Eastern Rhodopes
and the vicinity of Kardjali
Victor Marinov
The Rhodopes or the also called Rodopi Mountains are part of
the Rilo-Rhodopes massive, which is located in the south-southwest part of Bulgaria. This massive on the other hand is part of the
bigger Macedonian-Thracian massive which in general is considered
to be the oldest dry land on the Balkan Peninsula. To the south it’s
limited by the Vardar and the Izmir-Ankara zone. Some of the rocks
found there date back to the early Mesozoic or even the very late
Paleozoic. Their rock composition is quite diverse. The rocks in the
mountains themselves are Paleozoic or post Paleozoic plutonic but
those from the kettles and lower parts are much younger and
belong to the Pliocene period of Earth’s history. Nevertheless the
rock composition of the upper layers of the eastern part is volcanic
with a strong presence of old sedimentary rocks with both organic
and inorganic genesis that were once covered by the Vardar Ocean,
which was completely closed and disappeared by the late Jurassic.
Formation of the relief occurred in several important episodes.
First during the upper Paleozoic crust formed as a product of
magmatic activity, later on during the Mesozoic at approximately
170Ma as a part of the Alpine folding cycles the Rhodopes
experience series of compressions which culminated at
approximately 110-90Ma. A second episode of expansion at around
65-70Ma created a number of cores or domes of heavily
metamorphosed rocks. The domes were later on exhumed at
around 37-34,7Ma.
The elevation of the mountains is due to the postcollisional
subduction of oceanic crust and lower continental crust of the
Moesian platform beneath the Phodope belt. A rift within the
overriding Rhodope block opened that was coaxial with the
northward transport of the underriding Moesian platform. Upwelling
of the mantle derived melts from the underplating beneath the
Northeast-Southwest Rhodopes, which were strecthed and thinned
as a concequence. In the end this resulted in the generation of the
three modal alkaline, basic and acidic volcanic rocks by the partial
melting of the crust and asthenospheric segregation. Batholitic
magmas were generated by the partial melting of the undepleted
lower crustal amphibolites, middle and upper crustal gneissic rocks
and depleted lower crustal or subcontinental mantle. That is why it
is quite common to find intrusive formations within the regular
crust.
During the latest of Earth’s history periods the shape of the
mountains remained more or less unchanged because it was never
covered by glaciations due to it’s geographical position at low
latitudes and the relatively low height of approximately 1500m.
The accumulation of most of the industrially important deposits
of ores began during the late Alpine period. Earlier stages were
more relevant to the mineral deposition. The of significance in
between them are chromites, asbestos, talk, and quartz-goldpolimetal and quartz-galenite-sphalerite ores.
Given their unique nature of formation, the Rhodopes were and
still are a quite attractive zone for a diverse flora and fauna. They
were as well a strategic territory for many of the cultures and
civilizations that visited the peninsula. The mountains has been
populated first far back in history by prehistoric men, later on the
ancient Thracian civilization settled in the region. Afterwards the
Macedonian and Roman empire left their mark by leaving significant
amount of landmarks, many of which were related to the abundant
mineral springs. Nowadays the Rodopi Mountains remain a
profitable region for tourism both during summer and winter. The
mild relief made it possible for all age groups to feel comfortable
exploring its beauties. The natural world there includes so many
protected plant and animal species that in the eastern part alone 4
natural parks have been created biggest of which are “Yumruk
skala” (Fist Rock) and “Sredna Arda” (Middle river Arda). Extremely
rare species of continental significance can be found there residing
in the unique forest and rock habitats. Tourists and especially those
from foreign countries are often attracted to the mineral baths
where the healing power of the thermal waters are combined with
therapeutic cares of specialist and the easing effect of the
remarkable beauty of the environment.
Nevertheless the region is not problem-free. Heavily exploited
mining sites and agricultural tradition, dating back from before
Christ, affect both the bio and lithosphere. Subterranean waters
often are polluted by the waste sites that are being in use for a
longer time period than the projected life span when being built.
Besides they are way far from complying with any of the presentday standards and regulations of the EU. The main problem, as
often is the case in the neighboring countries such as Romania and
Macedonia, is that the waters the get most pollution are those at
shallow depths and it’s exactly those waters that later on the
population uses for irrigation and other household needs. Usually
the hot thermal springs derive their water supply from currents
bellow the water proof clay materials at depths bellow 50m, and
that is one of the reasons why no serious investments are being
made to improve the situation since most of the profiting
businesses related to it remain relatively unaffected.
Since most of the ore deposits are located at relatively low
depths the mining process in general is open. The gathering can be
done without creating galleries and digging deep. As a result the
relief is heavily affected by blasting and spiral mining. This not only
destructs natural habitats but populates the air in the vicinity with
dust and disturbs the surrounding biotopes with the relatively high
noise pollution. But as always the main source of problems are the
waste waters from metallurgical industries which are quite common
on the area. There are also some coal fields, which resulted from
the compression of residual biomass that formerly lied on the floor
of the shallow seas, but the impact on the environment due to them
is almost irrelevant.
