Introduction

The ages of detrital zircon grains in sandstones provide a direct evidence for the ages of bedrock in the source area. Interpretation of provenance should include recycling of resistant detritus, such as quartz and zircon grains, through multiple sedimentary systems of different ages. Generally, the sources of zircon-bearing sandstone are continental basement rocks, supplemented in many cases by supracrustal acid volcanic rocks (Stewart et al. 2001; McLennan et al. 2001; Dickinson and Gehrels 2003, 2008 and references therein).

The primary purpose of the study is to evaluate the provenance of these detrital zircons and its implication for early Paleozoic to Permian tectonic evolution of the Southern Gemericum Unit. A second issue will be addressed to the paleogeographic situation of this crustal fragment in the Peri-Gondwana realm. U–Pb detrital zircon ages, which proved the Neoproterozoic ages of 651 and 659 Ma from two Lower Paleozoic metaquarzites, were already known (Cambel et al. 1977).

The metasandstones were sampled from several stratigraphic levels of the Early Paleozoic Southern Gemericum basement and their Permian envelope (Figs. 1, 2). Although six samples are the minimal number to address the question of the provenance of the Southern Gemeric sandstones, the selected samples are characteristic of the same paleogeographic province and source areas. The magmatic zircon ages from the Southern Gemeric basement and its Permian envelope were taken into account (Vozárová et al. 2009, 2010), and we correlate the inherited grain ages from the core of magmatic zircons with the detrital zircon ages.

Fig. 1
figure 1

Geological sketch of the Southern Gemeric Unit showing localities of detrital zircon samples (modified according to the Geological map of Slovakia, 1/500000, Biely et al. 1996). Magmatic zircon ages are given for comparison purposes. Explanations: 1 Neogene sediments; 2 Meliaticum, Turnaicum and Silicicum Units; 3–4 Variscan Northern Gemericum basement units; 3 Klátov Group; 4 Rakovec Group; 5–11 Southern Gemericum Units: Permian, 5 Granitoids, 6 Štítnik Formation, 7 Rožňava Formation, 8–11 Gelnica Terrane, 8 Štós Formation, 9. Drnava Formation: a metasediments, b metavolcanites and their metavolcaniclastics; 10 Bystrý potok Formation: a metasediments, b metavolcanites and their metavolcaniclastics; 11 Vlachovo Formation: a metasediments, b metavolcanites and their metavolcaniclastics; 12 Zircon localities with zircon magmatic ages; SHRIMP zircon age data are taken from Vozárová et al. (2009, 2010), 13 Selected localities for the detrital zircon dating presented in this paper

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Fig. 2
figure 2

Detrital zircon sample locations tabulated on the chronostratigraphic correlation chart for metasedimentary rocks in the Southern Gemericum Unit. The timescale calibration follows the stratigraphic chart of Gradstein et al. (2004)

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The in situ U–Pb SHRIMP zircon dating, performed in the Centre of Isotopic Research, VSEGEI, Saint Petersburg, has been applied for detrital zircons from six Lower to Upper Paleozoic metasandstone samples from the Southern Gemericum Unit of the Inner Western Carpathians (Fig. 2). These metasandstone samples represent deposition in the Late Cambrian/Ordovician deep-water forearc basin and in the Permian continental overstep basin.

Geological setting and samples

The Alpine evolution of the Western Carpathians is characterized by a distinct northward migration of pre-orogenic and orogenic processes, which reflect individual stages of post-collisional rifting and extension of the Variscan continental crust, followed by the Alpine compression and nappe stacking. Taking into account the recent achievements in geological studies of the Mesozoic evolution, most authors prefer a triple division of the Western Carpathians, the Outer (OWC), Central (CWC) and Inner Western Carpathians (IWC) (Maheľ 1986; Kozur and Mock 1996, 1997; Plašienka et al. 1997 and references therein). The OWC, comprise sediments of the Late Tertiary Carpathian Foredeep and Tertiary accretionary wedge of the Flysch Belt, the CWC and IWC consist of principal thick-skinned crustal-scale superunits made up of the pre-Alpine crystalline basement and its Late Paleozoic/Mesozoic cover and several cover nappe systems. The Southern Gemericum Unit is accepted in the following text as a part of the IWC.

The classical definition of the Gemericum has to be changed fundamentally, as it was proved that the Mesozoic carbonate rock complexes, originally thought to be its envelope sequences, are in the allochthonous position (Kozur and Mock 1973a, b; Bajaník et al. 1983; Vozárová and Vozár 1992; Mello et al. 1997). Detailed investigations of the Early and Late Paleozoic rock complexes led to the subdivision of the formerly defined Gemericum into two tectonic units—the Northern and Southern Gemericum (Bajaník et al. 1983, 1984; Vozárová and Vozár 1988). Both consist of the pre-Carboniferous crystalline rock complexes and the late- to post-orogenic or just post-orogenic Variscan formations. In the envelope sequence, only the linkage between the Lower Triassic and Permian is evident (Fig. 1).

