Zasolenie skał karbońskich północnej części Lubelskiego Zagłębia Węglowego

Abstract

SALT CONTENTS IN CARBONIFEROUS ROCKS OF THE NORTHERN PART OF THE LUBLIN COAL BASINSummaryThe article presents the results of studies on the salt contents in the Carboniferous rocks of the Lublin region, between Parczew in the north, and Chełm Lubelski in the south. These are the first results of the research works begun in the area here considered in 1967. Examinations were made of 43 samples of the Carboniferous rocks along 5 selected sections (Fig. 1, Fig. 3). The samples represented sandstone deposits (26 samples), siltstone deposits (10 samples), and claystone deposits (7 samples), Westphalian and Namurian in age. The samples were taken at depth from 627 to 1300 metres. The examinations were made by means of rock extraction using distilled water. The formations in study rest on a flat, Old-Palaeozoic substratum, and are overlain with a series of Jurassic, Cretaceous, Tertiary and Quaternary deposits, several hundred metres in thickness (J. Porzyki, 1967). The series of this area are characterized by the following water-bearing horizons: 1 - in the Quaternary formations (a horizon locally connected with the top weathered series of the Cretaceous formations), and 2 - in the Jurassic fissured limestones (Fig. 3). The Cretaceous deposits make here an impermeable rock series, several hundred metres in thickness. The upper member of the Carboniferous (Westphalian) is characterized by a low water content. Here, the occurrence of water is related to some thin sandstone intercalations. The Namurian deposits reveal a greater sand content, and in consequence of this, the water content in this series is also greater. Down to a depth of about 500 metres, ground waters are mineralized as much as 1 g/l (type of mineralization: HCO3- (SO42-) – Ca2+ (Na+). This is a zone of the active exchange of waters. The zone of a low exchange of waters, that probably rests below 1000 metres, is represented by waters of HCO3- (Cl-) – Ca2+ (Na+) type. The researches on the ion-salt complex of the Carboniferous rocks have demonstrated that general mineralization ranges here from 1.10 to 7.36 mv/100 g of rock. Any increase in the general mineralization with the depth has not been observed. On the other hand, some differences have been noted as concerns salt content in rocks, depending upon their lithology. The lowest general mineralization has been found to occur in the ion-salt complex of a sandstone series, and the highest one - tin the ion-salt complex of a claystone series (Table 3). The chemical composition of the complex in study is characterized by a change in cations, which consists in a percentage predominance of the ions HCO3- or SO42- over the other ones. The predominance of the ion HCO3- appears distinctly in the siltstone deposits. In the sandstones and claystones, the situation changes, and either ion HCO3- or ion SO42- prevail. Ion Cl- occurs here in a small quantity. On the other hand, the cation composition is fairly stable. Ion Na+ + K+ prevails in all the samples examined, the ion Ca2+ being at the second place. Ion Mg2+ appears in a small amount, as compared with the total sum of the cations (Fig. 4). The author compares the results of the studies with those on analogous researches made in the earlier period within the Upper Silesian area (G. N. Kotlicka, 1966). It results from the comparison that the salt content of the Carboniferous rocks in the Lublin region is lower than that of the Upper Silesian area, since, in the Lublin region, it amounts to 7.36 mv, and in the Upper Silesian area - more than 30 mv/100 g of rock. Moreover, the chemical composition of the salt complex in the Lublin region is characterized by the predominance of the type HCO3- (SO42-) - Na+ (Ca2+) and in the Upper Silesian area – by the predominance of the type Cl- - Na+.