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Radiometric age analyses of rocks from the northern envelope of the Karkonosze massif, the Sudetes, Poland: a comparative geochronological study

Jarmołowicz-Szulc K., Halas S., Wójtowicz A.

Geochronometria

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2009

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Vol. 34

33-39

EN

K-Ar determinations have been conducted on the background of the earlier radiometric data in the eastern part of the northern Karkonosze-Izera envelope of the granite massif, composed of different varieties of granites, gneisses and mica schists. The values of the K-Ar age for minerals and rocks from the Karkonosze-Izera block lie in the wide interval ranging from 226.0 ± 6.7 Ma to 386.1 ± 3.0 Ma. The K-Ar age data obtained by volumetric method oscillate between 308 ± 21 and 372 ± 26 Ma. Most biotite K-Ar age values of the Izera granite-gneisses complex give an average age of 316.1 ± 3.3 Ma. They correspond to the cooling age of the Karkonosze pluton while the data below 300 Ma are minimum age values that postdate the last granite intrusion of the Krkonoše-Jizera pluton. The obtained results over 300 Ma are mixed apparent ages between the age of the Karkonosze and the Izera granite ages. The K-Ar dates in the studied region have been compared with fission-track (FT) ages of zircon and titanite in the same area which display another distribution pattern.

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The geological significance of the Rb-Sr whole-rockisochron of hornfelsed schists from the Izerskie Garby Zone, Karkonosze-Izera block, southernwest Poland

Fila-Wójcicka E.

Acta Geologica Polonica

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2004

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Vol. 54, no. 3

407--411

EN

Preliminary Rb-Sr isotope data for hornfelsed schists from the "Stanislaw" quarry in the Izerskie Garby Zone are reported. An isochron based on three points representing three whole-rock samples yields an age of 333 [plus-minus] 4 Ma (Visean) and an initial 87Sr/86Sr ratio of 0.709567. The Rb-Sr age of 333 [plus-minus] 4 Ma, indicating the date of the Rb-Sr system closure, can be interpreted as the cessation of contact metamorphism in the Izerskie Garby Zone. The age of 333 [plus-minus] 4 Ma is close to the peak of contact metamorphism in this zone. Contact metamorphism and silification in the Izerskie Garby Zone were genetically related to the activity of the Variscan Karkonosze pluton. Contact metamorphism was older than the biotite cooling at ca. 320 Ma.

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Occurrence and genetic relationships of uranium and thorium mineralization in the Karkonosze Izera Block (the Sudety Mts, SW Poland)

Mochnacka K., Banaś M.

Annales Societatis Geologorum Poloniae

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2000

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Vol. 70, No. 2

137-150

EN

The paper summarizes available data on uranium and thorium deposits and occurrences in the Karkonosze-Izera Block (the Sudety Mts, SW Poland). The following types were distinguished: 1. Mineralization in the Karkonosze granite and its pegmatites: 1.1 disseminated broeggerite in granite, 1.2 uranium minerals filling the cracks in granite, 1.3 disseminated uranium and U-Th minerals in pegmatites, 2. Mineralization in the metamorphic cover: 2.1 uranium and thorium mineralization in nests, 2.2 pitchblende-fluorite mineralization in veins and nests, 2.3 pitchblende mineralization in veins and nests, 2.4 pitchblende-polymetallic mineralization in veins and nests, 2.5 vein- and nest-type secondary uranium mineralization, 2.5.1 secondary accumulations with traces of primary mineralization, 2.5.2 secondary accumulations without trace of primary mineralization. The origin of these accumulations is mostly related to the Karkonosze Granite and its hydrothermal activity.

PL

W pracy przedstawiono informacje dotyczące występowania złóż i przejawów mineralizacji uranem i torem w bloku Karkonosko-Izerskim. Wyróżniono następujące typy okruszcowania: 1 Mineralizacja w granicie Karkonoszy i w pegmatytach 1.1. broeggeryt rozproszony w granicie, 1.2. mineralizacja uranowa wypełniająca szczeliny w granicie, 1.3. mineralizacja uranowa i uranowo-torowa w pegmatytach, 2. Mineralizacja w osłonie metamorficznej: 2.1. mineralizacja uranowa i torowa w postaci gniazd, 2.2. smółkowo-fluorytowa mineralizacja w formie żył i gniazd, 2.3. smółkowa mineralizacja w formie żył i gniazd, 2.4. smółkowo-polimetaliczna mineralizacja w formie żył i gniazd, 2.5. wtórna mineralizacja uranowa w formie żył i gniazd, 2.5.1 ze śladami mineralizacji pierwotnej, 2.5.2. bez mineralizacji pierwotnej. W większości przypadków są to wystąpienia genetycznie związane z granitem Karkonoszy i jego działalnością hydrotermalną.