Implication of Mineralogy and Isotope Data on the Origin of the Permian Basic Volcanic Rocks of the Hronicum (Slovakia, Western Carpathians)
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minerals Article Implication of Mineralogy and Isotope Data on the Origin of the Permian Basic Volcanic Rocks of the Hronicum (Slovakia, Western Carpathians) Ján Spišiak 1,* , Anna Vozárová 2, Jozef Vozár 3, Štefan Ferenc 1, Viera Šimonová 1 and Juraj Butek 1 1 Department of Geography and Geology, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, SK-97401 Banská Bystrica, Slovakia; [email protected] (Š.F.); [email protected] (V.Š.); [email protected] (J.B.) 2 Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, Mlynská Dolina, SK-84215 Bratislava, Slovakia; [email protected] 3 Earth Science Institute Slovak Academy of Science, Dúbravská cesta 9, SK-84005 Bratislava, Slovakia; [email protected] * Correspondence: [email protected] Abstract: The paper presents new geochemical data of the basic to intermediate volcanic rocks from the Hronic unit. The studied rocks are strongly altered and the primary mineral composition (clinopyroxenes, amphiboles, spinels, biotites, and plagioclases) is preserved only in some localities. The clinopyroxene corresponds to augite and primary amphiboles to pargasites. Spinels have a chemical composition similar to spinels from volcanic rocks. According to chemical composition, the studied basalts correspond to rift-related continental tholeiites. 143Nd/144Nd vs. 87Sr/86Sr isotopic 143 144 143 144 Citation: Spišiak, J.; Vozárová, A.; ratios of the basalts are scattered around the value of Nd/ Nd for CHUR, where Nd/ Nd 87 86 Vozár, J.; Ferenc, Š.; Šimonová, V.; ratios are relatively stable and Sr/ Sr values are relatively varied. According to isotopic ratio 207 204 206 204 Butek, J. Implication of Mineralogy of Pb/ Pb vs. Pb/ Pb, the basalt analyses lie in the field of EMII (mantle source enriched and Isotope Data on the Origin of the with crustal materials). The new results of U-Pb LA-ICP-MS dating of apatite point to an age Permian Basic Volcanic Rocks of the 254 ± 23 Ma (Lopingian). Hronicum (Slovakia, Western Carpathians). Minerals 2021, 11, 841. Keywords: Western Carpathians; Hronic Unit; Permian volcanic rocks; geochemistry; Sm/Nd and https://doi.org/10.3390/min11080841 Pb isotopes Academic Editors: Alexey V. Ivanov and Ivan Vlastélic 1. Introduction Received: 25 May 2021 Accepted: 28 July 2021 The Pennsylvanian–Permian continental sedimentary basin of the Hronicum repre- Published: 4 August 2021 sents a type of retroforeland basin [1,2], whose origin has been genetically associated with the convergent regime in the final stages of the Western Carpathian Variscan orogeny. Publisher’s Note: MDPI stays neutral This sedimentary basin is characterized by a huge amount of red-beds type siliciclastic with regard to jurisdictional claims in sediments accompanied by basic to intermediate volcanic rocks. Relics of the original filling published maps and institutional affil- of this sedimentation area are preserved in today’s Western Carpathian structure within a iations. system of superficial nappes, whereas they are completely tectonically detached from their original basement. The crustal character of the original basement was inferred from petro- logical analysis of sediments [3–5] as well as isotopic ages of clastic mica [6], monazite [7], and zircon [8]. The results documented an active continental margin crust provenance, Copyright: © 2021 by the authors. with dominant Devonian–Mississippian and Pennsylvanian magmatic sources. Licensee MDPI, Basel, Switzerland. This article studied basic to intermediate volcanic rocks whose genesis and chemical This article is an open access article composition are closely related to the tectonic processes that led to the formation of the distributed under the terms and Hronicum Pennsylvanian–Permian sedimentary realm. Previous analyses of the Hronicum conditions of the Creative Commons basalts/andesites have been focused on their field distribution and description of structural Attribution (CC BY) license (https:// relations and especially on their mineral and chemical composition [9–11]. They were creativecommons.org/licenses/by/ generally classified as rift-related continental tholeiites. 