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    Wyświetlanie 1-3 z 3
    Tytuł:
    Mineralogical, geochemical and stable isotope studies of kaolin deposits in north-west Gonabad district (eastern Iran)
    Autorzy:
    Zirjanizadeh, S.
    Rocha, F.
    Samiee, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059765.pdf
    Data publikacji:
    2018
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    kaolinite
    Iran
    REE
    O isotope composition
    Opis:
    Kaolin deposits, situated ~10 km north-west of Gonabad (eastern Iran), formed by the intrusion of hydrothermal fluids from a granite dyke in the western part of the study area, and the alteration of rhyolite, dacite and rhyodacite related to Eocene volcanism. There are four major kaolin quarries. The rocks in the investigated area are mainly slate, dacite, rhyolite, andesite-trachyandesite, and lithic and felsic tuffs. The mineralogical compositions of the kaolin deposits are dominated by quartz, kaolinite, dickite and illite with minor chlorite, montmorillonite, albite, hematite, pyrite and gypsum. Sanidine and plagioclase crystals in rhyolite-rhyodacite are sericitized and kaolinized. Whole rock chemistry of the kaolin deposits shows high contents of SiO2 and Al2O3. Enrichments of Sr in some samples demonstrate retention of Sr and depletion of Rb, Ba, Ca and K during hydrothermal alteration of sanidine and plagioclase within the volcanic units. The chondrite-normalized rare earth element patterns of the clay deposits show LREE enrichments (La/Lu)cn = 6.75 to 57.74, pointing to kaolinization in low-pH waters. The isotope composition of the kaolin (δ18O ~+5‰) is consistent with formation at isotopic equilibrium with water of hydrothermal/magmatic origin. The mineralogical composition, REE contents and elemental ratios in these deposits suggest provenance of the kaolin deposits mainly from felsic rocks and hydrothermal fluids. The O isotopic character also supports these results.
    Źródło:
    Geological Quarterly; 2018, 62, 2; 385--399
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Biostratigraphy, geochemistry and sedimentology of Middle to Late Jurassic strata in the Strážovce section (Strážovské vrchy Mts), Krížna Nappe of the Central Carpathians, Slovakia
    Autorzy:
    Michalík, J.
    Bąk, M.
    Lintnerová, O.
    Méres, Š
    Powiązania:
    https://bibliotekanauki.pl/articles/2060972.pdf
    Data publikacji:
    2017
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Oxfordian
    Kimmeridgian
    C isotope
    O isotope
    REE
    radiolarians
    basinal collapse
    Zliechov Basin
    Fatric Unit
    Oksford
    izotop C
    iIzotop O
    radiolarie
    Opis:
    The Jurassic / Lower Cretaceous sequence of the Strážovce section has been deposited in the central, axial part of the Zliechov Basin. Its most characteristic part – the Ždiar Formation consists of bedded siliceous radiolarian limestones and radiolarites. The radiolar¬ian assemblage typical of the North Tethyan Bioprovince lived during mid Oxfordian – Early Kimmeridgian in a warm upper part of the well stratified water column, partially near to the thermocline. Radiolarian abundance decreases upwards. Productivity decrease is quanti¬fied by the share of biogenic SiO2 as well as by high EFSi values during sedimentation of both the Ždiar and Jasenina formations. The geochemical data indicate relatively stable volume of the siliciclastic component of the rocks and a felsic character comparable to the Average Shale. The chemically homogeneous sedimentary signal indicates values of both CPA and EF ≤ 1 of Ti, Zr, Fe, Na, K, Rb, V and U. The values of EF > 1 signal enrichment of elements with affinity to carbonate minerals (Sr, Mn, P, Y, and Mg). Metal enrichment (Cu, Zn and Ni) indicates metal mobilization from other sources or due to carbonate diagenesis. In comparison to the Average Shale, decreased ΣREE´s and negative Cech and Euch anomalies could be regarded as a typical deep sea water signal. The differentiated REE record of higher calcareous beds of the Jasenina Fm. suggests basinal dysoxic conditions. The “bell-shape” of curves (normalized to shale) indicate that REEs were slightly affected by carbonate diagenesis. The Oxfordian / Kimmeridgian siliceous sedimentation in the Zliechov Basin was influenced probably more by monsoon-controlled input of land derived weathered material than by hydrothermal fluids from the bottom rifts.
    Źródło:
    Volumina Jurassica; 2017, 15, 1; 161--178
    1896-7876
    1731-3708
    Pojawia się w:
    Volumina Jurassica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cooling and warming of climate of the Earths Northern Hemisphere (on the basis of fluctuations of the oxygen isotope δ18O and dendrological data)
    Autorzy:
    Boryczka, Jerzy
    Stopa-Boryczka, Maria
    Unton-Pyziołek, Arleta
    Gieszcz, Piotr
    Miłaszewska, Małgorzata
    Powiązania:
    https://bibliotekanauki.pl/articles/2034147.pdf
    Data publikacji:
    2010-06-01
    Wydawca:
    Uniwersytet Warszawski. Wydział Geografii i Studiów Regionalnych
    Tematy:
    isotope δ18O
    Devon Island
    Pinus sylvestris
    Picea abies
    tree the ring widths
    solar radiation
    periods
    moment of inertia of planets
    mass momentum of largest planets
    forecast
    Opis:
    Content fluctuations of the oxygen isotope δ18O in the Devon Island ice core during the last 100 000 years are a measure of climate fluctuations in the Northern Hemisphere. The course of content of the oxygen isotope δ18O and the sums of solar radiation reaching the upper edge of the atmosphere are characterized by approximate minima and maxima (by positive correlation). This proves that, during the last hundred thousand years, climate fluctuations (cooling and warming) in the Northern Hemisphere were conditioned by long-term changes of the orbit and altitude of the Earth's axis. Climate fluctuation forecasts for the Northern Hemisphere were developed for the next 40 000 years on the basis of the established periods of change of the oxygen isotope δ18O and the known solar radiation periodicity. Climate changes in Europe during the last 25000 years were presented together with a forecast for 1000 years (according to organic substances in deposits and radiation) as well as climate changes in Europe in the period from -500 years BP to 2100 AD (according to δ18O and pine tree-rings). It showed that climate changes depended on the concentration of planet mass in relation to the ecliptic plane (from the gravitational impact of planets on the Sun). Concentration courses of planet mass in the Solar System and climate fluctuations in the Northern Hemisphere were compared. Of interest are examples of synchronic fluctuations, i.e. dispersal of planet mass in the Solar System, the widths of pine and spruce tree rings and air temperatures in Europe.
    Źródło:
    Miscellanea Geographica. Regional Studies on Development; 2010, 14; 47-58
    0867-6046
    2084-6118
    Pojawia się w:
    Miscellanea Geographica. Regional Studies on Development
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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