Evidence for multi-stage alteration of Schwarzwald lamprophyres
Lippolt, Hans J.; Siebel, Wolfgang
European Journal of Mineralogy Volume 3 Number 3 (1991), p. 587 - 602
published: Jun 14, 1991
manuscript accepted: Jan 23, 1991
manuscript received: Jun 27, 1990
ArtNo. ESP147050303011, Price: 29.00 €
Abstract Using the conventional K-Ar age determination technique, an attempt is made to reconstruct the time of plagioclase sericitization in altered lamprophyres. Twenty-seven mineral concentrates were extracted from dyke and host rock samples of the Central Schwarzwald (SW-Germany) and subjected to mineralogical and chronological analysis. The data was interpreted in terms of a two end-member mixing model consisting of plagioclase and seriate. For the lamprophyres, the age of sericitization ranges from Late Carboniferous to Jurassic. In contrast, the host rocks yield Jurassic to Cretaceous dates. The age pattern resulting from the dykes is interpreted as a mixture between synintrusive (auto-metasomatic) and Jurassic-Cretaceous (hydrothermal) alteration phases. Previous models involving single-stage auto-metasomatic alteration of lamprophyres cannot be supported by the present data from the Schwarzwald.