GREISENS OF EASTERN MONGOLIA AND SOME FEATURES OF THEIR ORIGIN
Titel:
GREISENS OF EASTERN MONGOLIA AND SOME FEATURES OF THEIR ORIGIN
Auteur:
Kalenov, A. D.
Verschenen in:
International geology review
Paginering:
Jaargang 6 (1964) nr. 1 pagina's 119-128
Jaar:
1964-01
Inhoud:
This study of the process of greisenization indicates the need of revision of the "Lindgren Law" of constant volume in metasomatic processes accompanying greisenization, i.e., the mass of the removed substance is always many times larger than that of the added. Mineralogically the greisens developed fall into four principal varieties which are: 1) muscovite-quartz, with quartz greatly predominant (not over 15%-25% muscovite); 2) muscovite-quartz, with a comparatively high muscovite content (30%-40%); 3) Muscovite greisens (up to 90% muscovite); and 4) albite-muscovite greisens with a 30 percent-40 percent Muscovite content. Metasomatic phenomena are much more vigorous in the forming of muscovite greisens than of muscovite-quartz greisens. Petrographic study of these greisen types indicates a) in the presence of high silica and low alkali saturations, potassic feldspars are decomposed first, replaced by quartz, and then by muscovite. In the presence of a high potassium salt saturation, the greisenization process may begin directly with a replacement of plagioclase by muscovite; b) in the presence of highly saturated greisenizing solutions, muscovitization is preceded by albitization of potassic feldspars with a subsequent replacement of albite by muscovite. The participation of mineralizers such as fluorine and boron in this process is inconspicuous. Robert M. Hutchinson
Tijdschrift beschrijving