2:15 PM - 2:30 PM
[HTT18-15] Sr-Nd-Fe isotopic constraints on the origin of Kiruna-type deposit in Zanjan, NW Iran
Keywords:iron oxide apatite deposit, Kiruna type, isotope, REE, hydrothermal, Iran
We focus on a Kiruna type deposit in Zanjan, Northwestern Iran. Magnetite-apatite deposit occurs in the Zanjan area, which is part of the volcano–plutonic belt of the Tertiary Alborz-Azarbaijan arc. In this study, Sr, Nd and Fe isotopes and trace element compositions including REEs in the ore mineral and host-rock samples were analyzed to constrain the origin of Kiruna type deposit in Zanjan.
Chemical compositions of major elements indicate that the Zanjan host rocks are monzonite to granite, metaluminous to peraluminous and I-type. The host rocks have LREE-enriched and HREE-flat patterns with slightly positive or slightly negative Eu anomalies. Trace element compositions show that the magnetites in the Zanjan IOA deposit has a Kiruna-type characteristic on V-Cr diagram.
The magnetite and apatite show LREE-enriched patterns with strong negative Eu anomalies, suggesting that both of the minerals were formed in the last stage of crystallization differentiation. Iron isotopic compositions of the magnetites show positive values indicating that high-temperature hydrothermal fluid contributed to the magnetite formation. The Sr and Nd isotopic compositions of the apatite are consistent with initial Sr and Nd isotope ratios of the Zaker quartz monzonite of the main host rock, indicating that the apatite has the same source of the host rock. The magnetites in the ore have slightly high Sr isotopic ratios and similar εNd values compared with the quartz monzonite, indicating that the magnetite has the same origin as the host rock but was slightly influenced by hydrothermal fluid.