Age constraints on the Pre-Variscan and Variscan thermal events in the Kamieniec Ząbkowicki Metamorphic belt (the Fore-Sudetic Block, SW Poland)

Jastrzębski, Mirosław; Żelaźniewicz, Andrzej; Budzyń, Bartosz; Sláma, Jiří; Konečný, Petr

doi:10.14241/asgp.2020.05

Cited by 4 publications

(18 citation statements)

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“…This is in agreement with the protolith age of an orthogneiss from the neighbouring Doboszowice Metamorphic Complex (Figure 1), which intruded the volcano-sedimentary succession at 488.4 ± 6.2 Ma (Mazur et al, 2010). It is also confirmed by recently published results of detrital zircon geochronology of micaschists from the KMB suggesting latest Neoproterozoic maximum age of deposition of these rocks (Jastrzębski et al, 2020). The whole succession was deformed and metamorphosed during the Variscan collision of the Brunovistulian and Saxothuringian microplates (Mazur & Józefiak, 1999;Mazur & Puziewicz, 1995).…”

Section: Introductionsupporting

confidence: 91%

“…Recent investigations indicate that crustal complexes of the Central Sudetes, including the KMB, may represent the eastern‐most extent of the Saxothuringian crust (e.g. Jastrzębski et al., 2020; Mazur et al., 2012; Oberc‐Dziedzic et al., 2018; Szczepański et al., 2019; Tab aud et al., 2021). The KMB can be considered as a portion of the Saxothuringian crust that has experienced metamorphism typical of subduction zones.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, chemical U–Th–total Pb electron probe microanalysis (EPMA) monazite geochronology data indicate an important regional tectono‐metamorphic event at c . 330 Ma (Jastrzębski et al., 2020). The volcano‐sedimentary succession of the KMB was intruded by syntectonic granitoids.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The age of metamorphism and related deformation is constrained in the central part of the Fore-Sudetic Block by 40 Ar-39 Ar dating of hornblende, yielding c. 376 Ma and 331.9 ± 1.7 Ma for hornblende-bearing rocks from the Kamieniec Metamorphic Belt and the neighbouring Niemcza Shear Zone respectively (Steltenpohl et al, 1993). Furthermore, chemical U-Th-total Pb electron probe microanalysis (EPMA) monazite geochronology data indicate an important regional tectono-metamorphic event at c. 330 Ma (Jastrzębski et al, 2020). The volcano-sedimentary succession of the KMB was intruded by syntectonic granitoids.…”

Section: Introductionmentioning

confidence: 99%

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Combined phase diagram modelling and quartz‐in‐garnet barometry of HP metapelites from the Kamieniec Metamorphic Belt (NE Bohemian Massif)

Szczepański

Zhong

Dąbrowski

et al. 2021

Journal Metamorphic Geology

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The Kamieniec Metamorphic Belt belongs to the Variscan Belt of Europe as the NE part of the Bohemian Massif. It comprises a supracrustal succession dominated by micaschists that has not been yet recognized as a high‐P, low‐T (HP–LT) metamorphic unit. Our work demonstrates the significance of metapelites in the study of HP metamorphism of the NE part of the Bohemian Massif. To reconstruct the P–T history of the Kamieniec Metamorphic Belt, we have investigated three samples using independent geothermobarometric techniques including phase diagram modelling, Si4+ content in white mica and quartz‐in‐garnet elastic barometry. Two samples contain mineral assemblages bearing a record of HP metamorphism followed by an LP event. The oldest assemblage is mostly preserved in the first generation of garnet and it comprises phengitic white mica and rutile. In one of the investigated samples, we also recognized chloritoid and inferred pseudomorphs after lawsonite composed of quartz, clinozoisite associated with margarite. The third of the investigated samples is strongly retrogressed and only contains the relics of phengitic white mica. All three samples contain a younger mineral assemblage comprising white mica with low Si4+ content and ilmenite. Mineral equilibria modelling indicates the P–T conditions of the HP event culminated at ~15.5–18 kbar and ~470–570℃, while the LP episode occurred at ~5–7 kbar and ~530–570℃. The Raman shift measured in quartz inclusions in garnet in samples with a well‐preserved record of the HP stage points to their entrapment at pressures between 11 and 16 kbar. The quartz inclusions within the strongly retrogressed micaschist sample exhibit Raman shifts corresponding to the LP episode at ~5–8 kbar. Discrepant results obtained for one of the samples are discussed in detail. Our investigations show that the supracrustal succession of the Kamieniec Metamorphic Belt contains a record of HP–LT metamorphism typical for subduction systems. A recently established tectonic model for the crystalline complexes exposed in the Bohemian Massif suggests that they were formed via the collision of the Saxothuringian, Teplá–Barrandian, and Brunovistulian domains. Therefore, we interpret the Kamieniec Metamorphic Belt as representing fragments of the Saxothuringian crust that experienced cold extrusion from below the Teplá–Barrandian domain in front of the rigid Brunovistulian indenter.

