Geochemistry of Rare Earth Elements in Iron Oxide and Apatite in Chadormalu Iron Ore Deposit, Bafq District, Iran

摘要

Chadormalu iron ore deposit is located in the Bafq district, central Iran. The Chadormalu iron oxide ores were emplaced along regional faults and associated with sub-alkaline magmas related to an extensional setting where rifting was important. Rare earth elements in iron oxide, apatite and host rocks were analyzed by ICP-MS, using the lithium metaborate fusion preparation method. A total of 4 analyses of apatite, 7 analyses of iron oxide (mainly magnetite) and 11 analyses of host rock have been made. The iron oxide of the studied area shows a pattern with 86.5～578 mg/kg REE, a strong LREE/HREE fractionation and negative Eu anomalies. The apatite of the Chadormalu iron ore deposit has a content of 13 685-15 610 mg/kg REE with a strong LREE/HREE fractionation and negative Eu anomalies. Apatite in sedimentary phosphorites has lower content of REE (<1 000 mg/kg) with Ce depletion which excludes a sedimentary origin of the studied ore deposit. The REE distribution in the intermediate to felsic host rocks is in similar to that of iron oxide and apatite but shows moderate LREE/HREE fractionation. The host rocks, the apatite and the iron oxide of the studied area have a similar REE pattern with negative Eu anomalies which indicates a probable common genesis. Geochemistry of apatite and iron oxide of the Chadormalu iron ore deposit is similar to other iron oxide-apatite ores of the world including those of Kiruna in Sweden.