U–Pb zircon ages and geochemistry of Kangareh and Taghiabad mafic bodies in northern Sanandaj–Sirjan Zone, Iran: Evidence for intra-oceanic arc and back-arc tectonic regime in Late Jurassic

• The Kangareh and Taghiabad bodies are mainly mafic rocks in the northwest Iran.
• 87Sr/86Sr and 143Nd/144Nd ratios infer depleted mantle source for these bodies.
• Chemical and isotope ratios confirm the intra-oceanic regime for these rocks.
• Our finding infers the accretion-type of continental growth of western of Iran.

The northern Sanandaj–Sirjan Zone (SaSZ) in northwestern Iran contains several granitoid and gabbroic bodies that are parallel to the Zagros Suture zone in a northwest–southeast direction. The fine-grained Taghiabad gabbro and coarse-grained Kangareh gabbroic bodies southwest of the Ghorveh in the northern SaSZ were crystallized at 158.0 ± 10.0 Ma and 148.3 ± 3.6 Ma, respectively, based on U–Pb zircon dating. The SiO2 contents of the Kangareh and Taghiabad rocks are similar and range from 45.5 to 51.5 wt.%, and the Al2O3 contents vary from 14 to 24 wt.%, with high Mg number (Mg# = 61–72% and 46–63%, respectively). The Taghiabad body has higher contents of TiO2, Fe2O3, and P2O5 than the Kangareh rocks. The Fe2O3 contents of the Taghiabad rocks vary from 6 to 15 wt.%, whereas those of the Kangareh rocks range from 5 to 9 wt.%. The TiO2 concentrations of the Taghiabad samples are high (1–3 wt.%), and these rocks can be classified as high Ti and Fe rocks. The chemical compositions of the two bodies show some clear differences. Positive εNd(t) values (+ 3 to + 8) and low initial 87Sr/86Sr ratios (0.7034 to 0.7054) indicate a depleted mantle source for both bodies. The variation and distribution of trace elements, REEs patterns, and initial 87Sr/86Sr–143Nd/144Nd ratios show that the Kangareh and Taghiabad bodies have high affinities to tholeiitic and alkaline magmatic series. These results suggest an arc and back-arc system regime in an intra-oceanic system than the Andean magmatic type regime for the origin of these bodies in the Middle to Late Jurassic period. These complexes merged with the northern SaSZ during accretion-type continental growth in the Late Jurassic.

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