Despite the long period of research conducted in the Western Outer Carpathians (WOC) the genesis and tectonic evolution of their crystalline basement is still poorly recognized (e.g. Żelaźniewicz et al., 2009; Buła et al., 2015). At present the crystalline basement is hidden below thick Upper Jurassic-Neogene flysch deposits of the WOC proper (e.g. Książkiewicz, 1977; Oszczypko and Ślączka, 1985; Golonka et al., 2009). Fragments of crystalline rocks, so-called exotics (e.g. Burtanówna et al., 1937; Wieser, 1948), interpreted to be derived from uplifted ridges (cordilleras, Książkiewicz, 1953) and transported by turbidity currents and debris flows into the adjoining flysch basins, offer the opportunity to investigate the geotectonic history of these no longer existing provenance areas of the Carpathian flysch (e.g. Wieser, 1949, 1985; Książkiewicz, 1965; Oszczypko, 1975; Malik, 1978; Oszczypko et al., 2016).
A number of studies concerning the palaeogeography of the WOC have used a range of geochronological methods including K-Ar mica dating (Poprawa et al., 2004, 2005, 2006; Haber and Hałas, 2001), Th-U-total Pb monazite dating (Hanžl et al., 2000; Budzyń et al., 2008; Salata and Oszczypko, 2010; Oszczypko et al., 2016) and U-Pb zircon geochronology (Michalik et al., 2006; Poprawa et al., 2006; Budzyń et al., 2011) to constrain the timing of magmatic and metamorphic processes recorded in the exotics. The general outcome of these investigations is that numerous exclusively pre-Alpine, in parts pre-Variscan ages were determined, but no obvious correlation of stratigraphic and tectonic position and/or geography emerged. From a methodological point of view this is due to the fact that especially K-Ar mica ages are sensitive to thermal and metasomatic overprint thus obscuring any primary geochronological signal directly dating igneous or metamorphic events. This published radiometric age data set is therefore not conclusive for the unambiguous identification of protolith and metamorphic ages.
The main purpose of our study is to present and discuss zircon U-Pb ages from two exotic mega blocks (a granite from Bugaj and an orthogneiss from Andrychów), representing the alimentary crystalline basement area of the WOC flysch. Due to the size of these two exotics (> 100 m) it can safely be assumed that their loci of deposition is far more proximal to their respective shedding ridge(s) than the probably more distally derived pebbles dated in previous studies. Additionally, the latter might easily be re-sedimented making any palaeogeographic implications drawn from ages derived from such rocks severely ambiguous. The presented results provide new information to the ongoing discussion of the late Neoproterozoic palaeogeography of tectonic units which intervene between the East European Craton (Baltica) and the lithotectonic units of the Variscan orogeny (e.g. Belka et al., 2000; Nawrocki et al., 2004; Żelaźniewicz et al., 2009; Buła et al., 2015).
The Western Carpathian Mountains are subdivided into the Inner Carpathians, consisting of pre-Alpine crystalline basement units covered by Late Paleozoic to mid-Cretaceous sediments (e.g. Oszczypko, 2004; Poprawa and Malata, 2006) and the Outer Carpathians, separated by the narrow, strongly tectonized Pieniny Klippen Belt (Fig. 1). The WOC are depicted as a complex nappe structure consisting of Upper Jurassic to Neogene flysch deposits, that were folded and thrusted onto the pre-Alpine European foreland during the upper Oligocene to the middle Miocene (e.g. Oszczypko, 1998, 2004; Oszczypko and Oszczypko-Clowes, 2003; Golonka et al., 2005; 2009; Oszczypko et al., 2006, Ślączka et al., 2006).
The crystalline basement constituting the pre-Alpine foreland (known only from boreholes) is divided into two basement blocks: the Upper Silesia Block (the northern part of the Brunovistulicum Terrane) to the West and the Małopolska Block to the East (Dudek, 1980; Buła, 2000; Finger et al., 2000; Żelaźniewicz et al., 2009; Buła et al., 2015). The Precambrian basement of the Upper Silesia Block is represented by a) Neoproterozoic (660–556 Ma) metamorphic and igneous rocks, b) Ediacaran anchimetamorphic flysch-type siliciclastics and c) Paleoproterozoic (2.0 Ga) metamorphic rocks with Archean (2.7 Ga) inheritance (Buła et al. 2015). The Neoproterozoic rocks of Małopolska Block are mainly represented by flysch-type series (Żelaźniewicz et al., 2009).
In the WOC several flysch basins were identified on the basis of lithostratigraphy (from south to north),
Three samples of crystalline rocks (Bu1, Bu2 and An) from exotic mega blocks (
Whole-rock samples were analysed by X-ray fluorescence (XRF) for major and large ion lithophile trace Elements (LILE) and by fusion and ICP-MS for high field strength elements (HFSE) and rare earth elements (REE) in the Bureau Veritas Minerals (Canada). Preparation involved lithium borate fusion and dilute digestions for XRF and lithium borate decomposition or aqua regia digestion for ICP-MS. LOI was determined at 1000°C. REE were normalized to C1 chondrite (Sun and McDonough, 1989).
