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Acta Geologica Polonica, Vol. XX (202X), No. X, pp. xxx–xxx
DOI: 10.24425/agp.2020.134558
Vestiges of Cambro-Ordovician continental accretion
in the Carpathian-Balkan orogen: First evidence
of the ‘Cenerian’ event in the central Serbo-Macedonian Unit
DARKO SPAHIĆ1*, ZORAN BOJIĆ1, DANICA POPOVIĆ1 and TIVADAR GAUDENYI2
1 Geological Survey of Serbia, Rovinjska 12, 11000 Belgrade, Serbia.
2 Geographical Institute “Jovan Cvijić” of the Serbian Academy of Sciences and Arts, Djure Jakšića 9, 11000
Belgrade, Serbia.
* Corresponding author: darkogeo2002@hotmail.com; darko.spahic@gzs.gov.rs
Darko Spahić: http://orcid.org/0000-0002-5832-0782
Tivadar Gaudenyi: https://orcid.org/0000-0002-1843-2384
ABSTRACT:
Spahić, D., Bojić, Z., Popović, D. and Gaudenyi, T. 202X. Vestiges of Cambro-Ordovician continental accretion
in the Carpathian-Balkan orogen: First evidence of the ‘Cenerian event’ in the central Serbo-Macedonian Unit.
Acta Geologica Polonica, XX (X), xxx−xxx. Warszawa.
In the Balkans, the Serbo-Macedonian Unit (SMU), Serbia, is thrust bounded by the composite Tethyan Vardar
Zone and the Carpatho-Balkanides. The SMU actually emerges from beneath the Neoalpine Miocene–Pliocene
deposits. Both provenance and geodynamic position of the SMU are poorly known and still debated. This paper
reviews the data hitherto published and includes some new field data interpretations. The SMU is composed of
a Neoproterozoic–Cambrian high-grade (para- and ortho-) gneiss with peraluminous magmatic arc components
(560–470 Ma). The SMU is in the contact with Neoproterozoic upper Ordovician–Carboniferous low-grade
metasedimentary succession of an accretionary wedge assembly represented by the Supragetic basement. The
SMU basement became folded, sheared and metamorphosed around 490–450 Ma. Paleomagnetic data point to
high southern latitudes and a peri-Gondwanan position of the SMU at that time, which concurs with glacioma-
rine evidence recorded from the upper Ordovician sediments at the base of an accretionary wedge succession.
Based on the published data and field survey in the Stalać region, we correlate the SMU with the pre-Mesozoic
gneiss terrane exposed in the Strona-Ceneri zone of the Alps. This terrane, identified as the Cenerian orogen
of the Alaskan subduction type, developed at an active margin of Gondwana during middle Ordovician times.
The SMU basement, with augen and migmatitic gneisses and arc-related peraluminous magmatic bodies, de-
veloped at this margin as part of the Cenerian belt or its equivalent. Such an orogenic edifice proved transient
and in the earliest Silurian the SMU fragments drifted away being bound for Baltica (amalgamated Moesian
microplate and Danubian terrane) to which they became accreted in the Carboniferous and included in the
southern European branch of the Variscan orogen (Marginal Dacides/Carpatho-Balkanides). Despite consider-
able Variscan and Alpine reworking, the pre-Variscan, Cenerian-type crustal assembly along with an inferred
boundary between the magmatic arc and the accretionary wedge, accompanied by back-arc/forearc deposits,
are still decipherable in the Western Balkan countries.
Key words: ‘Cenerian event’; North Gondwana; Serbo-Macedonian Unit; Supragetic basement;
Lower Paleozoic paleosuture; Migmatites; Shear zones.
2 DARKO SPAHIĆ ET AL.
INTRODUCTION
The ”Caledonian North African orogen” (Balin-
toni et al. 2011a) or “Cenerian-” i.e. “Sardic event”
apparently contributed to important geodynamic as-
sembly and amalgamation of the peri-Gondwanan
lithosphere (Zurbriggen 2015; Text-fig. 1a, b). A sig-
nificantly juvenile continental crust that developed
along the northern peripheries of Gondwana (Text-
fig. 1b) underwent progressive underthrusting and
suturing which brought about a highly mobile Lower
Paleozoic marginal orogenic belt (e.g., the eastern
segment of the North Gondwana, sensu Stephan et
al. 2019). It was composed of medium to high-grade
gneiss-dominated terranes that were soon tectonically
fragmented, detached and drifted away from their
original locations in early Paleozoic times (Zurbriggen
2015). The break up and dispersal of this vast marginal
belt (Text-fig. 1a, b) resulted in the northward drift of
several generations of peri-Gondwanan terranes (e.g.,
Murphy et al. 2001, 2006; Stampfli and Borel 2002;
Murphy and Nance 2004; Nance and Linemann 2008;
Nance et al. 2010; Franke et al. 2017; von Raumer
et al. 2017; Spahić et al. 2019a, b). A complex group
of microcontinents comprised of East Avalonian and
Armorican domains with dominantly Cadomian tec-
tonic elements drifted away and became basements for
the terrane agglomeration that formed the European
Variscan Belt from Iberia to the Balkans (e.g., Aleksić
et al. 1988; Neubauer 2002; Franz and Romer 2006;
Himmerkus et al. 2009; Meinhold et al. 2010; Oczlon
et al. 2010; Zagorchev et al. 2012; Balintoni et al.
2010a, b, 2014; von Raumer et al. 2013; Keppie and
Keppie 2014; Zurbriggen 2015; Antić et al. 2016;
Spahić and Gaudenyi 2018; Abbo et al. 2019; Šoster
et al. 2020; Text-figs 1c, 2). These Neoproterozoic–
Lower Paleozoic vestiges carry the newly identified
elements of the intra-Ordovician ‘Cenerian event’,
which underwent significantly obliterating overprints
and tectonic rearrangements during the Variscan and
Alpine orogenies (e.g., Plissart et al. 2017, 2018; Antić
et al. 2016, 2017; Spahić et al. 2019a, b; Text-figs 2, 3).
