Wyniki wyszukiwania - BazTech

1

Zastosowanie metody K-Ar do oznaczenia wieku deformacji skał metaosadowych formacji Yargait terranu Zavkhan (Khasagt, Mongolia) : wstępne wyniki badań

Sikora Rafał, Wójcik Antoni, Szczerba Marek, Bazarnik Jakub, Madej Stanisław

Przegląd Geologiczny

|

2021

|

Vol. 69, nr 7

448--453

EN

The SW margin of the Zavkhan terrane is significant for research on Paleozoic amalgamation of the Central Asian Orogenic Belt (CAOB). The study area is located in the western part of the Khasagt Mountains, western Mongolia. We present a new preliminary K-Ar dating of metasedimentary rocks from the Yargait Formation which were deformed during collision of the Zavkhan terrane with the Lake Zone terrane. Our results include two dating that are similar to earlier data by other authors (Stípskáetal., 2010; Bold et al., 2016b). The first dating equal to 544.1 ±13.7 Ma can be interpreted as the age ofmetamorphism and the subduction of the SW margin ofthe Zavkhan terrane under the Lake Zone terrane during the late Ediacaran-early Cambrian. The second dating of 441.1 ±11.7 Ma indicates the Late Ordovician - Silurian regional extension event.

2

Thermal history of Lower Palaeozoic rocks from the East European Platform margin of Poland based on K-Ar age dating and illite-smectite palaeothermometry - 481 – 509

Kowalska Sylwia, Wójtowicz Artur, Hałas Stanisław, Wemmer Klaus, Mikołajewski Zbigniew, Buniak Arkadiusz

Annales Societatis Geologorum Poloniae

|

2019

|

Vol. 89, No. 4

481--509

EN

Large-scale shale gas prospecting in the Polish part of the East European Platform did not discover large reserves of this resources. The article presents new research indicating that one of the reasons for the lack of shale gas relates to the thermal history of the Lower Palaeozoic rocks. Illite-smectite palaeothermometry was used to reconstruct the history of the platform and determine the maximum temperatures to which these rocks were subjected. The age of illitisation was also constrained using the K-Ar method. This method allowed precise dating of the maximum age of thermal transformations due to the deposition of numerous pyroclastic horizons (K-bentonite) throughout the entire geological profile from the Cambrian to the Silurian. Isotopic dating was made on over 53 samples of Lower Palaeozoic bentonites and low-grade metamorphic clays. These results were supplemented by analysis of the degree of thermal (smectite to illite) transformation in the profiles of 37 deep boreholes. 11 zones could be distinguished with different tectonic histories within the Polish part of the East European Platform edge. Maximum heating occurred in this region at about 320–340 Ma, corresponding to the Early Carboniferous or the turn of the Early and Late Carboniferous, phase A of the Variscan orogeny, known as the Sudetian phase. In the southern part of study area, the maximum of thermodiagenesis is slightly younger – 270–290 Ma, which responds to the Early Permian, the Asturian phase, the last phase of the Variscan orogeny. This means that the generation of hydrocarbons occurred before significant Mesozoic exhumation of the Polish part of the East European Platform, which led to the escape of a considerable amount of the gas generated. The study also presents the results of an interlaboratory comparison of illite age dating using the K-Ar and Ar-Ar methods. The comparison was conducted to find out what realistic error should be considered when interpreting geological K-Ar dating results.

3

What do the K-Ar ages of illite tell us about the diagenesis of Rotliegend sandstones of the Fore-Sudetic Monocline, SW Poland?

Biernacka J.

Geological Quarterly

|

2015

|

Vol. 59, No. 2

257--270

EN

The all available K-Ar data of authigenic illite from Rotliegend aeolian sandstones of the Fore-Sudetic Monocline, including the results from six samples examined in the present study, are reviewed in terms of their geological meaning, relation to diagenetic processes occurring in the sandstones, and implications for a petroleum system. The majority of ages fall in the range between 195 and 150 Ma, i.e. they correspond to Jurassic times. The results may be grouped in several time intervals, which are almost identical to those identified for Rotliegend sandstones of central and western Europe, and which are interpreted as pulses of intensive illite growth. The K-Ar data corroborate the long-held assumption that throughout the entire Southern Permian Basin Jurassic illite growth was triggered by the same, large-scale underlying processes, which manifested themselves in enhanced heat flow. These processes may also have caused the expulsion of hydrocarbons from source rocks.