Microprobe analyses of rock-forming and accessory minerals were undertaken in the Inter-Institutional Laboratory of Microanalyses of Minerals and Synthetic Substances, Warsaw, using a Cameca SX 100 electron microprobe operating in the wavelength-dispersive spectroscopic (WDS) mode with the following conditions: 15 kV accelerating voltage, 20 nA beam current, 1–5 μm beam diameter, peak count-time of 20 s and background count-time of 10 s.
The Rb-Sr and Sm-Nd analytical work was performed at the Laboratory of Geochronology, Department of Lithospheric Research, University of Vienna. Rb, Sr, Sm and Nd concentrations were determined from two different sample aliquots by isotope dilution (ID) using 87Rb-84Sr and 147Sm-150Nd spikes. Rb, Sm and Nd ID samples were measured as metals from a Re (single: Rb; double: Nd and Sm) filament using a Finnigan™ MAT262 mass spectrometer, while Sr ID and isotope composition (IC) and Nd IC samples were run on a ThermoFinnigan™ Triton TI TIMS machine. Maximum total procedural blanks were < 1 ng for Sr and 50 pg for Nd and were taken as negligible. Within-run mass fractionation for Nd and Sr isotope compositions (IC) was corrected to 146Nd/144Nd = 0.7219, and 86Sr/88Sr = 0.1194, respectively. Uncertainties on the Nd and Sr isotope ratios are quoted typical as 2σm. Errors for the 87Rb/86Sr and 147Sm/144Nd ratios, respectively, are taken as ±1%, or smaller, based on iterative sample analysis and spike recalibration. During the period of investigation a 143Nd/144Nd ratio of 0.511850 ± 0.000005 (n = 5) and a 87Sr/86Sr ratio of 0.710274 ± 0.000008 (n = 5) were determined for the La Jolla (Nd) and the NBS987 (Sr) international standards, respectively. Details of techniques, accuracy and data precision of Rb-Sr and Sm-Nd isotopic measurements are given by Thöni et al. (2008).
Zircon crystals were separated using standard techniques (crushing, hydrofracturing, washing, Wilfley table, magnetic separator and handpicking). The separation was carried out in the Institute of Geological Sciences, Polish Academy of Sciences, Cracow. Zircon grains were selected for the morphological study using scanning electron microscopy and then imaged by cathodoluminescence using a FET Philips 30 electron microscope (15 kV and 1 nA) at the Faculty of Earth Sciences, University of Silesia, Sosnowiec, Poland.
The LA-MC-ICP-MS (Laser Ablation Multi Collector ICP-MS) analytical work was performed in two sessions at the joint ICP-MS laboratory of the Department of Earth Sciences, Karl-Franzens-University Graz and the Institute of Applied Geosciences, Graz Technical University. Analytical procedures followed the methodology outlined in Klötzli et al. (2009). Zircon 206Pb/238U, 207Pb/206Pb, and 208Pb/232Th ratios and ages were determined using a 193nm Ar-F excimer laser (NewWave) coupled to a multi-collector ICP-MS (Nu Instruments Plasma II). Ablation using He as carrier gas was raster-wise according to the CL zonation pattern of the zircons. Line widths for rastering were 10–15 μm with a rastering speed of 5 μm/sec. Energy densities were 5–5.5 J/cm2 with a repetition rate of 10 Hz. The He carrier gas (0.7 l/min) was mixed with the Ar carrier gas flow prior to the ICP plasma torch. Ablation duration was 30 to 70 sec with a 30 sec gas and Hg blank measurement preceding ablation. Ablation count rates were corrected accordingly using the mean blank measurement intensities of the individual masses. Remaining counts on mass 204 were interpreted as representing 204Pb. Static mass spectrometer analysis was as follows: 238U and 232Th were measured in Faraday detectors, 208Pb, 207Pb, 206Pb, 204Pb+204Hg and 202Hg in discrete ion counter detectors. An integration time of 1 sec was used for all measurements. The ion counter - Faraday and inter-ion counter gain factors were determined before the analytical session using the reference zircon Plešovice (Sláma et al., 2008). The overall sensitivity for 206Pb on reference zircon Plešovice was
The samples collected from the Bugaj mega block are coarse-grained granite (
Studied rocks are peraluminous (ASI = 1.16–1.23) with silica contents around 60–71 wt.%, K2O ≥ Na2O and Rb/Sr ratios = 1.1–1.4 (Table 1). The rocks belong to the high K-calc-alkaline series and are intermediate between the ferroan and magnesian families of the Frost and Frost (2008) geochemical classification. Chondrite-normalized (Sun and McDonough, 1989) REE patterns show low LREE enrichment (CeN/YbN = 3.18–6.34) and a strong negative Eu anomaly (Eu/Eu* = 0.38–0.57; Table 1; Fig. 3b). Magma crystallization temperatures calculated on the basis of the Zr-saturation geothermometer of Watson and Harrison (1983) are in the range of 800–850°C
(Table 1). The primitive-mantle-normalized multielement diagram points to an arc-setting of the magma, with typical Nb and Ta negative anomalies, whereas the Batchelor and Bowden (1985) classification suggests a post-collisional to late-orogenic magmatic suite (Fig. 3b, 3c). Granodiorite-granite rocks show relatively high
Chemical composition and selected petrological indicators of Bugaj granitoid rocks.
