Petrological studies of the Neiden granite complex.

Abstract

The Neiden granite complex fits well into Raguin's group of \"anatectic granites with suites of migmatites\". In this area, supracrustals of the Bjørnevatn group have, together with their gneissgranitic basement, been subjected to ultrametamorphism. The resulting rocks are classified as gneissgranite, granodiorite and quartz monzonite, these granitoids being separated from the surrounding gneiss by a zone of transition migmatites. Certain features of this zone are best explained by assuming partial anatexis. The totality of observed phenomena can not be accounted for by any purely magmatic metasomatic hypothesis alone, and the proposed petrogenetic model is intended as a working hypothesis rather than a final conclusion. In addition to the conventional methods, studies of the geographical areal variation of Fe, K and Na content of the rock and radioactivity in the field were performed for one particular sub-area. The perhaps most interesting result of this variation study is the strong indication that granodiorite did form by some - practically in situ - transformation of rocks of the Bjørnevatn group. Trend surface analysis has been applied to these quantitative data, adding to the gradually accumulating experience with this method in geology.