4

Osady paleogeńskie w polskiej części niecki żytawskiej – nowe światło na problem wieku zapadliska tektonicznego

Kasiński J. R., Badura J., Pańczyk M., Pecskay Z., Saternus A., Słodkowska B., Urbański P.

Biuletyn Państwowego Instytutu Geologicznego

|

2015

|

nr 461

295--324

PL

Celem prac było rozpoznanie i zbadanie profilu osadów kenozoicznych na południowo-wschodnim obrzeżeniu niecki żytawskiej (ryft Ohrzy) u zbiegu granic Polski, Czech i Niemiec oraz określenie wieku skał osadowych i wulkanicznych związanych z wulkanizmem synsedymentacyjnym. Zlokalizowany w sąsiedztwie miejscowości Markocice otwór wiertniczy Opolno Zdrój PIG-1 osiągnął głębokość 200,0 m p.p.t. i został zatrzymany w utworach podłoża krystalicznego niecki żytawskiej; przewiercono nim cały profil serii osadowej wraz z wulkanitami. Próbki pobrane z rdzenia wiertniczego posłużyły do badań litologiczno-sedymentologicznych oraz laboratoryjnych, w tym do badań mineralogiczno-petrograficznych skał wulkanicznych i do oznaczenia wieku radiometrycznego metodą K-Ar (trzy próbki z rdzenia i jedna próbka referencyjna z odsłonięcia w sąsiedztwie otworu wiertniczego) oraz do badań zespołów sporowo-pyłkowych i fitoplanktonu obecnych w warstwie osadów węglistych nawierconej pod skałami wulkanicznymi (sześć próbek). Skały wulkaniczne datowano na 24,9–32,7 mln lat BP, a zatem utwory te mogły powstać nie później niż w późnym oligocenie. Wyniki badań palinologicznych nie pozwoliły na szczegółowe określenie wieku skał osadowych znajdujących się pod wulkanitami, jednak z superpozycji tych ostatnich wynika jednoznacznie, że są one starsze od górnego oligocenu, a zatem nie mogły powstać później niż we wczesnym oligocenie i stanowią zapewne ekwiwalent stratygraficzny formacji turoszowskiej. Wyniki badań przesuwają zatem początek sedymentacji utworów węglonośnych w niecce żytawskiej co najmniej do późnego paleogenu.

EN

The aim of the study was to identify and examine the Cenozoic strata in the southeastern margin of the Zittau Basin (Ohře Rift) at the crossborder of Poland, Czech Republic and Germany, and to determine the age of the sedimentary and volcanic rocks related to synsedimentary volcanic events. The Opolno Zdrój PIG-1 borehole, located near the village of Markocice, reached a depth of 200.0 m b.g.l. and it was stopped in the crystalline basement of the Zittau Basin, piercing the whole sedimentary series together with the volcanites. A number of sedimentological and lithological studies and laboratory examinations have been performed on samples taken from drill cores. They included (1) a mineralogical/ petrographic study of volcanic rocks and absolute age determination using the K-Ar method (three samples from the borehole and one reference sample from a neraby outcrop) and (2) research of pollen-spore and phytoplankton assemblages from a layer of lignite-bearing sediments lying below the volcanic rocks (six samples). This work determined the age of the covering volcanic rocks at the 24.9– 32.7 million years BP, and therefore, the lignite-bearing rocks may have been deposited no later than the Late Oligocene. Although the results of palynological studies did not allow detailed determination of the age of the sedimentary rocks lying below the volcanites, but the superposition of the latter shows evidently that they are older than the Late Oligocene. They could not have been deposited later than in the Early Oligocene and are probably a stratigraphic equivalent of the Turoszów Formation. Thus, the results move the beginning of sedimentation of the coal-bearing layers in the basin Zittau Basin at least to the Late Paleogene.