Sample No | Bu1 | Bu2 | BuC |
---|---|---|---|
SiO2 | 71.56 | 67.58 | 60.03 |
TiO2 | 0.38 | 0.7 | 0.98 |
Al2O3 | 14.13 | 14.89 | 16.63 |
Fe2O3T | 3.04 | 5.31 | 8.32 |
MnO | 0.06 | 0.09 | 0.14 |
MgO | 0.77 | 1.34 | 2.46 |
CaO | 0.92 | 1.5 | 1.89 |
Na2O | 3.36 | 3.83 | 3.33 |
K2O | 4.79 | 3.36 | 4.86 |
P2O5 | 0.11 | 0.22 | 0.18 |
LOI | 0.71 | 1.13 | 0.9 |
Total | 99.83 | 99.95 | 99.72 |
Sr | 121.2 | 128 | 152.3 |
Ba | 578 | 562 | 793 |
Rb | 135.6 | 146.9 | 219.3 |
Cs | 8.3 | 10.3 | 13.1 |
Th | 11 | 11.7 | 1.3 |
U | 2.6 | 1.4 | 10.1 |
Ga | 16 | 20.4 | 20.5 |
Cr | 82 | 109.5 | 116.3 |
Ni | 11 | 14 | 27.9 |
V | 43 | 75 | 135 |
Zr | 150.9 | 283.6 | 226.8 |
Hf | 4.9 | 7.6 | 6.2 |
Y | 42.9 | 37.9 | 27 |
Nb | 9.8 | 15.4 | 16.1 |
Ta | 0.8 | 1.1 | 0.9 |
La | 24.6 | 30.3 | 27.9 |
Ce | 52.6 | 62.4 | 61.9 |
Pr | 6.35 | 7.56 | 7.06 |
Nd | 24.7 | 30.6 | 27.3 |
Sm | 5.96 | 6.63 | 5.64 |
Eu | 0.75 | 0.87 | 1.01 |
Gd | 6.04 | 6.9 | 5.45 |
Tb | 0.99 | 0.99 | 0.89 |
Dy | 6.96 | 6.97 | 4.9 |
Ho | 1.49 | 1.3 | 0.95 |
Er | 4.32 | 3.62 | 3.1 |
Tm | 0.69 | 0.56 | 0.41 |
Yb | 4.56 | 3.67 | 2.69 |
Lu | 0.64 | 0.5 | 0.42 |
ASI | 1.17 | 1.23 | 1.21 |
#mg | 0.56 | 0.7 | 0.31 |
Rb/Sr | 1.12 | 1.15 | 1.44 |
ΣREE | 140.65 | 162.87 | 149.62 |
Eu/Eu* | 0.8 | 0.39 | 0.56 |
CeN/YbN | 3.18 | 4.68 | 6.34 |
ThN/UN | 1.04 | 2.06 | 0.03 |
TZr [°C] | 798 | 850 | 818 |
ThN/UN ratios (2.06 and 1.05 respectively), whereas the monzonitic enclave shows a strong positive U anomaly and a ThN/UN ratio of 0.03, suggesting a highly oxidised source (possibly mantle-type?) of the monzonitic magma (Fig. 3b; Table 1).
The whole-rock isotope geochemistry data of two Bugaj mega block samples are presented in Table 2 Both samples (
Rb-Sr and Sm-Nd whole rock isotope analysis of Bugaj granitoid rocks.
Isotope data | 87Rb/86Sr | ±2sm | 87Sr/86Sr | ±2sm | 147Sm/144Nd | ±2sm | 143Nd/144Nd | ±2sm | Sr(580 Ma) | Nd(580 Ma) | Nd(CHUR) |
---|---|---|---|---|---|---|---|---|---|---|---|
Bugaj1 | 3.154 | 0.032 | 0.756053 | 0.000004 | 0.1521 | 0.0015 | 0.512397 | 0.000004 | 0.729966 | 0.511819 | –1.4 |
Bugaj2 | 3.236 | 0.032 | 0.755499 | 0.000004 | 0.1366 | 0.0014 | 0.512428 | 0.000005 | 0.728739 | 0.511909 | 0.4 |
Contrary to the above the Sm-Nd isotope systematics of the two Bugaj mega block samples are dissimilar: 147Sm/144Nd ratios are 0.1521 ± 0.0015 (Bu1) and 0.1366 ± 0.0014 (Bu2). The 143Nd/144Nd ratios are 0.512397 ± 0.000004 and 0.512428 ± 0.000005, respectively. The resulting εNd580 are –1.4 and 0.4.
The sample (
The zircons are colourless or slightly pink, euhedral, normal to very long-prismatic, even to acicular (aspect ratios 1:1 to 1:10). Grain sizes vary in length from ca. 50 to 350 μm (Fig. 4). A small percentage of zircon grains show an unusual habit contrasting markedly with the prismatic and acicular crystals (Fig. 4, p6Bu81). This habit is tabular, strongly flattened on the [110] crystal face (elongation ratio < 1). The typology falls into the S4 subtype group of Pupin (1980).
The cathodoluminescence (CL) images reveal a complexity of the internal structure. A significant number of crystals shows igneous oscillatory growth zoning, with growth bands varying between fine and broad within individual grains (Fig. 5). Luminescence is variable, but mostly moderate. Some grains display a blurred, light grey zonation, present in the centre of the zircon crystals (Fig. 5, p3Bu01). A small number of inherited cores were observed in normal-prismatic crystals (Fig. 5).
