Węgiel brunatny z dolomitów kruszconośnych złoża cynku i ołowiu "Pomorzany" koło Olkusza

Abstract

Opisano wkładki węgla występujące w formach krasowych przyspągowej części profilu dolomitów kruszconośnych obszaru górniczego "Pomorzany" koło Olkusza. Scharakteryzowano formy morfo-logicznych skupień węgla oraz przedstawiono wyniki badań petrologicznych. Stwierdzono, że węgiel cechuje się niskim stopniem uwęglenia (miękki węgiel brunatny) i jest znacznie młodszy od morskich utworów triasu. Przedyskutowano genezę węgla w powiązaniu z geotektoniczną historią złoża Zn -Pb, ustalając że wypełnił on grawitacyjnie formy krasowe dolomitów przypuszczalnie w paleogenie.

BROWN COAL WITHIN ORE-BEARING DOLOMITES OF THE Zn-Pb DEPOSIT IN THE "POMORZANY" MINING AREA NEAR OLKUSZ

Epigenetic occurrences of brown coal within ore-bearing dolomites are well known in the Silesia--Cracow area. Due to their limited volume they are, however, insignificant from economic point of view (R. Althans, 1891; I. Lipiarski, 1971; M. Szuwarzyński, 1975).

The purpose of this paper is a presentation of coal sheds Qccurring in different karstic voids developed within the basal zone of Zn-Pb-bearing do10mites of the “Pomorzany” mining area near 0lkusz (Fig. 1). Channels developed along enlarged bedding joints and joint fractures (Fig. 3). underground cavities and jamas (Fig. 4), funnels and chimneys (Fig. 5) are the main karstic forms filled up with the coal sediment. The channels filled up with the coal are several metres long and up to 1 m broad; the coal deposit is also found as a filler in all lesser joints connected with main karstic channels.

The black colour and the dark brown scratch are characteristic features of distinguished petro-graphic types of coal. In the mass the coal filling is composed of semigloss gelatinous coal. It is hetero-geneous from physical point of view, since small particles of coal occur to be loosely arranged in globule-and fibrous-type aggregations with laminar and lenticular enclosures of gelatinous coal pitch-glossy in its glance and conchoidal in its fracture. Maximum thickness of the coal laminae is up to 10 mm and their extent in the range of a dozen or so. Coal filling up the karstic cavities is dull and markedly crumbled, thus showing the nature of weathered coal.

On the base of microscopic examination it appears evident that a gelinite is almost exclusively the main component of coal from the "Pomorzany" Mine; in laminae of gloss type the coal appears to be a homogeneous levigelinite.

The semi-gloss and the dull coal are composed' of globular aggregations of a porigelinite. There are also other, though rare, microcomponents such as a sporite and a macrinite as well as an undetermined organic remains, most likely chitinous, demonstrating a point fluorescence in blue-violet light.

Reflectivity R_m^o of levigelinitc has been measured in the range from 0.27 to 0.37%. Its mean value 0.31% is a representative one for the gelinite itself in its ortho-phase (a soft brown coal).

Also chemical examination has made it visible that coal of the "Pomorzany" Mine is the type of the lowest degree of coalification. About 64 per cent of C (following figures given .in per cent by weight), about 4.6 per cent of H, and about 4.6 per cent of S are representative figures connected with chemical composition of coal. As regards a water content its inherent moisture does not exceeds 11.8 per cent, an ash content has be found to be as much as 17.2 per cent. When considering the extraction,low tem-perature carbonization, and coke processes then applicability of coal under present study occurs to be none.

A high content (in the range of 93.5 - 96.5 per cent by weight) of both the free and the chemically bounded humic acid is a particular feature of coal. Its spectrum, in infra-red examination, shows presence of absorption bands typical for superior carboxylic acids as well as for their complex salts of humine and dopplerite types (Fig. 7; M. Wagner, 19820).

It is most likely that swampy areas within desalting sea bays over dolomites, with halophilous vegetation, were the main source of organic matter forming the coal sheds in dolomites. Organic gel, accumulated at the bay bottom, has been gravitationall transported through the karstified and brecciated dolomites and then deposited in them. On the other hand, type of mineralization of both the coal (marcasite type) and the dolomite fragments getted stuck in coal (marcasite-sphalerite type) makes it evident that karstified voids within dolomites have been filled up with coal in a period between lA and V phase of dolomitic mineraiization (M. Sass-Gustkiewicz, 1975).

Chemical and petrographic characteristics of coal and mode of its occurrence as well as tectonic history and way of dolomitic metallization indicate that most likely the coal under consideration originated in Paleogene.