Economic and Environmental Geology (자원환경지질)
- Volume 29 Issue 5
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- Pages.545-559
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- 1996
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- 1225-7281(pISSN)
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- 2288-7962(eISSN)
Geochemical Characteristics of Allanite from Rare Metal Deposits in the Chungju Area, Chungcheongbuk-Do (Province), Korea
충주지역 희유원소광상에서 산출되는 갈렴석의 지구화학적특성
- Park, Maeng-Eon (Dept. of Applid Geology, Pukyong National Univ.) ;
- Kim, Gun-Soo (Dept. of Geology, Pusan National Univ.) ;
- Choi, In-Sik (Center for Mineral Resources Research, Korea Univ.)
- Received : 1996.07.15
- Published : 1996.10.30
Abstract
Rare metal (Nb-Zr-REE) ore deposits are located in the Chungju area. Geotectonically, the rare metal ore deposits are situated in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits are distributed in Kyemyeongsan Formation which consist of schist and alkaline igneous rocks. Alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nd, Nd-Th group minerals. More than 15 RE and REE minerals are found in the ore deposits. Allanite, one of the Ce-La rich REE minerals belonging to the epidote group, is the most common mineral in the studied area. The allanite- bearing rocks may be devided into seven types by features of occurrence and mineral associations; zircon type (ZT), allanite-vein type (AT), feldspar type (KT), fluorite type (FT), quartz-mica type (QT), iron-oxide type (MT), and amphibole type (HT). The allanite veins (AT) and zircon rich rocks (ZT) contain the highest total REE contents. Differences in REE abundance can be interpreted in terms of varying portions of magmatic hydrothermal fluid. Petrographical and chemical data are presented for allanites which were collected from different types. The allanites show wide variations in optical properties, due in part to differences in their chemical composition (depending on the types) and to the degree of crystallinity of the individual specimens. Allanite metamicts in biotite are generally surrounded by well developed pleochroic haloes. Usually, allanite is accompanied by zircon and other REE-bearing minerals. CaO and total REE contents
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