Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
New information from known as well as unknown rocks in the surroundings of Lipnice nad Sázavou
Abstract
The highly magnetic cordierite paragneisses from Orlík at Humpolec were characterized by thermomagnetic curves and Mossbauer spectrometry. There is abundant magnetite, which evolved from hematite. The monazite ages range from 323 to 428 Ma, the higher values being interpreted as older grains with partial Variscan resetting; in one case an age of 768 Ma has been obtained. Elevated contents of S and Eu in monazite reflect oxidized environment. The poorly exposed fine-grained Lipnice gneiss represents a transition between paragneiss (relatively rich in Ca and Sr) and granite (probably the Pavlov type). The bands with anhedral poikilitic microcline alternate with „normal" paragneiss (plagioclase, quartz, biotite); it is not sure, however, if they were formed by partial melting or metasomatism. New and also revised older data show that the extent of Lipnice granite (characterized mainly with high Th) and Pavlov granite is much larger and more complicated. The only realistic explanation for chemical variability of all granites between the stocks of Melechov and Čeřínek lies in the composition of their protoliths, with magmatic processes having little significance.
