Ping Li

Hubei Province is a significant center for cultural and trade exchange in Central China. However, since no nephrite deposit has been discovered in Hubei, nephrite artifacts excavated within its jurisdiction must have been obtained from other regions. Tracing their provenance can contribute to our understanding of the trade exchange between ancient Hubei and other regions. In this study, the appearance, spectroscopy, and chemical compositions of nephrite artifacts excavated from the Fangjiagang Cemetery of the Eastern Zhou Dynasty, Hubei Province, were systematically studied, and their provenance was discussed. The characteristics of a weathered layer of raw nephrite material retained in one of the jade artifacts (M22:5) indicate it should be made from the placer nephrite of Hetian, Xinjiang. Infrared and Raman spectroscopy confirms that both the whitened and unwhitened areas in the samples are composed of tremolite, indicating that the whitening mechanism should be attributed to the etched structures caused by weathering rather than a change in the major mineral composition caused by high temperature. When no obvious appearance-based characteristics remain, chemical compositions become a crucial tool for discussing the provenance of jade artifacts. The chondrite-normalized rare earth element patterns for the samples suggest that their formation is associated with granite intrusion, implying that the placer nephrite of Hetian, Xinjiang; Xiuyan nephrite, Liaoning; Golmud nephrite, Qinghai; Xiaomeiling nephrite, Jiangsu; Vitim nephrite, Russia; and Chuncheon nephrite, South Korea, are potential sources. However, the trace element spider diagrams for the samples show a better match with those of the placer nephrite of Hetian. The placer nephrite of Hetian was used in Fangjiagang Cemetery, indicating that the trade exchange between the Eastern Zhou dynasty and the Hetian area had already been established.

Hydrogen and oxygen isotopes of ore-forming fluid of nephrite deposits have always been changing due to mixings between different fluids and oxygen isotope exchanges between the ore-forming fluid and country rocks, resulting in that the tremolite (or actinolite) has to constantly re-establish new isotope fractionation equilibriums with the dynamic fluid, which is of great significance to understand the genesis of hydrogen and oxygen isotopes of nephrite. Based on this, Taylor’s closed model and fluid mixing model are used to unravel the control of multi-stage evolution of ore-forming fluid on the δD and δ¹⁸O of nephrite. Although Taylor’s closed model is conducive to interpreting the genesis of nephrite with light δD and δ¹⁸O, such as Vitim nephrite, Russia, and Chuncheon nephrite, South Korea, it is unable to be effectively used in other nephrite. The fluid mixing model can quantitatively constrain proportions of different fluids during different ore-forming stages. Multiple solutions of ore-forming fluids of carbonate rock-related nephrite result from the absence of external constraints, such as isotope compositions of intrusive rocks, carbonate rocks, and meteoric water. Due to the generally heavy δ¹⁸O of country rocks, a small amount of meteoric water that enters the hydrothermal system in the later ore-forming stage is insufficient to offset the δ¹⁸O increment of nephrite caused by the oxygen isotope exchange between country rocks and water, which should be responsible for the abnormal heavy δ¹⁸O of Luodian nephrite, Dahua nephrite, Sanchakou nephrite, Xiaomeiling nephrite, etc., and not metamorphic water dominating their formation.

Hydrogen and oxygen isotopes of ore-forming fluid of nephrite deposit have always been changing due to mixings between different fluids and oxygen isotope exchanges between the ore-forming fluid and country rocks, resulting in that tremolites (or actinolite) have to constantly re-establish new isotope fractionation equilibriums with the dynamic fluid, which is of great significance to understand the genesis of hydrogen and oxygen isotopes of nephrites. Based on this, Taylor closed model and fluid mixing model are used to unravel the control of multi-stage evolution of ore-forming fluid on the δD and δ18O of nephrite. Although Taylor closed model is conducive to interpreting the genesis of nephrite with light δD and δ18O, such as Vitim nephrite and Chuncheon nephrite, it is unable to be effectively used in other nephrites. The fluid mixing model can quantitatively constrain proportions of different fluids during different ore-forming stages. Multiple solutions of ore-forming fluids of carbonate rock-related nephrites result from the absence of external constraints, such as isotope compositions of intrusive rocks, carbonate rocks and meteoric water. Due to the generally heavy δ18O of country rocks of carbonate rocks, a small amount of meteoric water that enters the hydrothermal system in the later ore-forming stage is insufficient to offset the δ18O increment of nephrite caused by the oxygen isotope exchange between country rocks and water, which should be responsible for the abnormal heavy δ18O of Luodian nephrite, Dahua nephrite, Sanchakou nephrite, Xiaomeiling nephrite, etc, not metamorphic water dominating their formation.