Characteristics of the Southern Gemericum Unit

The major part of the Southern Gemericum Unit is formed by the low-grade Early Paleozoic volcanic sedimentary sequence of the Gelnica Group (Snopko and Ivanička in Bajaník et al. 1983, 1984) (Fig. 1). Lesser extended pre-Permian low-grade complex is the Štós Formation, which is situated only in the SE part of the Southern Gemericum surface occurrences (Figs. 1, 2). There is a tectonic contact between the Gelnica Group and the Štós Formation rock complexes. A shallow north-vergent thrust plane is documented by the deep seismic profile data (Vozár et al. 1995). Both, the pre-Permian low-grade crystalline complexes are unconformably overstepped by the Permian continental sediments of the Gočaltovo Group (Figs. 1, 2). Due to the intensive Lower/Middle Cretaceous stacking and thrusting of the Inner Western Carpathians nappe units, the Southern Gemericum rock complexes are affected by the strong Alpine overprinting.

Three lithostratigraphic units have been identified within the Gelnica Group, from the bottom upwards, designated as—the Vlachovo, Bystrý potok and Drnava Formations (Figs. 1, 2). The Gelnica Group was generally described as a megasequence of the deep-water turbidite siliciclastic sediments, associated with the rhyolite–dacite volcanic/volcaniclastic rocks (Snopko and Ivanička in Bajaník et al. 1983). Marginal and distal turbidite facies were distinguished, latter accompanied with thin lenses of lydites and allodapic limestones. The acid to intermediate magmatic arc volcanism (Vozárová and Ivanička 1996) was highly explosive, which resulted in the redeposition of a vast amount of volcaniclastic material into the supposed forearc basin (Vozárová 1993a). Besides them, lesser metabasalts and their metavolcaniclastics occur, with chemical composition indicating various tectonic settings, similar to continental arc basalt, volcanic arc basalt, mid-oceanic ridge basalts and enriched mid-oceanic ridge basalts (Ivan 1994).

Palynological analysis indicated an Early Paleozoic age of the Gelnica Group sediments (Snopková and Snopko 1979; Ivanička et al. 1989). Biostratigraphical data, based on agglutinated foraminifers, proved the Late Cambrian/Ordovician to Early Silurian age of the Vlachovo and the Bystrý potok sedimentary sequences (Vozárová et al. 1998; Soták et al. 1999). U–Pb zircon age determinations gave 494 ± 1.6 Ma (the Vlachovo Formation), 465.8 ± 1.5 Ma and 463.9 ± 1.7 Ma (the Bystrý Potok and Drnava Formation; Vozárová et al. 2010), and thus, they are comparable with earlier assessed biostratigraphic data.

The Štós Formation rock complex overlies tectonically the Drnava Formation sequence of the Gelnica Group (Figs. 1, 2). It is dominated by the fine-grained metasandstones, with very often plane-parallel horizontal lamination, and metapelites. Sedimentary structures indicate the distal turbidite environment.

The regional metamorphism of the Gelnica Group and the Štós Formation rock assemblages did not exceed the low-temperature part of the greenschist facies conditions (Sassi and Vozárová 1987; Faryad 1991; Vozárová 1993b; Molák and Buchardt 1996). The time of this metamorphism is presumed to be probably Variscan, based on the occurrences of rock fragments from both complexes in the overlapping Permian conglomerates. The Gelnica Group and Štós Formation rock complexes are defined as a single Variscan tectonostratigraphic terrane, the Gelnica Terrane, based on structural, stratigraphic and metamorphic criteria (Vozárová and Vozár 1996).

The overlapping Permian metasediments of the Gočaltovo Group, consisting of the Rožňava and Štítnik Formations, constitute the Gelnica Terrane envelope sequence (Fig. 2). The Rožnava Formation is composed of cyclical quartzose metasandstones and metaconglomerates. Two horizons of rhyolites/dacites and their volcaniclastics are associated. In situ U–Pb (SHRIMP) zircon ages from the two volcanogenic horizons gave concordant ages of 275 Ma (Vozárová et al. 2009). The evidences for the Early Permian volcanic event at 276 ± 25 Ma in the first volcanogenic horizon of the Rožňava Formation were also recorded in the monazite grains, which were later rimmed by the Alpine newly formed monazite (Vozárová et al. 2008). The Štítnik Formation consists of a cyclically alternating sequences of sandy/shaly metasediments, with scarce thin lenses of phosphatic sandstones and dolomitic limestones in the upper part. Alluvial–lacustrine and near-shore marine and lagoonal sedimentary environments were identified. Flora and fauna found at the top of the Štítnik Formation testifies to the Late Permian age (Šuf 1963).

