The Moldanubian granitoid plutons of Austria: Chemical and isotopic studies bearing on their environmental setting

Abstract

The late Palaeozoic Moldanubian plutonic terrain of Upper Austria consists of granitoids that range from S-type to I-type in composition although many units show transitional compositional characteristics. The Austrian terrain displays some of the features of continent-margin “main-arc” batholiths: the expanded compositional range (monzodiorite to leucogranite) of the rock types, the high-Sr I-types and the low- to intermediate- 87 Sr 86 Sr initials (0.705–0.708) of these I-types. However, there are also important differences: the Austrian I-types are low-CaO and high-K 2O units, and transitional- and S-type granitoids are volumetrically dominant in the Austrian terrain. There is a scarcity of gabbros and an absence of rocks with positive- ϵ Nd initials. The Austrian terrain is dominated by granitoids of crustal or predominantly crustal origin. We suggest that these formed in an “inner-continental arc” setting rather than a main arc, and can be correlated with those of the Schwarzwald, F.R.G. Together, these are interpreted as components of a Moldanubian inner-continent plutonic belt.