Late Cretaceous alkali basalts of Talesh area: Implication for tectonic evolution of continental margin in the southern Eurasia (western Alborz)

Amani, Khadijeh; Delavari, Morteza; Amini, Sadraldin; Tabbakh Shabani, Amir Ali

Volume 7, Issue 1 (Spring & Summer 2021) KJES 2021, 7(1): 39-62 | Back to browse issues page

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Amani K, Delavari M, Amini S, Tabbakh Shabani A A. Late Cretaceous alkali basalts of Talesh area: Implication for tectonic evolution of continental margin in the southern Eurasia (western Alborz). KJES 2021; 7 (1) :39-62
URL: http://gnf.khu.ac.ir/article-1-2783-en.html

Late Cretaceous alkali basalts of Talesh area: Implication for tectonic evolution of continental margin in the southern Eurasia (western Alborz)

Khadijeh Amani ^*

¹, Morteza Delavari²

, Sadraldin Amini²

, Amir Ali Tabbakh Shabani²

1- Kharazmi University , goe.amani@gmail.com
2- Kharazmi University

Abstract: (718 Views)

Talesh alkali basalts (TAB), accompanied by Upper Cretaceous sedimentary units, are exposed in the western Alborz (North of Iran). Clinopyroxene, plagioclase, ± alkali feldspar are the main minerals in these rocks. The geochemical characters such as high contents of TiO₂ (1.68-2.96 wt.%), K₂O+Na₂O (3.09-9.06 wt.%), and high ratios of (La/Yb)_N (9.3-23.4), and Nb/Y>1(1.51-3.9), are consistent with their alkaline composition. In the primitive mantle-normalized multi-elements diagram, these rocks show enrichment of all incompatible elements that are similar to intraplate basalts or oceanic island basalts (OIB). The trace element ratios such as Zr/Y (5.52-10.80), Ta/Yb (1.12-2.65), Th/Yb (1.80-5.81), and Ti/Y (418-753) plot within the range of the alkali within plate basalt. Therefore, the Talesh area in the western Alborz recorded an intra-continental volcanic activity during the Late Cretaceous. This magmatism was generated by lower partial melting (3-7%) of an EMII-enriched asthenospheric mantle source of garnet lherzolite facies. The presence of the high-Ti alkali basalts in Talesh and other parts of western and central Alborz (such as southern Lahijan and Marzanabad basalts) to Georgia could be interpreted by forming a rift system on the southern margin of Eurasia from the Lesser Caucasus to the central Alborz during the Late Cretaceous.

Keywords: Alkali basalt, Late Cretaceous, Within plate, Talesh, Western Alborz, Eurasia

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Subject: Petrology
Received: 2021/04/17 | Accepted: 2021/09/1 | Published: 2021/08/1