Eoalpine (Cretaceous) very low- to low-grade metamorphism recorded on the illite-muscovite-rich fraction of metasediments from South Tisia (eastern Mt Papuk, Croatia)

Abstract

Eoalpine very low-to low-grade metamorphism related to Cretaceous orogenesis has been investigated in the Slavonian Mts, Croatia. Samples belonging to the Psunj metamorphic complex (PMC), the Radlovac metamorphic complex (RMC) and Permian-Triassic and Triassic sedimentary sequences (PTSS) were studied. The Kübler and Árkai indices of all the analysed samples indicate high-anchizonal to epizonal metamorphism. The degree of Eoalpine metamorphism tends to be constant in all samples implying that the different complexes passed through and recorded the same event. Measurements of illite-white K-mica b 0 -parameter of the RMC samples imply transitional low-to mediumpressure character of the metamorphism. These data together with K-Ar ages (~100-80 Ma) measured on illite-white K-mica rich < 2 m grain-size fractions point to Late Cretaceous very low-to low-grade regional metamorphism presumably related to the main nappe-forming compressional events in the Pannonian Basin and the Carpathians. The P-T-t (pressure-temperature-time) evolution of the studied area is in good agreement with similar scenarios in the surrounding areas of Tisia, but also in Eastern Alps, Carpathians and Pannonian Basin (ALCAPA).

Geochronology of granitoids from Psunj and Papuk Mts., Croatia

“…They are divided into two groups: 1 PT violet conglomerates (pebbles are phyllites, slates and/or metagraywackes) and 2 PT green-to grayish green-colour quartz sandstones and arkoses . The provenance and depositional history of very low-to low-grade metasedimentary rocks of the Radlovac Complex was investigated by Biševac et al (2010;. K-Ar ages (~100-80 Ma) measured on illite-white K-mica rich < 2 µm grain-size fractions pointed to Late Cretaceous very low-to low-grade regional metamorphism, presumably related to the main nappe-forming compressional events in the Pannonian Basin and the Carpathians (Biševac et al, 2010).…”

“…The provenance and depositional history of very low-to low-grade metasedimentary rocks of the Radlovac Complex was investigated by Biševac et al (2010;. K-Ar ages (~100-80 Ma) measured on illite-white K-mica rich < 2 µm grain-size fractions pointed to Late Cretaceous very low-to low-grade regional metamorphism, presumably related to the main nappe-forming compressional events in the Pannonian Basin and the Carpathians (Biševac et al, 2010). The provenance study of the Radlovac Complex metasedimentary rocks based on Th-U-Pb monazite chemical age dating, heavy mineral assemblage and whole-rock geochemistry led to the conclusion that the metasedimentary rocks of the Radlovac Complex represent the detritus of the local Variscan crust, and that the major source was felsic, igneous rocks, while Papuk Complex rocks were the dominant source material (Biševac et al, 2013).…”

Provenance of Paleozoic very low- to low-grade metasedimentary rocks of South Tisia (Slavonian Mountains, Radlovac Complex, Croatia)

“…2) rarely interlayered by fine-grained metapsammites. Based on the structural and paleofloristic data Jamičić (1988) assumed that the RC was metamorphosed during the late stages of the Variscan orogeny (Late Paleozoic; ~320-260 Ma), while Biševac et al (2010), using Kübler & Árkai indices accompanied by K-Ar dating of illite-muscovite rich fractions, found evidence for Cretaceous very low-to low-grade overprint (~100-80 Ma). The lower and middle parts of the RC are intruded by metabasic rocks which, according to Pamić & Jamičić (1986) show clear signs of metamorphic alteration with plagioclase metamorphosed into clinozoisite and sericite accompanied by newly formed sodic plagioclase, while clinopyroxene is moderately to strongly altered to fine-grained aggregate of chlorite, uralite and epidote.…”

“…Some authors attributed a great role to a late Variscan low-grade metamorphic event (Jamičić 1988), while new studies (Biševac et al 2010(Biševac et al , 2011 show the existence of Cretaceous low-T regional metamorphism in the area.…”

“…Read et al 1987;Rasmussen et al 2001Evans et al 2002;, 2009Wan et al 2007;Wilby et al 2007), all the more, as the bulk has relatively high Th and Y contents (Appendix). Bearing in mind the age dating and temperatures recorded on illite fractions presented in Biševac et al (2009Biševac et al ( , 2010, we can assume that the population of Th-and Y-monazites found in sample R15 are Alpine (Cretaceous).…”