LA-MC-ICP-MS U–Pb zircon data from exotic mega blocks (samples An and Bu1).
Sample | Blank corrected intensities | Concentrations | Atomic ratios | Ages | ||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
204Pb | 206Pb | 207Pb | 208Pb | 232Th | 238U | Pb | Th | U | Th/U | 206Pb 204Pb | 207Pb 235U | 206Pb 238U | 207Pb Rho 206Pb | 208Pb 206Pb | 208Pb 232Th | 238U 206Pb | 207Pb 206Pb | 206/238 age | 2SD | 206/207 age | 2SD | |||||||||
(V) ×10-6 | (V) ×10-4 | (V) ×10-5 | ×(10V) -5 | ×(10V) -3 | (V) ×10-2 | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (Ma) | ||||||||||||||||
p3An_02 | 6.10 | 39.0 | 23.0 | 51.0 | 11.0 | 6.30 | 10.1 | 24.4 | 139.9 | 0.17 | 908 | 8 | 0.6716 | 3.9 | 0.0795 | 3.8 | 0.48 0.0606 | 1.3 | 0.4316 | 4.9 | 0.0316 | 6.9 | 12.575 | 3.8 | 0.0606 | 1.3 | 493 | 19 | 624 | 29 |
p3An_03/1 | 7.00 | 68.0 | 41.0 | 97.0 | 28.0 | 10.0 | 17.7 | 64.8 | 140.6 | 0.46 | 1037 | 20 | 0.8044 | 6.3 | 0.0894 | 8.3 | 0.65 0.0642 | 4.3 | 0.4994 | 16.0 | 0.0228 | 13.1 | 11.189 | 8.3 | 0.0642 | 4.3 | 552 | 46 | 750 | 92 |
p3An_03/2 | 15.0 | 65.0 | 47.0 | 92.0 | 18.0 | 13.0 | 17.2 | 41.5 | 141.1 | 0.29 | 810 | 27 | 0.6698 | 10.3 | 0.0725 | 17.4 | 0.85 0.0681 | 16.1 | 0.4145 | 11.5 | 0.0357 | 22.5 | 13.799 | 17.4 | 0.0681 | 16.1 | 451 | 78 | 871 | 334 |
p3An_04/1 | 4.20 | 42.0 | 23.0 | 37.0 | 9.60 | 6.20 | 10.4 | 21.9 | 139.9 | 0.16 | 1241 | 8 | 0.7043 | 11.8 | 0.0873 | 10.8 | 0.46 0.0587 | 1.3 | 0.2440 | 11.8 | 0.0253 | 10.6 | 11.448 | 10.8 | 0.0587 | 1.3 | 540 | 58 | 554 | 29 |
p3An_04/2 | 4.90 | 35.0 | 20.0 | 41.0 | 11.0 | 4.90 | 9.1 | 25.3 | 139.7 | 0.18 | 1130 | 10 | 0.7178 | 12.0 | 0.0885 | 9.6 | 0.40 0.0591 | 2.5 | 0.3477 | 6.1 | 0.0224 | 10.3 | 11.295 | 9.6 | 0.0591 | 2.5 | 547 | 53 | 572 | 54 |
p3An_06/1 | 4.40 | 120 | 140 | 220 | 14.0 | 3.70 | 33.3 | 31.8 | 139.5 | 0.23 | 3187 | 14 | 7.2106 | 12.5 | 0.3956 | 13.2 | 0.53 0.1319 | 1.3 | 0.5778 | 4.2 | 0.0870 | 25.5 | 2.528 | 13.2 | 0.1319 | 1.3 | 2149 | 284 | 2123 | 23 |
p3An_06/2 | 5.00 | 190 | 200 | 98.0 | 7.90 | 9.20 | 47.1 | 18.1 | 140.4 | 0.13 | nd | nd | 4.2498 | 7.3 | 0.2650 | 8.7 | 0.59 0.1138 | 1.1 | 0.1669 | 23.5 | 0.0849 | 10.1 | 3.774 | 8.7 | 0.1138 | 1.1 | 1515 | 132 | 1861 | 20 |
p3An_07 | 4.70 | 64.0 | 38.0 | 80.0 | 25.0 | 10.0 | 16.5 | 58.1 | 140.5 | 0.41 | 1767 | 16 | 0.7138 | 9.9 | 0.0800 | 14.2 | 0.71 0.0646 | 3.7 | 0.3529 | 8.5 | 0.0219 | 14.5 | 12.500 | 14.2 | 0.0646 | 3.7 | 496 | 70 | 761 | 79 |
p3An_08 | 5.00 | 150 | 140 | 170 | 17.0 | 8.00 | 39.9 | 39.3 | 140.2 | 0.28 | 3863 | 15 | 3.0343 | 15.2 | 0.2317 | 15.5 | 0.51 0.0947 | 0.5 | 0.3318 | 5.8 | 0.0696 | 10.8 | 4.316 | 15.5 | 0.0947 | 0.5 | 1343 | 208 | 1521 | 9 |
p3An_09 | 6.60 | 70.0 | 43.0 | 120 | 31.0 | 10.0 | 18.8 | 70.9 | 140.5 | 0.50 | 1540 | 15 | 0.8438 | 9.6 | 0.0933 | 11.5 | 0.60 0.0644 | 3.7 | 0.4983 | 7.2 | 0.0267 | 10.5 | 10.717 | 11.5 | 0.0644 | 3.7 | 575 | 66 | 753 | 79 |