5

K-Ar dating of bentonite diagenesis in accretionary-wedge turbidites : case study from Western Outer Carpathians

Świerczewska A., Paul Z., Banaś M., Tokarski A. K.

Annales Societatis Geologorum Poloniae

|

2015

|

Vol. 85, No. 1

177--185

EN

Sixteen bentonite layers of Eocene–Oligocene age were sampled at thirteen sites in accretionary-wedge turbidite sequences, in the three innermost nappes of the Western Outer Carpathians. K-Ar dating was carried out for five of these layers to obtain the maximum burial ages. All of the ages obtained are older than the stratigraphic ages of the host strata. This relationship is due to significant contamination of the bentonites with non-authigenic minerals. This contamination resulted from rapid sedimentation during synsedimentary folding, which is a common feature in accretionary wedges. It follows that the K-Ar dating of bentonite layers in the turbidite sequences of accretionary wedges should be largely restricted to the very distal facies of turbidites or to pelitic intercalations within the turbidites.

6

Propagation of error formulas for K/Ar dating method

Hałas S., Wójtowicz A.

Geochronometria

|

2014

|

Vol. 41, no. 3

202--206

EN

In this paper has been derived the most relevant propagation of error formula in the case when argon peaks are measured. The most frequently cited formula published by Cox and Dalrymple deals with the isotope ratios, instead of isotope peaks heights, considered as independent variables.

7

Radiometric dating of the Tertiary volcanics in Lower Silesia, Poland. VI. K-Ar palaeomagnetic data from basaltic rocks of the West Sudety Mountains and their northern foreland

Birkenmajer K., Pécskay Z., Grabowski J., Lorenc M. W., Zagożdżon P. P.

Annales Societatis Geologorum Poloniae

|

2011

|

Vol. 81, No 2

115-131

EN

This article presents the sixth and final contribution in a series of papers focused mainly on the K-Ar dating of the Oligocene and Neogene (Miocene and Pliocene) intraplate basaltic volcanics of the Lower Silesia, SW Poland. The present paper includes 22 new K-Ar dates from the West Sudety Mountains and their northern foreland. The K-Ar dates range from 30.7 to 22.2 Ma. The data are supplied with geological description of the sampled outcrops, petrographic, geochemical and palaeomagnetic data of the analysed samples. Palaeomagnetic investigation confirmed the existence of two important volcanic episodes distinguished already in 1997: the reversed polarity Odra Event (mean age 28.2š1.2 Ma), and the normal polarity Gracze Event (mean age 26.28š1.8 Ma).

8

New data on the post-impact material in radiolarian horizons in Outer Flysh Carpathians and search for a source crater

Paul Z., Halas S., Wójtowicz A.

Geochronometria

|

2007

|

Vol. 27

17-22

EN

In the Outer Carpathians in Barnasiówka radiolarian shale formation, there is an intercalation underlied by bentonite. There were found very rare elements and minerals in this intercalation. It was recognized that this horizon has been filled with products of a big object collision with Earth. The age of the manganese-iron intercalation was determined by potassium-argon (K-Ar) dating of illites to be (89.3±1.2) Ma. Similar age, (85.2±0.6) Ma, was found for the post-impact glass from the Boltysh crater in Ukraine. It was concluded that the formation of this intercalation was synchronous with the Boltysh crater formation at the Cenomanian/Turonian boundary. The research for the K-Ar age of the crater creation in Logoisk (Belarus) established its formation to (124.2±1.2) Ma ago.

9

Low-blank crucible for argon extraction from minerals at temperatures up to 1550 C degrees

Halas S.

Geochronometria

|

2007

|

Vol. 27

1-3

EN

The new version of a double-vacuum crucible for fusion of small samples of refractory minerals has been described recently by Halas (2006). This novel type of high temperature crucible was further improved in the following important points: (1) The expensive material, tantalum, was replaced by much cheaper molybdenum which also appears to be significantly less corrosive in the presence of hot boron nitride ceramic used as the insulator, and (2) a versatile temperature controller was assembled from commercially available components.

