Carbonatite dykes at Bayan Obo, Inner Mongolia, China

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Authors:LeBas, M. J.; Keller, J.; Kejie, Tao; Wall, F.; Williams, C. T.; Zhang Peishan
Author Affiliations:Primary:
University of Leicester, Leicester, United Kingdom
Universität Freiburg, Federal Republic of Germany
Academia Sinica, China
British Museum, United Kingdom
Volume Title:Mineralogy and Petrology
Source:Mineralogy and Petrology, 46(3), p.195-228. Publisher: Springer-Verlag, Vienna, Austria. ISSN: 0930-0708
Publication Date:1992
Note:In English with German summary. 30 refs.; illus., incl. sect., 15 tables, geol. sketch map
Summary:Calcite-rich dykes occur in the thrust fold belt near the Bayan Obo REE deposit. They cut a thrust inlier of granitic migmatite within folded Bayan Obo group sediments of Proterozoic age. Cl, XRF and EPMA studies show that the rock is a calcite carbonatite with Sr-Mn-bearing calcite, magnesioriebeckite, apatite, pyrochlore, K-feldspar and biotite. One dyke was chosen for detailed analysis. Its margin is strongly REE-mineralized with much monazite developed adjacent to zoned apatite. Secondary alteration is marked by the introduction of Fe and Mn. The adjacent migmatite is fenitized to a magnesioriebeckite-albite rock. The sedimentary dolomite of the Bayan Obo group consists mainly of Mn-Sr-REE-bearing ferroan dolomite and contains bands of opaque grains, apatite, monazite-(Ce), fluorite and taeniolite. Many trace element and isotope similarities between the carbonatized dyke and the sedimentary dolomite are revealed, and the evidence supports the possibility that the dolomite is a dolomitized carbonatite tuff. The Bayan Obo REE mineralization also shows geochemical similarities with the mineralization seen in the carbonatites, and a possible genetic connection is presented. [R.E.S.]
Subjects:Alteration; Apatite; Calcite; Carbonates; Carbonatites; Dike swarms; Dikes; Dolomite; Fenite; Fenitization; Fluorides; Fold and thrust belts; Genesis; Granitic composition; Halides; Igneous rocks; Intrusions; Iron ores; Magmas; Metal ores; Metals; Metamorphic rocks; Metasomatic rocks; Metasomatism; Migmatites; Mineral assemblages; Mineral composition; Mineral deposits, genesis; Monazite; Niobates; Oxides; Phosphates; Plutonic rocks; Precambrian; Proterozoic; Pyrochlore; Rare earth deposits; Rare earths; Sovite; Tantalates; Trace elements; Upper Precambrian; Asia; Bayan Obo China; China; Far East; Inner Mongolia China; Niobotantalates
Abstract Numbers:93M/3046
Record ID:1995018218
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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