The Slavonian Mountains in Croatia, comprising the Psunj, Papuk and Krndija mountain ranges (
A – tectonic map with major tectonic units of the Alps, Carpathians and Dinarides (Schmid et al., 2016), with the position of the Slavonian Mts. (Croatia) marked by a black rectangle (B). B – The geology of the crystalline basement rocks of the Slavonian Mts. A simplified geological outline of the Slavonian Mts. (Psunj, Papuk and Krnidja) (according to Jamičić, 2001) with sampled locations: PSG-1 Omanovac Quarry (Psunj Mt.), 2PPG-32 Šandrovac Quarry (NW Papuk Mt.) and HEG-31 Kišeljevac Creek (S slope of Papuk Mt.). Legend: 1 – Graniotoids (G), 2 – Migmatites (Mi), 3 – Biotite-muscovite gneiss (Gmb), 4 – garnet-staurolite gneiss, kyanite gneiss, sillimanite gneiss, amphibolite, metagabbro, amphibole-schist, chlorite-sericite schist and flaser granitoids, and other different types of granitoids with marble. C – Schematic drawing of three series of basement rocks: the Psunj-Krndija, Papuk and Radlovac Complexes.
The pre-Alpine terranes of Tisia accompanied Slavonian inselbergs in Slavonia-Dravia Terrane (Slavonia Drava Unit), according to Kovács et al. (2000), or the Bihor nappe system, according to Schmid et al. (2008; 2016) (Villány-Bihor Zone or unit of Bleahu et al., 1996 and Haas and Péró, 2004; Papuk-Codru Zone of Haas, 2015) (
The most detailed reports on the geology of the Psunj and Papuk Mts. are geological 1/100,000 scale maps, Daruvar (Jamičić, 1989) and Orahovica (Jamičić and Brkić, 1987) sheets, and corresponding explanatory notes (Jamičić et al., 1987; 1989).
Jamičić (1988; 2001), based on petrographical and structural data, distinguishes three series of basement rocks: a) Psunj-Krndija Complex, b) Papuk Complex and c) Radlovac Complex (
Pamić and Lanphere (1991), and Pamić et al. (1988a; 1996) distinguish five main groups of crystalline rocks of the Pannonian Basin in the Slavonian Mountains and the surrounding basement: 1. the weakly metamorphosed (semimetamorphic) complex; 2. the progressively metamorphosed complex; 3. migmatites; 4. S-type granites and 5. I-type granites. They concluded that all of these were produced during the Hercynian orogeny.
The aim of this paper is to solve the basic geochronological question about the igneous age of monzogranites from Psunj and Papuk Mts. (Slavonia, Croatia). For this purpose, in-situ laser ablation U-Pb zircon dating was applied. The paper shows that the investigated granite intrusions had occurred earlier (in Late Devonian) than previous radiometric studies have reported.
The Basic Geological Map (1/100,000) of the Slavonian Mountains (Psunj, Papuk, and Krndija), Daruvar (Jamičić, 1989) and Orahovica (Jamičić and Brkić, 1987) sheets cover the area between the Sava and Drava Rivers, bordered by 45°20´ and 45°40´ north latitudes, and 17°00´ and 18°00´ east longitudes. A schematic geological map, simplified according to the geological map of Jamičić (2001) and including sampled locations, is presented in
Recent studies by Balen et al. (2006; 2013), Horváth et al. (2010) and Balen et al. (2015) have provided mainly monazite dating results for medium-grade metamorphic rocks (micaschist, gneiss and amphibolite) from the Psunj-Krndija Complex. These data have emphasised the occurrence of Cambrian–Ordovician ages (528 ± 7 and 465 ± 7 Ma; Balen et al., 2015), an Ordovician-Silurian metamorphic event at peak assemblage monazite growth reaching amphibolite facies conditions of
