Roland Gorbatschev

New work within globally integrated multidisciplinary projects continually changes the preconditions of Precambrian lithospheric research.
In regard to the Baltic Shield and adjoining parts of the Fennoscandian crustal segment, the results of our recent EUROBRIDGE work established the existence of a wide belt of 1.9-1.85 Ga (thus “syn-Svecofennian”) crust in the East-Baltic region, indicated the presence of a sizeable region of 1.84-1.75 Ga crust around the southern Baltic Sea, and demonstrated the importance in that region of 1.50-1.45 Ga quasi-collisional compression and deformation. In addition, we found that the termination of the Fennoscandia-Sarmatia collision to form the East European Craton occurred at 1.75 Ga, which coincides closely with the date when subduction in southern Sweden changed from northward to eastward, reckoned in present-day coordinates.
Otherwise, our work in regard to the “Fennoscandia-after-the-Svecofennian” theme continued to establish the course of the boundary between the 1.84-1.76 Ga crust in southeastern and the 1.73-1.67 Ga crust in southwestern Sweden, assess the geometries of rock belts of different age, and define migmatites of several generations ranging between ca. 1.8 and 0.9 Ga in age.
Contrary to a current opinion, the rocks to the west of the SW-SE Sweden boundary do not all belong to a homogeneous “TIB-2” group but vary substantially in chemistry and texture, also ranging from ca. 1.73 to 1.66 Ga in age.
In regard to the “TIB-1” 1.81-1.78 granitoid rocks, new structural and age data militate against the recent concept of a N-S striking continuous “Smålandian” orogenic belt, possibly even suggesting that the TIB-1 in southern Scandinavia are neither continuous with nor genetically strictly related to rocks of similar ages either in the Lofoten AMCG complex or Finnish Lapland.
As far as the “Protogine-Zone” tectonic boundary between SE and SW Sweden goes, new datings of cross-cutting rocks show that this complex structure took about one billion years to form. Thus it cannot be solely late Mesoproterozoic, Sveconorwegian.
Very important in the present context is the role of dolerite dyke swarms and syenite intrusions as discriminants between various generations of deformation and as indicators of extensional crustal regimes.