Geochemiczno-mineralogiczna charakterystyka marmurów dolomitowych ze złoża Rędziny

Abstract

GEOCHEMICAL AND MINERALOGICAL CHARACTERISTIC OF DOLOMITIC MARBLES FROM RĘDZINY DEPOSITSummaryThe deposit of dolomitic marbles at Rędziny forms a fragment of the contact zone of the Rudawy Janowickie Range. This fragment was metamorphosed in conditions of regional metamorphism and then as a result of plutonic intrusion of the Karkonosze granitoids. The deposit occurs in the form of a lense which has been wedged among schists.The results presented here are based on extensive lab work which comprised observation of rocks and minerals under the microscope, in thin sections and polished preparations, as well as X-ray, thermic, and geochemical analyses.Dolomite, which occurs in well-crystallized blasts, is the main component of dolomitic marbles. It is accompanied by secondary calcite and incidental siderite. In addition there are also forsterite, pyroxene (diopside, diallage), actinolite, garnet, those minerals which are typical of contact-changed dolomites. Among non carbonate minerals which form fine veinlets in marbles, the most common are those of the serpentine group (chrisotile, antigorite, hydrated serpentine); they originated during the post-metamorphic stage. Talc was formed as a result of the metamorphism of serpentines and the activity of circulating solutions. Sepiolite (parasepiolite) has also been identified here; ore minerals are represented by haematite, pyrite, and chalcosite.Dolomitic marbles at Rędziny are characterized by low concentrations of trace elements which correspond to average concentrations of trace elements, typical of carbonate rocks. This may indicate that the granitoid intrusion of the Karkonosze was not active during the metamorphic processes in dolomites. It is only locally that the influence of hydrothermal solutions can be traced: some parts of the deposit show a larger amount of Fe, Cu, and Ni. Larger amounts of Ni and Co occur in serpentines; a higher content of Cu has been observed in talc and sepiolite. Larger amounts of Zn occur in marbles, close to ore-bearing parts of the rocks.