In the central part of Psunj Mt. and in the connection zone between Papuk and Krndija Mts., Late Devonian coarse-grained sandstones and graphite-bearing slates (
The central parts, eastern and northern slopes of Papuk Mt. comprise of biotite gneisses and muscovitebiotite gneisses, micaschists, homogeneous and heterogeneous migmatites, granitoids, pegmatites and aplites (Jamičić et al., 1987; 1989). Granitoids of the NW part of the Mt. Papuk have a mineral composition corresponding to granite, granodiorite, quartzdiorite and leucocratic tonalite varieties, and can be found as distinct large bodies, lenses or veins in migmatites (Vragović, 1965). The succession of metamorphic zones imperceptibly grading into each other (Papuk Mt.) could be followed continuously as a progressive metamorphic sequence, with following metamorphic index minerals: chlorite → biotite → garnet → staurolite → sillimanite (Raffaelli, 1964). In addition, andalusite was found in these schists by Pamić et al. (1988b). Less abundant micaschists can be found at the northern slope of Papuk Mt. Gneisses and micaschists continuously grade to migmatites in all locations (Jamičić et al., 1989; Pamić and Lanphere, 1991). Pegmatites and aplites occur as veins, irregular nests in the migmatitic zone, in the zone of muscovite-biotite gneiss and in granitoid bodies (Horvat et al., 2002; Kovács Kis et al., 2004 and references therein). Pegmatites contain large pink, pinkish gray or gray feldspars as megacrysts (Jamičić et al., 1989). Amphibolites and amphibole schists are intercalated in the migmatites and gneisses. Based on microscopic descriptions, major element data, and oxygen isotope geochemistry, Pamić and Marci (1990) and Pamić et al. (2002) summarised the petrography and geochemistry of the amphibolites of Mts. Psunj and Papuk, documenting that all of them represent orthoamphibolites. Serpentinites featuring relicts of peridotite were found only in one Papuk Mt. location and in the central part of Psunj Mt. (Jamičić and Brkić, 1987; Jamičić, 1989). Granitoid plutons within the migmatitic complex are composed mainly of S-type granites and subordinate intermediate rocks (Pamić and Lanphere, 1991). Horvat and Buda (2004) published syncollision and postcollision magmatism affinity for seven samples from the Papuk Complex, monzogranite and granodiorite types, using multi cationic parameters R1 and R2 (de la Roche et al., 1980), classifying majority of them as S-type and I/S-type as well.
The process of phyllonitisation is detected in the whole area and it is one of the features of retrograde metamorphism.
The geochemistry of amphibole monzogranite from Psunj Mt. and of different granitoid types of Papuk Mt. were originally presented by Horvat and Buda (2004). Of these samples, sample from Psunj Mt. (Omanovac Quarry, the PSG-1 sample) and two from Papuk Mt. (Šandrovac Quarry, the 2PPG-32 sample and Kišeljevac Creek, the HEG-31 sample) were selected for further geochronological investigations (
Mineral separation was carried out at Eötvös Loránd University (Budapest, Hungary) using standard techniques (crushing, hydro-fracturing, washing, heavy liquids and magnetic separation). 80 (PSG-1), 74 (2PPG-32) and 105 (HEG-31) zircon crystals, were hand-picked and mounted in 1-inch epoxy-resin mounts according to their translucency and grain size at the University of Vienna (Austria). Zircon grains were imaged by panchromatic cathodoluminescence on a VEGA/TESCAN SEM (15 kV and 8 nA) at the Geological Survey of Austria (GBA Vienna, Austria).
