Zircon U-Pb, geochemical and isotopic constraints on the age and origin of A- and I-type granites and gabbro-diorites from NW Iran

Moghadam H. S., Li Q., Griffin W. L., Stern R. J., Chiaradia M., KARSLI O., ...Daha Fazla

LITHOS, cilt.374, 2020 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 374
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1016/j.lithos.2020.105688
  • Dergi Adı: LITHOS
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aquatic Science & Fisheries Abstracts (ASFA), Chemical Abstracts Core, Geobase, INSPEC, Pollution Abstracts
  • Recep Tayyip Erdoğan Üniversitesi Adresli: Evet

Özet

The continental crust of NW Iran is intruded by Late Cretaceous I-type granites and gabbro-diorites as well as Paleocene A-type granites. SIMS and LA-ICPMS U-Pb analyses of zircons yield ages of 100-92 Ma (Late Cretaceous) for I-type granites and gabbro-diorites and 61-63 Ma (Paleocene) for A-type granites. Late Cretaceous gabbro-diorites (including mafic microgranular enclaves; MMEs) from NW Iran show variably evolved signatures. They show depletion in Nb and Ta on N-MORB-normalized trace-element spider-diagrams and have high Th/Yb ratios, suggesting their precursor magmas were generated in a subduction-related environment. Gabbro-diorites have variable zircon epsilon Hf(t) values of +1.2 to +8, delta O-18 of 6.4 to 7.4 parts per thousand and bulk rock epsilon Nd(t) of -1.4 to similar to +4.9. The geochemical and isotopic data attest to melting of subcontinental lithospheric mantle (SCLM) to generate near-primitive gabbros with radiogenic Nd isotopes (epsilon Nd(t) = similar to +4.9) and high Nb/Ta and Zr/Hf ratios, similar to mantle melts (Nb/Ta similar to 17 and Zr/Hf similar to 38). These mafic melts underwent further fractionation and mixing with crustal melts to generate Late Cretaceous evolved gabbro-diorites.