The Melechov Granite Massif

Geoscience Research Reports 33, 2000 (GRR for 1999), pages 91–93

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Abstract

The Melechov Granite Massif (MGM) represent the nothernmost part of the South Bohemian Pluton (SBP). The MGM is composed of three intrusive units: 1. Lipnice fine-grained muscovite-biotite monzogranite, 2. Kouty fine-grained two-mica alkali-feldspar granite, 3. ring stock of the Melechov hill comprising outer zone of coarse-grained two-mica Melechov alkali-feldspar granite and inner zone of fine-grained two-mica Stvořidla alkalifeldspar granite. The Lipnice granite (69-71% SiO2) comprise frequent gneissic xenoliths and relicts of sillimanite in muscovite. Remarkable, and within the SBP unique, is its high content of Th (40-60 ppm), which allowed to identify its areal extend using field gamma-ray spectrometry. The Kouty granite (71-75% SiO2) building the outer parts of the MGM is rather inhomogeneous due to assimilation of country rock. It comprises small bodies of muscovite-rich granites and pegmatite dykes. The Melechov ring stock is a product of two stages of crystallisation of one parental magma (71-74% SiO2): Marginal coarse-grained facies crystallised slowly from fluid-rich melt. After tectonically induced release of fluids, the residual fast crystallised rapidly as fine-grained central facies.