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Hubei, China
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The Miaoya Nb-REE deposit is located ~215 km SE to SSE of Xian in Hubei, China (#Location: 32° 29' 2"N, 109° 55' 3"E)

The deposit was discovered by the Northwest Geological Bureau in 1963 during a regional radiological survey and delineated between 1971 and 1980, but had not been mined as of 2020.

It is located just to the north of the southern margin of the broad Qinling Orogen, Central China, which lies along the collisional boundary between the North China and Yangtze cratons. It also lies on the southwestern rim of the the ~120 km diameter Wudang Shan metamorphic core complex, the northern half of which is composed of High Pressure blueschist rocks dated at 237 to 232 Ma (Ar/Ar; phengite and glaukamphibole/riebeckite; Mattauer et al., 1985; Ratschbacher et al., 2003; Hacker et al., 2004; Faure et al., 2008). For details of the setting and geology of the Qinling Orogen see the East Qinling Mo Belt record and the geotectonic map of the eastern half of the orogen.

The entire Miaoya deposit is hosted within the lens-shaped, 2900 x 500 to 800 m Miaoya syenite-carbonatite complex (Wang et al., 2020). The complex was emplaced along the structural contact between Neoproterozoic metaspilites, keratophyres and coeval agglomerates and tuffs, and a sequence of Silurian to Devonian carbonaceous sericite schists interbedded with dolomitic limestone and marble. The complex is interpreted to have been emplaced during an extensional phase of the orogen (Wang et al., 2020).

The complex is predominantly syenitic in composition and is zoned from a fine-grained texture in the centre, through xenomorphic granular in the middle and porphyritic on the outer edge (Zhang, et al., 2019). The mineralogical composition of the syenite is relatively homogenous, predominantly composed of K feldspar with lesser microcline, biotite, albite, plagioclase, quartz and sericite, together with minor zircon, monazite and kaolinite, nioboaeschynite, pyrochlore and Fe-Ti oxides, and have positive Nb, Ta, Zr and Hf anomalies with primitive mantle-normalised patterns. Euhedral K-feldspar crystals constitute over 70 vol.% of the rock, and are classified as orthoclase and microcline based on their microstructures. Zircon occurs as individual 0.2 to 1 mm long grains or mineral aggregates that are euhedral to subhedral (Su et al., 2019; Wang et al., 2020).

There are two types of carbonatite: calciocarbonatites and ferrocarbonatites. Calciocarbonatites consist mainly of calcite, apatite and biotite, together with allanite, monazite, bastnäsite(-Ce), and parisite-(Ce). Ferrocarbonatites, which are the later products of the complex, occur as dykes cutting both calciocarbonatites and syenites. They contain ankerite, calcite, apatite and fluorite, bastnäsite-(Ce), and parisite-(Ce). The carbonatites have lower Nb, Ba, U, Th and Zr, but higher P, Sr and REE concentrations than the associated syenites. However, both rock types have similar zircon U-Th-Pb ages (440 to 430  Ma), and nearly identical initial 87Sr/86Sr ratios of 0.70325 to 0.70413, and εNd(t) values of 2.5 to 3.2, implying that they were derived from a common source of carbonated silicate magmas (Su et al., 2019).

The deposit comprises more than 40 REE-Nb orebodies with an estimated reserve of 1.21 Mt of contained REE
2O3 (Wang et al., 2020).

A variety of REE-bearing minerals were formed, including bastnäsite, parasite, monazite, allanite and REE-rich apatite (Li, 1980). The occurrence of syenite and carbonatite is spatially closely associated. It is speculated that they have a common source and are the products of partial melting of the mantle (Su et al., 2019).

Zhang et al. (2019) dated bastnäsite and monazite from the deposit. They found there was a close association between the monazite grains and the major minerals of both the syenites and carbonatites (e.g., K-feldspar or calcite), but that the monazite also commonly had complex internal textures. Different domains of monazite yield two groups of U-Pb ages at 414 ±11 Ma (n=5) and 231 ±2 Ma (n=21), whereas the bastnäsite has an age of 206 ±4 Ma (n=14). The earlier age was obtained from homogenous monazite grains and was found to be in good agreement with zircon U-Pb ages of the Miaoya syenite-carbonatite complex. It was therefore considered to represent the timing of the major REE mineralising event at the deposit. The younger ages of 231 to 206 Ma were obtained from monazite grains with complex internal textures and bastnäsite in late veinlets, assumed to represent secondary, consecutive REE remobilisation events, possibly related to the compression process during formation of the Qinling Orogenic Belt (Su et al., 2019).

The most recent source geological information used to prepare this decription was dated: 2012.    
This description is a summary from published sources, the chief of which are listed below.
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  References & Additional Information
   Selected References:
Lu, J., Chen, W., Ying, Y., Jiang, S. and Zhao, K.,  2021 - Apatite texture and trace element chemistry of carbonatite-related REE deposits in China: Implications for petrogenesis: in    Lithos   v.398-399, 20p. doi.org/10.1016/j.lithos.2021.106276
Su, J.-H., Zhao, X.-F., Li, X.-C., Hu, W., Chen, M. and Xiong, Y.-L.,  2019 - Geological and geochemical characteristics of the Miaoya syenite-carbonatite complex, Central China: Implications for the origin of REE-Nb-enriched carbonatite: in    Ore Geology Reviews   v.113, 20p. doi.org/10.1016/j.oregeorev.2019.103101
Wang, Z.-Y., Fan, H.-R., Zhou, L., Yang, K.-F. and She, H.-D.,  2020 - Carbonatite-Related REE Deposits: An Overview: in    Minerals (MDPI)   v.10, 26p. doi:10.3390/min10110965.
Wu, B., Hu, Y.-Q., Bonnetti, C., Xu, C., Wang, R.-C., Zhang, Z.-S., Li, Z.-Y. and Yin, R.,  2021 - Hydrothermal alteration of pyrochlore group minerals from the Miaoya carbonatite complex, central China and its implications for Nb mineralization: in    Ore Geology Reviews   v.132, 20p. doi.org/10.1016/j.oregeorev.2021.104059.
Ying, Y., Chen, W., Lu, J., Jiang, S.-Y. and Y. Yang, Y.,  2017 - In situ U-Th-Pb ages of the Miaoya carbonatite complex in the South Qinling orogenic belt, central China: in    Lithos   v.290-291, pp. 159-171.
Ying, Y.-C., Chen, W., Chakhmouradian, A.R., Zhao, K.-D. and Jiang, S.-Y.,  2023 - Textural and compositional evolution of niobium minerals in the Miaoya carbonatite-hosted REE-Nb deposit from the South Qinling Orogen of central China: in    Mineralium Deposita   v.58, pp. 197-220.
Ying, Y.-C., Chen, W., Simonetti, A., Jiang, S.-Y. and Zhao, K.-D.,  2020 - Significance of hydrothermal reworking for REE mineralization associated with carbonatite: Constraints from in situ trace element and C-Sr isotope study of calcite and apatite from the Miaoya carbonatite complex (China): in    Geochimica et Cosmochimica Acta   v.280, pp. 340-359.
Zhang, W., Chen, T., Gao, J.-F., Chen, H.-K. and Li, J.-H.,  2019 - Two episodes of REE mineralization in the Qinling Orogenic Belt, Central China: in-situ U-Th-Pb dating of bastnasite and monazite: in    Mineralium Deposita   v.54, pp. 1265-1280.

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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