Iulian Gavat, Stefan Airinei, Radu Botezatu, Mircea Socolescu, Scarlat Stoenescu and Ion Vencov
Abstract
The geological interpretation of the gravitational anomalies and of those
of the vertical component of the magnetic field of the earth has made possible
the preliminary study of the basement's structure with the aid of the gravimetric
and magnetic characteristic features of the tectonic elements in the Carpathians
and in front of the Carpathians.
In order to trace the lines, there were taken into account a whole series of
mapping aspects, which express the results produced by the structural relations,
by the contacts between masses of rocks with different petrographical composition
or by the presence of effusive or intrusive masses of eruptive rocks.
The structural relations are shown by lines traced almost entirely on account
of the gravimetric works, which express: mass relations that imply crustal
and even subcrustal volumes (lines of the first order, I), relations that affect
at least two tectonic units (lines of the second order, II), relations between
compartments of a single unit (lines of the third order, III). The structural
lines are in agreement with the areas having a very strong gradient or with
the limits between compartments having a different gravimetric situation.
The contacts between masses of rocks with different petrographical composition
were illustrated with the aid of the magnetometric results. They represent
the limits of separation between volumes of the basement having different magnetic
features. The basement of the great tectonic units is separated by major magnetic
lines. Inside, there were traced subordinate delimitations with the aid of
minor lines. Sometimes, the magnetic limits are doubled by gravimetric lines,
in which cases they may represent faults.
The eruptive masses are shown in the magnetic map with the aid of positive
anomalies disposed in ranges of different extensions. The lines connecting
these maxima disclose, in an indirect manner, the existence of crustal features,
on which great igneous masses have accumulated. In connection with these lines,
there can be observed fields of fractures with regional or local distributions
of intrusions or effusions of eruptive magmas.
For the platform, there were given the delimitations of the basement compartments,
having a different petrographical composition (with the aid of six principal
magnetic lines), the chief structural elements determined by gravimetry, and
the subordinated structural features.
In the areas of Alpine-Carpathian folding, there were shown the deep faults
which affect their basement and also the extensions and the structures of the
units composing this basement. These faults have penetrated the deep structure
of the mountainous system, of the depressions and of the basement of the fore-Carpathian
through.
On the ranges of positive magnetic anomalies, worked by intrusive and effusive
eruption, there were traced four kinds of structural lines, according to the
age of the eruptions: Paleozoic (linked with the basement of the platforms),
Mesozoic (diabases in the Western Mountains), Banatitic and Neogene.
In conclusion, the authors emphasize the efficiency of the correlation of the
specific magnetic and gravimetric anomalies for the study of the deep structure
of the platforms and mountainous areas, of the fields of crustal and regional
fractures linked with eruptive formations of different ages and with the associated
metamorphic formations. The structural relations between the great tectonic
divisions are defined in a more evident manner by the presence of the regionally
coupled anomalies (
Z and Bouguer). Several chief tectonic elements, especially
those of crustal importance, established with the aid of the studied anomalies,
exceed the territory of the Romanian People's Republic and may be correlated
with those established in the adjoining countries. On several regional or crustal
fractures there are industrial concentrations of useful minerals whose economic
importance has been emphasized by the authors.