Metasandstones petrography

The metasandstones of the Gelnica Terrane correspond to poorly sorted coarse- to fine-grained quartzose and lithic graywackes. The general differences between mineral compositions of the individual Gelnica Terrane metasandstones are expressed by the average petrofacies parameters given in QFL %, QpLvLs %, QmFLt % and QmQpL % (Table 1). Among the mineral grains, quartz is dominant (on average, 70–80%), with a variable content of monocrystalline quartz grains (on average ratios Qp/Qm from 0.43 to 0.56). Feldspars are generally a little substituted (on average, 3–6%), mostly represented by Na–Ca feldspars and only sporadic K-feldspars (on average P/F ratio from 0.64 to 0.74; Table 1). Relics of clastic mica occur rarely, not exceeding of 0.5%. A particularly significant class of detrital grains is rock fragments (on average, 17–27%). In general, volcanic fragments prevail over those of metasediments (on average Lv/L ratio from 0.73 to 0.84; Table 1). According to Dickinson’s criteria (1970), a considerable part of the Gelnica Terrane metasandstone matrix is represented by “pseudomatrix”. The process of low-grade recrystallization and deformation of former clay matrix and sedimentary/metasedimentary rock fragments is responsible for the “graywackization” of metasandstones and relative increase in matrix and stable components in their texture.

Table 1 Average detrital modes (in percentages) from the Gelnica Terrane metasandstones and their Permian overlap sequence
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The heavy mineral studies of the Gelnica Terrane metasandstones proved the similarity of these assemblages (Table 2).

Table 2 Heavy mineral assemblages from analyzed metasandstone samples (in percentages)
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The classification of the Gočaltovo Group metasandstones varies from quartzose arenites and wackes to lithic wackes (Table 1). Among the heavy mineral associations, rounded zircon grains are dominant (50% and more; Table 2).

Analytical methods

The SHRIMP procedures used in this study are similar to those reported by Williams (1998, and references therein). Zircons were mounted in epoxy, polished until sectioned in half, and photographed. Cathodoluminiscence (CL) and backscattered electron (BSE) images of the zircons grains were prepared prior to analysis. The U-Th–Pb analyses were made using SHRIMP II and the data calculation with the SQUID Excel Macro of Ludwig (2000). Data for each spot were collected in sets of five scans through the mass range. The spot-size diameter was 25 μm, and primary beam intensity was about 4 nA. The Pb/U ratios have been normalized relative to a value of 0.0668 for the 206Pb/238U ratio of the TEMORA reference zircons, equivalent to an age of 416.75 Ma (Black et al. 2003). The uncertainties given for individual analyses (ratios and ages) are at the one σ level; however, the uncertainties in calculated concordia ages are reported at two σ levels.

Results

The detrital zircon grains fall into five separable age populations defined by peaks on the relative histogram plots (Fig. 3). Each of the grain populations can be related to potential Precambrian sources, lying within the interior of the peri-Gondwana realm or to Paleozoic orogenic belts along its margin. The following populations of zircon grains have been distinguished: population A—the Paleoproterozoic/Neoarchean zircon grains with ages ranging from 1.75 to 2.6 Ga; population B—the Mesoproterozoic zircon grains with ages from 0.9 to 1.1 Ga; population C—the Neoproterozoic zircon grains with ages from 560 to 807 Ma; population D—the Early Paleozoic zircon grains, with ages from 497 Ma to 450 Ma; population E—the Carboniferous zircon grains, which is subdivided into two subpopulations—the Mississippian E 1 , with the time span from 369 to 334 Ma, and the Pennsylvanian E 2 , with the time span 309–301 Ma.

Fig. 3
figure 3

Adopted detrital zircons ages histograms for the six analyzed samples. The black columns indicate concordant ages and the gray columns stand for the discordant age data. The bracketing age values were calculated in the span limits from −10 to 10. The gray columns represent data from ± 10 to ± 25% of discordant ages

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Ages from the Gelnica Terrane detrital zircons: Detrital zircons from the Lower Cambrian/Ordovician Gelnica Group metasandstones and from the Štós Formation were derived from the four different lithostratigraphic horizons. Fifty-one ages of the analyzed detrital zircons form a broad 206Pb/238U age distribution between 0.56 and 2.62 Ga (Tables 3, 4). Generally, they could be distinguished into three main populations: the Paleoproterozoic/Neoarchean population A, the Mesoproterozoic population B and the Neoproterozoic population C. Only two grains (3.8% of the total) have miscellaneous ages falling outside these three significant key grain populations. Compared with the dominant Precambrian age populations, they show younger 206Pb/238U ages (452 ± 8.4 Ma, 430.4 ± 8.4 Ma, Table 3; the CL images in the electronic supplement), embracing part of the age range of population D (Fig. 3). These younger zircons do not have elevated U content (Table 3) and show Th/U ratios ~ 0.33. Thus, it could be considered that these zircons reflect a magmatic crystallization, similar to those found in zircon crystallized in the felsic to intermediate Gelnica Group volcanic rocks. As the magmatic arc volcanism was the important source of clastic detritus in the former deep-water Gelnica Group sedimentary basin (Vozárová 1993a), they could have also been derived from the synsedimentary magmatic arc volcanism of the Gelnica Group. However, these two ages are younger than the magmatic zircon ages obtained from the in situ Gelnica Group volcanic horizons (from 494 to 464 Ma; Vozárová et al. 2010). These younger zircon age data may imply the duration of the Gelnica magmatic arc volcanism and adjacent forearc depositionary system until the Late Ordovician, which agrees with previous biostratigraphic data (Vozárová et al. 1998).