p3An_10 | 5.80 | 55.0 | 32.0 | 93.0 | 28.0 | 7.20 | 14.7 | 63.3 | 140.1 | 0.45 | 1259 | 2 | 0.8063 | 5.7 | 0.0950 | 5.6 | 0.49 0.0613 | 0.9 | 0.4459 | 2.9 | 0.0224 | 8.3 | 10.523 | 5.6 | 0.0613 | 0.9 | 585 | 33 | 649 | 20 |
p3An_11 | 6.90 | 24.0 | 17.0 | 33.0 | 8.5 | 3.50 | 6.3 | 19.4 | 139.5 | 0.14 | 580 | 19 | 0.9325 | 10.9 | 0.0969 | 9.3 | 0.43 0.0690 | 8.6 | 0.3371 | 12.2 | 0.0261 | 15.1 | 10.317 | 9.3 | 0.0690 | 8.6 | 596 | 55 | 899 | 177 |
p3An_12/1 | 4.60 | 47.0 | 27.0 | 10.0 | 2.2 | 6.90 | 11.0 | 5.1 | 140.0 | 0.04 | nd | nd | 0.6993 | 8.5 | 0.0850 | 9.1 | 0.53 0.0595 | 0.7 | 0.0568 | 8.1 | 0.0301 | 7.2 | 11.764 | 9.1 | 0.0595 | 0.7 | 526 | 48 | 587 | 15 |
p3An_12/2 | 4.90 | 19.0 | 12.0 | 16.0 | 5.5 | 2.40 | 4.8 | 12.5 | 139.3 | 0.09 | 473 | 11 | 1.0174 | 17.2 | 0.1134 | 15.9 | 0.46 0.0642 | 3.8 | 0.2989 | 40.0 | 0.0204 | 18.4 | 8.821 | 15.9 | 0.0642 | 3.8 | 692 | 110 | 750 | 80 |
p3An_13 | 25.0 | 52.0 | 67.0 | 110 | 19.0 | 13.0 | 15.1 | 43.7 | 141.1 | 0.31 | 193 | 40 | 0.9691 | 11.9 | 0.0507 | 22.8 | 0.96 0.1481 | 17.2 | 0.6235 | 26.8 | 0.0780 | 39.6 | 19.741 | 22.8 | 0.1481 | 17.2 | 319 | 73 | 2324 | 295 |
p2Bu_01 | 14.0 | 44.0 | 37.0 | 63.0 | 12.0 | 5.80 | 11.8 | 27.5 | 139.8 | 0.20 | 341 | 14 | 0.8705 | 5.0 | 0.0947 | 4.0 | 0.40 0.0624 | 3.7 | 0.2605 | 7.2 | 0.0209 | 7.4 | 10.560 | 4.0 | 0.0624 | 3.7 | 583 | 23 | 688 | 79 |
p2Bu_05 | nd | 44.0 | 28.0 | 85.0 | 12.0 | 4.50 | 12.0 | 27.2 | 139.6 | 0.19 | nd | nd | 0.8737 | 6.3 | 0.1071 | 6.6 | 0.52 0.0592 | 0.9 | 0.5936 | 20.8 | 0.0263 | 8.7 | 9.341 | 6.6 | 0.0592 | 0.9 | 656 | 43 | 573 | 19 |
p2Bu_08 | 6.80 | 58.0 | 38.0 | 81.0 | 11.0 | 6.60 | 15.3 | 26.3 | 140.0 | 0.19 | 1018 | 11 | 0.7378 | 6.4 | 0.0896 | 7.1 | 0.55 0.0597 | 1.1 | 0.3524 | 8.2 | 0.0217 | 6.6 | 11.157 | 7.1 | 0.0597 | 1.1 | 553 | 39 | 592 | 25 |
p2Bu_10/1 | 50.0 | 85.0 | 93.0 | 180 | 190 | 16.0 | 24.6 | 435.3 | 141.5 | 3.08 | 931 | 187 | 0.7942 | 38.6 | 0.1102 | 177.8 | 2.31 0.0287 | 1356 | 0.0650 | 3667 | 0.0207 | 217.6 | 9.073 | 177.8 | 0.0287 | 1356 | 674 | 1199 | - | - |
p2Bu_10/2 | 25.0 | 180 | 120 | 270 | 38.0 | 20.0 | 47.8 | 87.8 | 142.3 | 0.62 | 946 | 6 | 0.7912 | 8.6 | 0.0928 | 9.0 | 0.52 0.0611 | 2.9 | 0.3029 | 10.6 | 0.0221 | 7.9 | 10.776 | 9.0 | 0.0611 | 2.9 | 572 | 52 | 643 | 62 |
p2Bu_19 | 17.0 | 89.0 | 57.0 | 76.0 | 9.70 | 10.0 | 22.4 | 22.1 | 140.6 | 0.16 | nd | nd | 0.7638 | 3.2 | 0.0967 | 3.1 | 0.49 0.0575 | 0.4 | 0.3044 | 42.1 | 0.0244 | 5.9 | 10.339 | 3.1 | 0.0575 | 0.4 | 595 | 18 | 510 | 9 |
p2Bu_23 | 14.0 | 110 | 130 | 270 | 11.0 | 4.30 | 33.5 | 26.1 | 139.6 | 0.19 | 992 | 1 | 4.6704 | 5.0 | 0.3121 | 4.5 | 0.45 0.1084 | 1.3 | 0.5018 | 4.7 | 0.0751 | 6.1 | 3.204 | 4.5 | 0.1084 | 1.3 | 1751 | 78 | 1773 | 25 |
