Występowanie siarczków w łupkach dictyonemowych obniżenia podlaskiego

Abstract

W łupkach dictyonemowych stwierdzono następujące siarczki: piryt, sfaleryt, galenę, markasyt i chalkopiryt. Poszczególne odmiany mikrolitofacjalne łupków, takie jak łupki czarne, brunatne oraz występujące lokalnie łupki z fosforanami, charakteryzują się zróżnicowaniem w wykształceniu siarczków. Ustaloną sukcesję mineralną wymienionych siarczków.

OCCURRENCE OF SULPHIDES IN THE DICTYONEMA SHALES OF THE PODLASIE DEPRESSION

The paper presents the results of studies on sulphide mineralization from the Dictyonema shales (Tremadocian) of NE part of the Podlasie Depresslion. The term “Dictyonema shales” is here used in historical meaning as it also comprises "Bryograptus shales". Identifications of sulphides were made for particular microlithofacies varieties of shales such as: black shales, brown shales and shales yielding phosphates. Sulphides were identified under ordinary light microscope and using X-ray-structural analysis.

Sulphides found to occur in black shales include: pyrite, sphalerite, galenite, marcasite and chalcopyrite. Brown shales mainly yield pyrite and some amounts of sphalerite, marcasite and chalcopyrite and the shales with phosphates - pyrite. Pyrite predominates in shales of all the types, forming layers and laminae, nodules (Table I), .single idiomorphic grains, framboidal accumulations (Table II) and post-diagenetic veinlets (Table III, fig. 6). All the remaining sulphides of the Dictyonema shales form single, dispersed grains (Table V) or, sometimes, accumulations of the nest type (Table VI, fig. 13).

The microscopic studies hitherto carried out have revealed the following mineral succession of sulphides: pyrite I + marcasite. - sphalerite + galenite + chalcopyrite + siderite - pyrite II - calcite - post-diagenetic pyrite. Pyrite I was formed in early-diagenetic period, pyrite II - in late diagenetic, and pyrite III - in postdiagenetic. Marcasite is accompanying pyrite I in both black and brown shales. Chalcopyrite usually occurs in paragenesis with sphalerite in the brown shale horizon and with galenite and sphalerite in the black shale horizon (Table IV, fig. 10). Sphalerite and galenite occur in a close paragenesis in basal part of the black shale horizon (Table IV, fig. 9).