Table 3 U–Pb (SHRIMP) detrital zircon ages from the Vlachovo and Bystrý potok Formation metasandstones
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Table 4 U–Pb (SHRIMP) detrital zircon ages from the Drnava and Štós Formation metasandstones
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Figure 3 displays the spectra of U–Pb ages for individual detrital zircon grains in these four metasandstone samples. Each of the analyzed samples contains three distinguished zircon grain populations. The main differences are in their proportions. The population C is dominant in the samples from Vlachovo (Vl-1) and Drnava (Dr-1) metasandstones (58–62%), whereas the population A (29–19%) and population B (14–19%) are less frequent. The Bystrý potok metasandstone sample (Bp-1) contains the predominance of the population A (47%) and relatively distinct accumulation of the population B (27%). The age span of zircon populations in the Štós Formation, (sample St-VII) even in a small number of analyzed grains, presents only A and C populations, whereas 1 discordant zircon age figure data belong to population B (population A = 4 grains and population C = 4 grains). Most of the zircon analyses plot on the concordia or close to concordia (Figs. 4, 5, 6, 7).

Fig. 4
figure 4

Concordia plots for detrital zircons of the Vlachovo Formation sample [VL-1]. The uncertainties in calculated concordia ages are reported at two σ levels. a Concordia plot for the all adopted zircon age data, b detail of the lower part of the concordia plot ranging from 450 to 1,150 Ma

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Fig. 5
figure 5

Concordia plots for detrital zircons of the Bystrý potok sample [Bp-1]. The uncertainties in calculated concordia ages are reported at two σ levels. a Concordia plot for the all adopted zircon age data, b detail of the lower part of the concordia plot ranging from 400 to 1,100 Ma

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Fig. 6
figure 6

Detrital zircons’ concordia plots for the Drnava Formation sample [Dr-1]. The uncertainties in calculated concordia ages are reported at two σ levels. a Concordia plot for the all adopted zircon age data, b detail of the lower part of the concordia plot ranging from 500 to 1,100 Ma

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Fig. 7
figure 7

Detrital zircons’ concordia plots for the Štós Formation sample [St-VII]. The uncertainties in calculated concordia ages are reported at two σ levels. a Concordia plot for the all adopted zircon age data, b detail of the lower part of the concordia plot ranging from 530 to 670 Ma

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The analyzed zircons are mostly pink, but colorless varieties also occur. Some zircon grains are well-rounded, consisting with the supposed sedimentary recycling processes. The euhedral crystals suggest a proximal source. Concentric oscillatory zoning typical of magmatic growth is visible in the majority of analyzed zircon grains. A strong variation has been observed in the zoned domains within individual crystals. Commonly, the regular growth zoning is interrupted by textural discontinuities, along which the original growth zoning is resorbed and succeeded by the newly growth-zoned zircon. The zircon xenocrysts occur as cores mantled by the newly grown magmatic zircon. Xenocrystic cores are commonly separated from their rims by the geometrically irregular surfaces, separating subrounded, probably detrital, unzoned and/or chaotically zoned cores from the oscillatory growth-zoned rims.

The analyzed spots correspond to small and moderate U content (from 49 to 716 ppm) and relatively high Th/U ratios (> 0.3), which are typical of magmatic origin (Tables 3, 4; Fig. 8). A smaller number of analyzed spots contain widely ranged U concentration (more than 1,100 ppm or less than 16 ppm), with variable Th/U ratios (0.07–0.34). The low values of Th/U ratios (less than 0.1) indicate a probably metamorphic source for some analyzed zircons.