10

K-Ar dating of amphiboles from andesite of complex dyke in Dubie (Southern Poland)

Lewandowska A., Banaś M., Zygoń K.

Geochronometria

|

2007

|

Vol. 27

11-15

EN

This study presents the results of radiometric K-Ar measurements on separated amphiboles from the andesite of the Dubie complex dyke. The data obtained cover the period of (291.3 ± 6.4) Ma, which corresponds to Carboniferous-Permian transition. The age is contemporaneous to the rhyodacitic and basaltoid volcanism of the Kraków region.

11

Radiometric dating of the Tertiary volcanics in Lower Silesia, Poland. V. K-Ar and palaeomagnetic data from Late Oligocene to Early Miocene basaltic volcanics of the North-Sudetic Depression

Birkenmajer K., Pécskay Z., Grabowski J., Lorenc M. W., Zagożdżon P. P.

Annales Societatis Geologorum Poloniae

|

2007

|

Vol. 77, No 1

1-16

EN

This is the fifth contribution to geochronological, petrologic-geochemical and palaeomagnetic studies of the Tertiary basaltoids of Lower Silesia, Poland. It covers the area of the North-Sudetic Depression close to its contact with the Fore-Sudetic Block (6 new sites). The oldest K-Ar date was obtained from basanite plug at Sichów (BP-34: 27.80ą1.27 Ma) located exactly on the Sudetic Marginal Fault. It determines the age of the fault as Late Oligocene. Five other sites (BP-35-39) yielded radiometric ages between 20.07ą0.90 Ma and 18.72ą0.81 Ma (Early Miocene). The volcanics investigated are typical within-plate basaltoids represented by ankaratrite and basanite. The Late Oligocene Sichów intrusion (BP-34) is normally magnetized, the Early Miocene basaltic rocks (ankaratrite BP-39 and basanites: BP-35-38) reveal reversed magnetization.

PL

Piąta część datowań K-Ar i badań paleomagnetycznych trzeciorzędowych wulkanitów Dolnego Śląska obejmuje odsłonięcia tych skał w obszarze niecki północnosudeckiej, w sąsiedztwie sudeckiego uskoku brzeżnego. Otrzymano sześć dat w granicach 27,80š1,27 Ma (późny oligocen: Sichów, BP-34) – 18,72š0,81 Ma (niższy miocen = burdygał: Wilków, BP-37). Późnooligoceńska data dla ankaratrytowego czopu Sichowa (BP-34), który znajduje się na sudeckim uskoku brzeżnym, określa taki wiek tego uskoku. Zbadane skały bazaltowe – bazanity i ankaratryty (melabazanity) są typowymi przedstawicielami wulkanizmu sródpłytowego. Skład chemiczny ogniska magmowego podlegał ewolucji, co przejawiło się w badanych skałach wzrostem zawartości potasu i kobaltu w okresie czasu między wyższym oligocenem a niższym miocenem. Czopy ankaratrytu i bazanitu zostały zbadane pod względem paleomagnetycznym: najstarszy z nich, 27,80 Ma (BP-34: ankaratryt) wykazuje namagnesowanie normalne, pozostałe pięć, 20,07–18,72 Ma (BP-39: ankaratryt; BP-35–38 – bazanity) wykazuje namagnesowanie odwrócone.

12

K-Ar evidence for a Mesozoic thermal event overprinting burial diagenesis of the Carboniferous Upper Silesia Coal Basin

Banaś M., Bylina P., Środoń J.