The LA-ICP-MS analytical work was performed at the joint ICP-MS laboratory of the Department of Earth Sciences, Karl-Franzens-Universität Graz and the Institute of Applied Geosciences, Graz Technical University. Analytical procedures were identical to the methodology outlined in Klötzli et al. (2009). Zircon U-Th-Pb isotopic and elemental ratios were determined using a 193nm ArF excimer laser (NewWave) coupled to a multi-collector ICP-MS (Nu Instruments II). Ablation using He as carrier gas was raster- and spot-wise according to the CL zonation pattern of the zircons. Line widths for rastering were 10–15 μm with a rastering speed of 10 μm/sec. Energy densities were
The mass and elemental bias and mass spectrometer drift of both U/Pb and Pb/Pb ratios, respectively, were corrected applying the “intercept method” developed by Sylvester and Ghaderi (1997). The calculated 206Pb/238U and 207Pb/206Pb intercept values were corrected for mass discrimination from analyses of the Plesovice reference zircon measured during the analytical session using a standard bracketing method (Klötzli
The Plešovice reference zircon (Sláma et al., 2008) was also used as secondary standard in order to test the overall reproducibility of the analytical method. A total of 13 measurements made during the analytical session resulted in a concordia age of 337.1 ± 0.6 Ma (2σ, decay-constant errors included, MSWD concordance = 0.21, probability of concordance = 0.64). This is within error identical to the accepted reference 206Pb/238U date of 337.13 ± 0.37 Ma (Sláma et al., 2008).
Mineral abbreviations used here follow those used by Slovenec and Bermanec (2003).
The PSG-1 sample originates from a homogeneous granitic body from Omanovac Quarry in the Rogoljica Valley (W Psunj Mt) (
Representative sample (PSG-1) from Omanovac Quarry (Psunj Mt., Croatia): A – macrophotography (R coin = 16 mm); B–D microphotographs (crossed nicols). Abbreviations: Qtz – quartz, Kfs – K-feldspar, Pl – plagioclase, Amp – amphibole.
No biotite is found in the PSG-1 sample, and plagioclase occurs in small amounts. Plagioclase is almost pure albite (0.5 mol% Or, 98–97 mol% Ab, 1–2 mol% An). The average K-feldspar composition is 96 mol % Or, 4 mol % Ab, 0 mol % An. The amphibole is a ferro-hornblende (Horvat and Buda, 2004). The PSG-1 sample is classified as amphibole monzogranite according to A–P–Q ternary classification diagram for plutonic rocks (IUGS, 1973), and as monzogranite in the chemical-mineralogical classification of Debon and Le Fort (1983) (Q=199, P= –39). It has a relatively high concentration of REE (330 ppm), with a strong negative Sr and Eu anomaly. Elevated ΣREE and a negative Eu anomaly indicate a typical magmatic fractional crystallisation of this monzogranite (Horvat et al., 2015a).
The 2PPG-32 sample is from Šandrovac Quarry (NW Papuk Mt) (
Representative sample (2PPG-32) from Šandrovac Quarry (Papuk Mt., Croatia): A – macrophotography (scale in cm); B–D micro-photographs (crossed nicols). Abbreviations: Qtz – quartz, Kfs – K-feldspar, Pl – plagioclase, Bi – biotite, Ms - muscovite.
The HEG-31 sample is from a magmatic body in the gneiss zone at the S slope of Papuk Mt. (
Representative sample (HEG-31) from Kišeljevac Creek (Papuk Mt., Croatia): A–D microphotographs (crossed nicols). Abbreviations: Qtz – quartz, Kfs – K-feldspar, Bt – biotite.
Zircon grain sizes from the PSG-1 sample vary from 70 to 120 microns in length, with aspect ratios of 1:2. Zircon crystals are subhedral, colourless and clear, with distinct internal zonation features: CL dark, idiomorphic, sometimes rounded cores are followed by a CL bright to dark alteration zone or a dark alteration zone which is sometimes zoned (
Cathodoluminescence images of dated zircon crystals separated from the amphibole monzogranite (PSG-1) from Omanovac Quarry, Psunj Mt., Croatia. The white rectangles and circles mark the in-situ laser-ablation track used for U/Pb dating, (ø = 10–15–20 μm), and they are not in scale. Measurement numbers are listed in Table 1.
Concordia plot of LA-MC-ICP-MS U-Pb zircon analytical results for the PSG-1 sample.
Zircon crystals from the 2PPG-32 sample are euhedral, long-prismatic, with grain size from 100 to 150 micron in length, with aspect ratios of 1:2. CL images of sections through zircon crystals reveal a typically magmatic zircon with oscillatory zoning, plus different alteration rims (zones) in the zircon grains. Within the oscillatory zonation one, two or even three CL-dark zones can be distinguished (
Cathodoluminescence images of dated zircon crystals separated from the monzogranite (2PPG-32) from Šandrovac Quarry, Papuk Mt., Croatia. The white rectangles mark the in-situ laser-ablation track used for U/Pb dating, (ø = 10–15 μm) and they are not in scale. Measurement numbers are listed in Table 1.
