Rila Monastery Nature Park Management Plan - part - usaid

February 2004
There is a clearly defined lithological boundary, with imposed concordance in the
gneiss-migmatic complex, but in most cases the contacts are tectonic. This suite is
made up of diverse gneisses, gneiss-schists and schists, amphibolites, marbles,
metamorphogenic skarns and calciphires. The principal lithological variety are the
fine-grained biotitic gneisses, at places containing garnet and graphite. They make up
some 70% of the composition of the suite and are dark-gray or gray with a parallel,
foliate or pinstriped texture. They consist of plagioclase, quartz, and red to reddishbrown
biotite, granite epidote and rutile. In the proximity of granite intrusions these
take on a striped or fine-grained texture. The remaining rock types appear as layers of
different orientation and thickness amid the fine-grained biotite gneisses.
The muscovites and bi-mica gneisses and gneisso-schists are unevenly distributed
across the suite, but on the whole dominate its upper levels. Marbles are relatively
well represented in the lower levels of the suite, but can also be seen in the middle
levels. They form a number of distinct layers, in associations with amphibolites,
leptinites, calciphires and fine-grained biotite gneisses. In the area around Rila
Monastery and Lake Skakavitza, they associate with kyanite, amphibolites and
amphibole-biotite gneisses. The marbles are unevenly dolomitized and skarnized.
Aplitoid-pegmatoid granites form an irregular body with a complex configuration
between Kirilova Polyana and the Skakavitza River. At the point of contact there can
be found granitoids, as small, structureless bodies, or close to it, metamorphites,
embedded in the metamorphic framework. Their contacts are clearly defined,
intrusive, with numerous layered veins or apophyses. The larger bodies comprise
xenoliths of varying sizes, usually oriented in the direction of the extension. The
granites usually have an unevenly grained or striped texture, with a
hypodiamorphogranular structure, gradually transforming into pegmatite, aplitiod,
and in some cases, metasomatic. They are made up of plagioclase-potassium feldspar,
biotite, muscovite, garner and ortite. From a petrochemical point of view, the granites
are relatively homogeneous.
Tectonically, this part of Rila has a rather complex structure, the result of a polycyclic
and polyphase tectonic evolution. The block is made up of the rocks of the gneissmigmatic
complex, among which granitoids are intruded. The planar structures have a
northwest southeast strike and dip at 30 0 -70 0 , mainly to the southwest, following the
outlines of the Rila batholite. Around the Kalin pluton, a re-orientation of the strike in
a north-by-northeast direction is observed. The principal macrostructure in this part of
Rila is the Malyovitza antiform. A number of sub-parallel forms are established
between the town of Sapareva Banya and Golyam Mechi Peak. The first of these, a
well-defined anticline, with its fold axis oriented in a north-by-northwest direction.
This fold can be traced south of Sapareva Banya, along the upper course of the River
Otovitsa, the Eleshnitsa River, Pchelino locality, up to a point northeast of Tsarev
Peak. The core of the anticline is made up of amphibolites. Sub-parallel of it, a little
off to the east, lays a syncline. To the west of these two folds, between the sources of
the River Eleshnitsa, along the right-hand slope of its valley, up to its point of
confluence with the Rilska River, lie two isoclinal folds with their axes oriented in an
almost perfect north-south direction. The cores of these two are made up fine-grained
biotite granites, and their limbs, of amphibolites. Between Rila Monastery, the Iliyna
River, and southwest of the Radovichka River, another synclinal structure can also be
traced, with its axis parallel to the above described. Near its point of contact with the
Rila Monastery Nature Park
Management Plan -Draft
2004 - 2013
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