Geological Survey of Finland, Special Paper 46 - arkisto.gsf.fi

To establish the landscape and geological features
of the tectonic zones in the Khibiny Mountains,
morphometric, remote sensing and fi eldwork methods
were applied to study the relief and composition
of the rocks. Based on decoding of the aero- and
satellite images, and of the morphometric analysis,
a sketch map of the multi-ordered lineaments
(tectonic zones) was compiled. Spatial position and
order of lineaments was defi ned in accordance with
the order of the river valleys developing along the
tectonic zones. During the fi eld work, a verifi cation
of distinguished lineaments was done and landscape
features of tectonic zones beyond river valleys were
defi ned. Published data were also used.
The Khibiny massif represents the ordered hierarchic
system of structural elements, named as tectonic
blocks. The block structure is conditioned by
the development of the multirange discontinuities
(from microfracturing and contacts between the
crystals to faults, extending hundreds kilometers).
These discontinuities are caused by the interaction
of the main geodynamic processes: continental
drift, tectonic activity, and elastic resistance of
the Khibiny massif rock. These factors defi ne the
hierarchic fi eld of natural tensions and cause the
destruction of the massif due to disconnection and
displacement along the structural discontinuities of
different orders that segregate the Khibiny massif
and form tectonic blocks of different ranges. The
natural tensions and strength characteristics of the
structural forms are determined by the dimension
of the related volumes (i.e. by the dimension of the
block structures of different orders).
The rocks of northeast Fennoscandian Shield are
under horizontal crustal compression because of adjacent
ocean-fl oor spreading and continental drift.
During the Mesozoic and Cenozoic, the tectonic
uplift of the Khibiny massif resulted in the partial
loss of horizontal compression existing deep in the
Earth’s crust, leading to the extension of the rising
rock masses. Due to these processes, non-uniformly
scaled vertical cracks are revealed and the sheeting
of thin rocks occurs in near-surface parts of the
Earth’s crust. In other words, the tectonic zones
form. Within these tectonic zones the rocks are
loosened and shattered. The higher erosion intensity
Geological Survey of Finland, Special Paper 46
Landscape and geological features of tectonic zones in the Khibiny Mountains,
Kola Peninsula, NW Russia
METHODS
RESULTS AND DISCUSSION
The main theoretical prerequisite for distinguishing
the tectonic zones is based on the assumption
that the lineaments are surface expressions of
tectonics breaking the earth crust. In this case, the
position of the lineaments is outlined mainly by the
river valleys and other negative topographic forms.
The river valleys are developed along the tectonic
zones by selective erosion, for example, the order of
the river valley depends on the intensity and depth
of the tectonic zone responsible for its formation. In
the water divides, the lineaments are traced by the
alternate negative topographic forms and are manifested
in the rock composition. The fi ve orders of
the lineaments were established within the Khibiny
Mountains (Korsakova et al. 2005; Fig. 1).
occurs in the tectonic zones because disintegrated
rock masses are subjected to denudation-accumulation
processes.
Geological features of tectonic zones are presented
by the linear weathering crust, preglacial sediments
(breccia, conglomerate, gravelite, clay), weathered
and disintegrated hard rock that were observed in
exposures and revealed by drilling under the glacial
sediments during the prospecting and exploration
within the Khibiny Mountains (Armand 1964,
Mel’nikov 2002). Disintegrated hard rock contains
schpreustein and epigenetic minerals – hydromica,
nontronite, hydrohematite, limonite, chalcedony,
anatase.
Distribution of the disintegrated rocks, linear
weathering crust and preglacial sediments is confi
ned to the river valleys, gorges, hollows and saddles
in interstream areas. For example, the linear zones
of shattered rocks were found in the saddle between
Bolshoy Yuksporr and Maly Yuksporr plateaus, in
Apatity and Pod’emny cirques and in adjacent interstream
areas along the deep saddles in the valley
of Poachvumjok River. All these zones are traced
by the lineaments of the 4th and 3rd orders (Fig. 1,
points 1, 2, 3, 4, correspondingly). The 2nd order
lineaments are seen in the intensively fractured and
altered rock with limonitized apatite, underlying
the glacial sediments and ancient thick diluvium in
the valley of Saami river (Fig 1, point 5; Fig. 2),
the fractured altered ryschorites revealed by drilling
and trenching in Juksporlak mountain pass (Fig.
1, point 6). The melteygite fragments with gouges
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