169 Geologische Rundschau 76/1 [ 169-175 [ Stuttgart 1987 Greisenization (a review) By M. STEMI'ROK, Prague':') With 6 figures and 5 tables Zusammenfassung Vergreisung ist ein postmagmatischer Vorgang, der mit der Entstehung leukokrater SiO2-reicher Granite verbun- den ist. In seinem Verlauf sind Feldsp~iteund Fe-Glimmer zersetzt. Die Auswirkung yon Vergreisung auf verschie- dene Gesteinstypen sowie der Charakter der vergreisenden Fluide wird diskutiert. Abstract Greisenisation is a postmagmatic process associated with the origin of leucocratic high silica granites, In its course feldspars and Fe-micas are decomposed. The changes cau- sed by greisenisation in various rock types are discussed and the data on the nature of greisenising fluids are summari- zed. R6sum6 La greis~nisation est un processus postmagmatique asso- ci6 ~i la formation des leucogranites riches en silice. Au cours de ce processus, les feldspaths et les micas ferreux sont d6compos6s. La note discute les modifications appor- t6es par la greis6nisation dans les roches de diverses natures; eIle r6sume les donn6es relatives fi la nature des fluides res- ponsabtes du ph6nombne. KpaTKoe coAep~KaHHe Fpet~I3eHl,13aliHSt I;IBY/~IeTCSt HOCTMaFMaTHqeCKHMFIpo- I~eCCOM, CB~3aHHblM C o6pa3OBaHHeM .rIeI~IKOKpaTHblX FpaHHTOH~OB,~OFaTbIX KpeMHe3eMOM. B TeqeHHFI 3TO- ro npouecca pa3:xaranncb noyleBbie UlnaTbII4~eYre30co- zlep~aulttx cnro~I. O6cy~;/aeTc~ BYlH~HHe rpel~I3eHH3a- tmu Ha pa3nHqHble nopoRbI H xapaKTep qbJItoH~oB, BhI3blBaIO1LIHX Fpet~I3eHH3aHHIO. Introduction Greisenisation is a characteristic metasomatic pro- cess accompanying the origin of some metallogeneti- cally specialized granitoids. It belongs to postmag- matic alterations which commonly change the mine- *) Author's address: M. STEMPROK, Ust~edni fistav geolo- gickf~, Malostransk8 n~im. 19, 11821 Praha 1, CSSR. ralogical composition of granites in several sequen- tial stages after their emplacement. Potash and so- dium metasomatic alterations (feldspatizations) pre- cede the greisenization but they may also follow it (table 1). The occurrences of greisens are limited either to the contact zones of metalliferous plutons (essen- tially their apical parts) or to their intermediate enve- lope. They can be differentiated into joint-controlled and pervasive greisens in dependence on the charac- ter of the conduit channel. The joint-controlled grei- sens follow commonly regionally distributed fault and fissure systems in the granites or their envelopes. In definitions of greisenization the following aspects are usually stressed: 1) greisenization is a me- tasomatic process which is related to the origin of high silica leucocratic granitoids (70-75 % SiO2), 2) it acted on solid rocks without a significant participa- tion of reactions in a liquid portion of the granite body, 3) in its course mineral changes occurred cha- racterized by the decomposition of biotite and felds- pars and remobilization of silica and alumina in the rock. Thus the greisenization is defined as a granite-rela- ted post-magmatic metasomatic process in the course of which biotite and feldspars became instable. They were replaced by complex aggregates of micas, quartz, topaz, fluorite and tourmaline with a consi- derable import of some elements such as tin, tung- sten, molybdenum or beryllium. Greisen classifications As the greisenization is a typical granite related process most greisens are formed by the alteration of granitoids. Such greisens are well defined and easily recognized. Similar greisen types originate by the re- placement of alumosilicate rocks which are close to granitic composition, such a various gneisses, gray- wackes, arkoses etc. The classifications can be based on qualitative or quantitative criteria. The qualitative classifications consider the combination of the prin- cipal greisen constituents in the rock (a list is given in