Magmatic origin of Th-REE mineralization at the Se-Chahun ore deposit: based on geochemical and stable isotope data

Examination of geochemical distribution pattern of trace and rare earth elements in the rocks affected by metasomatic processes revealed a magmatic origin for Th-REE mineralization at the Se-Chahun ore deposit. Chondrite and primitive mantle-normalized patterns of REE and trace elements for the rhyolitic host rocks (which formed in a subduction setting) compared with the patterns of the Th-REE mineralization zone also provides evidence that the origin of the Th-REE mineralization zone is similar with rhyolitic magma or a magmatic chamber from which the rhyolitic magma was originated. This is also supported by oxygen and hydrogen isotopic data in actinolite paragenetically associated with Th-REE bearing minerals. Thorium minerals at the Se Chahun ore deposit include huttonite and thorite. O and H isotopic data for actinolite paragenetically associated with Th-silicates revealed a magmatic source for Th-REE mineralizing fluids in the ore deposit δD and δ18O for actinolite paragenetically associated with Th silicates are calculated between -73.29 to -42.04 and 6.65 to 7.71, respectively, which lie within the field of magmatic fluids.