Fig. 8
figure 8

Th/U ratios of detrital zircons from the Gelnica Terrane and its Permian cover versus 206Pb/238U timescale. All data from spots were analyzed by SHRIMP. Most zircons have Th/U ratios in the range of 0.1–2.3, similar to those found in zircon crystallized in felsic to intermediate magmatic rocks. Only small part of ratios, lower than 0.1, is conforming to metamorphic provenance (~360 Ma, ~790 Ma, 630–670 Ma)

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Ages from the Gočaltovo Group detrital zircons: The detrital zircons of the overlapping Permian deposits have been analyzed from the two stratigraphic horizons, (i) the basal Rožňava Formation (Ro-1; 15 age data; Table 5) and (ii) the upper Štítnik Formation (12-LA; 16 age data; Table 5). In the both zircon samples, grains were identified corresponding to the populations A, B and C (Fig. 3). Among the Rožňava Formation detrital zircon ages, the Neoproterozoic population C is clearly dominant (11 age data = 74%), followed by the Mesoproterozoic population B (3 age data = 20%). All detrital zircon ages from the basal Rožňava Formation show concordant ages (Fig. 9) between 574 Ma and 2.04 Ga. The Th/U ratios > 0.3 (Table 5; Fig. 8) express a magmatic origin, which is documented by the characteristic growth zoning. Several zircons, with the ages around 634 and 671 Ma and very low Th/U ratios (Table 5; Fig. 8; ranging from 0.02 to 0.19), represent the most probably metamorphic provenance. This indicates that in the Precambrian source area existed magmatic as well as metamorphic rocks. They correspond to the time span, indicating the mid-Neoproterozoic tectonothermal events, which could be generally attributed to accretion of juvenile arc crust along the West Gondwana margin (Strachan et al. 1996; Murphy et al. 2004b).

Table 5 U–Pb (SHRIMP) detrital zircon ages from the Rožňava and Štítnik Formation metasandstones
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Fig. 9
figure 9

Concordia plots for detrital zircons of the Rožňava Formation sample [Ro-1]. The uncertainties in calculated concordia ages are reported at two σ levels. a concordia plot for all adopted zircon age data, b detail of the lower part of the concordia plot ranging from 560 to 720 Ma

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Generally, the analyzed zircon spots correspond to small and moderate U content, ranging between 56 and 706 ppm.

The time span of the detrital zircon ages from the Štítnik Formation (sample 12-LA) is relatively wider compared with that of the basal Rožňava Formation, ranging from 301 Ma to 2.4 Ga (Fig. 3). In addition to the previous three populations, another two zircon populations increased. They are the following: the Early Paleozoic population D, with the time span of 497 to 450 Ma, and the Carboniferous population E, which is subdivided into two subpopulations—the Mississippian E 1 , with the time span of 369 to 334 Ma, and the Pennsylvanian E 2 , with the time span of 309–301 Ma. The population E is dominant, with cc. 50% of the grains, following by the population D with cc. 25% grains. Finally, the Precambrian population A + B + C is formed by only 4 grains and indicates recycling from the older crust.

The concordia plot (Fig. 10) of the detrital zircon ages from the Štítnik Formation shows average concordia ages at 471 ± 8.7 Ma (four grains), 350 ± 9.7 Ma (five grains) and 305.6 ± 6.6 Ma (three grains). The assessed Paleozoic ages are important for the geological interpretation. A minority of the ages give Neoproterozoic (731 ± 15 Ma), Mesoproterozoic (912 ± 27 Ma) and Paleoproterozoic fingerprints (1,986 ± 33 Ma). The main part of the analyzed detrital zircons belongs to the small and moderate U content characteristics, with Th/U ratios (Fig. 8) ranging from 0.3 to 1.0. Only two of them contain more than 1,000 ppm U, with extremely low Th/U ratios (0.002–0.14; Table 5). These low Th/U ratios could indicate a metamorphic origin. The further detrital zircon grains, with moderate U contents and low Th/U ratios in their rim, indicate the metamorphic overprinting around the growth-zoned magmatic zircon grains.

Fig. 10
figure 10

Detrital zircons’ concordia plots for the Štítnik Formation sample [12/La]. The uncertainties in calculated concordia ages are reported at two σ levels. a Concordia plot for all adopted zircon age data, with detail of the concordia plot ranging from 460 to 500 Ma, with concordia age 471.4 ± 8.7 Ma; 2σ decay–constant errors included; b detail of the lower part of the concordia plot ranging from 280 to 400 Ma; at 350 ± 9.7 Ma concordia age 95% confidence, decay const. errs included. At concordia ages 471.4 ± 8.7 Ma and 305.6 ± 6.6 Ma 2σ decay–constant errors included

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Discussion

Provenance of the pre-Permian succession: The provenance study based on in situ U–Pb (SHRIMP) ages of detrital zircon grains from the Early Paleozoic metasandstones of the Southern Gemericum Gelnica Terrane is combined with age data from the inherited zircons of the Late Cambrian/Ordovician synsedimentary metavolcanic rocks (Vozárová et al. 2010). Thus, the 29 inherited zircon age data from the associated Gelnica Group metavolcanic rocks were calculated with the all pre-Permian detrital zircon ages, which represent together a collection of the 82 zircon ages.