Volumina Jurassica

|

2006

|

Vol. 4, no. 1

39-39

EN

K-Ar dating of mixed-layer illite-smectite from clay fractions extracted from pyroclastic horizons was used to address the controversy about the age and mechanism of the thermal alteration of Carboniferous rocks from the Upper Silesia Coal Basin (USCB). The clay fractions were investigated by x-ray powder diffraction (XRD) in order to select for dating the samples rich in illite-smectite and to evaluate the K-Ar dates for possible contamination by K-bearing pre-diagenetic minerals of pyroclastic or epiclastic origin. The K-Ar dates document intense Variscan tectonic burial illitization produced by thrusting (ca. 290 Ma) in the SW of the basin, and the lack of intense burial illitization in the NE, which is consistent with sedimentological models of the basin. The burial illitization in its final phase (<30% S in illite-smectite) involved incorporation of measurable amounts of ammonium cation in the illite structure (substitution for potassium). Advanced illitization in the NE of the basin is much younger than its tectonic inversion (uplift and erosion started in Permian), and the corresponding K-Ar dates have to be interpreted as the result of a Mesozoic thermal event, which produced widespread pervasive illitization at shallow depth. This event was dated at 175 Ma, but it may have started earlier and could have lasted longer. This conclusion is consistent with widespread evidence of a major Mesozoic thermal event all over Central Europe, produced by rifting and lithospheric thinning during the opening of the Tethys and Atlantic oceans. This study demonstrates that smectite illitization histories may be very complex, and that the nature of the illitization mechanism results in mixed K-Ar dates encompassing pro-longed or multiple illitization histories. Dating of several grain-size fractions may help unravel such histories. When a calibration using data from Neogene sedimentary basins is applied, vitrinite reflectance and % S in I-S indicate similar paleotemperatures of tectonic burial diagenesis in the USCB, but they produce very different estimates of the temperature of the thermal event.

13

Nowe dane o wieku i petrologii kenozoicznych bazaltoidów dolnośląskich

Badura J., Pécskay Z., Koszowska E., Wolska A., Zuchiewicz W., Przybylski B.

Przegląd Geologiczny

|

2006

|

Vol. 54, nr 2

145-153

EN

Fifteen samples of basaltoid rocks have been analysed from the Lower Silesia, SW Poland, some of them from localities close to the Sudetic Marginal Fault. K-Ar datings have been made on whole rock samples, using the methodology applied by the Institute of Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary. Most of the samples give ages ranging between 21- 38 Ma, whereas that derived from a borehole in the Mokrzeszów Graben has been dated to 44 Ma. Another borehole sample (Jeżów Sudecki B-5), close to the Intrasudetic Fault, is of 59 Ma age. On the other hand, the supposedly "Quaternary" basaltoids from Dębowiec area fall into the interval of 29–30 Ma. The southeasternmost occurrences of the Lower Silesian basaltoids at Nowa Cerekiew display two generations of effusive activity: the older lava flows (26 Ma) are cut by plugs dated to 22 Ma. The Oligocene–Lower Miocene (26-33 Ma, 20'24 Ma) rocks represent alkali basalts and basanites. The alkali basalts consist of phenocrysts of olivine (chrysolite), altered to a different degree, and clinopyroxene (salite). In the matrix, clinopyroxene (Ti-salite), olivine (hyalosiderite), plagioclases (labradorite–andesine), and opaque minerals (titanomagnetite, ilmenite) occur. The basanites contain phenocrysts of altered olivine (chrysolite) and clinopyroxene (salite). Their matrix consists of clinopyroxene (Ti-salites), olivine (hyalosiderite), nepheline, plagioclases (bytownite–andesine), and opaque minerals. On the TAS diagram, samples of the studied basaltoids plot mainly in the fields of basalts and basanites/tephrites. The bimodality of some samples falling into two fields of basalts and basanites/nephelinites on the TiO2/Zr-Nb/y diagram results from their distinct geochemical signature.

