Haüyne Alkaline Basaltoids Found in the Lesser Caucasus (Kapan District, Armenia) and Their Middle Pleistocene Age

Abstract

The results of isotope–geochronological study of Quaternary mafic volcanism in the Kapan neovolcanic center (Southern Armenia) are discussed. The rocks studied are represented by alkaline basaltoids with haüyne as the main foid (ordanchites and haüyne basanites), which are unique for the Caucasian Region. As is evidenced from the K–Ar age results, the lavas of Kapan district were erupted in the Calabrian age of the Pleistocene during two separate pulses of magmatic activity (1.1–1.2 and ~0.9 Ma). The composition of igneous rocks is characterized, first of all, by the spatial position of volcanic vents without an evident correlation between the petrologic–mineralogical characteristics of the lavas and the time of their eruption. The youngest magmatic activity in the Kapan center is probably an echo of the Middle Pleistocene large-scale volcanism in the adjacent Syunik Highland. However, it is evident that the mantle source of haüyne alkaline basaltoids had specific geochemical features.