Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with roll-back, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calc-alkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K-and Na-alkalic and ultrapotassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.

Abstract:The Poiana Botizei-ible -Toroiaga-Rodna-Bârgău intrusive area (PBTTRB), northwest Romania, known as the "Subvolcanic Zone", is located between the Gutâi (NW) and Călimani (SE) volcanic massifs. It consists of rocks displaying a wide range of compositions and textures: equigranular or porphyritic with holocrystalline groundmass (gabbro-diorites, diorites, monzodiorites and granodiorites), and/or porphyritic with fine holocrystalline or glassycryptocrystalline groundmass, similar with effusive rocks: basalts, basaltic andesites, andesites, dacites and rhyolites. The time-span of intrusive rocks emplacement is similar with the nearest calc-alkaline volcanic rocks from Gutâi (NW) and Călimani (SE) massifs. They are represented by stocks, laccoliths, dykes and sills typical for an upper crustal intrusive environment. In the absence of biostratigraphic evidence, a comprehensive K-Ar study of intrusive rocks using whole rock samples, groundmass and monomineral fractions (biotite, hornblende) has been carried out in order to understand the magmatic evolution of the area. The oldest K-Ar ages recorded in the analysed rocks are close to 11.5 Ma and magmatism continued to develop until about 8.0 Ma. The inception of intrusion emplacement in the PBTTRB is coeval with intrusive activity spatially related to volcanism within the neighbouring Gutâi and Călimani massifs. However, its culmination at ca. 8 Ma ago is younger than the interruption of this activity at ca. 9.2 Ma in Gutâi and Călimani Mts where intrusive activity resumed for ca. 1 Myr. These circumstances strongly suggest that the geodynamic evolution of the area controlled the development of both volcanic and intrusive activity and their reciprocal relationships. The overall geological data suggest that in the PBTTRB intra-lithospheric transpressional-transtensional tectonic processes controlled the generation and emplacement of intrusive bodies between ca. 12-8 Ma.

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Earlier geological work in the Oa -Gutâi Mts (OG), Eastern Carpathians, has revealed the extensive presence of shallow subvolcanic intrusive bodies, both exposed on the surface and covered by Paleogene-Neogene sedimentary sequences and Neogene volcanic formations. This study is based on detailed mapping and sampling of the OG Neogene intrusive magmatic rocks. Thirty seven representative intrusions (sills, dykes, microlaccoliths, etc.) were selected for radiometric dating. These intrusions show a wide variety of petrographic rock-types: from microgabbros to microgranodiorites and from basalts to andesites. However, the intrusions consist of typical calc-alkaline, medium-K rocks, similar to the volcanic rocks which outcrop in the same areas. The K-Ar age determinations on whole-rock samples of intrusions yielded ages between 11.9 Ma and 7.0 Ma (from Late Sarmatian to Middle Pannonian). The results are in good agreement with the common assumption, based on the biostratigraphic and geological data, that large volumes of intrusions have formed during the paroxysm of the intermediate volcanic activity in the OG. Except for the Firiza basalt intrusive complex of the Gutâi Mts (8.1-7.0 Ma), the OG intrusions show similar K-Ar ages as the intrusions of the "Subvolcanic Zone" and Călimani Mts from Eastern Carpathians. The timing of the OG intrusive magmatism partially overlaps with the timing of the intrusive magmatic activity in the Eastern Moravia and Pieniny Mts. The systematic radiometric datings in the whole OG give clear evidence that the hydrothermal activity related to the epithermal systems always postdates intrusion emplacement.