Abstract
Nephrite is a high-valued gem material, whose geographical origin determination is a topic of interest to both consumers and producers since the geographic origin determines its price and reputation. In the present study, we suggest a two-step method for discriminating geographical origins of nephrite based on the rare earth element (REE) contents combined with chemometrics. In the first step, the REE contents of nephrite samples were determined by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), combined with previously reported data—the chondrite-normalized REE distribution pattern; the REE parameters of nephrite samples from six origins, namely Xinjiang, Qinghai, Russia, Guangxi, Guizhou, and Liaoning were then compared. In the second step, origin discriminant models were established by linear discriminant analysis (LDA), and the accuracy of the model was evaluated by leave-one-out cross-validation (LOOCV). The results showed that the REE contents were significantly different among the six nephrite origins with regional characteristics, which makes it possible to trace the origin. Using chondrite-normalized REE distribution patterns, the six nephrite origins can be divided into three separate groups: Xinjiang−Qinghai−Russia, Luodian−Dahua, and Xiuyan. Xiuyan nephrite can be directly distinguished from the other origins due to its unique REE distribution pattern. In the second step, the LDA discrimination models were performed on the remaining two groups. For the Luodian−Dahua group, the accuracy of the original classification and LOOCV were 97.9% and 85.4%, which indicated REE combined with LDA could effectively identify Luodian nephrite and Dahua nephrite. For the Xinjiang−Qinghai−Russia group, the accuracy of the original classification and LOOCV was 74.1% and 63.9%, respectively. Overall, this work proves that a combination of REE analysis and chemometrics has a certain feasibility and broad application prospects for geographical origin, and the same methodology can be applied to study the origin of other gem materials.
Funder
the Center for Innovative Gem Testing Technology, China University of Geosciences
Subject
Geology,Geotechnical Engineering and Engineering Geology
Reference54 articles.
1. Tang, Y., Chen, B., and Jiang, R. (1994). Chinese Hetian Nephrite, Xinjiang, Xinjiang People’s Publishing House.
2. Geochemistry and petrology of nephrite from Alamas, Xinjiang, NW China;J. Asian Earth Sci.,2011
3. The Tashisayi nephrite deposit from South Altyn Tagh, Xinjiang, northwest China;Geosci. Front.,2019
4. Geological situation and characteristics of Qinghai nephrite from Golmud in Qinghai Province;Geol. Build. Mater.,1996
5. Study of the minerogenetic mechanism and origin of Qinghai nephrite from Golmud, Qinghai, Northwest China;Sci. China Earth Sci.,2016