Tectonic patterns in the central Baltic Shield

Abstract

A network of several sets of subparallel lineaments, extending over the Baltic Shield into the surrounding areas of Paleozoic and later rocks, has been identified in Nimbus satellite imagery. The observed lengths of several lineaments exceed 1 000 km. Each set is distributed all over the Shield. Ground data collected in Finland indicate the following. The strikes of foliation of the Precambrian schists and gneisses are concentrated into eight dominant trends, each parallel to a given set of the lineaments. The strike frequency maxima of the Bouguer gravity isolines and the dominant trends of the basement scarps and trenches fall in these same directions. Schist belts, tanging in age up to 2 800 m.y., as well as the boundaries of the major structural and lithologic units, are aligned with or parallel to the lineaments, which also separate blocks differing in altitude and in rate of recent land-uplift. The data suggest that the lineaments represent a permanent abyssal shear-net system, which has contributed to the evolution of the Shield since Early Precambrian times. The system possibly extends over the surrounding ocean floor.

A pattern of tectonic zones in the western part of the East European Platform

“…6 ) . In Finland, the tectonic zone roughly follows the boundary between pre-Svecokarelian and Svecokarelian sequences (tectonic zone IIa by Tuominen et al 1973). The tectonic zone I11 is accompanied by mineralizations of heavy metals, expecially Cu and Ni.…”

Rare Earth Elements in Middle Precambrian Volcanic Rocks of Finland, with a Discussion of the Origin of the Rocks

“…In the most prominent shear zone in Finland (Kahma 1974;Mikkola & Niini 1968;Tuominen et al 1973), which seems to separate calcalkalic and tholeiitic magma series, is situated the main sulfide ore belt (Fig. 1).…”

Extensive Coverage of Marine Mineral Concretions Revealed in Shallow Shelf Sea Areas

“…The glacial sediments consist mainly of diamicton (till), glaciofluvial formations, and glacial (varved) clays and silts, and post-glacial sediments are mainly fine grained sediments. The crystalline bedrock is characterized by several ancient tectonic lineaments and fracture zones that divide the bedrock into blocks, also evident on the seafloor (Härme, 1961;Tuominen et al, 1973;Winterhalter et al, 1981).…”