Concordia plots of LA-MC-ICP-MS U-Pb zircon analytical results (Table 1) for the 2PPG-32 sample.
Zircon grains sizes from the HEG-31 sample vary in length from 70 to 130 microns. Zircon crystals are euhedral to subhedral, both long- and short prismatic, with aspect ratios of 1:2 to 1:3 (
Cathodoluminescence images of dated zircon crystals separated from the biotite monzogranite (HEG-31) from Kišeljevac Creek, Papuk Mt., Croatia. The white rectangles mark the in-situ laser-ablation track used for U/Pb dating, (⌀ = 10–15–20 μm), and they are not in scale. Measurement numbers are listed in Table 1.
Concordia plots of LA-MC-ICP-MS U-Pb zircon analytical results (Table 1) for the HEG-31 sample (calculated with a forced upper intercept at 207Pb/206Pb = 0.85 ± 0.05).
Zircon laser-ablation MC-ICP-MS U-Th-Pb data including the 206Pb/238U minimum ages.
204Pb | 206Pb | 207Pb | 208Pb | 232Th | 238U | ±2SE | ±2SE | ±Rho 2SE | ±2SE | ±2SE | ±2SE | ±2SE | ±2SE | ±2SD | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Spot # | (mV) ×10–6 | (mV) ×10–3 | (mV) ×10–4 | (mV) ×10–4 | (mV) ×10–2 | (mV) ×10–1 | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (Ma) | |||||||||||
PSG-1 | ||||||||||||||||||||||||||
PSG-1_0139_10a | 1.40 | 0.66 | 0.49 | 0.79 | 0.41 | 0.19 | 608 | 1 | 0.448 | 2.89 | 0.0600 | 2.77 | 0.48 | 0.0542 | 0.41 | 0.355 | 4.54 | 0.019 | 1.55 | 16.67 | 2.77 | 0.0542 | 0.41 | |||
PSG-1_0139_10b | 3.20 | 0.75 | 0.58 | 0.98 | 0.56 | 0.23 | 227 | 78 | 0.453 | 2.22 | 0.0605 | 1.84 | 0.41 | 0.0542 | 0.79 | 0.378 | 3.85 | 0.017 | 2.46 | 16.53 | 1.84 | 0.0542 | 0.79 | |||
PSG-1_0139_35 | 2.20 | 3.50 | 2.60 | 5.20 | 2.80 | 0.99 | 1271 | 63 | 0.481 | 2.11 | 0.0644 | 2.37 | 0.56 | 0.0541 | 0.77 | 0.308 | 5.34 | 0.018 | 5.80 | 15.53 | 2.37 | 0.0541 | 0.77 | |||
PSG-1_0139_37 | 2.20 | 3.90 | 2.90 | 7.60 | 4.30 | 1.10 | 2088 | 8 | 0.408 | 5.68 | 0.0546 | 5.85 | 0.51 | 0.0543 | 0.29 | 0.530 | 3.62 | 0.015 | 2.84 | 16.33 | 5.85 | 0.0543 | 0.29 | |||
PSG-1_0139_38 | 2.20 | 2.00 | 1.60 | 3.20 | 1.30 | 0.45 | 1363 | 2 | 0.421 | 1.43 | 0.0570 | 0.86 | 0.30 | 0.0540 | 0.66 | 0.389 | 0.80 | 0.017 | 1.17 | 16.55 | 0.86 | 0.0540 | 0.66 | |||
PSG-1_0139_40 | 1.70 | 2.30 | 1.70 | 3.10 | 1.80 | 0.71 | 1682 | 3 | 0.406 | 2.56 | 0.0537 | 2.91 | 0.57 | 0.0546 | 0.31 | 0.404 | 3.98 | 0.017 | 2.84 | 16.62 | 2.91 | 0.0546 | 0.31 | |||