The majority of the studied inherited grains from the Gelnica Terrane magmatic zircons belong to the previously defined detrital zircon populations—A, B and C (27 of total; 93%; Fig. 11). Among them, the Neoproterozoic population C is dominant (18 of total; 67% of tabulated), with less frequent Mesoproterozoic population B (5 grains; 18%) and Paleoproterozoic/Neoarchean population A (4 grains; 15%). The only notable exceptions are two selected older grains, with ages of 2.8 and 3.1 Ga, falling outside the population A. Generally, the distributions of the inherited zircon ages confirm the trend corresponding to the detrital zircon ages, as 96% of the Gelnica detrital zircon grains fall within the Precambrian populations A, B and C. The above-summarized data document the unambiguous dominance of the population C, within the detrital zircon age assemblage as among the inherited zircon ages. The dominance of the high Th/U ratios (> 0.3) within the age population C suggests a derivation from mid- to late-Neoproterozoic igneous rocks. This observation exclude any provenance connection of the Gelnica Terrane with Baltica and Siberia cratons since they remained magmatically inactive during much of this period (Hartz and Torsvik 2002; Murphy et al. 2004a, b). The time span of the population C between 807 and 560 Ma is compatible with a series of magmatic and tectonometamorphic events connected with the Avalonian–Cadomian or “pan-African” orogenic events (c. 750 to 540–530 Ma) along the periphery of the Supercontinent Gondwana (peri-Gondwana realm; Nance and Murphy 1994, 1996; Unrug 1997; Linnemann et al. 2000, 2004, 2008; Nance et al. 2002, and references therein). In fact, among 43 analyzed grains of the population C, the great majority of them (40 grains) have been tabulated in the time span from 750 to 540 Ma. These results document clearly the provenance of the majority of detrital and inherited zircons from the Avalonian–Cadomian juvenile crust. The presence of the three detrital zircon ages around 800 Ma does not contradict to this interpretation. They may correspond to the early origin of the Cadomian–Avalonian arc along the Gondwana margin (Murphy et al. 2000; Fernández-Suárez et al. 2000).

Fig. 11
figure 11

Compilation histogram showing the detrital zircon ages of the Gelnica Terrane and its Permian cover with indication of the main Paleozoic and Precambrian tectonothermal events. The inherited zircon ages are included in the single column together with the detrital zircon ages. In addition, they are supplemented with the magmatic zircon ages from the Late Cambrian/Ordovician and Permian synsedimentary volcanites. All magmatic zircon ages, as well as the inherited grain zircon age data, are taken from Vozárová et al. (2009, 2010). The bracketing age values were calculated in the span limits from −10 to 10

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A characteristic feature of both studied detrital and inherited zircon age spectra is the presence of Mesoproterozoic zircons (14 grains—population B, which form c. 17% of all the studied grains). The dominant parts of them fall into the time span from 0.9 to 1.1 Ga (10 grains), and only few grains spanned from 1.3 to 1.4 Ga (4 grains). These zircon age spectra document the affinity of the Gelnica Terrane provenance to the Avalonian part of the peri-Gondwana active margin. The Grenvillian zircon ages (0.9–1.1 Ga) signal proximity of the Gelnica source area to the West Gondwana realm, possibly to the Amazonian craton. The Avalonian terranes are generally characterized by the presence of Mesoproterozoic ages in their source area (Nance and Murphy 1994; Winchester et al. 2006). The Paleoproterozoic to Neoarchean age data (population A = 24 grains), determined from the detrital and inherited zircons of the Gelnica Terrane, also confirm a source area with an affinity to the Amazonian craton, with the following distribution of ages: > 2.3 Ga—9 grains from the total; 2.2–1.95 Ga—9 grains from the total; 1.8–1.55 Ga—2 grains from the total; and 1.55–1.3 Ga—4 grains from the total.

Provenance of the Permian succession: Since the Permian sediments represent the overlap sequence of the Paleozoic Gelnica Terrane, the detrital zircon ages from the basal Rožnava Formation reflect the recycling process from the underlying Gelnica Terrane rock complexes, as the source area. Comparing with this observation, the majority of the detrital grains analyzed from the Štítnik Formation reflect the Paleozoic sources, accreted within the Variscan collision suture. The metamorphic rim within older detrital zircon grains reflects the Late Cambrian/Ordovician, (497 to 441 Ma) as well as the Late Devonian/Mississippian (369 to 334 Ma) metamorphic tectonothermal events in their source area. The unique magmatic zircon age of 337 Ma is coeval with these tectonothermal events. They reflect metamorphic/melting processes, corresponding to the main phase of the Late Devonian collision stage, which have been succeeded by extensional collapse of the thickened Variscan crust. The magmatic zircons of the subpopulation E 2 overlap the magmatic igneous activity accompanied by the rapid Late Variscan post-orogenic extension (Broska et al. 1990; Bibikova et al. 1990; Petrík and Kohút 1997). It is coeval with the first stage of the origin of the post-orogenic sedimentary basins in the Central Western Carpathians (Vozárová 1998).