p2Bu_30 | 7.80 | 88.0 | 56.0 | 170 | 22.0 | 10.0 | 24.0 | 50.8 | 140.6 | 0.36 | nd | nd | 0.7806 | 9.3 | 0.0978 | 7.6 | 0.41 0.0578 | 1.7 | 0.3649 | 33.3 | 0.0237 | 14.5 | 10.229 | 7.6 | 0.0578 | 1.7 | 601 | 46 | 524 | 37 |
2Bu_32 | 9.90 | 54.0 | 35.0 | 50.0 | 5.80 | 5.90 | 13.7 | 13.3 | 139.9 | 0.09 | 801 | 3 | 0.7487 | 5.2 | 0.0931 | 5.6 | 0.54 0.0584 | 0.7 | 0.2113 | 22.7 | 0.0269 | 5.1 | 10.742 | 5.6 | 0.0584 | 0.7 | 574 | 32 | 546 | 15 |
p2Bu_35/1 | 8.60 | 59.0 | 38.0 | 53.0 | 6.10 | 6.90 | 14.8 | 14.1 | 140.0 | 0.10 | 723 | 8 | 0.7295 | 5.2 | 0.0877 | 7.3 | 0.70 0.0598 | 2.1 | 0.2684 | 25.8 | 0.0252 | 16.0 | 11.405 | 7.3 | 0.0598 | 2.1 | 542 | 40 | 597 | 45 |
p2Bu_35/2 | 7.80 | 84.0 | 56.0 | 39.0 | 4.10 | 8.90 | 20.4 | 9.5 | 140.4 | 0.07 | 863 | 74 | 0.8119 | 24.6 | 0.0960 | 34.0 | 0.69 0.0606 | 6.9 | 0.1682 | 122.6 | 0.0356 | 36.3 | 10.420 | 34.0 | 0.0606 | 6.9 | 591 | 201 | 624 | 149 |
p3Bu_01/1 | 11.0 | 61.0 | 51.0 | 69.0 | 55.0 | 12.0 | 15.8 | 125.9 | 140.9 | 0.89 | 546 | 30 | 0.7773 | 8.6 | 0.0692 | 4.3 | 0.25 0.0839 | 9.0 | 0.4171 | 20.2 | 0.0128 | 21.3 | 14.460 | 4.3 | 0.0839 | 9.0 | 431 | 19 | 1290 | 176 |
p3Bu_01/2 | 4.60 | 15.0 | 11.0 | 17.0 | 11.0 | 2.10 | 3.8 | 25.3 | 139.2 | 0.18 | nd | nd | 0.8730 | 17.3 | 0.0946 | 11.9 | 0.35 0.0646 | 19.5 | 0.3371 | 54.8 | 0.0198 | 24.3 | 10.569 | 11.9 | 0.0646 | 19.5 | 583 | 69 | 762 | 412 |
p3Bu_01/3 | 17.0 | 48.0 | 42.0 | 120 | 83.0 | 8.30 | 14.0 | 189.3 | 140.3 | 1.35 | 453 | 22 | 0.8695 | 6.4 | 0.0800 | 9.1 | 0.71 0.0814 | 10.4 | 0.9599 | 19.5 | 0.0218 | 15.0 | 12.506 | 9.1 | 0.0814 | 10.4 | 496 | 45 | 1232 | 204 |
p3Bu_03/1 | nd | 1.80 | 1.10 | 1.20 | 0.740 | 0.250 | 0.4 | 1.7 | 138.9 | 0.01 | nd | nd | 0.9325 | 36.6 | 0.1145 | 39.4 | 0.54 0.0599 | 6.2 | 0.2290 | 15.0 | 0.0153 | 106.6 | 8.736 | 39.4 | 0.0599 | 6.2 | 699 | 276 | 599 | 135 |
p3Bu_03/2 | 4.20 | 0.780 | 0.51 | 0.57 | 0.390 | 0.110 | 0.2 | 0.9 | 138.9 | 0.01 | 40 | 11 | 0.9258 | 14.2 | 0.1104 | 13.4 | 0.47 0.0609 | 4.3 | 0.2333 | 6.9 | 0.0196 | 16.7 | 9.054 | 13.4 | 0.0609 | 4.3 | 675 | 90 | 636 | 92 |
p3Bu_04 | 4.00 | 0.980 | 0.67 | 0.50 | 0.350 | 0.150 | 0.2 | 0.8 | 138.9 | 0.01 | nd | nd | 0.8442 | 21.7 | 0.0930 | 23.3 | 0.54 0.0646 | 9.0 | 0.1726 | 20.3 | 0.0140 | 70.5 | 10.749 | 23.3 | 0.0646 | 9.0 | 573 | 133 | 761 | 189 |
p3Bu_09/1 | 42.0 | 33.0 | 52.0 | 120 | 76.0 | 7.30 | 10.8 | 175.0 | 140.1 | 1.25 | 199 | 25 | 2.1793 | 196.9 | 0.1178 | 133.3 | 0.34 0.1021 | 96.8 | 0.7533 | 129.5 | 0.0158 | 695.3 | 8.488 | 133.3 | 0.1021 | 96.8 | 718 | 957 | 1663 | 1791 |
p3Bu_09/2 | 5.80 | 35.0 | 24.0 | 75.0 | 29.0 | 5.50 | 9.7 | 66.8 | 139.8 | 0.48 | 720 | 4 | 0.8187 | 4.0 | 0.0926 | 2.4 | 0.29 0.0645 | 3.6 | 0.9196 | 17.5 | 0.0279 | 4.4 | 10.799 | 2.4 | 0.0645 | 3.6 | 571 | 13 | 758 | 76 |
