Korelacje geochemiczne w wapieniu cechsztyńskim rejonu Wrześni

Abstract

Rozpatrzono występowanie pierwiastków: Cu, Pb, Ni, V, Cr, Ba, Sr, F, B, Ga; Fe, Ti i Mn w wapieniu cechsztyńskim otworu Grundy Górne IG 1 w celu uzyskania informacji geochemicznych o warunkach sedymentacji i stopniu przeobrażeń tych utworów na etapie diagenezy. Zaobserwowano wyraźną zależność koncentracji badanych pierwiastków od składników głównych osadów: dolomitów, części nierozpuszczalnych i anhydrytów. Badania koncentracji i zależności korelacyjnych Sr, F i Mn w poszczególnych odmianach genetycznych mogą służyć jako wskaźnik trwałości składu minerałów głównych (węglanów) oraz stopnia przeobrażeń, jakim uległy w procesach diagenetycznych. Omówiono znaczenie statystycznego określenia zależności korelacyjnych pierwiastków dla rozważań dotyczących odmian geochemiczno-facjalnych i korelacji osadów węglanowych.GEOCHEMICAL CORRELATIONS IN THE ZECHSTEIN LIMESTONE IN THE WRZEŚNIA AREAThe content of Cu. Pb, Ni, V. Cr, Ba, Sr, F, B, Ga, Fe, Tt and Mn in Zechstein Limestone rocks from the borehole column Grundy Górne IG 1 was analysed to obtain geochemical data on conditions of sedimentation of these deposits and the degree of their alteration during diagenesis. In the studied section, changes in facies conditions are clearly displayed by distribution of titanium, iron and chromium (concentration of these elements is controlled by terrigenous component - clay minerals and rock detritus), showing a specific bipartity in development of the deposits (Fig. 3). The concentration of these elements was found to be markedly dependent on major components of the deposits: dolomites, insoluble parts and anhydrites. Mathematical techniques (Tables 2-5) were used in geochemical interpretation to test whether or not these elements are actually genetically affined and in which associations they occur in both the studied interval as a whole and individual mineral components. The elements Fe, Ti,. Cr, Ni, Sr, F and Pb are clearly related to insoluble matter of the deposits, i.e. detrital and clay fractions. Dolomite is the other important mineral component which bears a decisive influence on distribution of the bulk of F, Cu, Ni, Mn and Ba and subordinate amounts of Ti, Cr and Fe here. No positive correlation was found between Sr and dolomite. This gives support to the point of view of several authors which treat insoluble components and composition and degree of recrystallization of carbonates as factors bearing decisive influence on concentration of Sr in carbonate rocks.The correlation between Sr and anhydrite was found to be highly positive (r = 0.96), giving support to the assumed connections of Sr and sulfates and the importance of the former as an index of diagenetic processes in carbonate Zechstein deposits. The content of Sr also appeared related to that of insoluble components (r = 0.59). Distribution of content of Sr indicates alteration of carbonate Ca I rocks from the ' borehole Grundy Górne IG 1 .at early diagenetic stage. Comparisons with Zechstein Limestone sections from other parts of Poland (Fig. 4) made it possible to establish microfacies setting of the studied rocks. In the area of the borehole Grundy Górne IG 1, the sedimentation of the Ca1 deposits was taking place in relatively deep and quiet· zone of the basin, comparable with that of relatively complete Ca1 sections in northern part of the Fore-Sudetic Monocline.