Strefa kontaktu zwietrzałych granitoidów osłony intruzji ełckiej z osadami piaskowca pstrego

Abstract

CONTACT ZONE BETWEEN THE WEATHERED GRANITOIDS OF THE EŁK INTRUSION COVER AND THB BUNTER SEDIMENTSSummaryThe granitoids encountered in the Drygały la, Drygały 1, and Rydzewo boreholes are the immediate cover of the Ełk syenite intrusion. Drilling cores provided material from the direct contact between the altered granitoids and the Bunter sediments. Relics of the weathering products that form nests are mixed – along with crystalline rock fragments - with sedimentary material. The main constituents of the preserved weathering products are montmorillonite, illite-montmorillonite mixed-layers and, to a lesser extent, kaolinite. Additionally numerous concretions with predominating calcite and manganese concretions (pyrochroite) have been recognized. The values of the alkaline index of weathering and the index of distribution of iron and trace elements point to a moderate degree of leaching of most the elements or to secondary accumulation due to infiltration of mineralized waters. The preserved contact zone between the rocks and the Bunter is indicative of early denudation of the granitoids weathering products originated probably in Proterozoic times.