The martite locally blocked and was incorporated into the younger bands of granular hematite. [UNVERIFIED CONTENT] Rare-earth mine in Baiyun'ebo or Bayan Obo. CO2 content was determined by using coulometric titration (Jackson and others, 1987). Because this ore type does not occur as a mappable unit, it is incorporated in banded ore types 2a (FH) and 2b (AeM) shown in figure 8. d. Monazite-phlogopite-alkali amphibole-magnetite banded ore (type AmpM, fig. They are 796-48,270, 796-48,277, 796-48,278, and 796-48,280 (table 14). 5). g. The fluorite content of the ores also makes it the world's largest fluorite d eposit. Fluorite and other gangue minerals, such as aegirine in 7B31-10 and apatite in 7B31-23 and 7B37-1, may be present. Dolostone marble having relatively high REE content, and monazite-hematite-apatite banded ores (table 6). AFC Energy Aktie 65.463 Tages-Trading-Chancen am Freitag den 04.12.2020 Diskussion 17:03:36 Dow und S&P schaffen nach Jobdaten erneut Rekorde Nachricht 16:43:06 On the basis of textural relations for all these samples of marble-hosted disseminated ore, alkali amphiboles replaced small amounts of monazite, and the amphibole, in turn, was replaced by magnetite. Wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) was used for analyzing unmineralized and weakly mineralized dolostone marble. EPMA data on REE content of apatites (table 5) are also in good agreement with data obtained by the SXRF method (Chen and others, 1993). younger than the H8 unit. Figure 21. It has 35.7 wt. Monazite from sample 34-24, with an internal isochron mineral age of 532+-3.1 Ma, is the next least radiogenic and has a 208Pb/204Pb initial ratio of 34.89+-0.15. Figure 8. Also widespread was the metasomatic replacement of host rocks by gangue minerals such as fluorite, aegirine augite, phlogopite, alkali amphibole, fine granular apatite, albite, and microcline. Because of the extremely fine grain size of most of the ore and gangue minerals in the Bayan Obo area, interference microscopy was used for identification of the minerals in DPTS's (Chao and Xie, 1990). percent) (table 14), which are low for La2O3 and uniquely high for Nd2O3 at Bayan Obo. A NASA Terra satellite image taken in 2006 showing the expanding Bayan Obo mine in China. BAYAN OBO MongolIA InneR MongolIA MongolIA CHINA Mapped Area Highway Paved road Railroad N 0 20 km 0 20 miles FIgURe 7. Furthermore, the H8 unit crops out over an area 16 km long and 2-3 km wide, an outcrop area much greater than that of any known igneous carbonatite. Sm-Nd monazite isochron age for bastnaesite and riebeckite is 1200 to 1300 Ma, whereas Th-Pb and Sm-Nd age of Ba-REE-F carbonates and aeschynite is 474 to 402 Ma. West Mine, Bayan Obo deposit (Bayun-Obo deposit; Baiyunebo deposit), Bayan Obo, Bayan Obo mining district, Baotou City (Baotou Prefecture), Inner Mongolia, China Bayan Obo deposit (Bayun-Obo deposit; Baiyunebo deposit), Bayan Obo, Bayan Obo mining district, Baotou City (Baotou Prefecture), Inner Mongolia, China . Locally, small amounts of REE minerals such as cebaite occur in low-grade, disseminated magnetite ores dominated by aegirine augite. 5, and 7B36-1B), with or without fluorite. The high MnO content of metasomatic alkali amphiboles generally seems to be characteristic of late-stage Fe mineralization. The monazite of sample 7B30-20 has about equal concentrations of La2O3 (13.60 wt. The geology of the region north of the Kuanggou fault, which is broken by many extensional and thrust faults, is distinctly different from that of the mine area, and the stratigraphic sequence there has been designated as an undifferentiated unit of Proterozoic to Paleozoic sedimentary rocks. At the end of the 1980s, China rapidly developed a mine in Bayan Obo, which has huge deposits of niobium. percent) than sample 7B37-3. 7). The mines north of the town are the largest deposits of rare-earth metals yet found and, as of 2005, responsible for 45% of global rare-earth metal production. Thin sections also show mortar texture wherein granulated fine-grained quartz occurs between large quartz grains. Geologic sketch map of the Bayan Obo region (modified from Institute of Geochemistry, 1988). Photomicrographs of a doubly polished thin section of sample 796-48,277, a low-grade ore consisting of alkali amphibole (mga), monazite (m), and magnetite (mt), as well as relict grains of the limestone marble host rock. An absolute mineral paragenetic sequence can be partially established on the basis of absolute ages of episodes of REE mineralization and the unique chemical compositions and isotopic ratios of the different