The region is famous for the Ag and Au rich ores reaching up to
9 g/tonn for Ag and 4 g/tonn for Au. Of relevant importance are the
Pb-Zn, Cu and Wolfram deposits. The main techniques for
extracting the metals are:
Froth-floating - used for sulphide ores. Oils can wet
sulphides. Oil floats on water. Sulphide ores are first ground to
powder and water is added. Then pine oil is added and the emulsion
is agitated by passing compressed air. Oil and froth float on the
surface along with the sulphide ore. The gangue particles being
insoluble in oil remain at the bottom of the water tank. The froth is
removed and allowed to settle down. This is called the froth-floating
process. This process is used for sulphide ores of Cu, Pb and Zn
Hydraulic washing - done by washing the ores with
streams of water. If an ore is heavier or denser than the gangue,
then the gangue particles are washed way with the stream. The
heavier or denser ore particles remain behind and can be collected.
Hydraulic washing is done for ores that have tin or lead, as they are
found to be heavier than the gangue
Chemical Separation – usually applied for Ag and Au.
Some foreign companies are now planning to exploit new sites by
using Arsenic which although is far more efficient than any other
method is extremely toxic to the environment and would require the
construction of special isolated dump sites for the residual
production. Local population is in general against the usage of this
element although the investing companies ensure to follow and
even perform better than the required by the current EU
regulations.
The problem is that because of the economical strain that the
country’s industry is going through the last 15 years most of the
facilities for ore processing can no longer maintain the previous
level of contamination control and often it happens that the residual
waters are dumped directly into the river waters, which in general
are considered to be suitable for consummation since their pH level
varies in the range of 6,6 to 7,3, but after being contaminated with
mining industry residuals present a serious threat. On a couple of
occasions a very small mine for Uranium ores had accidental leeks
into one of the feeder flows of river Maritza which endangered all
life along the stream even beyond the national border since that
river flows out to Greece. Fortunately the amounts released were
too small to inflict any relevant and long lasting effects on to the
environment.
But after all what the Rhodopes are most popular about from
geological point of view are the unique rock formations. The so
called “Rock mushrooms”, the “Rock wedding”
the “Rock window”, the “Pyramids of Kardjali” and the “Golden
Bridges” are an absolute must for any tourist visiting those
mountains and a trip to them is included in the packages of all
companies offering touring services. Most of those forms are
products of compression of volcanic ash sediments that were
deposited on the sea floor around 50Ma back in the Eocene.
Weathering of the unequally hardened layers of the riolite tuffs
produced the strange forms that commonly resemble the shape of a
mushroom.
Average size veries between 2,5x2,5x2,5m and 15x7x10m (Wide x
Long x Tall). Coloration in yellowish, pinkish and rusty are usually
due to the inclusion of iron and manganese oxides, seladonite
mineral is responsible for the greenish shine.
Of great importance are also some of the caves in the eastern
Rhodopes, seven of which are already declared national natural
treasure. Most of them were formed, as usual, in sedimentary rocks
by natural processes of erosion reaching depths of approximately
650m. On average they are divided into 3 floors. They host unique
species of animals on a global scale. In the “Tilkin” and “Karangil”
caves is the only place in the world where you can find the blind
cave beetle and the cave spider (Centromeros Milleri) which spend
their entire life inside the cave without ever seeing daylight. Other
caves such as the “Karabekirova” where hosting prehistoric men
during the neolite. Drawings and primitive bone and rock tools were
found inside along some bone fragments of early humans. Other
caves like “Snejinkite” (The snowflakes) and the “Brujlianina” found
implication in the more recent history as being included in the
architecture of some fortresses by the end of first millennium A.D.
There are composed of a number of smaller caves interconnected to
each other by small passages. The length of a single extremity
exceeds 150m. Artificial caves called “The labyrinth” were formed in
the interval I-III century A.D. because the site was exploited for
gold mining by the Romans. The galleries are horizontal and reach
up to 450 into the rock.
The most relevant feature linked to the geological past of the
Rodopi Mountains is the sacred Thracian city Perpericon.
It is
distinguished to be among top ten of the world’s most important
relics of the ancient civilizations along with Stone Hendge, Machu
Piccho and the Egyptian pyramids. It represents a sanctuary
complex entirely made of rock blocks with no cementing material
inbetween and incisions into the surrounding rock. The earliest
sings of culture there are traced to be from the late Neolite. The
upper part of the the Acropolis is surrounded by a 2,8m thick wall
The site is currently being restored and new roads and
supporting infrastructure is being built around so that in the near
future it can become one of the main points of interests for tourism.
As presented in this report the Rhodopi Mountains and
especially their eastern part represent an unique collection of
geological features which led to the development of many
formations of cultural, biological and industrial importance both on
national and international scale. Although some parts of it have
already been declared as preserved areas the restrictions that the
law imposes over such parks mostly govern the usage of the
biogenic products and have little or no relevance to the preservation
of the geological records stored there. That is why I believe that if
taking into account the importance of the region this should be a
first among candidates when a law for geological parks is
introduced.
References:
http://www.bgd.bg/geology04.htm
http://annual.mgu.bg/2003/bg/svityk1/svityk1_contents.
htm
http://www.bgd.bg/istoria1.htm
http://kardjali.bg/?pid=5,24
http://www.bankwatch.org/issues/eib/nhwc/downloads/ei
a-resume_bg_revised_last_not_marked-bg.pdf
http://www.bluelink.net/water/zbr/mesta/hidrolojko_opis
anie.htm
http://home.att.net/~cat6a/metals-IX.htm
http://www.kardjalionline.com/docs/kardjali_county_info.doc
http://www.journey.bg/bulgaria/bulgaria.php?guide=425