Geology topics

Research about Croatia

Source-linked reports with geographic coverage including Croatia.

3 recordsLinked to original sources

USGS2010

Tertiary volcanic rocks from the southern Pannonian Basin, Croatia

The Tertiary volcanic rocks of the southern part of the Pannonian Basin are related to a sequence of tectonic events that occurred along the northern margin of the Dinarides when subduction ceased and after uplift of the region in middle Eocene time. The oldest rocks are andesites and dacites erupted during an Egerian to Eggenburgian marine transpression phase. In early Miocene time (about 17 Ma), rifting started, probably caused by the rise of the mantle, resulting in E-W extension and strike-slip faulting leading to formation of the Pannonian Basin. The initial rifting was accompanied by trachyandesitic volcanism of Karpathian age, followed by Badenian-age (15 to 13 Ma) volcanic activity producing basalts, andesites, and dacites. During these volcanic phases the Pannonian Basin, or the Paratethys, probably was periodically connected with the Mediterranean Sea. The final period of volcanism (about 9 to 7 Ma) produced alkalic basalts and basalts and occurred in fresh-water environments. These volcanic rocks have had a complex petrological evolution, related to an active continental margin. Egerian-Eggenburgian andesites and dacites can be explained by upper crustal assimilation with fractional crystallization (ACF) of primary basalt magma. The three younger associations originated by partial melting of rocks from both the upper mantle and the lower crust. Their evolution was accompanied by crustal contamination.

Carpathian Basin, Pannonian Basin↗

USGS2000

Geochemistry and geodynamics of a Late Cretaceous bimodal volcanic association from the southern part of the Pannonian Basin in Slavonija (Northern Croatia)

In this paper we present petrological and geochemical information on a bimodal basalt-rhyolite suite associated with A-type granites of Late Cretaceous age from the South Pannonian Basin in Slavonija (Croatia). Basalts and alkali-feldspar rhyolites, associated in some places with ignimbrites, occur in volcanic bodies that are interlayered with pyroclastic and fossiliferous Upper Cretaceus sedimentary rocks. The petrology and geochemistry of the basalts and alkali-feldspar rhyolites are constrained by microprobe analyses, major and trace element analyses including REE, and radiogenic and stable isotope data. Basalts that are mostly transformed into metabasalts (mainly spilites), are alkalic to subalkalic and their geochemical signatures, particularly trace element and REE patterns, are similar to recent back-arc basalts. Alkali-feldspar rhyolites have similar geochemical features to the associated cogenetic A-type granites, as shown by their large variation of Na 2 O and K 2 O (total 8–9%), very low MgO and CaO, and very high Zr contents ranging between 710 and 149 ppm. Geochemical data indicate an amphibole lherzolite source within a metasomatized upper mantle wedge, with the influence of upper mantle diapir with MORB signatures and continental crust contamination. Sr incorporated in the primary basalt melt had an initial 87 Sr/ 86 Sr ratio of 0.7039 indicating an upper mantle origin, whereas the 87 Sr/ 86 Sr ratio for the alkali-feldspar rhyolites and associated A-type granites is 0.7073 indicating an apparent continental crust origin. However, some other geochemical data favour the idea that they might have mainly originated by fractionation of primary mafic melt coupled with contamination of continental crust. Only one rhyolite sample appears to be the product of melting of continental crust. Geological and geodynamic data indicate that the basalt-rhyolite association was probably related to Alpine subduction processes in the Dinaridic Tethys which can be correlated with recent back-arc basins. The difference in geological and isotope ages between the bimodal basalt-rhyolite volcanism with A-type granite plutonism (72 Ma) and the final synkinematic S-type granite plutonism (48 Ma) can be taken as a lifetime of the presumed BARB system of the Dinaridic Tethys. Remnants of this presumed subduction zone can be traced for 300 km along the surrounding northernmost Dinarides.

Pannonian Basin↗

USGS1996

Hercynian I-type and S-type granitoids from the Slavonian mountains (southern Pannonian Basin, northern Croatia)

Two genetically different groups of Hercynian granitoids occur in the Slavonian Mountains which are included in the southern Pannonian Basin. I-type granitoids occur in Barrovian-type progressive metamorphic sequences which originated during the Hercynian orogeny from the Late Silurian to Lower Carboniferous magmatic-sedimentary complex. S-type granitoids, enriched in incompatible trace elements, are accompanied by penecontemporaneous migmatites which originated from rocks of the same progressive metamorphic sequences and lower continental crust. I-type granitoids are represented mostly by granodiorite and monzogranite impoverished in incompatible trace elements, with rare diorite and monzodiorite and basic to intermediate rocks. Hercynian age of the crystalline rocks is supported by numerous K-Ar, 40Ar-39Ar and Rb-Sr measurements carried out mostly on monomineralic concentrates. About 20 representative samples of S-type and I-type granites and associated rocks were selected from over 1000 samples and analyzed in detail for major and trace elements, including REE, Sr and O isotopic compositions; microprobe chemical composition of the main rock-forming minerals was determined. Although most major and trace element diagrams do not provide the best genetic discrimination between the Slavonian granitoids, Sr and O isotope composition, REE data and some other data for the S-type granitoids are indicative of their sedimentary and continental crust source, whereas the I-type granitoids were derived by partial melting of the upper mantle with slight crustal contamination.

Slavonian mountains, southern Pannonian Basin↗