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2. Mineralogy and Geochemical Characteristics of Scheelite Deposit at Xuebaoding in Pingwu, Sichuan Province, China.
- Author
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Cao, Qinyuan, Shi, Miao, Yuan, Ye, Ma, Shiyu, and Lu, Haoyu
- Subjects
LASER ablation inductively coupled plasma mass spectrometry ,GEMS & precious stones ,RARE earth metals ,SCHEELITE ,ORE genesis (Mineralogy) ,MINERALOGY - Abstract
Featuring subtle lithological alterations in the host rocks and containing colossal gemstone crystals, the scheelite deposit at Xuebaoding in the Pingwu region of Sichuan Province exhibits characteristics typical of a vein-like hydrothermal-type deposit. The scheelite from the Xuebaoding region is renowned for its high saturation of color, perfect crystal shape, and pure color. In this study, its crystal structure and mineralogical, geochemical, and in situ Sr-Nd isotope characteristics are all systematically characterized. Our objective is to determine the source of ore-forming materials, the timing of the mineralization, and the chemical composition of scheelite, including major elements, trace elements, and rare earths elements (REE). The scheelite samples were analyzed with a variety of methods such as polarizing microscopy, X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), electron probing, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In addition, conventional gemological tests were performed using instruments including gemstone microscopes, GI-UVB ultraviolet fluorescent lamps, grating spectroscopy, etc. The results demonstrate that scheelite exhibits a high refractive index, excellent crystallinity, and a granular structure. Clear color bands and ring structures are observed within the minerals, accompanied by interference colors of light blue, blue, and yellow. Additionally, the mineral components are relatively concentrated, with muscovite and illite serving as accessory minerals. Furthermore, the chemical composition of scheelite reveals a WO
3 /CaO mass ratio that approaches or exceeds the ideal value. Moreover, it exhibits a wide range of variations in total rare earth element (∑REE) content, which is characterized by an enrichment of light rare earths (LREE), significant negative Eu anomalies, and insignificant Ce anomalies. In addition, the metallogenic formation of scheelite can be estimated to have occurred during the Toarcian stage in the Lower Jurassic Epoch period, approximately 183 Ma. The study further revealed that A-type granite serves as the genesis type of scheelite, with most of the ore-forming materials originating from the upper crust and a few derived from younger crustal sources. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
3. Overview of Gemstone Resources in China.
- Author
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Yu, Xiao-Yan, Long, Zheng-Yu, Zhang, Yi, Qin, Li-Jie, Zhang, Cun, Xie, Zhi-Rong, Wu, Yu-Rui, Yan, Ying, Wu, Ming-Ke, and Wan, Jia-Xin
- Subjects
GEMS & precious stones ,IRON ores ,SPODUMENE ,MALACHITE ,GARNET ,TOURMALINE ,ZIRCON ,ORE deposits - Abstract
Gemstones are minerals of gem qualities used for adornment and decoration with the attributes of beauty, durability and rarity. Traditionally, although China has been regarded as the most important source for nephrite, over the past decades, a large variety of gemstone resources have been newly discovered in China owing to continuous exploration works. The vast land with various geological and geochemical backgrounds is rich in gemstone resources with potential for new deposits discoveries. In pegmatites, gemstones are related to granitic magma events and mainly occur in pegmatitic cavities, such as tourmaline, aquamarine, spodumene, spessartine, moonstone, quartz, apatite, and topaz. The eruption of Tertiary basaltic magma provides gem-quality sapphire, spinel, olivine, garnet, and zircon. The supergene oxidation zones of some copper and iron deposits in Hubei and Anhui province host gem-quality turquoise and malachite. Moreover, the formation of the nephrite deposit in China is mostly related to the carbonatite and serpentinite rocks involved in the metamorphic-metasomatic processes. This paper comprehensively introduces the distribution of gemstones deposits, as well as the gemological and mineralogical characteristics of gemstones in China. Our present investigation provides insights into the gemstone potential of China for further exploitation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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4. Turquoise Ornaments and Inlay Technology in Ancient China.
- Author
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QIN XIAOLI
- Subjects
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TURQUOISE jewelry , *GEMS & precious stones , *NEOLITHIC Period , *PENDANTS (Jewelry) , *COMPOSITE materials ,DESIGN & construction - Abstract
Most turquoise objects from early Neolithic sites in China are pendants made of a single material. From the later Neolithic period, however, people started to create turquoise ornaments with two or more composite materials. Ornaments were inlaid with turquoise and other materials using new techniques. In the Early Bronze Age, the turquoise production process reached its peak. At the Erlitou site, archaeologists found a large dragon-shaped turquoise mosaic, a variety of animal-shaped turquoise decorations, and turquoise workshops. The purpose of this paper is to understand the importance of turquoise products in the formation process of early state formation in China by analyzing the following topics: the technological evolution of turquoise manufacture, the combination of composite materials, the use of adhesive in turquoise inlay, and the associated production processes as they developed from the Neolithic to Early Bronze Age. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
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5. Zircon U-Pb geochronology and elemental and Sr–Nd isotope geochemistry of Permian mafic rocks in the Funing area, SW China.