generations of REE minerals. After more than 2 years of testing, the 232Th/208Pb internal isochron method was adopted for dating REE minerals (Wang and others, 1994). The Bayan Obo Iron Mine in the district is a large-scale operation extracting iron, rare earth, niobium and other valuable metals, covering a total area of 48 square kilometers with five major ore bodies. Figure 2. Figure 6. On the basis of sequential stratigraphic analysis, Qiao and others (1991) correlated the Bayan Obo Group with the Chartai Group and interpreted both groups as having been deposited on the North China Platform or craton (fig. Baotou's giant mine in Bayan Obo, Inner Mongolia near Baotou City, produces the bulk of the world's rare earths and does so as a byproduct of iron ore minin . 4; Wang, 1985) that took place at the northern edge of the North China Platform or craton. Most massive Fe ores contain less than 3 wt. Partial chemical composition and internal isochron mineral ages of monazites and bastnaesites of Bayan Obo. percent) of ferroan dolomite from H8 dolostone marble of Bayan Obo. Two DPTS's (parts A and B) were needed for large samples, which extended for a distance of more than 6 cm across the bands. Photomicrographs of a doubly polished thin section of sample 796-48,517 showing relict banded ore consisting of folded monazite and granular hematite surrounded and replaced by late-stage, fresh magnetite. The presence of small amounts of MgO in these samples is probably due to the presence of phlogopite observed in the hand specimen, whereas Fe comes from fine granular aegirine augite and magnetite. Ilmenite is present locally, particularly in the late-stage banded ores. percent). EPMA data on LREE's of monazite and bastnaesite (table 14) are in general agreement with the published average chemical composition of 17 monazite and 22 bastnaesite samples from Bayan Obo, determined by wet chemical methods (Zhang and Tao, 1986, p. 99). In order to … Most monazites with different internal isochron ages, chemical compositions, and initial 208Pb/204Pb ratios were probably brought in at different times and deposited by different hydrothermal solutions. Phlogopite, commonly associated with the various generations of alkali amphiboles, replaces host dolostone or limestone marble. This magnesio-riebeckite is high in FeO (22.74 wt. This section was subsequently described in greater detail by Chao and others (1992). Bayan Obo deposit (Bayun-Obo deposit; Baiyunebo deposit), Bayan Obo, Bayan Obo mining district, Baotou City (Baotou Prefecture), Inner Mongolia, China : Super large polygenic REE-Fe-Nb deposit (Bayan-Obo type), discovered as an iron deposit in 1927. Only a few examples of textural evidence of metasomatic replacement at Bayan Obo are illustrated here. By far China, and the world’s leading rare earth producer is China Northern Rare Earth Group High-Tech Co which owns the giant Bayan Obo mine in Baotou, Inner Mongolia. Figure 13. Pb ratio. Less common REE minerals are parisite and cebaite (table 1). Evidence for the earliest episodes of granular hematite mineralization is found in sample 8B35-2, where fine-grained hematite with associated Nb-rutile replaced monazite with an age of 474+-4.5 Ma (table 14), and therefore crystallized after that date. Figure 32. Internal isochrons of monazite from two samples (490,330 and 34-24) of Bayan Obo ores showing ages and 208Pb/204Pb initial ratios. percent, respectively, table 15). In Bayan Obo village, which was the site of the Bayan Obo mine, the sheep often have external and internal double teeth, and the wool of the sheep is quite ugly. Albite also occurs in veinlets in some banded ores and in late-stage albite-hornblende veins cutting H9 pelitic host rocks. data, 1988), the H8 carbonate rocks were probably deposited as a limestone unit, which was dolomitized after lithification by addition of large quantities of Mg and Fe to form the principal mineral, ferroan dolomite. By far China, and the world’s leading rare earth producer is China Northern Rare Earth Group High-Tech Co which owns the giant Bayan Obo mine in Baotou, Inner Mongolia. Additionally, concentrations of gallium can be found in bauxite, a sedimentary rock typically mined for aluminium. The chemical compositions and internal isochron ages of monazites and bastnaesites are given in table 14, arranged according to internal isochron ages. Die oft verwendete abgekürzte Bezeichnung Seltene Erden statt Metalle der Seltenen Erden ist missverständlich. Baotou’s giant mine in Bayan Obo, Inner Mongolia near Baotou City, produces the bulk of the world’s rare earths and