Nowy zespół mineralny w leukokratycznej strefie Jordanowa k. Sobótki i jego znaczenie genetyczne

Józef Lis, Hubert Sylwestrzak

Abstrakt


NEW MINERAL MASSIF IN LEUCOCRATIC ZONE OF JORDANÓW NEAR SOBÓTKA AND ITS GENETIC SIGNIFICANCE

Summary
Leucocratic rocks varying in mineral composition, texture and the mode of occurrence are fairly common in serpentinite massifs in the Lower Silesia. Because of large difficulties in their classification, the rocks are still treated as ,,leucocratic rocks" or „alterated leucocratic zone".
Leucocratic rocks became the subject of vivid interest after discovery of nephrite at the boundary of serpentinite and ąuartz-zoisite rocks at Jordanów. Nephrite was also found in some other localities (Mleczna, Tomice, Piotrówek and Trzebnik) always in close relation to the occurrence of leucocratic rocks. Detailed mineralogical studies on leucocratic zone at Jordanów either confirmed or revealed the presence of minerals such as diopside, zoisite, clinozoisite, grossular, chrome hydrogarnet, vesuvian, diaspore, hydrargillite, albite, oligoclase, K-feldspar, prehnite, pumpellyite, desmine, quartz, chalcedony, opal-hyalite, calcite, dolomite, actinolite, tremolite, tale, saponite, vermiculite, clinochlore, chrysotile, antigorite, goethite and magnetite. The views on the origin of leucocratic rocks embedded in serpentinites may be divided into three groups. According to those of the first group, these rocks are genetically related to gabbro magma, whereas the second group assumes relations to relic solutions of serpentinites (peridotites) and the third - to magma of granitoids of the Strzelin massif or other granitoids. Small nests of pegmatites with specific suger-like albite and biotite aplites were found within the leucocratic zone at Jordanów. These rocks are characterized by the presence of several hitherto unknown minerals, clearly evidencing genetic relation with Strzegom granitoids. This gives further support to earlier views assuming that at least some leucocratic veins found in serpentinites are related to derivatives of granite magma.

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