Cadomian tectonic evolution of Iran: records of an unusually hot and broad extensional convergent margin on the northern margin of Gondwana


Sepidbar F., Homam S. M., Ghaemi F., Stern R. J., Jun H., KARSLI O., ...More

International Geology Review, vol.66, no.7, pp.1352-1372, 2024 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 66 Issue: 7
  • Publication Date: 2024
  • Doi Number: 10.1080/00206814.2023.2238219
  • Journal Name: International Geology Review
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Agricultural & Environmental Science Database, Aquatic Science & Fisheries Abstracts (ASFA), Geobase, INSPEC, Pollution Abstracts
  • Page Numbers: pp.1352-1372
  • Keywords: active margin, Cadomian, Kariznou region, NE Iran, Proto-Tethys Ocean
  • Karadeniz Technical University Affiliated: Yes

Abstract

The continental crust of Iran is dominated by abundant calc-alkaline and alkaline plutonic and volcanic rocks and by rifted basins filled with mostly terrigenous sedimentary rocks that formed at a Late Ediacaran to Cambrian extensional convergent plate margin along the northern margin of Gondwana. Here we present new zircon U–Pb age, geochemical, and isotopic data from plutonic (granite-granodiorite) and metamorphic (gneiss) rocks in the Kariznou region of NE Iran to provide insights into the nature of the Cadomian convergent margin of Iran. Geochemical data indicate calc-alkaline signatures, characterized by strong depletions in Nb, Ta, P, and Ti and arc-like trace element patterns. New zircon U–Pb ages show that calc-alkaline granitoids and granitic gneiss formed at ~564 to 537 Ma and 538 Ma, respectively. Bulk rock Sr-Nd isotopic data of calc-alkaline rocks have εNd(t) = –5.42 to −5.53 and −6.93 to −7.43 for granite and gneiss, respectively. The gneisses show stronger interaction with and/or re-melting of older continental crust than do granitic rocks. We interpret Kariznou magmatic rocks as forming in association with strong extension accompanied by crustal assimilation. Extension initiated ~570 Ma with the deposition of Late Ediacaran sediments, and magmatism began at 545–535 Ma, generating calc-alkaline magmas. The tectonomagmatic evolution of the Kariznou region encapsulates the prolonged transition of Cadomian Iran from a strongly extensional convergent margin, possibly as a result of oblique oceanic subduction and slab roll-back of the subducting Proto-Tethys oceanic lithosphere, culminating in the formation of an Early Palaeozoic passive margin on the northern side of Gondwana.