Temat: alkaline basaltic rocks - Katalog OPAC zbiorów

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Tytuł:: Tournaisian 40Ar/39Ar age for alkaline basalts from the Lublin Basin (SE Poland)
Autorzy:: Pańczyk, M.
Nawrocki, J.
Powiązania:: https://bibliotekanauki.pl/articles/2059639.pdf
Data publikacji:: 2015
Wydawca:: Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:: alkaline basaltic rocks
Ar-Ar geochronology
Carboniferous
Lublin Basin
Opis:: The main aim of this study is to define precisely the age of the alkaline basalts occurring within the lowermost part of Carboniferous succession in the northeastern part of LublinBasin(drill core Parczew IG-7 and IG-9; SE Poland). The new, whole-rocks 40Ar/39Ar data constrain the age of volcanic activity and emplacement of alkaline basalts to the Late Tournaisian (348 ± 0.8 Ma) with possible prolongation to the Middle Visean (338.5 ± 0.7 Ma). The younger age is however of evidently poorer quality than the older one. The new data caused to correlate the volcanic processes occurring within the Lublin Basin with alkaline intrusions drilled inNE Poland inside the Paleozoic cover of the East European Platform. They also correspond to the volcanoclastic levels defined in different parts of the Trans European Suture Zone in Poland.
Źródło:: Geological Quarterly; 2015, 59, 3; 473--478
1641-7291
Pojawia się w:: Geological Quarterly
Dostawca treści:: Biblioteka Nauki

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Tytuł:: Stephanian-Early Permian basaltic trachyandesites from the Sławków and Nieporaz-Brodła Grabens near Kraków, Southern Poland
Autorzy:: Lewandowska, A.
Rospondek, M. J.
Nawrocki, J.
Powiązania:: https://bibliotekanauki.pl/articles/191897.pdf
Data publikacji:: 2010
Wydawca:: Polskie Towarzystwo Geologiczne
Tematy:: Upper Carboniferous/Permian volcanism
a-a lava flows
autoclastic breccias
basaltic trachyande-sites
transitional calc-alkaline to alkaline rocks
hydrous magma
Opis:: In the Kraków-Lubliniec section of the major Hamburg-Kraków-Dobrogea Fault Zone (HKDFZ), the Stephanian-Early Permian magmatic activity was simultaneous with subsidence/uplift of formed blocks. In the proximity of the uplifted areas the sedimentation started with fanglomerates, distally passing into playa siltstone and was accompanied by volcanism. In the Nieporaz-Brodła graben, basaltic trachyandesite a-a lava flows with autoclastic breccias reach ca. 150 m in thickness. The weathering recorded as adhesive rims around breccia clasts reflects palaeosoil formation during quiescence periods between the eruptions. The eruptions were effusive although scoriaceous lava indicates high volatile content of the magma. The water content before eruption had to be over 2 wt. percent. Only then the crystallisation model predicts accurately the type, composition and order of the crystallising phases. Thus, the basaltic trachyandesite magma originated from a source containing hydrous phase (i.e., amphibole or phlogopite). All the studied basaltic trachyandesites had fayalitic olivine on their liquidus reflecting the crystallisation stage in a magma chamber at crustal depths. During final decompression on the magma ascent due to water exsolution, the olivine was followed by plagioclase, spinel, augite, ilmenite, apatite, K-feldspar and residual high-K rhyolitic glass. The high potassium content of these volcanics was thus a primary feature reflecting the source geochemistry and differentiation trend, and its consequence was potassium metaso- matism. Due to water exsolution the glass was altered, however, homogenous interstitial glass survived in some rocks. The glass is strongly enriched in incompatible trace elements, showing that it is a highly fractionated residual melt fraction of the basaltic trachyandesite magma. Thus, the glass geochemistry reflects the trend of fractional crystallisation indicating that co-occurring K-rich felsic rocks were not derived from the same magma. All the basaltic trachyandesites studied have calc-alkaline to alkaline affinity. They contain fayalitic olivine and are low in MgO <5 wt. %, Cr and Ni, the features characteristic for evolved magmas. They show significant negative Sr/Sr*> 0.5-0.80 and small Eu/Eu* > 0.9-1.0 anomalies suggesting fractionation of plagioclase. The Eu/Eu* anomaly is probably compensated by amphibole retaining in the source. Negative Nb, Ti anomalies suggest Fe-Ti oxide fractionation characteristic for calc-alkaline evolution trend. A significant enrichment in LREE relatively to HREE (La/Yb > 10) indicates subduction-related metasomatism. However, the described tectonic context is inconsistent with subduction related characteristics. Concluding, the observed geochemical characteristics indicate remarkable role of water in magma evolution. The volcanism was related to strike-slip dextral movement along the Kraków-Lubliniec section of HKDFZ, transformed into crustal extension and subsidence, the features typical for the formation of pull-apart basins, in the late stages of the Variscan orogen evolution.
Źródło:: Annales Societatis Geologorum Poloniae; 2010, 80, No 3; 227-251
0208-9068
Pojawia się w:: Annales Societatis Geologorum Poloniae
Dostawca treści:: Biblioteka Nauki

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