Paleogeographic implications

Cadomian, Cambrian/Ordovician as well as the Variscan zircon ages were described recently from the crystalline and magmatic rocks of different part of the Western Carpathians basement (Cambel et al. 1990; Poller et al. 2000; Gaab et al. 2005, 2006; Putiš et al. 2008, 2009; Kohút et al. 2008, 2009). In conformity with these data, Putiš et al. (2008) interpret the affinity of these basement fragments to the Cadomian terranes or to Armorica (s. l.).

Our data are compatible with derivation of the studied sediments from the Avalonian arc of the peri-Gondwana margin, since the evaluated zircon ages signalize all main events of the Avalonia evolution (see Nance et al. 2002; Murphy et al. 2004b; Linnemann et al. 2008 and references therein). The dominant presence of the Neoproterozoic 750 to 540 Ma and Mesoproterozoic 0.9–1.1 Ga zircon populations is here a diagnostic feature (Fig. 11). The first reflects the multistage development of the Avalonian arc and its accretion to the West Gondwana and the second the preceding origin of the Mesoproterozoic juvenile crust. In fact, the Mesoproterozoic zircon ages (Grenvillian source) are characteristic for the Avalonian terranes (Nance and Murphy 1994; Winchester et al. 2006) and the paleogeographic location close to the Amazonia craton can be concluded (Murphy and Nance 1989; Keppie et al. 1991; Nance et al. 2002). The zircon ages 650–570 Ma (population C) document the Neoproterozoic magmatic arc volcanism provenance. Similar magmatic ages were described in many Avalonian–Cadomian terranes, including the Saxo-Thuringian Zone, Iberian and Armorican Massifs, Sudetes, Teplá-Barrandian and Moldanubian Zones, Brunovistulian block, Southern Poland, Central Dobrugea (Kröner et al. 2000; Fernández-Suárez et al. 2002; Gutiérrez-Alonso et al. 2003; Murphy et al. 2004a; Friedl et al. 2000, 2004; Mazur et al. 2004; Źelaźniewicz et al. 2004, 2009; Linnemann et al. 2007, 2008 and references therein), as well as in the Alpine basement (Neubauer 2002 and references therein) and in the Minoan terranes of the Mediterranean area (Zulauf et al. 2007). However, the presence within the Gelnica Terrane sedimentary rock complexes of the Mesoproterozoic (Grenvillian) detrital zircon ages, which are used to discriminate the Avalonian–Amazonian terranes from the Cadomian–Armorican terranes (Nance and Murphy 1994, 1996; Winchester et al. 2006), allows us to interpret the geological connection of the Gelnica Terrane source area to the Avalonian–Amazonian realm. The Paleoproterozoic to Neoarchean zircon ages of population A are compatible with those of the Amazonian craton: [Central Amazonia— > 2.3 Ga, Maroni-Itacaiúnas—2.2–1.95 Ga, Ventuari-Tapajós—1.95–1.8 Ga, Rio Negro-Juruena—1.8–1.55 Ga and Rondonian-San Ignacio—1.55–1.3 Ga] (Tassinari and Macambira 1999).

The deep-water mass flow and turbidite type of the Gelnica Terrane Late Cambrian/Ordovician sedimentary system, intercalated with magmatic arc volcanism, represent a relic of a forearc basin filling, which was situated along an active Avalonian continental margin. Several horizons of allodapic limestones were recognized among this huge mass of siliciclastic and volcaniclastic sediments. The presence of redeposited carbonate sediments indicates the Ordovician position of this basin in a more northerly and warmer climatic domain, comparing with the northern Gondwana margin. This suggests more similarities to the Avalonian type of terranes than to the Cadomian type of terranes. Information about the Silurian to Carboniferous evolution of the Gelnica Terrane is still lacking. The only relevant information may be the discordant position of the Early Permian continental clastics on the slightly deformed and metamorphosed Gelnica Terrane rock complexes. The Precambrian detrital zircon age spectrum from the basal Permian sediments reflects strong recycling from the underlying Early Paleozoic Gelnica Terrane. Only the detrital zircon age spectra from the Late Permian part of the overlap sequence contain two younger detrital zircon age populations. The first assemblage, the Late Cambrian/Ordovician population D, could confirm the Avalonian proximity to the Gelnica Terrane. The second population E reflects the thermal relaxation the Variscan collisional belt, which was accompanied by the Meso- and Late Paleozoic partial melting and magmatic intrusions. This interpretation presumes a derivation of detritic material by a long river transport to the rift-related Permian sedimentary basin from the newly formed Variscan orogenic chain. The presence of the Variscan zircon ages in the Late Permian sequence documents a megashear transform detachment of the Gelnica Terrane to the Variscan collision belt. Both, the Gelnica Terrane rock complexes as well as their Permian overlap sequences underwent strong polystage metamorphic overprinting during the Alpine orogenic event (CHIME monazite data Vozárová et al. 2008).

