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Neoproterozoic ophiolite exotic blocks in the Outer Western Carpathians, southern Poland : a record of the fast ocean-floor cooling and alterations

Gawęda Aleksandra, Szopa Krzysztof, Waśkowska Anna, Golonka Jan, Krzykawski Tomasz, Kalinichenko Tatiana

Geological Quarterly

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2023

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Vol. 67, No. 1

art. no. 9

EN

Ophiolitic blocks, represented by metagabbro and serpentinite containing relict pyroxene, olivine, baddeleyite, zirconolite, Ni-pyrite and pyrrhotite, were found as exotic blocks in an olistostrome in the Magura Nappe, Outer Western Carpathians. The geochemical and isotopic features of the blocks suggest they represent mantle-derived rocks, with within-plate geochemistry signatures, modified by subduction, with lithospheric mantle input. A U-Pb apatite cooling age (614 ±3 Ma) is within age uncertainty of a published U-Pb zircon magmatic crystallization age (~614 Ma) implying rapid post-crystallization cooling. Pervasive alteration with replacement of primary minerals by low-temperature assemblages is observed in all rock fragments and is interpreted as contemporaneous with shearing. The secondary mineral assemblages and temperature modelling allow the interpretation that the pervasive ocean-floor metamorphism is the alteration in these meta-mafic rocks. These ophiolitic fragments can be linked to the Neoproterozoic break up of Rodinia/Pannotia.

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Silesian Ridge in the light of petrological analyses and LA-ICP MS U-Pb analyses of the cohesive debrites from the Istebna Formation (Silesian Nappe, Outer Western Carpathians, Poland)

Szczuka Monika, Gawęda Aleksandra, Waśkowska Anna, Golonka Jan, Szopa Krzysztof, Chew David, Drakou Foteini

Geological Quarterly

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2022

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Vol. 66, No. 2

art. no. 20

EN

Exotic clasts present in flysch deposits of the Western Outer Carpathians enable investigation and reconstruction of the eroded crystalline basement of the Silesian Ridge. The flysch rocks of the Istebna Formation (Jasnowice Member: Paleocene) in the Silesian Nappe contain magmatic and metamorphic clasts derived from the Silesian Ridge basement. The crystalline rock fragments acquired from cohesive debrites were analyzed petrographically and geochemically, and zircon and rutile crystals were subject to LA-ICP-MS U-Pb dating. Granitoid clasts yielded Meso-Variscan U-Pb zircon ages (325.7 and 330.6 Ma), with older (Neoproterozoic to Paleoproterozoic) inherited cores and eNd330 = –12.0 (TDM age of 1.98 Ga). The orthogneiss clast yielded a protolith age of 1635 Ma and fingerprint of thermal reworking at ~288 Ma. Zircon crystals from the detrital clasts yielded similar U-Pb zircon ages to the granitoid clasts (311.5 to 391 and 331 Ma). The rutile crystals from sandstone yielded concordia age of 344.7 Ma. Zircon crystals from paragneiss, interpreted as a granitoid envelope, yielded 238U/206Pb ages between 557 and 686 Ma and include an inherited core of age ~1207.4 ±33.8 Ma. Age data from exotic clasts and the detrital zircon and rutile fraction suggest the core part of the Silesian Ridge was a Neoproterozoic to Mesoproterozoic envelope intruded by Meso-Variscan granitoid plutons.

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Cadomian protolith ages of exotic mega blocks from Bugaj and Andrychów (Western outer Carpathians, Poland) and their palaeogeographic significance

Burda Jolanta, Woskowicz-Ślęzak Beata, Klötzli Urs, Gawęda Aleksandra

Geochronometria

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2019

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Vol. 46, no. 1

25--36

EN

This study presents the first zircon U-Pb LA-MC-ICP-MS ages and whole-rock Rb/Sr and Sm/Nd data from exotic blocks (Bugaj and Andrychów) from the Western Outer Carpathians (WOC) flysch. The CL images of the zircon crystals from both samples reveal typical magmatic textures characterized by a well-defined concentric and oscillatory growth zoning. A concordia age 580.1 ± 6.0 Ma of the zircons from the Bugaj sample is considered to represent the crystallization age of this granite. The zircon crystals from the Andrychów orthogneiss yield an age of 542 ± 21 Ma, interpreted as the uppermost Proterozoic, magmatic crystallization age of the granitoid protholith. The initial (at ca. 580 Ma) 87Sr/86Sr ratios of the Bugaj granitoids (0.72997 and 0.72874) are highly radiogenic, pointing to the assimilation of an older, possibly strongly Rb enriched source to the Bugaj melt. The Nd isotope systematics (εNd580 –1.4 and 0.4) also point to a significant contribution of such a distinct mantle source. On the basis of the sequence of magmatic events obtained from U-Pb zircon ages, we suggest that exotic mega blocks deposited to the WOC basins were related to the Brunovistulicum Terrane. They belong to the group of Vendian/Cambrian granitoids representing the latest, posttectonic expression of the Cadomian cycle.

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Continuous magma mixing and cumulate separation in the High Tatra Mountains open system granitoid intrusion, Western Carpathians (Poland/Slovakia): a textural and geochemical study

Gawęda Aleksandra, Szopa Krzysztof, Włodyka Roman, Burda Jolanta, Crowley Quentin, Sikorska Magdalena

Acta Geologica Polonica

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2019

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Vol. 69, no. 4

549--570

EN

In this study the formation of the polygenetic High Tatra granitoid magma is discussed. Felsic and mafic magma mixing and mingling processes occurred in all magma batches composing the pluton and are documented by the typical textural assemblages, which include: mafic microgranular enclaves (MME), mafic clots, felsic clots, quartz-plagioclase-titanite ocelli, biotite-quartz ocelli, poikilitic plagioclase crystals, chemically zoned K-feldspar phenocrysts with inclusion zones and calcic spikes in zoned plagioclase. Geochemical modelling indicates the predominance of the felsic component in subsequent magma batches, however, the mantle origin of the admixed magma input is suggested on the basis of geochemical and Rb-Sr, Sm-Nd and Pb isotopic data. Magma mixing is considered to be a first-order magmatic process, causing the magma diversification. The cumulate formation and the squeezing of remnant melt by filter pressing points to fractional crystallization acting as a second-order magmatic process.