GEOLOGIJA 40, 241-245 (1997), Ljubljana 1998
Granites of Straža and their sedimentary roof
(SW Serbia)
Graniti Straže i njihova sedimentna povlata
(JZ Srbija)
Zlatko Radovanović, Danica Popović, Radmilo Jovanović & Divna Jovanović
Geological Institut "Gemini",
Karadjordjeva 48, YU-11000 Belgrade
Key words: granite, roof rocks. Lower Triassic age, non-melange tectonic setting
Ključne reči: granit, povlatne stene, donjotrijaska starost, nemelanžna tektonska
građa
Abstract
In many localities on N, NE and SE hillslopes of Murtenica Mt. several varieties
of red granites are exposed. The roof rock of granites consists of different Lower
Triassic sedimentary rocks which discordantly overlie the granites. They are the
Kladnica clastites Fm., Seisian clastites. Bioturbate Fm. and Conglomeratic sand-
stones and conglomerates.
Apstrakt
Na S, SI i JI padinama planine Murtenice na više lokaliteta pojavljuju se različiti
varijeteti crvenih granita. Povlatu granita čine razni tipovi donjotrijaskih sedime-
nata koji preko njih leže diskordantno. To su: Klastiti Kladnice, Sajski klastiti,
Bioturbatna formacija i Konglomeratični peščari i konglomerati.
In many localities on N, NE and SE hillslopes of Murtenica Mt. (section Kokin Brod,
1:25000) were noticed and studied small masses of granites-granitoides named the gra-
nites of Straža. Earlier, they have never been investigated in more detail. The authors
consider the age of granites to be Lower Triassic (T e r z i c, 1957; Markovi ć, 1968),
Neogene (Ć i r i ć et al., 1980), Carboniferous, or older than Carboniferous, and the
rock intensively tectonically reworked (K a r a m a t a et al., 1996). In our investiga-
tions we studied some new features of the granites. The outcrops are mostly in the vi-
cinity of villages Ljubiš, Gornja Bela Reka, Jasenovo and Ojkovica (Fig. 1), and in lo-
calities Cmi vrh, Gornja ravan, Jadžici and Žunici, on hills Zabrdje and Brkovica
glavica, on N hillside of Karaula and in the Metaljka area (Kučani). The localities of
granite exposures are mostly covered, so the relations between granites and overlying
formations are difficult to observe. They are usually disintegrated to grus, but better
242
Zlatko Radovanovid, Danica Popović, Radmilo Jovanovid & Divna Jovanović
Fig. 1. Geographie position and geology of Murtenica Mt.
1 Diabases and spilites; 2 Bedded limestones of Jurassic age;
3 Olistostrome melange; 4 Limestones of Triassic age;
5 Volcanic-sedimentary Sirogojno Formation; 6 Bioturbate
Formation; 7 Conglomeratic sandstones and conglomerates;
8 Granites
SI. 1. Geografski položaj i geologija planine Murtenice
1 Dijabazi i spiliti; 2 Slojeviti krečnjaci jurske starosti;
3 Olistostromski melanž; 4 Krečnjaci trijaske starosti; 5 Vul-
kanogeno-sedimentna formacija Sirogojna; 6 Bioturbatna
formacija; 7 Konglomeratični peščari i konglomerati; 8 Gra-
niti
preserved rocks are found in localities Zabrdje and Brkovica glavica. Strong tectonic
movements and blocky composition (blocks are separated by vertical faults) are typi-
cal for this area (Radovanovid et al., 1996). Some authors consider granites of
Granites of Straža and their sedimentary roof__243
this area as blocks-olistoliths in the Diabase-Cherty Formation (K aramata et
al., 1994). However, we found the granites in tectonic position with "rigid" unmelan-
ged, bedded limestones of Jurassic age (Jovanovc et al., 1994; Radovanović
et. al., 1996). These various rocks (i.e. granites and bedded limestones of Jurassic age)
were brought to the same level along vertical faults, and their olistostromal character
is excluded.
Granites and granitoids occur in small masses of metric to decametric dimensions
in numerous localities. They are characterized by red colour of various intensity de-
pending on size and types of mineral grains, and can be easily recognized in the field.
They are often cataclastic, even schistose and weathered to grus.
