Late Eocene subduction-related magmatism in northwest Iran: Zircon U-Pb geochronology and Sr-Nd-Pb isotopic constraints from the Bukan intrusions
Journal of African Earth Sciences, cilt.246, 2027 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 246
- Basım Tarihi: 2027
- Doi Numarası: 10.1016/j.jafrearsci.2026.106412
- Dergi Adı: Journal of African Earth Sciences
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Geobase, INSPEC, Zoological Record
- Anahtar Kelimeler: Isotope, Metasomatized mantle, Mineral chemistry, Monzonite, Sanandaj-Sirjan zone, Subduction
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
The Bukan intrusive bodies, exposed in the northern part of the Sanandaj-Sirjan Zone (NW Iran), ranges in composition from quartz-diorite to quartz-monzodiorite. Zircon U-Pb dating indicates that these rocks crystallized during the Late Eocene (36.51 ± 0.42 Ma to 37.08 ± 0.17 Ma). Mineral chemistry reveals augitic pyroxene and normally zoned plagioclase, with cores ranging from labradorite to andesine. Chondrite-normalized REE patterns display mild light REE enrichment, relatively flat HREE patterns, and minor negative Eu anomalies, while the primitive-mantle normalized diagram show pronounced negative Nb and Ta anomalies. Mineralogical and geochemical features classify these rocks as metaluminous, I-type plutonic rocks. Major and trace element variations suggest that magmatic differentiation was controlled mostly by fractional crystallization of a mantle-derived magma, with limited crustal contamination. The initial isotopic ratios are characterized by (87Sr/86Sr)(i) = 0.7044–0.7051, (143Nd/144Nd)(i) = 0.51259–0.51267, and εNd(t) = 0.15–1. Coupled with the trace element geochemistry, these isotopic signatures indicate involvement of mantle-dominated parent magma. Pb isotopes also display a narrow range: 206Pb/204Pb(i) = 18.56–18.65, 207Pb/204Pb(i) = 15.62–15.66, and 208Pb/204Pb(i) = 38.57–38.70, with slightly elevated 206Pb/204Pb(i) values extending toward the GLOSS field, indicating incorporation of slab-derived sediment. The I-type signature and strong negative Nb and Ta anomalies suggest a genetic link to subduction processes beneath the Sanandaj-Sirjan zone, originating from partial melting of an metasomatized subcontinental lithospheric mantle (SCLM) source.