- Author
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Mei-Fu Zhou, Jun-Hong Zhao, Liang Qi, Wenchao Su, and Ruizhong Hu
- Subjects
ZIRCON ,GEMS & precious stones ,SILICATE minerals ,BASALT ,VOLCANIC ash, tuff, etc. ,MAGMAS ,DIORITE - Abstract
Mafic-layered intrusions and sills and spatially associated andesitic basalts are well preserved in the Funing area, SW China. The 258±3 Ma-layered intrusions are composed of fine-grained gabbro, gabbro and diorite. The 260±3 Ma sills consist of undifferentiated diabases. Both the layered intrusions and volcanic rocks belong to a low-Ti group, whereas the diabases belong to a high-Ti group. Rocks of the high-Ti group have FeO, TiO
2 and P2 O5 higher but MgO and Th/Nb ratios lower than those of the low-Ti group. They have initial87 Sr/86 Sr ratios (0.706–0.707) lower and ɛNd (−1.5 to −0.6) higher than the low-Ti equivalents (0.710–0.715 and −9.6 to −4.0, respectively). The high-Ti group was formed from relatively primitive, high-Ti magmas generated by low degrees (7.3 –9.5%) of partial melting of an enriched, OIB-type asthenospheric mantle source. The low-Ti group may have formed from melts derived from an EM2-like, lithospheric mantle source. The mafic rocks at Funing are part of the Emeishan large igneous province formed by a mantle plume at ∼260 Ma. [ABSTRACT FROM AUTHOR]- Published
- 2006
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6. U-Pb and Hf-isotope analysis of zircons in mafic xenoliths from Fuxian kimberlites: evolution of the lower crust beneath the North China craton.
- Author
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Jianping Zheng, Griffin, W. L., O'Reilly, Suzanne V., Fengxiang Lu, Chunmei Yu, Ming Zhang, and Huimin Li
- Subjects
ZIRCON ,INCLUSIONS in igneous rocks ,GEMS & precious stones ,SILICATE minerals ,KIMBERLITE ,CRATONS - Abstract
Mafic xenoliths from the Paleozoic Fuxian kimberlites in the North China craton include garnet granulite, and minor pyroxene amphibolite, metagabbro, anorthosite and pyroxenite. The formation conditions of the amphibolites are estimated at 745-820 °C and 7.6-8.8 Kb (25-30 km); the granulites probably are derived from greater depths in the lower crust. LAM-ICPMS U-Pb dating of zircons from four granulites reveals multiple age populations, recording episodes of magmatic intrusion and metamorphic recrystallisation. Concordant ages and upper intercept ages, interpreted as minimum estimates for the time of magmatic crystallisation, range from 2,620 to 2,430 Ma in three granulites, two amphibolites and two metagabbros. Lower intercept ages, represented by near-concordant zircons, are interpreted as reflecting metamorphic recrystallisation, and range from 1,927 to 1,852 Ma. One granulite contains two metamorphic zircon populations, dated at 1,927±55 Ma and 600-700 Ma. Separated minerals from one granulite and one amphibolite yield Sm-Nd isochron ages of 1,619±48 Ma (
143 Nd/144 Nd)i=0.51078), and 1,716±120 Ma (143 Nd/144 Nd)i=0.51006), respectively. These ages are interpreted as recording cooling following metamorphic resetting; model ages for both samples are in the range 2.40-2.66 Ga. LAM-MC-ICPMS analyses of zircon show a range in176 Hf/177 Hf from 0.28116 to 0.28214, corresponding to a range of eHf from -34 to +12. The relationships between207 Pb/206 Pb age and eHf show that: (1) the granulites, amphibolites and metagabbro were derived from a depleted mantle source at 2.6-2.75 Ga; (2) zircons in most samples underwent recrystallisation and Pb loss for 100-200 Ma after magmatic crystallisation, consistent with a residence in the lower crust; (3) metamorphic zircons in several samples represent new zircon growth, incorporating Hf liberated from breakdown of silicates with high Lu/Hf; (4) in other samples metamorphic and magmatic zircons have identical176 Hf/177 Hf, and the younger ages reflect complete resetting of U-Pb systems in older zircons. The Fuxian mafic xenoliths are interpreted as the products of basaltic underplating, derived from a depleted mantle source in Neoarchean time, an important period of continental growth in the North China craton. Paleoproterozoic metamorphic ages indicate an important tectonic thermal event in the lower crust at 1.8-1.9 Ga, corresponding to the timing of collision between the Eastern and Western Blocks that led to the final assembly of the North China craton. The growth of metamorphic zircon at 600-700 Ma may record an asthenospheric upwelling in Neoproterozoic time, related to uplift and a regional disconformity in the North China craton. [ABSTRACT FROM AUTHOR]- Published
- 2004
- Full Text
- View/download PDF
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