PSG-1_0139_52 | 1.70 | 1.00 | 0.75 | 1.40 | 0.73 | 0.28 | 887 | 3 | 0.454 | 4.96 | 0.0607 | 4.94 | 0.50 | 0.0543 | 0.37 | 0.375 | 3.52 | 0.018 | 3.02 | 16.49 | 4.94 | 0.0543 | 0.37 | |||
PSG-1_0139_61 | n.d. | 0.93 | 0.69 | 1.30 | 0.67 | 0.25 | - | - | 0.469 | 4.35 | 0.0619 | 4.71 | 0.54 | 0.0544 | 0.50 | 0.341 | 4.39 | 0.020 | 1.89 | 16.15 | 4.71 | 0.0544 | 0.50 | |||
PSG-1_0139_63 | n.d. | 1.40 | 1.00 | 1.90 | 0.96 | 0.39 | - | - | 0.490 | 2.49 | 0.0644 | 3.87 | 0.78 | 0.0547 | 1.21 | 0.396 | 18.9 | 0.020 | 5.92 | 15.52 | 3.87 | 0.0547 | 1.21 | |||
2PPG-32 0140 01 | 3.40 | 3.10 | 2.70 | 4.70 | 1.20 | 0.41 | ||||||||||||||||||||
2PPG-32_0140_03 | 7.60 | 2.10 | 2.20 | 5.20 | 1.20 | 0.27 | 132 | 45 | 0.458 | 4.76 | 0.0610 | 2.18 | 0.23 | 0.0545 | 2.38 | 6.549 | 2.46 | 0.031 | 4.51 | 16.40 | 2.18 | 0.0545 | 2.38 | |||
2PPG-32_0140_05 | 6.60 | 6.40 | 6.10 | 13.00 | 2.90 | 0.86 | 2095 | 11 | 0.454 | 3.79 | 0.0606 | 1.72 | 0.12 | 0.0544 | 1.45 | 5.657 | 2.87 | 0.032 | 4.72 | 16.49 | 1.72 | 0.0544 | 1.45 | |||
2PPG-32_0140_13a | 5.50 | 8.30 | 7.30 | 7.80 | 2.10 | 1.00 | 1196 | 12 | 0.452 | 5.75 | 0.0603 | 2.60 | 0.48 | 0.0545 | 0.61 | 3.580 | 9.32 | 0.040 | 8.35 | 16.59 | 2.60 | 0.0545 | 0.61 | |||
2PPG-32_0140_13b | 2.90 | 5.00 | 4.40 | 8.60 | 2.00 | 0.62 | 2367 | 10 | 0.450 | 4.44 | 0.0602 | 2.00 | 0.56 | 0.0542 | 1.02 | 5.297 | 7.70 | 0.034 | 3.32 | 16.62 | 2.00 | 0.0542 | 1.02 | |||
2PPG-32_0140_15 | 3.10 | 3.40 | 3.00 | 5.90 | 1.50 | 0.45 | 1445 | 8 | 0.452 | 3.29 | 0.0599 | 1.48 | 0.35 | 0.0547 | 1.59 | 4.594 | 2.24 | 0.026 | 25.2 | 16.69 | 1.48 | 0.0547 | 1.59 | |||
2PPG-32_0140_16 | 3.10 | 2.00 | 1.90 | 5.80 | 1.40 | 0.26 | 651 | 7 | 0.448 | 4.09 | 0.0599 | 1.83 | 0.73 | 0.0543 | 1.11 | 8.610 | 4.85 | 0.035 | 5.11 | 16.69 | 1.83 | 0.0543 | 1.11 | |||
HEG-31_0137_03a | 1.90 | 2.20 | 1.70 | 2.50 | 1.40 | 0.66 | ||||||||||||||||||||
31_0137_03b | 2.70 | 9.00 | 6.90 | 5.00 | 2.30 | 2.70 | 5680 | 267 | 0.442 | 69.8 | 0.0587 | 61.8 | 0.44 | 0.0546 | 4.91 | 0.149 | 140 | 0.024 | 171 | 17.04 | 61.8 | 0.0546 | 4.91 | |||
HEG-31_0137_04 | 2.10 | 0.41 | 0.40 | 0.51 | 0.12 | 0.10 | 942 | 13 | 0.569 | 22.3 | 0.0622 | 15.6 | 0.35 | 0.0673 | 4.26 | 0.225 | 27.9 | 0.037 | 19.1 | 16.08 | 15.6 | 0.0673 | 4.26 | |||