At Straža occur biotitic granites with porphyroidal quartz diorites and elongated
lenses of pegmatites. The porphyroidal quartz diorites are dark red coloured with
phenocrysts of plagioclase and microlites of plagioclase, biotite, amphibole, clino-
pyroxene, small quantities of quartz and alcaline feldspars. Small, partly resorbed
enclaves of quartzites are noticed. In the vicinity of village Spasojevici fine-grained,
dark red coloured porphyroidal granodiorites are exposed which gradually pass in
coarse-grained varieties. In the granitoid mass of Mumlavski potok (Hajdučka voda)
occur homblende-biotitic granites and granitoides. In the Zabrdje locality leucocra-
tic granites are cut by small masses of light red coloured aplites. The metamorphic
roof rock of granites was not found till nowadays.
As roof rocks of granites-granitoids appear various types of sedimentary rocks of
the Lower Triassic age. In the investigated area four types of sedimentary roof rock
were established: the Kladnica clastites Fm., Seisian clastites, Bioturbate Fm. and
Conglomeratic sandstones and conglomerates. The covered contacts and complex
tectonic relations often prevent to establish the clear relations between granites and
the overlying beds.
The most rarely as roof rock are the Kladnica clastites Fm., found at localities Cmi
vrh, W hillslope of Zabrdje, and on road Jadžici-Jagnjilo (Žunici). At locality Cmi
vrh over granites lie red quartz conglomerates and sandstones of the channel facies
of braided river deposits (Jovanović, 1996). Paleodeposits of the braided river
channel facies are on the road Jadžici-Jagnjilo too.
The Seisian clastites (Dimitrijevic et al., 1987) only rarely appear over gra-
nites. They directly overlie granites in localities Jadžina stena, W part of Djunatovac
and S part of Brkovica glavica. They are uneven in thickness (10-30 m), and often lie
under limestones of the Bioturbate Fm. and over the Conglomeratic sandstones. They
are thin bedded (beds not thicker than 5 cm), parallel and rarely cross-laminated.
They are represented by ferruginous-carbonate sandstones that pass into sandy li-
mestones or by very micaceous sandstones. Clastites are composed of quartz grains
which are predominating (angular, undulóse, well sorted), parallel sericite concentra-
tions and Fe-calcite of euhedral shapes. The cement is silica-ferruginous or calcite-
ferruginous.
Bioturbate Fm. (Dimitrijevic et al., 1987) represents the highest level of the
Lower Triassic beds in this area, because it overlies the Kladnica clastites Fm., Seisian
clastites and Conglomeratic sandstones and conglomerates. On Straža, where they di-
rectly overlie granite, cm-accordion folds were observed (some parts of Biotiirbate
Fm. are moved over granites, some tectonically reduced). The same case occurs at lo-
cality Mumlavski potok (Hajdučka voda). The thickness of formation is less than 20 m.
It consists of very thin to thin micritic limestones partially enriched in clayey, silty or
sandy fraction, and with visible bioturbations. The limestones can be dolomitized.
244_Zlatko Radovanović, Danica Popović, Radmilo Jovanović & Divna Jovanović
Conglomeratic sandstones and conglomerates are the most frequent roof rock of
granites-granitoides. They are located on both banks of Kraljev potok, on Brdo and
Kolovoz, in Jadjići and Djunatovac, in Gornja ravan, Brkovica glavica and along the
line Ilidi-Bjeliborje. Contacts with granitic rocks are usually covered, but the mine-
rals derived from granitic rocks are clearly visible and they are distinguished from
granites with difficulty. Because of high content of feldspars they are arkosic and su-
barkosic, and characterized by red colour owing to presence of feldspars, and green
colour when chlorite is abundant. In localities Gomja ravan, Jadžina stena. Krst and
Zabrdje they are underlain by Seisian clastites and at locality Sanduk by the Biotur-
bate Fm.
Conglomerates are not compact, usually schistose, with well rounded fragments (3-
10 mm), reddish and greenish in colour. Predominate the mono- and poly crystalline
quartz and fragments of rocks: quartz sandstones, cherts, schists, shales. They are ce-
mented by sandy or silty matrix or by silica with chlorite and sericite concentrations.
