REE resource evaluation of some alkaline granites and their weathered crust in South Korea

Abstract

A reconnaissance chemical study was made on four granitic bodies in South Korea, on which high REE contents are expected. Triassic foliated granite of the Daegang body occurring along the boundary between the Yeongnam-Ogcheon terrains contains average REE+Y content of 414 ppm and the L/HREE ratio is 8.4. Triassic Hamchang granite of the Ogcheon terrain is composed of high-alkali and high-REE group, averaged as 508 ppm REE+Y, with L/HREE=19.0, and low-alkali and low-REE group averaged as 127 ppm REE+Y with L/HREE=23. On the contrary, the early Jurassic Hapcheon syenite at southeastern margin of the Yeongnam massif is low in REE+Y (171-217 ppm). The Paleogene Gigye granite in the Gyeongsang basin, which can be a split-off part along the Yangsan fault from the REE-rich alkaline Namsan body, contains 200-300 ppm REE+Y. Soil samples were collected from the weathered crust of these granitoids and compared with those of unweathered granitoid values.The soil values are generally lower than those of the unweath-ered granites in the Daegang granite (414 ppm REE+Y in rock vs. 240 ppm REE+Y in soil) and Gigye granite (342 vs. 243 ppm REE+Y), indicating most of the REE leached out during the weathering. The loss-and-gain is unclear on the Hamchang granite and Hapcheon syenite. No clear enrichment of REE during weathering has been so far observed on the granitic bodies in South Korea.