p3Bu_10 | nd | 16.0 | 10.0 | 30.0 | 12.0 | 2.50 | 4.4 | 26.7 | 139.3 | 0.19 | nd | nd | 0.7826 | 1.9 | 0.0956 | 1.7 | 0.44 0.0592 | 0.6 | 0.6439 | 3.7 | 0.0284 | 2.2 | 10.459 | 1.7 | 0.0592 | 0.6 | 589 | 10 | 576 | 13 |
p3Bu_12 | 5.40 | 32.0 | 20.0 | 31.0 | 12.0 | 4.90 | 8.1 | 26.9 | 139.7 | 0.19 | 567 | 6 | 0.7593 | 11.7 | 0.0936 | 10.2 | 0.44 0.0588 | 3.2 | 0.4832 | 241.3 | 0.0287 | 19.4 | 10.679 | 10.2 | 0.0588 | 3.2 | 577 | 59 | 559 | 69 |
p3Bu_13/1 | 4.60 | 24.0 | 15.0 | 23.0 | 8.10 | 3.60 | 6.0 | 18.6 | 139.5 | 0.13 | nd | nd | 0.7762 | 3.9 | 0.0943 | 4.9 | 0.63 0.0596 | 1.9 | 0.5016 | 75.8 | 0.0295 | 21.6 | 10.603 | 4.9 | 0.0596 | 1.9 | 581 | 28 | 589 | 41 |
p3Bu_13/2 | 6.80 | 15.0 | 9.90 | 8.10 | 6.40 | 2.30 | 3.6 | 14.7 | 139.3 | 0.11 | 346 | 61 | 0.8443 | 39.7 | 0.0908 | 21.5 | 0.27 0.0670 | 27.5 | 0.2070 | 122.8 | 0.0159 | 110.5 | 11.014 | 21.5 | 0.0670 | 27.5 | 560 | 120 | 838 | 573 |
p3Bu_14 | 4.00 | 16.0 | 9.80 | 15.0 | 5.90 | 2.40 | 4.0 | 13.4 | 139.3 | 0.10 | 119 | 15 | 0.7477 | 4.0 | 0.0892 | 4.6 | 0.58 0.0607 | 0.9 | 0.5905 | 20.3 | 0.0288 | 5.2 | 11.216 | 4.6 | 0.0607 | 0.9 | 551 | 25 | 630 | 20 |
p3Bu_15 | 5.30 | 2.10 | 1.60 | 3.20 | 1.70 | 0.320 | 0.6 | 4.0 | 138.9 | 0.03 | 52 | 12 | 0.9670 | 14.2 | 0.0905 | 13.8 | 0.49 0.0762 | 7.9 | 0.5176 | 12.7 | 0.0196 | 17.1 | 11.045 | 13.8 | 0.0762 | 7.9 | 559 | 77 | 1099 | 158 |
2RSE 2-sigma relative standard error (in %), Rho the error correlation between the 206/238 and 207/235 ratios.
Crystal domains targeted for dating are characterized by the presence of a well-developed fine-scale oscillatory growth zonation (Fig. 5). 25 dates on 19 crystals were gained (Table 3, Fig. 5). Individual 206Pb/238U dates range from 1751 ± 78 Ma to 431 ± 19 Ma, whereas 207Pb/206Pb dates range from 1773 ± 25 Ma to 510 ± 9 Ma, respectively. No systematic difference between the two populations could be detected. Thus the final age calculation took into account all analysed crystals of the Bugaj1 sample. One analysis (Bugaj1_p2bu_023A) is concordant at an age of ca. 1760 Ma (Fig. 6a). 14 dates form a sub-concordant (discordance < 5%) cluster with a lower intercept date of 580.1 ± 6.0 Ma (Fig. 6b, model 1 solution, anchored at 207Pb/206Pb = 0.85 ± 0.05, MSWD = 1.8, Probability of fit = 0.031). These crystals show a mean Th/U of 0.16 ± 0.07. Three sub-concordant analyses (discordance < 5%), characterized by comparably high Th/U (0.30 ± 0.04), form a cluster with a lower intercept date of 662 ± 37 Ma (not shown, model 1 solution, anchored at 207Pb/206Pb = 0.85 ± 0.05, MSWD = 0.12, Probability of fit = 0.89). This lower intercept date is statistically distinguishable from the former one, also based on the disparate Th/U ratios of the two clusters. The remaining 7 analyses are highly discordant with high Th/U ratios (0.72 ± 0.35), again statistically distinguishable from the former two clusters.