The Early Paleozoic Gelnica Terrane can be interpreted as a part of the peri-Gondwana terranes, most probably situated in the east-Avalonia realm, north of the evolving Rheic Ocean, but in the proximity of the Cadomian terranes, like the “Avalonian satellites” of von Raumer et al. (2003; von Raumer and Stampfli 2008). The history of the Gelnica Terrane throughout the Silurian, Devonian and Carboniferous is enigmatic because of lack of the relevant sedimentary and magmatic rock complexes. However, its accretion history deviates significantly from the typical Avalonian terranes. Carboniferous, most probably Pennsylvanian, accretion to Laurussia is supposed for the Gelnica Terrane (Vozárová 1998), as in the case of the other Cadomian terranes preserved in the western European Variscides as well as in the Variscides of the Alpine realm. This event was connected with the evolution of the Bashkirian deep-water turbidite basin, preserved within the Turnaic Unit, in the tectonic overlier of the Southern Gemericum Unit (Vozárová and Vozár 1992) and, at last, followed by the rift-related Permian continental sedimentation accompanied by the Kungurian acid post-orogenic volcanism (Fig. 11) (275 Ma zircon SHRIMP ages; Vozárová et al. 2009).

Murphy and Nance (1989), Murphy et al. (1999), Fernándéz-Suárez et al. (2002) suggested that important terrane migration along a major dextral strike-slip zone took place on the N Gondwanan margin. Formation of this transform fault zone is supposed to have terminated the Cadomian–Avalonian arc magmatism at the end of the Neoproterozoic-Cambrian period. Amazonian terranes moved eastward and were incorporated into the realm of the Cadomian terranes prior to the deposition of the Mid-Ordovician Armorican quartzites. Stampfli and Borel′s (2002) reconstructions of the Early Ordovician show a lateral continuation of the Avalonian type of crustal pieces at the Gondwana margin. Von Raumer et al. (2003) defined the main plate-tectonic units containing Cadomian basement, Neoproterozoic to Cambrian active margin setting and Ordovician accretion stages. The latter belongs to the Hun superterrane, formerly situated at the eastern continuation of Avalonia along the Gondwana border (Stampfli and Borel 2002 and references therein). All these different crustal pieces were strongly overprinted during the Variscan and/or Alpine events and became the part of Variscan or Alpine tectonostratigraphic units.

The Gelnica Terrane passed through contrasting geodynamic stages, from a Late Cambrian/Ordovician active margin setting and later to a large dextral emplacement in which it was incorporated into the Variscan collision belt in the Pennsylvanian. This last stage was followed by the widespread Permian extension. It is supposed that the Gelnica Terrane should have been a part of the composite Avalonian-Hun active margin chain and later become a part of the Rheno-Hercynian Hanseatic Terrane. The Rheno-Hercynian Hanseatic terranes collided during the main Meso-Hercynian period (Tournaisian-Visean) with the Galatian ribbon Terrane (von Raumer and Stampfli 2008; von Raumer et al. 2009). The Meso-Hercynian event admits also the presence of the 369–334 Ma old metamorphic rims occurring on the detrital zircons within the Štítnik Formation zircon assemblage. The Hanseatic-Rheno-Hercynian position was also presupposed by Kohút (2006) for a part of the crystalline basement rocks of the Považský Inovec Mts. in the Central Western Carpathians. The Late Carboniferous transtensional/transpressional events may explain the final juxtaposition of the Gelnica Terrane into the future Alpine terranes.

Conclusions

  1. 1.

    In situ U–Pb (SHRIMP) dating of the detrital zircons from the Late Cambrian/Ordovician metasandstones of the Gelnica Terrane (the Southern Gemeric Unit) yielded mostly Neoproterozoic ages with important age clusters of Mesoproterozoic and Paleoproterozoic ages.

  2. 2.

    Evaluation of the detrital zircon age data confirms the proximity of the Gelnica Terrane source area to peri-Gondwana terranes, with a dominant input from the Avalonian–Cadomian arc.

  3. 3.

    The presence of the Grenvillian Mesoproterozoic ages suggests that the Gelnica Terrane provenance has an Avalonian–Amazonian affinity.

  4. 4.

    Even though the post-Ordovician evolution of the Gelnica Terrane is enigmatic, the presence of the metamorphic detrital zircon grains with time span of 497–441 Ma indicates a record of Late Cambrian/Ordovician tectonothermal events within the wider source area, which is characteristic of the Avalonian terranes.

  5. 5.

    The Late Carboniferous accretion of the Gelnica Terrane to the Laurussia margin is similar to many European Cadomian terranes. Thus, the Gelnica Terrane was dextrally displaced from a location in the Avalonia–Amazonia domain, but rifted off earlier than the typical Cadomian terranes and escaped from the Late Ordovician glaciation.

  6. 6.

    The geodynamic evolution of the Gelnica Terrane in Variscan time prefers a close connection to the Hanseatic Terrane.