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Section: Introductionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Combined phase diagram modelling and quartz‐in‐garnet barometry of HP metapelites from the Kamieniec Metamorphic Belt (NE Bohemian Massif)

Szczepański

Zhong

Dąbrowski

et al. 2021

Journal Metamorphic Geology

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“…The dates with −7.3 to +7.3% discordance originate from monazite domains containing 586–2,940 ppm U, whereas dates with +7.8%–15.1% discordance were obtained for domains containing higher concentrations of 4,940–9,200 ppm U. The age disturbance was possibly enhanced by moderate degree of radiation damage that affects monazite (Budzyń et al., 2020; Nasdala et al., 2020; Seydoux‐Guillaume et al., 2018) and induced by late recrystallization at high‐ T conditions and common Pb incorporation, which has been reported for monazite altered during processes at various temperature conditions (cf., Didier et al., 2013; Holder et al., 2015; Jastrzębski et al., 2020; Seydoux‐Guillaume et al., 2012; Skrzypek et al., 2017). In granulites, these data together with the same lower intercept and U–Pb concordia ages of 369.6 ± 1.6 Ma and 370.0 ± 5.1 Ma, respectively (Figure 9d,e), constrain decompression to have occurred at high temperatures.…”

Section: Discussionmentioning

confidence: 99%

Eo‐Variscan metamorphism in the Bohemian Massif: Thermodynamic modelling and monazite geochronology of gneisses and granulites of the Góry Sowie Massif, SW Poland

Jastrzębski

Budzyń

Żelaźniewicz

et al. 2021

Journal Metamorphic Geology

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In the Variscides of central Europe, the tectonothermal history of a few units jointly assigned to the Teplá-Barrandian/Bohemian microplate had already terminated in the Devonian. One of these is the Góry Sowie Massif (GSM; Sudetes, SW Poland), mainly consisting of variably migmatitic gneisses with subordinate granulite and peridotite inserts. The eo-Variscan evolution of the GSM was completed in five tectonothermal stages; however, the timing and pressure-temperature (P-T) conditions of the individual stages remain unclear because isotopic ages overlap within error, and previous P-T estimates have been determined without reference to these ages. Our thermodynamic modelling and LA-ICP-MS U-Pb and electron probe microanalysis (EPMA) U-Th-total Pb monazite geochronology provide new insights into the early Variscan multistage evolution of the GSM. The new P-T-time (t) data show that granulites were metamorphosed concurrently with gneisses but at different depths and temperatures. During subduction of Saxothuringia beneath Teplá-Barrandia at 395-390 Ma, the granulites of crustal provenance experienced high-P-high-T conditions (740-750°C, 17-18 kbar) and came in contact with the overlying mantle.Slab break-off gave rise to decompression from conditions of ~17 kbar/840°C to 11-12 kbar/850-860°C, which continued at 380-370 Ma when the granulites were sheared off and extruded as tectonic slices to lower-middle crustal depths, where gneisses were undergoing metamorphism and migmatization under amphibolite facies conditions. In the gneisses, the oldest monazite date of c. 390 Ma constrains the age of the early tectonometamorphic event D 1 . Two subsequent events (D 2 and D 3 , sillimanite grade) occurred under conditions of 660-680°C and 5-9 kbar at 380-375 Ma, when, in various parts of the future massif, the gneisses were (re)folded and migmatized due to heat arising from underplated mantle. Isostatic exhumation was accompanied by pegmatite intrusions (D 4 ) at 370 Ma and subsequent orogenic collapse (D 5 ). Concurrently, high temperature conditions (~700°C) promoted a disturbance of the U-Pb system in monazite in some granulites.

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Provenance of the early Palaeozoic volcano-sedimentary successions from eastern part of the Central Sudetes: implications for the tectonic evolution of the NE Bohemian Massif

Szczepański,

Kaszuba,

Anczkiewicz

et al. 2023

Geol. Mag.

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The Kamieniec Metamorphic Belt (KMB) and the Doboszowice Metamorphic Complex (DMC) expose a fragment of the pre-Variscan volcano-sedimentary cover preserved in the Fore-Sudetic Block in the NE part of the Bohemian Massif. We present the age of detrital and magmatic zircon grains and the bulk rock chemical composition of rock samples from the KMB and the DMC to better understand the evolution of the early Palaeozoic Gondwana margin. The zircon age spectra were acquired by U–Pb LA–ICP–MS dating and represent two groups that differ by maximum depositional age (MDA). The paragneiss from the DMC displays the MDA at 456 Ma, whereas the mica shist from the KMB displays the MDA at 529 Ma. Older age peaks in both groups of samples are represented by the Neoproterozoic and less frequent the Paleoproterozoic and Archean. The data presented indicate that the rock successions were sourced from the Cadomian orogen and deposited in the basins that developed on the Gondwana margin. Our results support the suggestion that the crystalline basement in the eastern part of the Fore-Sudetic Block has an affinity to the Trans-Saharan Belt or West African Craton and was part of a Gondwana shelf. The final stage of evolution of the studied successions was related to the Variscan thermal overprint. Based on presented data, we support the idea that the suture separating the Brunovistulian domain from the rest of the Gondwana-derived terranes is not related to the closure of the Rheic Ocean and represents a local feature.

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Age constraints on the Pre-Variscan and Variscan thermal events in the Kamieniec Ząbkowicki Metamorphic belt (the Fore-Sudetic Block, SW Poland)

Cited by 4 publications

References 0 publications

Combined phase diagram modelling and quartz‐in‐garnet barometry of HP metapelites from the Kamieniec Metamorphic Belt (NE Bohemian Massif)

Combined phase diagram modelling and quartz‐in‐garnet barometry of HP metapelites from the Kamieniec Metamorphic Belt (NE Bohemian Massif)

Eo‐Variscan metamorphism in the Bohemian Massif: Thermodynamic modelling and monazite geochronology of gneisses and granulites of the Góry Sowie Massif, SW Poland

Provenance of the early Palaeozoic volcano-sedimentary successions from eastern part of the Central Sudetes: implications for the tectonic evolution of the NE Bohemian Massif

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