of jade material of the Red Mountain Culture in the Neolithic Age in Chinese history where there are two types of raw material of nephrite jades, namely gravel nephrite jade (Hemo Yu in Chinese) and old nephrite jade (Lao Yu in Chinese). In the present paper, Laser Raman spectrum technique was applied to analyze the graphite enclaves in the nephrite jades of the two types of materials. The results show that the graphite enclaves in the two types of jades have different characteristics of Raman spectra, indicating that they probably were formed under different geological conditions, or originated from different ore-forming periods or were exploited from different section of ore body. Hence, laser Raman spectrum technique could be used as a supplementary measure for nondestructive detection to determine the occurrence of jades.