ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

is located near the southern margin of this area. In the periglacial
condition of the last scandinavian glaciation (Vistulian)
the drainage basin topography has been smoothed.
Simultaneously loess like deposits covered the elavated
plateaus. The present river channels are inset within Pleistocene
fluvioglacial deposits or Holocene alluvia.
The fertile soils, dense network of streams and favourable
climatic conditions caused a long history of intensive human
occupation. The area has been inhabited since ancient
times. By the end of thirteenth century a lot of new settlements
has been founded here. As a result, an intensive
deforestation and subsequent soil erosion started here. The
eastern tributaries of the Odra river drain area of Upper
Silesia coalfield developed in early nineteenth century as
an industrial area.
There is evidence that an extensive agricultural settlement
of loess plateaus caused their nearly complete deforestation.
As a result, considerable slope erosion an overbank
deposition on the valley floor took place. Vertical sequences
of these alluvial series are usually 1 to 1.5 m thick with
organic remnants at the base dated back 900-1000 A.D.
The higher irregularity composition of fine grain sediments
upwards of these deposit and simultaneous 2-3 times increasing
of zinc concentration are typical here.
The overbank units build up a youngermost inset terraces
in tributaries draining the coalfield regions are rhytmically
stratifield and contain coal admixture. Here lead and especially
cadmium concentrations rise drastically by near order
of magnitude. This peak levels of Pb and Cd recorded
here are atributed to nineteenth century rapid growth of
mining industry and urbanization.
NINA T. KOCHNEVA & VICTOR YU. ALEKSEYEV
Structural and geomorphological investigations
in studies of ore distribution
Institute of Ore Deposits, Petrography, Mineralogy and Geochemistry
(Igern), Staromonetnyi Per., 35, 109017 Moscou, Russia
Structures of the present relief are inherited, and their features
can be used for metallogenic investigations. In the
Laboratory of Metallogeny of Ore Regions, the special
method was worked out by the authors in collaboration
with LN. Tomson and V.S. Kravtsov to represent structures
of the period of magmatic reactivation and great ore
formation through the analysis of present-relief forms. To
do this, linear and area structural elements of the present
relief were studied in ore regions with regard to their geotectinic
and phisico-climatic features. Data on endogene
and exogene agents forming a present-day relief were of
especial significance to recognize tectonic elements. Area
structures were recognized with the Method of Generalized
Horizontals in combination with the analysis of distri-
232
bution of different genetic types of relief; linear elements
were primarily identified with decoding of aerial and cosmic
photographs through both typical pictures of river system
and many other indirect signs.
The area and linear elements identified were used to compound
a generalized scheme of the present tectonic appearance
which had often been composed of fragments of
structures differed in foundation age. To find out the principle
structures which were contemporary with ore formation,
a complicated combination of different-age tectonic
elements was compared with geological data.
Studies of several large regions, the Carpathians-Dinars­
Balkans, the Andes, the Sierra Madre, the Caucasus and
Transcaucasus, the Central Asia, the Chuckchee Peninsulla,
the Transbaikalia, the Bulgarian (in cooperation with I.
Vaptsarov, and the Serbian (in cooperation with M. Petkovich),
were carryed out and the great significance of structures
superimposed on more ancient structural zones was
revealed for ore distribution. Arch uplifts, focus structures,
and linear penetrating zones are some of them. As all these
structures have some morphological features they can be
recognized in the present relief.
A cross demention of arch uplifts ranges from 5000 to 100
km. Their feature is development of peripheral and central
depressions. A metallogenic zoning is usually determined
by large arch uplifts while smaller structures (200-50 km)
control ore regions. The East Transbaikalian Arch Uplift
(it has developed since Cretaceous) was identified and studied
in detail with the Structural and Geomorphological
Method. Concentric elements of the uplift control fluorite
and antimony-mercury mineralization belts.
Focus structires (their usual cross dimentions are less than
100 krn) are often distinguished by radial-circular fault systems.
Their structural features are usually related to areas
of magmatic rocks which the structures are built of. To
identify them, all the geomorphological signes are applied.
Ore centers of different metallogenic characters are usually
placed within focus structures. For instance, the Lashkerek
Focus Structure (volcanic, complex-built), the Central
Asia, is reviewed below. Its central section is occupyed
with the youngest volcanic rocks (C 3-P1 ) of acid composition
while the oldest rocks (C 2-C3 ) are developed along its
periphery. Daughter domes complicating the periphery are
centres for the development of intrusions, extrusions, and
explosions and hold gold and base-metal ore occurences
and deposits.
Linear penetrating zones of faults are hardly decoded through
geological data: they are of shadowy character and
can be only identified with complex studies [Metallogeny
of Shadowy Lineaments and Concentric Structures, 1984].
A hypsometric anomalies and a specific structural plans
are developed in the present relief along these structures.
For instance, the Klichka-Darasun Penetratung Zone, the
Eastern Transbaikalia, is characterized by the highest (in
the surroundings) hypsometric level and composed of
small linear structural elements striked as the general
structure. The zone cuts the general structural plan of the
area and controls all the largest mineral deposits of the
Transbaikalia.