Thus, it requires hydrothermal alteration to be relatively minor, confined to postmagmatic changes, since more advanced alteration of biotite into muscovite rather than vermiculite arrests further development of microcracks and leads to the development of friable granite. Grusification sensu stricto was primarily caused by vermiculitization of biotite which resulted in volumetric expansion and the development of transmineral microcracks with non-accordant pore surfaces. 24 / THE WEATHERING MAGAZINE / RUST 18 The T kit tow chain was weathered in exactly the same way as Friul Model tracks. The origin of smectite and alteration of biotite into muscovite are likely to be connected with circulation of hydro-thermal fluids too. John Murphy 1 The engine jet-pipes we are painting are cast in resin, so it is best to prime the parts prior to painting with the metallic colours. 19 When painting weld seams it is important to rst spray the surrounding areas in a very dark grey or black to simulate the burn marks caused by the heat from the welding process. Mineralogical observations such as complete albitization of plagioclase and crystalliza-tion of secondary quartz revealed an important role of hydrothermal alteration at the early stage of grusification.
Four types of altered granites have been distinguished, including compact and friable granite, typical grus, and localized heavy altered zones. In this work, a wide range of mineralogical and chemical methods performed on 43 samples from three representative outcrops and a reference site is used to determine the influence of hydrothermal and weathering fluids on the development of granitic gruses from the coarse grained Karkonosze granite. Granitic gruses are usually considered as a product of deep weathering, but the influence of hydrothermal fluids was also noticed.
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