Hipergeniczne przeobrażenia diabazów z obszaru łysogórskiego Gór Swiętokrzyskich

Bolesław J. Kowalski

Abstract


Podano wyniki analiz chemicznych i geochemicznych zwietrzelin diabazowych obszaru łysogórskiego w Górach Świętokrzskich. Zwietrzeliny te reprezentują typ chlorytowo-kaolinitowo-illitowy; wzbogacone są w Al2O3, Fe2O3, H2O+, Cr, przy zmniejszonym udziale MgO, CaO, Na2O, SiO2, Mn i Sr. Profil pionowy o grubości 7,3 - 43,1 m powstawał cyklicznie w zmieniających się warunkach środowiska hipergenicznego, poczynając od permu, przez mezozoik, trzeciorzęd, po czwartorzęd włącznie.

HYPERGENETIC ALTERATIONS OF DIABASES IN THE ŁYSOGÓRY AREA OF THE GÓRY ŚWIĘTOKRZYSKIE MTS

Diabase dykes found by drillings in the Łysogóry area of the Góry Świętokrzyskie Mts (Fig. 1) were studied in detail. The studies showed the presence of marked weathering zone, 7.3 to 43.1 m thick (Table 1). Rocks of that zone differ from underlying ones in colour, chemical and mineral composition and structural-textural properties.

The gathered samples of weathered and unweathered diabases were analysed for chemical composition (Table 2), trace elements (Table 3) and clay minerals (Figs. 2 - 3). The weathered material is characterized by increase in share of Al2O3, Fe2O3, H2O+ and Cr, at the expense of MgO,. CaO, Na2O, SiO2, Mn and Sr (Tables 2 - 3). The group of clay minerals is here represented by chlorite, kaolinite and iIIite.

The weathering profile of the studied diabases has originated at least in three Cycles. First cycle was connected with continental conditions prevailing in the Permian and some shorter time intervals in the Mesozoic. Weathering processes were developing under warm but arid conditions when diabase intrusions became situated within the extent of weathering zone after denudation of the Góry Świętokrzyskie orogen. Chlorite, iIIite and montmorillonite originated at that time.

The second weathering cycle coincides with continental conditions prevailing in the Tertiary, following erosion of Mesozoic cover of the Paleozoic sockle of the Góry Świętokrzyskie Mts. It was. connected with intense action of hydrolysis and accompanying solution of alkaline compounds and silica, proceeding under warm and humid and, at the end of Tertiary, alternating arid and humid climatic conditions (M. Störr, 1975; M. Tyczyńska, 1957). Montmorillonite from the Permian times became transformed into kaolinite. In that cycle, the weathering cover presumably also became enriched in illite and chlorite.

The third, Quaternary cycle was primarily connected with cold Pleistocene climate. In that cycle, the existing weathering covers presumably became once more enriched in iIlite and chlorite.


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