14

Low-Grade metamorphism of permian mafic rocks from the Gorzów Wielkopolski block (Fore Sudetic Monocline, Nw Poland): age and mechanism

Bylina Paweł

Mineralogia

|

2006

|

Vol. 37, iss. 1

3--50

EN

The metavolcanic rocks in the Gorzów Wielkopolski area (NW Poland) are andesite-basalts and andesites derived from contaminated within-plate subalkaline basalt melts. K-Ar dating of primary K-feldspar yields an extrusion age of 285±5 Ma. This new date suggests that these rocks may be the youngest dated Permo-Carboniferous volcanic rocks within the eastern margin of the North German Basin. Petrological and micro-thermometric data indicate that the volcanic rocks were altered by a sub-greenschist facies, metamorphic process that proceeded within temperatures and pressures ranging from 195-290°C and 63-96 MPa, respectively. The major metamorphic phases, corrensite, pumpellyite, laumontite and prehnite, formed due to interaction between the original volcanic rock and low-saline Na2SO4-rich hydrothermal fluids. Numerical modelling indicates fluid flow in fractures as the most probable explanation for the low-grade hydrothermal metamorphism. Model calculations suggest that the process was of short duration, ca 140-250 years. K-Ar dating reveals three Mesozoic episodes at 121±2 Ma, 188-190 Ma and 149±4 Ma that can be ascribed to the metamorphism. These ages are similar to previously determined Mesozoic ages from altered volcanic- and clastic rocks in the North German Basin and in the Polish Basin.

XX

Zmienione skały wulkaniczne występujące w okolicach Gorzowa Wielkopolskiego są andezytami i andezytobazaltami, które powstały ze stopu właściwego dla subalkalicznych bazaltów wewnątrzpłytowych zanieczyszczonego materiałem skorupowym. Datowanie izotopowe pierwotnych skaleni potasowych metodą K-Ar określiło wiek erupcji na 285±5 Ma. Otrzymany wiek sugeruje, że skały te mogą być najmłodszymi permokarbońskimi skałami wulkanicznymi z dotychczas badanych na wschodnim brzegu Basenu Północnoniemieckiego. Petrologia skał z okolic Gorzowa Wlkp. oraz wyniki badań inkluzji fluidalnych w minerałach wskazują na proces metamorficzny odpowiadający warunkom facji subzieleńcowej (f. prehnitowo-pumpellyitowej). Proces ten przebiegał w temperaturach od 195 do 290°C i przy ciśnieniach od 63 do 96 MPa. Główne minerały metamorficzne, tj. corrensyt, pumpellyit, laumontyt i prehnit, krystalizowały w wymienionym zakresie warunków p-T, w wyniku reakcji zachodzącej pomiędzy skałą macierzystą i słabo zasolonymi roztworami hydrotermalnymi zawierającymi Na2SO4. Na podstawie wyników modelowania numerycznego wskazano na szczelinowy przepływ roztworów hydrotermalnych jako najbardziej prawdopodobną przyczynę obserwowanego procesu metamorficznego. Obliczenia sugerują też krótki czas trwania tego procesu: od 140 do 250 lat. Datowania izotopowe metodą K-Ar ujawniły istnienie trzech mezozoicznych epizodów metamorficznych związanych z badanym procesem, które miały miejsce 188–190 Ma, 149±4 Ma i 121±2 Ma. Wieki te są podobne do innych mezozoicznych dat izotopowych otrzymanych ze zmienionych skał wulkanicznych i klastycznych, występujących w Basenie Polskim i Północnoniemieckim.

15

Age relationships between Miocene volcanism and hydrothermal activity at Mt Jarmuta, Pieniny Klippen Belt, West Carpathians, Poland

Birkenmajer Krzysztof, Pécskay Zoltán, Szeliga Wojciech

Studia Geologica Polonica

|

2004

|

Vol. 123

279-294

EN

In the Pieniny Volcanic Arc (Miocene), the northernmost volcanic arc of the West Carpathians, hydrothermal activity produced some ore-bearing veins associated with moderate-size andesite intrusions. They were subjected to prospecting and mining for gold, silver and lead for a short period at the beginning of the 18th century. K-Ar dating of secondary chlorine-biotite from the mineralized zone at Mt Jarmuta, yielded a K-Ar date of 11.35š0.45 Ma. This K-Ar date fits well with the average K-Ar age (11.34š0.50 Ma) obtained on unaltered andesite sills exposed at Mt Jarmuta. It indicates a close age-relationship between the emplacement of the andesite intrusion and the subsequent ore-mineralization during Miocene (Sarmatian) time.