HEG-31_0137_05 | 2.10 | 1.00 | 0.79 | 0.50 | 0.25 | 0.30 | 1492 | 3 | 0.475 | 1.78 | 0.0625 | 1.85 | 0.52 | 0.0551 | 0.39 | 0.120 | 3.14 | 0.020 | 2.06 | 15.99 | 1.85 | 0.0551 | 0.39 | |||
HEG-31_0137_06 | 2.30 | 2.20 | 1.60 | 3.80 | 1.90 | 0.65 | 1545 | 6 | 0.466 | 2.52 | 0.0629 | 1.89 | 0.37 | 0.0543 | 0.45 | 0.580 | 14.0 | 0.017 | 11.0 | 15.89 | 1.89 | 0.0543 | 0.45 | |||
HEG-31_0137_10 | 2.10 | 1.50 | 1.10 | 2.70 | 1.50 | 0.46 | 245 | 540 | 0.457 | 6.57 | 0.0613 | 8.60 | 0.65 | 0.0540 | 4.63 | 0.415 | 36.1 | 0.018 | 5.22 | 16.31 | 8.60 | 0.0540 | 4.63 | |||
HEG-31_0137_15 | 1.80 | 1.10 | 0.88 | 3.10 | 0.83 | 0.16 | 762 | 3 | 0.722 | 4.26 | 0.0863 | 4.41 | 0.52 | 0.0609 | 0.66 | 0.793 | 5.30 | 0.029 | 1.95 | 11.59 | 4.41 | 0.0609 | 0.66 | |||
HEG-31_0137_16 | n.d. | 3.90 | 2.90 | 3.80 | 1.90 | 1.20 | - | - | 0.405 | 16.3 | 0.0546 | 15.0 | 0.46 | 0.0541 | 0.47 | 0.260 | 17.8 | 0.017 | 23.4 | 18.30 | 15.0 | 0.0541 | 0.47 | |||
HEG-31_0137_20 | 1.90 | 2.20 | 1.70 | 2.10 | 0.91 | 0.54 | 1560 | 1 | 0.388 | 2.97 | 0.0527 | 2.49 | 0.42 | 0.0539 | 0.34 | 0.313 | 4.98 | 0.017 | 3.41 | 18.96 | 2.49 | 0.0539 | 0.34 | |||
HEG-31_0137_23 | 2.10 | 2.00 | 1.50 | 1.80 | 0.99 | 0.62 | 1176 | 1 | 0.440 | 0.58 | 0.0584 | 0.57 | 0.49 | 0.0548 | 0.28 | 0.201 | 1.64 | 0.018 | 0.82 | 17.12 | 0.57 | 0.0548 | 0.28 | |||
HEG-31_0138_05 | 1.80 | 1.20 | 0.90 | 1.70 | 0.83 | 0.28 | 1076 | 1 | 0.452 | 0.94 | 0.0606 | 0.87 | 0.46 | 0.0545 | 0.51 | 0.477 | 1.96 | 0.017 | 1.61 | 16.50 | 0.87 | 0.0545 | 0.51 | |||
HEG-31_0138_06a | 1.80 | 0.37 | 0.31 | 0.41 | 0.23 | 0.09 | 571 | 3 | 0.448 | 3.58 | 0.0570 | 2.24 | 0.31 | 0.0571 | 2.12 | 0.247 | 3.53 | 0.017 | 5.71 | 17.53 | 2.24 | 0.0571 | 2.12 | |||
HEG-31_0138_06b | n.d. | 0.83 | 0.63 | 1.00 | 0.49 | 0.22 | - | - | 0.432 | 6.01 | 0.0572 | 5.92 | 0.49 | 0.0543 | 1.60 | 0.346 | 8.74 | 0.017 | 10.4 | 17.49 | 5.92 | 0.0543 | 1.60 | |||
HEG-31_0138_14 | 2.80 | 2.40 | 2.50 | 3.60 | 0.80 | 0.34 | 2723 | 2 | 0.590 | 3.15 | 0.0664 | 1.13 | 0.18 | 0.0643 | 2.02 | 0.411 | 1.86 | 0.016 | 6.90 | 15.05 | 1.13 | 0.0643 | 2.02 | |||
HEG-31_0138_19 | 2.50 | 2.60 | 2.00 | 4.60 | 2.40 | 0.78 | 1166 | 22 | 0.475 | 3.28 | 0.0614 | 2.37 | 0.36 | 0.0558 | 2.06 | 0.771 | 2.05 | 0.018 | 3.78 | 16.28 | 2.37 | 0.0558 | 2.06 | |||
