Petrology of a 1.95 Ga granite-granodiorite-tonalite-trondhjemite complex and associated extrusive rocks in the Knaften area, northern Sweden

Abstract Two granite-granodiorite-tonalite-trondhjemite (TTG) complexes intruded mafic-intermediate volcanic and volcaniclastic rocks at 1954-1940 Ma in the central part of the Knaften area, which lies in the northern part of the Palaeoproterozoic Bothnian Basin, in the central part of the Fennoscandian Shield, northern Sweden. The regional metamorphism was upper greenschist to amphibolite facies. The granitoid complexes are subdivided texturally into three types of intrusions. Contact relationships show that the most coarse-grained type is the oldest, followed by a medium-grained type and finally an aplitic-pegmatitic type intrusion. Felsic dykes that cut the granitoids form the youngest intrusive event. Myrmekitic/symplectitic textures or graphic intergrowths show that the later intrusive phases were more volatile-rich. The granitoids are high-level intrusions, and formed the root-zone of a volcano. Close to, but outside the granitoid complexes, compositionally similar felsic porphyry dykes occur. A pac...