The Neogene Carpathian are is a complex magmatic are, extending from Slovakia into
Romania. The Transcarpathian region in SW Ukraine comprises the central part of this
are and was active in the Middle-Late Miocene. The volcanic structures of the Transcarpathian
region can be: divided into three major areas: a-Outer Arc; b-Intermediate zone; c-Inner
Arc. This division reflects the basic tectonic features of the Ukrainian Carpathians,
but differs From other parts of the Carpathian are. The Outer Arc consists of a number
of overlapping stratovolcanic structures, generally composed of lava flows, domes,
dykes/sills, volcanic necks and lahars of basaltic andesite, andesite and dacite composition.
In the Inner Arc, tuffs, ignimbrites and ash deposits of dacite, rhyodacite and rhyolite
are abundant. Lava flows of andesitic and basaltic-andesitic composition are present,
together with domes of dacite and rhyolite. The Intermediate zone is composed of lava
domes and small andesitic shield volcanoes. New K/Ar data obtained From 57 volcanic
rock samples has yielded K/Ar ages of 13.4-9.1 Ma. This time interval (similar to
4.5 million years) is similar to that of the neighbouring Carpathian volcanic regions
to the west (Tokaj Mts., Hungary) and to the east (Calimani, Romania). Badenian rhyolitic
tuffs buried within the Transcarpathian area represented the earlier phases of magmatism,
but they have been dated only by biostratigraphic methods. Thus, there is no evidence
in this area for any along-are migration of volcanism, unlike in the Eastern Carpathians
of Romania. Formation of volcanic structures started simultaneously in both Outer
Arc and Inner Arc volcanic areas (13.4 Ma). Different peaks of volcanic activity were
observed: (a) between 13.0-11.5 in the Inner Arc, interpreted as the major period
of generation of a complex of resurgent domes related to formation of a caldera, probably
situated toward the central part of the Transcarpathian depression, and (b) between
11.2-10.5 Ma in the Outer Arc, representing the main period of volcano generation,
The end of the volcanic activity (9.5-9.1 Ma) was scattered and less voluminous.
