Minerały wtórne w anortozytach i norytach intruzji suwalskiej

Abstract

SECONDARY MINERALS IN ANORTHOSITES AND NORITES OF THE SUWAŁKI INTRUSIONSummaryThe secondary minerals distributed in different forms in the rocks have been investigated under the X-ray diffraction and microscopes (electron and optical). Three secondary mineral associations have been distinguished: a - minerals in forms of small pockets in moderate weathered rocks, related to hipergenic alterations, b - minerals in fissures and veins, connected mainly with a crystallization of hydrothermal solutions, c - minerals in larger pockets in the contact zone of sedimentary rocks with the crystalline platform, representing the relict material after the destroyed weathered horizons. The yellowish green minerals occurring in the small pockets composed mainly of kaolinite and mixed-layer illite-montmorillonite. It is the products of alteration of plagioclases and biotite. Dark green and brown minerals of the small pockets are, in general, represented by nontronite with some kaolinite and illite-montmorillonite. Amorphous iron hydroxides and some ferric oxides (maghemite, goethite, lepidocrocite) are associated with these minerals. This group of the secondary minerals is related to the initial stage of alteration of pyroxenes, magnetite and ilmenite. White or yellowish brown minerals occurring in fissures and veins composed mainly of calcite with some goethite and with admixture of kaolinite and mixed-layers illite-montmorillonite. The mineral pockets of the contact zone contain kaolinite and in some cases gypsum with various admixtures of quartz. The associations of secondary minerals of the initial stage of weathering of anorthosites and norites indicate that these rocks have been altered in alkaline environments without leaching and under the additional influence of hydrothermal solutions.