16

Radiometric dating of the Tertiary volcanics in Lower Silesia, Poland

Birkenmajer K., Pécskay Z., Grabowski J., Lorenc M. W., Zagożdżon P. P.

Annales Societatis Geologorum Poloniae

|

2004

|

Vol. 74, No 1

1-19

EN

The Tertiary volcanic rocks of the Fore-Sudetic Block (FSB), Lower Silesia (Poland), exposed between Strzelin in the east and Legnica in the west, typically represent within-plate basalts. Petrologically, they consist mainly of alkali basalts, basanites, tephrites and ankaratrites. 16 new K-Ar dates are recorded, spanning the Oligocene (31 Ma) through Early Miocene (Burdigalian c. 18 Ma) time. The majority of these K-Ar dates plot around two significantly different ages: 27š1.5 Ma, and 20š1.5 Ma. They indicate the presence in the FSB of two distinct separate phases of Tertiary vulcanicity: (i) the first phase, mainly Late Oligocene (Chattian), with a peak at c. 27; (ii) the second phase, Early Miocene (Aquitanian-Burdigalian), with a peak at about 20 Ma. These phases seem to be separated by a gap in vulcanicity about 3 Ma long at the Oligocene/Miocene boundary. Correlation of K-Ar-dated volcanic activity in the FSB with specific radiometrically-dated polarity intervals, poses some problems, and cannot be regarded definite at this stage of investigations. Considering the whole set of K-Ar and palaeomagnetic data from 40 sites, between the Opole area in the east and the Legnica area in the west, we suggest that volcanism of the first phase (Oligocene), although significantly spread out in time across multiple reversals, took place mostly during two well-defined, previously recognized events: (i) an older, reversed Odra event (within the C9r chron: 28.1š1.2 Ma); and (ii) a younger, normal Gracze event (within the C8n chron: 26.5š1.1 Ma). The second phase (Early Miocene) volcanism includes mainly a continuous set of reversely magnetized sites (mostly a single reversed C6r chron: 20.5š0.87 Ma).

17

Glaucony from the condensed Lower-Middle Jurassic deposits of the Križna Unit, Western Tatra Mountains, Poland

Jach R., Starzec K.

Annales Societatis Geologorum Poloniae

|

2003

|

Vol. 73, No 3

183-192

EN

Lower-Middle Jurassic glaucony-bearing deposits crop out in the Polish part of the Križna Unit in the Western Tatra Mts. These deposits, up to 20 cm thick, consist of glaucony-rich marls and limestones. The glaucony grains constitute up to 30% volume of the deposits. They represent an evolved stage of glauconitization since they contain more than 7% K2O. The content of Al2O3 is high (up to 19.97%, average 16.98%) while the content of Fe2O3 is low (not more than 23.48%, average 12.84%). These features are interpreted as a product of diagenetic processes. The glaucony-bearing deposits were formed at an upper bathyal depth and their rate of deposition was very low, what allowed long-lasting evolution of the glaucony grains. The K-Ar age of the glaucony grains is much younger than the biostratigraphic age of the studied section. The lowering of the K-Ar dates is interpreted as a result of loss of radiogenic Ar from the lattice of the glaucony.

18

Radiometryczne datowanie wybranych minerałów potasowych z mioceńskich formacji solonośnych wschodniego Przedkarpacia

Wójtowicz A., Hryniv S. P., Bilonizhka P. M.

