Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 12. 1985. (Budapest, 1985)

FRAGMENTA MINERALOGICA et PALAEONTOLOGICA 12. 1985 P- 518 Petrochemistry of the Neogene and Quaternary basaltic volcanism in the Carpathian Basin By EMBEY-ISZTIN, A., PELTZ, S. and PÓKA, T. (Received November 29, 1984) Abstract: For the first time, petrochemical character based on the major element chemistry of young basalts from the whole of the Carpathian Basin area is considered and discussed at some length. The older Miocene-Pliocene basalts are calc-alkaline in nature, while the younger, Plio-Pleistocene basalts are alkaline. These latter ones cover however a very wide range of composition from the olivine tholeiites to the extremely undersaturated melilite nephelinites. The degrees of partial melting and/or differentiation have been estimated. During the Neogene two kinds of basaltic volcanism occurred in the Carpathian Basin that can be distinguished from each other both by their tectonic settings and petrochemical characteristics. The older one manifested itself mainly in the Miocene but in the Eastern Carpathians also in the Pliocene in close association with more acidic basaltic andésites, andésites, dacites, and rhyolites as a result of a subduction process. On the contrary, the younger basaltic activity took place during Plio-Pleistocene times. The volume of these volcanic products is rather restricted and the geographical distribution of individual volcanoes or volcanic regions does not show any regularity. Some volcanic regions are situated close to the Alp-Carpathian Mountain Range, e.g. the volcanoes of the Basin of Graz, Austria and the Persani Mts in the Eastern Carpathians, Transylvania (Fig. 1), while others are dispersed in the Pannonian Basin, e.g. the volcanoes of the Little Hungarian Plain and the Balaton Highland. Basalts of this group show alkaline affinity and they should be considered as typical within-plate basalts (EMBEY-ISZTIN 1981), the origin of which is connected with a rising mantle diapir. In the following a brief account on the petrochemistry of the different basaltic regions will be given. Basalts of Transylvania and the Banat Region At the end of the Neozoic eruptive activity a volcanism of restricted development compared to the andesitic and dacitic ones occurred over the territory of Eastern Part of the Carpathian Basin; however the mineralogical composition of its volcanic products is varied (basanites, nepheline basalts, olivine basalts, basaltic andésites, as likewise its manifestation forms: explosive, effusive, intrusive). The regions comprising basaltic rocks in accordance with the chemical classification are as follows: the Northwestern Banat, the Northern part of the Poiana Rusca Mts, the Metaliferi Mts, the Cälimani Mts, and the Persani Mts (Fig. 1).