Mineralogy and Geochemistry of Nephrite Jade from Yinggelike Deposit, Altyn Tagh (Xinjiang, NW China)

Abstract

The historic Yinggelike nephrite jade deposit in the Altyn Tagh Mountains (Xinjiang, NW China) is renowned for its gem-quality nephrite with its characteristic light-yellow to greenish-yellow hue. Despite the extraordinary gemological quality and commercial significance of the Yinggelike nephrite, little work has been done on this nephrite deposit, due to its geographic remoteness and inaccessibility. This contribution presents the first systematic mineralogical and geochemical studies on the Yinggelike nephrite deposit. Electron probe microanalysis, X-ray fluorescence (XRF) spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio mass spectrometry were used to measure the mineralogy, bulk-rock chemistry and stable (O and H) isotopes characteristics of samples from Yinggelike. Field investigation shows that the Yinggelike nephrite orebody occurs in the dolomitic marble near the intruding granitoids. Petrographic studies and EMPA data indicate that the nephrite is mainly composed of fine-grained tremolite, with accessory pargasite, diopside, epidote, allanite, prehnite, andesine, titanite, zircon, and calcite. Geochemical studies show that all nephrite samples have low bulk-rock Fe/(Fe + Mg) values (0.02–0.05), as well as low Cr (0.81–34.68 ppm), Co (1.10–2.91 ppm), and Ni (0.52–20.15 ppm) contents. Chondrite-normalized REE patterns of most samples exhibit strong to moderate negative Eu anomalies (0.04–0.67), moderate LREE enrichments, nearly flat HREE patterns, and low ΣREE contents (2.16–11.25 ppm). The nephrite samples have δ18O and δD values of 5.3 to 7.4‰ and –74.9 to –86.7‰, respectively. The mineralogy, bulk-rock chemistry, and O–H isotope characteristics are consistent with the dolomite-related nephrite classification. Based on mineral paragenetic relationships, three possible mineral crystallization stages are recognized: (1) diopside formed by prograde metasomatism; (2) nephrite jade formed by retrograde metasomatism and replacement of Stage I anhydrous minerals; (3) hydrothermal alteration after the nephrite formation. Features of transition metal contents indicate that the color of the Yinggelike nephrite is likely to be controlled by the Fe2+, Fe3+, and Mn. Yellowish color is related to Mn and especially Fe3+, while greenish color is related to Fe2+. Our new mineralogical and geochemical results on the Yinggelike nephrite provide better constraints on the formation of other nephrite deposits in the Altyn Tagh Mountains, and can facilitate future nephrite prospecting and research in the region.

Weathered Cortex of Eluvial–Deluvial Jadeite Jade from Myanmar: Its Features, Formation Mechanism, and Implications

“…Studies of the textures and mineral components of weathered cortexes have gemological applications in terms of identifying and grading raw jadeite and in the design and manufacture of jade pieces from Myanmar. Moreover, such studies can improve our understanding of the changes in jadeite jade caused by weathering from other localities, such as Guatemala (e.g., Xing et al [19]), and of the changes in other rough jade pieces due to weathering, such as nephrites from China and Russia (e.g., Jiang et al [20], Wang and Shi [21]), as well as the differences from the weathering of multiple-mineral rocks.…”

Nephrite from Xinjiang Qiemo Margou Deposit: Gemological and Geochemical Insights

“…Based on their genesis, nephrites can be classified into two distinct types: dolomite marble type (D-type) and serpentinite type (S-type) [1,10,[14][15][16]. Serpentinite-type nephrite forms at the contact between serpentinized peridotite and acidic to intermediate intrusions or metasediments.…”

“…Meanwhile, S-type nephrite, which is more widely distributed globally, has renowned and representative deposits in Hualian, Taiwan, Manasi, Xinjiang, China; East Sayan, Siberia, Russia; British Columbia, Canada; New Zealand; Poland; and Bulgaria. Meanwhile, dolomite marble-type nephrite is mainly found in the contact zones between magnesian marble and magmatic rocks [13][14][15][16][17]. The origin of nephrite deposits in the Xinjiang region is attributed to the contact metamorphism of magnesium carbonate rocks adjacent to local granite bodies [13,14].…”

A multi-strategy linear discriminant analysis (LDA) method coupled with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for discriminating the geographical origin of nephrite

“…The formation of D-type nephrite is related to dolomite replacement by silicic uids associated with "granitic" plutonism. 1 The historical signicance or supply of important D-type nephrite deposits include a host of localities in China like Xinjiang, [2][3][4][5] Golmud in Qinghai, 6 and Xiuyan in Liaoning, 7 together with other noteworthy sources worldwide at Chuncheon in South Korea, 8 Baikal region in Siberia, Russia, 9,10 Cowell in South Australia, 11 Złoty Stok in SW Poland 12 and Val Malenco in Italy. 13 Certainly, there are many more nephrite deposits on the globe that are not mentioned here as to this date these deposits have been either supply-inuenced or of good quality.…”