Przegląd Geologiczny

|

2002

|

Vol. 50, nr 7

625-629

PL

Mioceńskie złoża siarczanów potasowo-magnezowych wschodniej części zapadliska przedkarpackiego występują w 2 poziomach stratygraficznych. Niższy należy do eggenburgu, wiek wyższego jest dyskusyjny - ottnang lub baden. Metodą K/Ar określiliśmy wiek radiometryczny 24 próbek minerałów skałotwórczych, takich jak langbeinit i kainit, wiek 4 próbek kainitu i leonitu z żyłek i pojedyncze próbki minerałów czapy gipsowo-ilastej, tj. syngenitu i pikromerytu. Wiek radiometryczny większości próbek langbeinitu mieści się w granicach 13,6-14,6 Ma. Tylko 2 próbki są młodsze a jedna nieco starsza. Porównując wieki próbek langbeinitu ze Stebnika (eggenburg) i złoża kałusko-hołyńskiego (ottnang? baden?) nie stwierdziliśmy znaczącej różnicy. Próbki kainitu dały niższy wiek radiometryczny z powodu podatności tego minerału na wpływ podwyższonej temperatury i mieszczą się w szerszym zakresie-od 7,2 do 9,9 Ma. Próbki kainitu i leonitu z żyłek są jeszcze młodsze (2,9-6,1 Ma). Minerały czapy gipsowo-ilastej okazały się, zgodnie z przypuszczeniami, współczesne. Naszym zdaniem nowe dane zaprezentowane w niniejszej pracy nie są powiązane z wiekiem stratygraficznym złóż soli potasowo-magnezowych, a odzwierciedlają jedynie czas powstania minerałów. Tworzenie się minerałów skałotwórczych powiązane jest ze zjawiskami tektonicznymi w procesie geologicznego rozwoju regionu.

EN

Miocene K-Mg sulfate deposits of the eastern part of the Carpathian Foredeep occur in two stratigraphic horizons. The lower one belongs to Eggenburgian stage, and the age of upper one is still debatable - either Ottnangian or Badenian. Wehavedeter-mined the radiometric age of 24 samples of selected rock-building minerals like langbeinite and kainite, 4 samples ofkainite and leonitefrom veins and single samples of minerals from the gypsum-clay cap over salt deposits like syngenite and pikromerile with K/Ar method. Radiometric age of most langbeinite samples varies from 13.6 to 14.6 Ma. Only 2 samples are younger and one seems to be older. Comparison of ages of langbeinite samples from Stebnyk (Eggenburgian) with that from Kalush-Holyn deposits (Ottnangian? Badenian?) does not show significant differences. Radiometric age data determined for kainite samples are younger because of its compliance on higher temperatures and they vary in wide range-from 7.2 to 9.9 Ma. Samples ofkainite and leonitefrom veins are younger (2.9-6.1 Ma). Minerals from the gypsum-clay cap are recent, as we had supposed. In our opinion the new data presented here do related to the not indicate stratigraphic ages of K-Mg salts deposits, but the only time of the origin of minerals. The origin of rock-building minerals is connected with tectonic events in the history of geological development of region.

19

Radiometric Dating of the Tertiary Volcanics in Lower Silesia, Poland. I. Alkali Basaltic Rocks of the Opole Region

Birkenmajer K., Pecskay Z.

Bulletin of the Polish Academy of Sciences. Earth Sciences

|

2002

|

Vol. 50, nr 1

31-50

EN

K-Ar dating was carried out on the Tertiary alkali basaltic rocks represented by melanephelinite and melabasanite lavas and plugs in the Opole region, Lower Silesia (Poland). The most probable geological age of the volcanic activity in this area is given by the mean K-Ar age of the melabasanites, calculated at 26.5 Ma: Late Oligocene (Chattian, middle part). Some melabasanite plugs yielded K-Ar dates significantly older than those from the lavas which - by good geological evidence - pre-dated them. This might be explained by the presence of excess argon in the plugs.

20

K-Ar Dating of Biotite from the Kudowa Zdrój Granitoids (Central Sudetes, SW Poland)

Bachliński R., Hałas R.

Bulletin of the Polish Academy of Sciences. Earth Sciences

|

2002

|

Vol. 50, nr 2

113-116

EN

K-Ar dating of the biotite from the Kudowa Zdrój granitoids based on 7 samples yields 275.4 Ma to 338.2 Ma. Average age of K-Ar dating (328.7 Ma) is well correlated with the ago obtained by Rb-Sr whole rock method (331 š 11 Ma). The age in two samples might show partly loss of argon.