Basiska bergarter, gångbergarter, sedimentbergarter och breccior i Vaggerydssyenit : en undersökning i protoginzonen vid Vaggeryd

Sammanfattning: The Protogine Zone is a system of steep shear zones running approximately parallel to the boundary between the Svecofennian and the Southwest Scandinavian orogens of southern Sweden. The geological nature of the zone is not very well known, mainly because detailed mapping has not begun until recently. This work is the beginning of an attempt to start changing this situation. An area of l km², situated 3 km north of Vaggeryd in north-western Småland, has been mapped in detail. The main rock types in the investigated area are syenite and finegrained mafic rocks. Associated with these two rock types are breccias. Other rock types include volcanics and sandstones. There is also a Fe-Ti mineralization. The syenites consist of perthitic potash feldspar (36-84 %, mean value 61 %), plagioclase (0-19 %, mean value 5 %), clino- and orthopyroxene (0-18 %, mean value 9 %), occasional olivine, apatite (mean value 2 %) and opaques (mean value 6 %). Syenites, aged about 1200 Ma, appear at a number of locations along the Protogine zone. They are thought to be closely related to the zone. So are also the mafic rocks called "hyperites". Radiometric datings of some "hyperites" have shown that they are about 1450 Ma old. There is however evidence of several generations of these rocks, so some could be younger than this. Several details concerning the breccias made the writer infer that the breccia is rheomorphic, and also that the syenite and the mafic rocks have intruded at approximately the same time. Such details include xenoliths of the mafic rocks in the syenite, veins of syenite in the mafic rocks, red feldspar-crystals and also partly assimilated syenite xenoliths in the mafic rocks. In the mapped area there is also a mafic dike intruding the syenite, and chilling against it. These facts should also mean that at least some of the mafic rocks along the Protogine Zone are younger than 1450 Ma. The volcanic and sedimentary rocks, which appear in the syenite, are also interesting. A comparison between the volcanics of the mapped area and the facts known about other volcanic rocks in Småland has been made. The volcanics outside the mapped area all seem to be older than 1700 Ma. The volcanics of the investigated area intrude both the 1200 Ma old syenite and the mafic rocks, and are therefore younger than these. The sedimentary rocks locally preserve primary sedimentary textures, but they are mostly contact metamorphosed. The main ore minerals of the investigated mineralization, which appear in mafic rock are ilmenite, hematite and magnetite. There are three other known mineralizations along the Protogine zone containing Fe-Ti minerals, alloccuring in "hyperite": Långtjärn, Smålands Taberg and Ranshult.