A new tectonic-geochemical approach using LA-ICP-MS to constrain the provenance of East Asian carbonate-related nephrite

Abstract

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.