Minerały ilaste osadów neogenu niecki orawsko-nowotarskiej

Andrzej Wiewióra, Ryszard Wagner

Abstract


Zbadano skład granulometryczny oraz, na podstawie analizy derywatograficznęj i rentgenostrukturalnej frakcji < 2 mm, skład minerałów ilastych iłów lignitowych z Lipnicy Wielkiej oraz młodszych od nich warstw z Domańskiego Wierchu. Stwierdzono frakcjonalną budowę i cykliczność osadów oraz związane z tym zróżnicowanie ilościowe i jakościowe minerałów ilastych. W obu profilach zidentyfikowano te same minerały ilaste: beidelit, chloryt i illit, nie wykryto natomiast kaolinitu. W Lipnicy Wielkiej tworzą one jeden tylko zespół beidelit > chloryt > illit, natomiast na Domańskim Wierchu kilka zespołów tych samych minerałów, będących w różnych proporcjach ilościowych.

 

CLAY MINERALS OF THE NEOGENE SEDIMENTS IN THE ORAWA-NOWY TARG BASIN

 

Neogene sediments of the lignite clayey formation (noncalcareous silts and clays) from Lipnica Wielka and clayey sediments from Domański Wierch (calcareous silts and clays) were subjected to derivatographic and granulometric analyses. Minus 2 mm fractions were analysed by the DTA and X-Ray methods.

Granulometric data (Table 1 and 2) indicate marked fractional differentiation of the studied strata and they prove cyclic changes of the sedimentation environment.

The sediments from Lipnica Wielka are composed of clay minerals, quartz and organic matter (fig. 1) and those from the Domański Wierch – of clay minerals, quartz and calcite. The latter are nearly organic matter-free (fig. 3) but sometimes they contain siderite, dolomite, geothite and pyrite.

The clay minerals content is varying from 25 per cent in silts to 55 per cents in clays. In the clay fraction of all the studied samples were identified the following minerals: beidellite, chlorite and illite. They vary, however, with respect to the proportions and crystallinity.

In the formation of the lignite clays the major clay mineral is beidellite prevailing quantitatively over chlorite, but chlorite occurs in higher concentrations than illite. In the sedimentation cycle of the profile labelled III-b, it may be observed increase in the structure order of chlorite and decrease in the structure order of beidellite, related to the changes in its interlayer space (fig. 1 and 2, samples 1–3). In the sedimentation cycle of the profile labelled 1–5, the beidellite and chlorite are characterized by the relatively well-ordered structures (fig. 2, samples 9 and 10).

In the sediments of the Domański Wierch, proportions between clay minerals are nearly equal.

The exceptions are here sample 11 representing the youngest sediments and sample 14 from the middle of the profile, where beidellite prevails quantitatively over chlorite and. mite (Table 3).

One distinguished assemblage of clay minerals: beidellite > chlorite > illite in the noncalcareous lignite clay sediments, quantitatively differentiated assemblages of the quantitatively the same minerals in the calcareous sediments of the Domański Wierch and absence of kaolinite are clearly different from the clay minerals assemblages of the terrestial Neogene sediments of the Polish Lowland.

 


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