Publication details
Mineralogie a geneze zelené plazmy – specifického produktu zvětrávání serpentinitů (moravské moldanubikum, Český masiv)
| Title in English | Mineralogy and genesis of green plazma – specific weathering serpentinite product (Moravian Moldanubicum, Bohemian Massif) |
|---|---|
| Authors | |
| Year of publication | 2015 |
| Type | Article in Periodical |
| Magazine / Source | Bulletin mineralogicko-petrologického oddělení Národního muzea v Praze |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | plasma; green quartz; chalcedony; moganite; tridymite; weathering; serpentinite; Moldanubian Zone; Bohemian Massif |
| Description | Dark green variety of microcrystalline quartz-chalcedony mixture (plasma) is a specific product of lateritic weathering in serpentinized peridotites. In western Moravia, its occurrences are regionally limited to a few serpenitinized bodies. Plasma forms mostly oval nodules with variously developed zonation (dark core, a lighter rim and white edge). Typical microscopic feature is vermiform texture, mainly in marginal zones. Raman spectroscopy, X ray powder diffraction analysis and WR study of individual zones showed that plasma consists of micro- to non-crystalline polymorphic modifications of SiO2 with variable contents of H2O (quartz, chalcedony, moganite, tridymite, opal-CT); its color is due to submicroscopic pigment (chlorite, smectite) component. The sporadic relict minerals from serpentinite (amphibole, clinochlore, Cr-diopside, titanite, zircon) are also preserved. Newly formed minerals are represented by accessory pyrite, barite and very rare carbonate-apatite. Plasma formed in subaerial, partially reducing conditions from the Cretaceous to Paleogene in the deepest part of weathering crust covering serpentinites; possible interaction between the serpentinite residuum and overlying Miocene marine sediments as a plasma-forming factor is not excluded. |