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 components and evolution of subcontinental lithospheric mantle beneath the North China Craton and the Yangtze Craton is a current topic in the geological study of China and the carbon isotopic composition of diamond is one of the most direct probes into cratonic lithospheric mantle processes. In this paper, in-situ SIMS (Secondary Ion Mass Spectrometry) techniques were used to analyze the carbon isotope compositions at different internal growth zones of diamonds from Shandong and Liaoning in the North China Craton and Hunan in the Yangtze Craton. It was found that the carbon isotopic range of diamonds from the North China Craton are rather distinct from those of the Yangtze Craton; the former has a range of −6.0/‰ to −2.0‰ (relative to VPDB) with an average value of −3.0‰ in their core areas, which is consistent with global peridotitic diamonds; the diamonds from the Yangtze Craton, however, have a carbon isotopic range from −8.6‰ to −3.0‰ with an average value of −7.4‰ in their core areas, being more consistent with global eclogitic diamonds. The variations of carbon isotope ratios between different internal growth zones in individual diamonds were different in the three diamond localities studied. There was a clear correlation between changes in carbon isotopic composition and phases of diamond dissolution and new growth, while no correlation was observed between δ ¹³C and internal inclusions. The variations suggest that the carbon isotopic compositions of mantle fluids were changing during the process of diamond crystallization, and that the heterogeneity of the carbon isotopic composition in mantle carbon reservoirs was a more important factor than carbon isotope fractionation in controlling the carbon isotopic compositions and their variation in diamonds. In addition, the preliminary results of in-situ nitrogen analyses demonstrated that the variation of carbon isotopic compositions between the core and outer growth zones does not correlate with nitrogen abundances, implying either that diamonds crystallized in an open environment or that the carbon isotopic composition and nitrogen contents in mantle fluids were controlled by other, not yet understood factors. The experimental results provide hints that the isotopic composition of carbon and its original sources were different in metasomatic fluids controlling diamond formation in the mantle beneath the North China Craton and the Yangtze Craton.

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.