does so as a byproduct of iron ore mining. f. H8 limestone marble with disseminated monazite closely associated with significant amounts of extremely fine grained granular apatite, with or without bastnaesite, magnetite, and granular hematite (sample 398-46,305). A total of 14 monazite samples and 3 bastnaesite samples were separated from Bayan Obo disseminated and banded ores by the Tianjin Geological Research Academy laboratory in Tianjin and the USGS laboratory in Reston, Va. Bayan Obo is an industrial mining town based on rare earth production (as well as iron and niobium), metallurgy and machinery manufacturing in Inner Mongolia, China.Self-proclaimed “Hometown of Rare Earths” [1], it is the largest rare earth element (REE) mineral deposit in the world, accounting for 45% of worldwide REE production in 2019 [2].]. Therefore, we conclude that the REE's in unmineralized Bayan Obo dolostone marble are present only in detrital apatite and that RE2O3 contents greater than about 800 ppm in fine-grained dolostone marble are due to weak epigenetic mineralization. The RE2O3 contents of the four samples listed in table 10 range from 36.42 to greater than 48.10 wt. No direct evidence of rifting involving the Bayan Obo Group in the mine region was observed, although rifting was cited by Wang and others (1991) on the basis of geophysical evidence and the reported occurrence of volcanic rocks in the Chartai and Bayan Obo Groups. Concentrations of LREE's (La, Ce, Nd, and Pr), U, Th, and Pb and initial 208Pb/204Pb ratios constitute the eight chemical parameters used to distinguish monazites and bastnaesites in this study. Chemically, aegirine augite and local, sparse martite are reflected by the total Fe present (Fe2O3 ranges from 6.86 to 20.0 wt. percent Fe2O3 and 17.80 wt. Chemical composition (wt. Selection of ore types for chemical analysis was based on mineral assemblages. Mineralogy of the Bayan Obo ore For example, in sample 796-48,277, a drill hole sample of low-grade, disseminated monazite-magnetite ore that contains abundant alkali amphibole (figs. Both optical microscopy and SEM were used for textural analysis of mineral replacement relations. Röntgenite-(Ce), etc. These banded ores consist of prominent bands containing abundant monazite and bastnaesite. Three types of alkali amphiboles, namely, metamorphic, metasomatic, and metasomatic-metamorphic, were dated. International Journal of Applied Ceramic Technology 12 (S1), 41-48. Radiometric ages of minerals in sample 8B7: A, Internal isochron showing mineral age of the bastnaesite (555+-11 Ma), which replaced the host dolostone marble; B, 40Ar/39Ar plateau showing age (395.5+-4.4 Ma) of the coexisting alkali amphibole. Bayan Obo is a mining district abundant in mineral resources. The effect of metamorphism on mineral ages was estimated by Chao and others (1992, 1993). [6] Bao Wei L., Lei Bo D., and Xue Feng Z., et al (2015). percent SiO In this sample, the monazite was determined to be 432+-8.5 Ma (table 14 and fig. High-Fe, REE, and fluorite banded ores (table 9). Replacement textures observed in the field and petrographically from DPTS's are the most important criteria, and are aided by corroborative criteria such as chemical compositions and radiometric isotopic ages of various generations of ore and gangue minerals. On the basis of the age of this alkali amphibole, the Bayan Obo banded ores are interpreted to have formed before 400 Ma. 5), with bastnaesite only (samples 34-24, not shown in fig. Apatite occurs locally. Because of the heterogeneity and erratic variation of mineral assemblages in bands in banded ores, the chemical composition of an ore is not expected to correlate with the modal mineral composition of the corresponding DPTS. The rapid urbanization of China and associated demand for land resources necessitates remediation, redevelopment, and reclamation of contaminated soil. percent). Monazite and alkali amphiboles are replaced and cut by fresh magnetite. China's Bayan Obo mine produces around half the world's supply of the 17 'rare earth' metals - metals crucial to high-end electronics such as mobile phones, telephones, hi … Chemical composition (wt. It is under the administration of Baotou City, the downtown of which is more than 120 kilometres (75 mi) to the south. La un moment dat, întreaga Mongolie se afla sub ocupație chineză, dar, odată cu căderea dinastiei Qing la începutul secolului XX, Mongolia � 8. DPTS's show the presence of detrital quartz, which accounts for the high concentration of SiO2, and small elongate aggregates of fine-grained monazite, which account for the RE