Middle Eocene arc magmatism from Armenia with new insights into tectonic evolution of the Arabia-Eurasia collision zone
Journal
Lithos
Journal Volume
526-527
Start Page
108442
ISSN
0024-4937
Date Issued
2026-04
Author(s)
Lin, Yu-Chin
Pang, Kwan-Nang
Galoyan, Ghazar
Melkonyan, Rafael
Lee, Hao-Yang
Yang, Jin-Hui
Abstract
Eocene magmatism affecting northwestern Armenia, Lesser Caucasus, was distinctive in terms of magmatic distribution, particularly its close spatial association with the Amasia-Sevan-Hakari suture zone, raising the question of whether this activity reflects episodic subduction or a continuous history. Here, we characterize a set of Eocene igneous rocks in northwestern Armenia using radiometric dating and geochemical analysis. Magmatic duration established by zircon U-Pb and 40Ar/39Ar geochronology ranges from ∼47 Ma to ∼41 Ma. The rocks are characterized by a basalt-andesite-dacite association, calc-alkaline affinity, and arc-like trace element signature. Their whole-rock Sr-Nd isotopic compositions are depleted mantle-like (87Sr/86Sr(i) = 0.70360 to 0.70467, εNd(t) = +6.1 to +2.5), which, together with positive εHf(t) of zircon (+14.3 to +6.1), implies relatively recent derivation from the convecting mantle. Generally, these geochemical traits are consistent with hydrous fractional crystallization of a calc-alkaline basaltic parental magma. In view of recent plate tectonic reconstructions, we propose that the accretion of the South Armenian Block during ∼80–75 Ma triggered a southward subduction jump. This tectonic reorganization resulted in a ∼ 30 Myr magmatic hiatus, which is consistent with the physical jumping time for subduction transference, before establishing an ephemeral Eocene magmatic arc directly upon the suture zone between this microcontinent and the Eurasia margin. The studied calc-alkaline system was subsequently terminated by the arrival of the Anatolide-Tauride Block at ∼41 Ma, which triggered a regional shift towards alkaline magmatism. Collectively, these findings highlight the utility of the magmatic record in reconstructing successive accretions in continental collision zones.
Subjects
Armenia
Eocene magmatism
Ephemeral arc
Subduction jump
Successive accretions
Publisher
Elsevier BV
Type
journal article