Conglomeratic sandstones are often called "granitic" since their mineral composi-
tion is similar to granites (minerals of granites are reworked in this sandstones). Red
coloured fledspars are usually fragmented, sericitized or argillized. Presence of chlo-
rite caused the green colour. Besides the feldspars which give arkosic character to
rock and confirm its granitic provenance, the quartz is present (unsorted, undulated,
often corroded). The sandstones are massive, rarely banded or schistose. They can be
silicified (line Ilici-Bjeliborje), or they pass into siltstones (Jadžici and Brdo). Silica
cement with chlorite and sericite is the most common, and ferruginous matter is pre-
sent too.
Conclusion
On the basis of investigations of granites and granitoids, and their sedimentary roof
rock in the Ljubiš-Jasenovo area (Murtenica Mt.), we consider the granites of Straža
Lower Triassic or Paleozoic in age. They represent the same level as the bedded lime-
stones of Jurassic age, and have not the olistostromal character.
Graniti Straže i njihova sedimentna povlata
Na više lokaliteta, na padinama planine Murtenice uočene su i ispitane manje
mase granita-granitoida koje smo zajedničkim imenom nazvali granitima Straže.
Tereni na kojima se graniti pojavljuju su uglavnom jako pokriveni, pa je teško po-
smatrati njihov odnos sa drugim formacijama. Često su grusificirani. Ovo područje
(Radovanović et al., 1996) se karakteriše intenzivnom tektonikom i blokov-
skom gradjom (pri čemu su blokovi razdvojeni vertikalnim rasedima). Iako granite
ovog područja neki autori (К aramata et al., 1996) smatraju blokovima-olistoliti-
ma u okviru Dijabaz-rožnačke formacije, mi smatramo da su u tektonskom odnosu sa
"krutim", nemelanžiranim, slojevitim krečnjacima jurske starosti, jer su duž verti-
kalnih raseda ove različite tvorevine dovedene u isti nivo, pri čemu je isključen nji-
hov olistostromni karakter.
Graniti i granitoidne stene se pojavljuju u manjim masama m-Dm dimenzija. Odli-
kuju se crvenom bojom različitih nijansi u zavisnosti od veličine i vrste mineralnih
Granites of Straža and their sedimentary roof_	245
sastojaka, te su lako prepoznatljivi na terenu. Često su kataklazirani, čak škriljavi i
grusificirani. Kao sedimentna povlata granitskih-granitoidskih stena pojavljuju se
različiti varijeteti sedimentnih stena donjotrijaske starosti. To su: Klastiti Kladnice,
Sajski klastiti, Bioturbatna formacija i Konglomeratični peščari i konglomerati. Veli-
ka pokrivenost terena i složeni tektonski odnosi sprečavaju da se uoči jasna veza
izmedju granita i formacija koje leže preko njih.
Najredje se kao povlata preko granita pojavljuju klastiti Kladnice, predstavljeni,
npr. na lokalitetu Crni vrh, crvenim kvarcnim konglomeratima i peščarima kanalskih
facija upletenih reka (Jovanović, 1996). I Sajski klastiti (Dimitrijević &
Dimitrijević, 1987) se redje pojavljuju kao povlata granita. Leže ili direktno
preko granita, ili su često ispod krečnjaka Bioturbatne formacije, a preko konglome-
ratičnih pescara. Bioturbatna formacija (Dimitrijević & Dimitrijević,
1987) predstavlja najviši nivo donjotrijaskih krečnjaka na ovom području, jer često
leži preko sve tri pomenute formacije. Formacija je male debljine sa karakterističnim
bioturbacijama. Kao povlata granita-granitoida najčešće se pojavljuju konglomerati-
čni peščari i konglomerati. Kontakti sa granitima su obično pokriveni, ali su u njima
jasno vidljivi minerali iz granitskih stena. Zbog visokog procenta feldspata predstav-
ljaju arkoze i subarkoze. Crvenkasti su ili zeleni.
Proučavajući granite-granitoide Straže i njihovu sedimentnu povlatu na padinama
Murtenice, na teritoriji izmedju Ljubiša i Jasenova, došli smo do izvesnih zaključaka
koji su bitni za razrešavanje geologije ovog područja. Granite i dalje smatramo pre-
trijaskim, odnosno stenama paleozojske starosti. Ne smatramo ih olistolitima, jer su
izraženom tektonikom dovedeni u isti nivo kao i jurski slojeviti krečnjaci, a da pri
tom nije bilo melanžiranja.
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