HEG-31_0138_29 | 2.80 | 0.77 | 0.67 | 1.20 | 0.56 | 0.23 | 429 | 2 | 0.493 | 2.12 | 0.0599 | 1.10 | 0.26 | 0.0594 | 1.83 | 0.445 | 6.18 | 0.021 | 4.88 | 16.69 | 1.10 | 0.0594 | 1.83 | |||
HEG-31_0138_33 | 2.80 | 2.20 | 1.70 | 1.90 | 1.90 | 0.66 | 1803 | 6 | 0.469 | 2.26 | 0.0613 | 2.63 | 0.58 | 0.0553 | 0.76 | 0.231 | 3.71 | 0.018 | 12.0 | 16.32 | 2.63 | 0.0553 | 0.76 | |||
HEG-31_0138_37 | 1.70 | 2.20 | 1.70 | 2.30 | 1.30 | 0.64 | 1482 | 1 | 0.468 | 1.29 | 0.0624 | 1.37 | 0.53 | 0.0544 | 0.19 | 0.294 | 4.61 | 0.017 | 1.30 | 16.03 | 1.37 | 0.0544 | 0.19 | |||
HEG-31_0138_40 | 2.60 | 4.00 | 3.10 | 3.10 | 1.40 | 0.97 | 1509 | 6 | 0.470 | 2.76 | 0.0611 | 1.72 | 0.31 | 0.0555 | 1.13 | 0.167 | 8.52 | 0.019 | 3.49 | 16.36 | 1.72 | 0.0555 | 1.13 | |||
HEG-31_0138_41 | 1.70 | 1.30 | 0.99 | 1.10 | 0.57 | 0.40 | 1086 | 1 | 0.422 | 1.02 | 0.0562 | 0.96 | 0.47 | 0.0545 | 0.32 | 0.294 | 5.27 | 0.016 | 4.24 | 17.79 | 0.96 | 0.0545 | 0.32 |
The oldest exposed rocks of the Slavonian Mts. occur in the Psunj-Krndija Complex according to research by Jamičić (1988; 1989; 2001), and this was confirmed by recent data by Balen and co-authors (2006; 2013; 2015). Different types of granitoids and gabbro intrusions are associated with these metamorphic rocks, but large amounts of granite are also found in the Papuk Complex (Jamičić et al., 1987, 1989) (
The PSG-1 sample is from a granitic body in the Rogoljica Valley in the western part of Psunj Mt. (
The 2PPG-32 sample is from Šandrovac Quarry in the NW part of the Mt. Papuk, where basalts and andesites dykes (Lugović, 1983) intersect various metamorphic rocks ranging from the chlorite- to amphibolite-facies in association with different varieties of granitic rocks (Jamičić, 1989). This muscovite-biotite monzogranite has a eutectic composition and a peraluminous character (ASI = 1.20) (Horvat and Buda, 2004). The analysed sample has a Na2O content of 3.92 and a K2O content of 3.80, and belongs to the I-type according to the Chappell and White (1984) criteria. The relationship between the wt% SiO2 content and the aluminium saturation index (ASI = 1.20) for the 2PPG-32 sample suggested an S-type character.
