Original paper

Hydrothermal alteration of the Strzelin granite, SW Poland

Ciesielczuk, Justyna; Janeczek, Janusz

Abstract

The Strzelin granite in SW Poland is seen in hand specimens as a fresh rock, except for bleached, approximately 5-mm-thick zones around numerous hydrothermal veins. Detailed investigations revealed, however, that at least 20 % of the whole intrusion was significantly affected by hydrothermal fluids. The degree of the alteration of the granite ranges from apparently unaltered granite to heavily altered rocks, which consist of almost no primary minerals. The mineral assemblage of hydrothermally altered granite is the same as in the hydrothermal veins and consists of hydrothermal quartz, feldspars, chlorite, titanite, muscovite, sericite, prehnite, clinozoisite, laumontite, saussurite, kaolinite and calcite. Laumontite replaced both K-feldspars and plagioclase. Mass balance calculations suggest the input of calcium and water to the highly altered granite associated with silica removal that caused decrease in rock volume. Hydrothermal mineral assemblages in the Strzelin granite formed at P-T conditions corresponding to zeolite facies and even incomplete prehnite-pumpellyite facies of low-grade metamorphism.

Keywords

hydrothermal alterationgranitelaumontitemass balancestrzelinpoland