4.0/). Minerals 2021, 11, 841. https://doi.org/10.3390/min11080841 https://www.mdpi.com/journal/minerals Minerals 2021, 11, 841 2 of 28 In this paper, we briefly review the main characteristics of the Permian magmatism in the Hronic unit domain and present new chemical and isotopic data in an attempt to provide some insights into its origin and significance. The main goal of this study is to bring new petrological and geochemical data and identify in more detail the sources of magmas and differentiation processes, and thus infer the relationships with the geotectonic setting of the studied area. Therefore, nine additional samples were collected from the Hronicum Permian volcanic rocks for a better temporal covering of the Hronic formation (Table1). The studied samples were collected from the Permian volcanites of the 1st and 2nd eruption phases as well as from the dykes crossing Pennsylvanian sediments. Table 1. Location of samples. Sample GPS Rock Type Sample Locality No. Coordinates Malužinská dolina Valley, cliff 48◦57.1820 N M-1 coarse-grained gabbro-diorite dyke on the right slope of the forest 19◦48.7830 E road 812 m a.s.l. Malužinská dolina Valley, cliff 48◦57.1820 N M-1A fine-grained gabbro-diorite dyke on the right slope of the forest 19◦48.7830 E road 812 m a.s.l. Hodruša Valley, SE from the Malužiná Village, cliff on the 48◦57.5520 N M-2 andesite/basalt-2nd eruption phase right slope of the forest road, 19◦50.0510 E 870m a.s.l. Malužinská dolina Valley, 48◦57.5440 N M-3 andesite/basalt-2nd eruption phase forest road cut, 1.4 km SE from 19◦50.0910 E Malužiná Village, 770 m a.s.l. N from the Liptovská Tepliˇcka Village, abandoned quarry 48◦59.0380 N M-4 andesite/basalt-1st eruption phase along the Šuˇnava-Liptovská 20◦05.3530 E Tepliˇckaroad, 890 m a.s.l. Benkovský potok Valley, small 49◦00.4680 N M-5 basaltic andesite-1st eruption phase quarry at the left side of the 19◦59.7470 E forest road, 832 m a.s.l. S from the Hranovnica Village, forest road at the left slope of 48◦57.9700 N M-7 basaltic andesite-1st eruption phase the Vernár-Hranovnica state 20◦17.5660 E road, 694 m a.s.l. West end of the Nižná Boca 48◦56.9150 N M-8 coarse-grained gabbro-diorite dyke Village, 860 m a.s.l. 19◦46.1570 E 49◦00.5210 N M-9 andesite/basalt-2nd eruption phase Kvetnica quarry, 725 m a.s.l. 20◦17.0850 E 2. Geological Background The Hronic nappe system (Figure1) structurally represents the highest tectonic unit in the Central Western Carpathians. There is no generally accepted opinion about the structure and composition of the Hronic nappe system and its palaeogeographic position. A lot of theories have emerged in the past four decades of research, with current defini- tion of Hronicum as a rootless superficial nappe system [12,13] that mostly comprises a Carboniferous–Permian volcano-sedimentary sequence and Triassic carbonate sediments (with significant similarities of the latter to the Oberostalpine-type). Jurassic-Lower Creta- ceous sediments are preserved only locally [14]. Minerals 2021, 11, 841 3 of 28 Minerals 2021, 11, x FOR PEER REVIEW 3 of 27 Figure 1. SimplifiedFigure 1. geologicalSimplified sketchgeological map sketch of the map Western of the Carpathians Western Carpathians [15] and schematic [15] and geologicalschematic mapgeological of the Hronicum map of the Hronicum Pennsylvanian–Permian sequence on the northern slopes of the Nízke Tatry Pennsylvanian–Permian sequence on the northern slopes of the Nízke Tatry Mts. showing sample locations [15]. Mts. showing sample locations [15]. The allochthonous position of Hronicum superficial nappes relative to basement The allochthonousimplies an position ultra-Veporic of Hronicum origin. superficial Hronicum nappes probably relative comes to frombasement the area im- that originally plies an ultra-Veporicexisted betweenorigin. Hronicum the Veporicum probab andly comes Gemericum from the units area [16 that–18 ].originally The southernmost ex- tectonic isted between occurrencesthe Veporicum of Hronic and Gemericum debris were units recognized [16–18]. along The thesouthernmost line Luben ítectonick–Margecany (tectonic occurrences of contactHronic Veporicum/Gemericum).debris were recognized along Generally, the line the HronicumLubeník–Margecany nappes rest (tec- directly on the Fa- tonic contact Veporicum/Gemericum).tricum unit, except for Veporicum Generally, zone the whereHronicum Hronicum nappes directly rest directly overthrust on the crystalline the Fatricum unit,complex except of Veporicumfor Veporicum [19]. zone where Hronicum directly overthrust the crystalline complex Theof Veporicum original basement [19]. of the Hronicum is currently undetermined. The character of The originalthe basement Pennsylvania–Permian of the Hronicum terrestrial is currently siliciclastic undetermined. sediments The suggests character that of they originated the Pennsylvania–Permianfrom a sedimentary terrestrial basin siliciclastic located onsediments the continental suggests crust. that Thisthey opinionoriginated is also supported from a sedimentaryby findings basin located of some on mylonitized the continental granitoid crust. tectonic This opinion slices belowis also the supported basal part of the lower by findings of somepartial mylonitized Hronicum nappegranitoid [20 ,tectonic21]. The slices age of below the source the basal area part (310–340 of the Ma)lower was determined partial