The HEG-31 sample, biotite monzogranite from the Kišeljevac Creek valley (the S slope of Papuk Mt.) is the small granitoid intrusion found within the gneiss, with significant contact aureole and marble formation. This field observation confirmed the intrusion of siliceous melt, for which it was determined as having a peraluminous character (ASI = 1.08). The analysed sample has a 3.36 wt% Na2O content and a 4.30 wt% K2O content, and belongs to the transitive zone between the S- and I-type according to Chapell and White (1984) criteria. Biotite in this sample is red-brown in colour (
It can be assumed that the monzogranite rocks in question cannot be classified as strictly S- or I- type (Pamić et al., 1996 and Pamić and Jurković, 2002).
The first K-Ar and Rb-Sr ages for metamorphic and associated igneous rocks from Mts. Papuk, Psunj and Krndija in Slavonia were reported by Pamić et al. (1988a and references therein). Particular data reported in Pamić et al. (1988a), compared to samples present in this work, are 155.2 ± 3.7 Ma K-Ar ages for biotite-hornblende granite from Rogoljica (W Psunj Mt.) on hornblende and 93.6 ± 2.3 Ma on biotite; 335.2 ± 8.4 Ma K-Ar ages for pegmatite from the Šandrovac location (the NW part of the Papuk Mt.) on muscovite and 321.5 ± 8 Ma K-Ar ages for Bi-granite from Kišeljevac (the S slope of Papuk Mt.) on biotite. The same authors obtained two groups of older ages from 421 to 658 Ma and from 352 to 376 Ma on hornblende from amphibolites (K-Ar measurements). These discordant ages were subsequently checked by 40Ar-39Ar spectra measurements on muscovite and biotite from paragneisses and mica schists. In five from seven ages ranging between 337 and 321 Ma, one sample yielded 264 Ma and one 430 Ma (Pamić
The application of the in-situ laser ablation U-Pb zircon dating method provides the absolute rock ages of one sample from the Papuk Complex (2PPG-32, Šandrovac Quarry, Papuk Mt.) and two samples from the Psunj-Krndija Complex (PSG-1, Omanovac Quarry, Psunj Mt. and HEG-31, Kišeljevac Creek, Papuk Mt.). The cathodoluminescence images reveal the oscillatory zoning pattern through all zircon crystals, which are interpreted as stemming from magmatic zircon growth from a silicic melt. The U-Pb results for all three representative granitoid samples from different intrusive bodies are, therefore, interpreted to represent intrusion ages: 380 ± 4 Ma for the monzogranite from Omanovac Quarry (W Psunj Mt.), 382 ± 2 Ma for the monzogranite from Šandrovac Quarry (NW Papuk Mt.) and 383 ± 5 Ma for the monzogranite from Kišeljevac Creek (S slope of Papuk Mt.).
These results suggest Late Devonian magmatic activity, and show that the investigated granitoid intrusions had occurred earlier than previous radiometric studies have suggested.
In-situ LA-MC-ICP-MS U-Pb zircon dating provides following new geochronological insights into the evolution of crystalline rocks of the Slavonian Mts. – Psunj and Papuk:
1) 380 ± 4 Ma intrusion age of the monzogranite from Omanovac Quarry, Psunj Mt.
2) 382 ± 2 Ma intrusion age of the monzogranite from Šandrovac Quarry, Papuk Mt. and
3) 383 ± 5 Ma intrusion age of the monzogranite from Kišeljevac Creek, Papuk Mt.
The study showed that the granitoid intrusions in question had occurred earlier (in Late Devonian) than previous radiometric studies have reported, confirming multistage granitoid magmatism in the Slavonian Mts. The pre-Variscan elements are a relevant fact, hidden by Variscan and Alpine marks. As relics, they occur today as poly-metamorphic and migmatite domains in the Slavonian Mts. in Croatia.