Econ. Environ. Geol. 2012; 45(6): 643-659

Published online December 31, 2012

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Mineralogy and Mineral-chemistry of REE Minerals Occurring at Mountain Eorae, Chungju

Byoung-Woon You1, Gill Jae Lee2* and Sang Mo Koh2

1Geology and Earth Environment Science, Chungnam National University
2Miveral Resources Research Division, Korea Institute of Geoscience and Mineral Resources

Correspondence to :

Gill Jae Lee

gill@kigam.re.kr

Received: September 5, 2012; Accepted: December 20, 2012

Abstract

The Chungju Fe-REE deposit is located in the Kyemyeongsan Formation of the Ogcheon Group. The Kyemyeongsan Formation includes meta-volcanic rocks and pegmatite hosted REE deposit which show different kind of REE-containing minerals. The meta-volcanic rocks hosted REE deposits’ main REE minerals are allanite, zircon, apatite, and sphene, whereas the pegmatite hosted REE deposits is mainly composed of fergusonite, and karnasurtite, zircon, thorite. The meta-volcanic rock hosted major REE mineral is allanite as the form of aggregation and contains 23.89-29.19 wt% TREO (Total Rare Earth Oxide), 4.71-9.92 wt% La2O3, 11.30-14.33 wt% Ce2O3, 0.11-0.29 wt% Y2O3, 0.15-0.94 wt% ThO2, as a formula of (Ca, Y, REE, Th)2.095(Mg, Al, Ti, Mn, Fe3+)2.770(SiO4)2.975(OH). Accompanying REE in a coupled substitution for Ca2+ (M1 site) and Al3+-Fe2+ (M2 site) leads to a large chemical variety. Due to the allanite’s high contents of Fe, it belongs to Ferrialanite. The pegmatite hosted deposit’s dominant REE mineral is fergusonite as prismatic or subhedral grains associated with zircon, fluorite and karnasurtite.Geochemical composition of the fergusonite(YNbO4) suggests substitution of Y-REE and Y-Th in A-site, and Nb-Ta-Ti in B-site, furthermore the proportion of Y2O3 and Nb2O5 is oddly 1:1.5 comparing to the ideal ratio 1:1 and Nb is higher than Y, also A-site Y actively substitutes with REE. Karnasurtite in pegmatite variously ranges 9.16-22.88 wt% Ce2O3, 2.15-9.16 wt% and La2O3, 0.44-10.8 wt% ThO2, as a calculated formula (Y, REE, Th, K, Na,Ca)1.478(Ti, Nb)1.304(Mg, Al, Mn, Fe3+)0.988(Si, P)1.431O7(OH)4·3H2O. Firstly the 870-860 Ma is the initial age of the supercontinent Rhodinia dispersal and subsequent A-1 type volcanism, which contains Fe, REE, and HFS(High Field Strength elements; Nb, Zr, Y etc.) elements in Fe-rich meta-volcanic rocks dominant Kyemyeongsan Formation, might mineralized allanite. Another synthesis is that regional metamorphism at late Paleozoic 300-280 Ma(Choet al., 2002) might cause allanite mineralization. Also pegmatite REE mineralization highly related to the granite intrusion over the Chungju area in Jurassic(190 Ma; Koh et al., 2012). Otherwise above all, A-1 type volcanism at the same time of the Kyemyeongsan Formation development, regional metamorphism and pegmatite, might have caused REE mineralization. Although REE ore bodies display a close spatial association, each ore bodies display temporal distinction, different mineral assemblage and environment of ore formation.

Keywords allanite, fergusonite, karnasurtite, REE, Mountain Eorae

Article

Econ. Environ. Geol. 2012; 45(6): 643-659

Published online December 31, 2012

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Mineralogy and Mineral-chemistry of REE Minerals Occurring at Mountain Eorae, Chungju

Byoung-Woon You1, Gill Jae Lee2* and Sang Mo Koh2

1Geology and Earth Environment Science, Chungnam National University
2Miveral Resources Research Division, Korea Institute of Geoscience and Mineral Resources

Correspondence to:

Gill Jae Lee

gill@kigam.re.kr

Received: September 5, 2012; Accepted: December 20, 2012

Abstract

The Chungju Fe-REE deposit is located in the Kyemyeongsan Formation of the Ogcheon Group. The Kyemyeongsan Formation includes meta-volcanic rocks and pegmatite hosted REE deposit which show different kind of REE-containing minerals. The meta-volcanic rocks hosted REE deposits’ main REE minerals are allanite, zircon, apatite, and sphene, whereas the pegmatite hosted REE deposits is mainly composed of fergusonite, and karnasurtite, zircon, thorite. The meta-volcanic rock hosted major REE mineral is allanite as the form of aggregation and contains 23.89-29.19 wt% TREO (Total Rare Earth Oxide), 4.71-9.92 wt% La2O3, 11.30-14.33 wt% Ce2O3, 0.11-0.29 wt% Y2O3, 0.15-0.94 wt% ThO2, as a formula of (Ca, Y, REE, Th)2.095(Mg, Al, Ti, Mn, Fe3+)2.770(SiO4)2.975(OH). Accompanying REE in a coupled substitution for Ca2+ (M1 site) and Al3+-Fe2+ (M2 site) leads to a large chemical variety. Due to the allanite’s high contents of Fe, it belongs to Ferrialanite. The pegmatite hosted deposit’s dominant REE mineral is fergusonite as prismatic or subhedral grains associated with zircon, fluorite and karnasurtite.Geochemical composition of the fergusonite(YNbO4) suggests substitution of Y-REE and Y-Th in A-site, and Nb-Ta-Ti in B-site, furthermore the proportion of Y2O3 and Nb2O5 is oddly 1:1.5 comparing to the ideal ratio 1:1 and Nb is higher than Y, also A-site Y actively substitutes with REE. Karnasurtite in pegmatite variously ranges 9.16-22.88 wt% Ce2O3, 2.15-9.16 wt% and La2O3, 0.44-10.8 wt% ThO2, as a calculated formula (Y, REE, Th, K, Na,Ca)1.478(Ti, Nb)1.304(Mg, Al, Mn, Fe3+)0.988(Si, P)1.431O7(OH)4·3H2O. Firstly the 870-860 Ma is the initial age of the supercontinent Rhodinia dispersal and subsequent A-1 type volcanism, which contains Fe, REE, and HFS(High Field Strength elements; Nb, Zr, Y etc.) elements in Fe-rich meta-volcanic rocks dominant Kyemyeongsan Formation, might mineralized allanite. Another synthesis is that regional metamorphism at late Paleozoic 300-280 Ma(Choet al., 2002) might cause allanite mineralization. Also pegmatite REE mineralization highly related to the granite intrusion over the Chungju area in Jurassic(190 Ma; Koh et al., 2012). Otherwise above all, A-1 type volcanism at the same time of the Kyemyeongsan Formation development, regional metamorphism and pegmatite, might have caused REE mineralization. Although REE ore bodies display a close spatial association, each ore bodies display temporal distinction, different mineral assemblage and environment of ore formation.

Keywords allanite, fergusonite, karnasurtite, REE, Mountain Eorae

    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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