Zircon grains are euhedral, up to 300 μm long, with aspect ratios from 1:1 to 1:3 (Fig. 7). They are clear, yellow and greenish yellow in colour.
In CL images a variably developed oscillatory growth zoning is the prominent feature of all analysed grains, as shown by moderate to weak luminescence. Some crystals display core-rim structures. The cores are characterized by oscillatory growth zoning with high/moderate CL intensity (Fig. 8).
Crystal domains targeted for dating are characterized by the presence of a well-developed fine-scale oscillatory growth zonation (Fig. 8). 15 dates on 10 crystals were gained (Table 3, Fig. 8). Individual 206Pb/238U dates range from 2149 ± 284 Ma to 319 ± 73 Ma, whereas 207Pb/206Pb dates range from 2324 ± 295 Ma to 554 ± 29 Ma, respectively. One analysis (Andrychów_p3an_06A) is concordant at an age of 2123 ± 23 Ma (Fig. 9a). 7 dates form a sub-concordant (discordance < 5%) cluster with a mean Th/U of 0.23 ± 0.11. Two lower intercept dates can be calculated: i) 549 ± 29 Ma with an upper intercept at 2432 ± 1500 Ma (not shown, model 1 solution, MSWD = 0.99, Probability of fit = 0.42); ii) 542 ± 21 Ma with the upper intercept fixed at 2123 ± 23 Ma of analysis Andrychów_p3an_06A (Fig. 9b, model 1 solution, MSWD = 0.86, Probability of fit = 0.53).
The calculated upper intercept value of 2432 ± 1500 Ma of i) is well within uncertainty with the concordant age value of 2123 ± 23 Ma used for the calculation in ii). Also the two lower intercept ages are identical within their uncertainty limits.
The remaining analyses either are strongly discordant (discordance > 10%) or sub-concordant (discordance < 5%) at 207Pb/206Pb ages between 2324 ± 295 Ma and 624 ± 29 Ma. The Th/U ratios of these analyses are identical to the former one (0.18 ± 0.06).
Exotics represent one of the most important sources of information about Carpathian alimentary areas, indirectly indicating their geotectonic history. For both exotic mega blocks (sample Bugaj and sample Andrychów) igneous formation ages were derived from the zircon U-Pb data.
The Cadomian age (580.1 ± 6.0 Ma) from sample
The Sr and Nd whole-rock isotope data are controversial. The initial (at
The biotite K-Ar age of 485 ± 10 Ma (Haber and Hałas, 2001) indicates either slow cooling to
In the Andrychów sample, the lower intercept age of 542 ± 21 Ma, obtained from zircon domains exhibiting a fine-scale oscillatory growth zonation in the CL images, is interpreted as the uppermost Proterozoic to Cambrian magmatic crystallization age of the granitic precursor of the orthogneiss. The concordant age at 2123 ± 23 Ma represents Palaeoproterozoic inheritance. There is no evidence for a Variscan (Devonian-Carboniferous) or Alpine (Neogene) metamorphic overprint, neither from the zircon U-Pb age systematics nor from the zircon mineral chemistry,
The U-Pb zircon ages presented in this study are consistent with published results (monazite Th-U-total Pb dating, K-Ar dating of muscovite and biotite), reported from clastic material supplying Silesian basin from the Brunovistulicum and/or Małopolska Terranes as northern source areas (Poprawa et al., 2004, 2005, 2006; Budzyń et al., 2008, 2011).
The sequence of events obtained from U-Pb zircon ages from Bugaj and Andrychów exotic mega blocks shows similarities to magmatic-metamorphic events identified in the Brunovistulicum Terrane. These events include: a) terrane collision with deformation, metamorphism and plutonism at ca. 650–620 Ma; b) arc-type granitoid intrusions at
Our investigations thus support the connection of the exotic mega blocks with the Avalonian-Cadomian orogenic belt during the Neoproterozoic (Żelaźniewicz et al., 2009).
For both exotic mega blocks (Bugaj and Andrychów) igneous formation ages could be derived from the zircon U-Pb data. These are 542 ± 21 Ma for the orthogneiss from Andrychów and 580.1 ± 6.0 Ma for the granitoid from Bugaj.
The U-Pb zircon ages, derived from > 100 m sized exotic mega blocks, directly reflect the presence of substantial amounts of a proximal ‘Cadomian’ aged crust proper in the vicinity of the WOC basement. This is a marked difference to earlier published data, which are derived from cm-dm sized pebbles only. As these can easily be derived from re-sedimented sources the ages do not necessarily reflect direct derivation from a ‘Cadomian’ basement, inasmuch as transport distances are not known.
Exotic mega blocks deposited to the WOC basins were related to the Brunovistulicum Terrane. They belong to the group of Vendian/Early Cambrian granitoids, representing the latest, post-tectonic expression of the Cadomian cycle.