The Cenerian event (accretion of “continental”
vs. oceanic lithospheres) corresponds somewhat to
the well-recognized Ordovician convergence sys-
tems, likewise the east Australian Lachlan fold belt,
Fammatian, Humberian, Taconic and Grampian
orogenies (Balintoni et al. 2011a; Zurbriggen 2015,
2017a; Stephan et al. 2019; Meinhold et al. 2011
and references therein). All these Ordovician oro-
genic systems are characterized by recycled conti-
nental crust. In contrast, the ‘Cenerian event’ has
important differences in the plate-tectonic context
(Zurbriggen 2017a). The constraints for a recently de-
scribed Ordovician “Cenerian orogeny” (Zurbriggen
2015, 2017a) are built upon the crystalline vestiges
embedded within a pre-Variscan basement assem-
blage in the Swiss- and Italian Alps (Strona-Ceneri
zone; Franz and Romer 2006; Zurbriggen 2015; Text-
fig. 2). The Strona-Ceneri zone, interpreted as a ter-
rane of northern Gondwanan descent, is comprised
of (1) paragneiss having pelitic and greywacke proto-
liths, (2) banded amphibolites (metaandesites) and (3)
abundant peraluminous orthogneisses. Both litholog-
ical contacts and foliation planes in the orthogneisses
are moderately to steeply dipping and involved in
km-scale folds with generally steep axial planes
and fold axes. The vestiges of the Lower Paleozoic
Cenerian orogeny in the Swiss and Italian Alps are
interpreted as an analog of the modern-day Alaskan
type accretionary orogen (Zurbriggen 2015, 2017a).
The Alaskan model of the pre-Variscan geodynamic
mechanism of encrustation and crustal growth offers
an alternative to the well-established orogenic-type
convergent plate margin model. The ‘Cenerian event’
illustrates a protracted amalgamation of an ancient
continental crust above peri-Gondwanan subduc-
tion zones (overriding position; Text-fig. 1a, b). The
culmination of crustal growth/amalgamation oc-
curred during the Ordovician (defined as the “Intra-
Ordovician event”; Text-fig. 1a).
The aim of this work is to examine whether in the
Western Balkans/Balkans/Northeast Mediterranean
allochothonous crustal inlier, known as the “Serbo-
Macedonian Massif” or Serbo-Macedonian Unit
(SMU), which is mainly composed of gneisses with
peraluminous magmatic signature and carries wide-
spread records of Neoproterozoic–Ordovican mag-
matism and anatexis (Table 1), may be comparable
to the Strona-Ceneri terrane as revealed in the Alps.
The SMU arcuate gneiss-dominated terrane is ex-
posed in Central Serbia, Bulgaria, North Macedonia,
Greece (Text-figs 1, 2 and 3). The examination and
tectonic reconstruction have been mainly based on
literature sources and completed by field observa-
tions made in the Stalać region, Serbia.
THE ‘CENERIAN EVENT’
A cluster of Neoproterozoic peri-cratonic north
Gondwana-derived microcontinents interacted with
former Rodinian cratons up to early Paleozoic times
(Unrug 1997; Murphy et al. 2004, 2006; Kearey et
al. 2009; Text-fig. 1a). Erosion of the Neoproterozoic
Pan-African orogenic hinterland coupled with a pro-
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 3
Text-fig. 1. a – Late Ordovician (ca. 450 Ma) configuration of continents redrawn after Zurbriggen (2014 and references therein). The ‘Cenerian
belt’ is represented as a segment of a much larger Cambro-Ordovician active margin along the north Gondwana. Rodinian cratonic segments
included. b – Reconstruction of Gondwana in the Cambrian showing the main Serbo-Macedonian Unit. Location of peri-Gondwana Terranes
modified after Stampfli et al. (2002). Abbreviations: AA – Austro-Alpine, Ad – Adria, DH – Dinarides-Helenides, Is – Istanbul zone, SM –
Serbo-Macedonian. SGU – Supragetic basement. c – Distribution of the peri-Gondwanan terranes within the European basements westward
of the Trans European Suture zone (TESZ). Red arrow pinpoints the area of the Serbo-Macedonian Unit. Modified after Balintoni et al. 2014
and references therein.
4 DARKO SPAHIĆ ET AL.
Text-fig. 2. Distribution of Avalonian-Cadomian peri-cratonic microcontinents embedded into what is now Western-Central-southeast Europe,
showing the basement units of the South Carpathians (inset from Draguşanu et al. 1997) and east Serbia. The Alpine-overprinted Carpathian-
Balkan segment documents a section of the Rheic suture. The position of the investigated pre-Variscan suture is at a considerable distance
relative to the main Variscan convergence system which is closer to western Moesia.
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 5
tracted secondary erosion of exhumed metamorphic
basements in the continental interior (e.g., north-cen-
tral African cratons; Avigad et al. 2017; Text-fig. 1b)
enabled voluminous clastic sediment supply into the
adjoining proarc foredeep (subduction zones). Once
transported and incorporated into a nearby subduction
trench, huge inflows of clastic material (“mud pile”),
were amalgamated to produce large-scale near-craton
agglomerations of emerging Cambro-Ordovician con-
tinental crust (Zurbriggen 2017a). Unlike modern-day
subduction processes, the ongoing Lower Paleozoic
subduction was under the influence of the immense
infill of clastic material. During the subduction of a
downgoing slab, mantle-derived magmas were ini-
tially emplaced into the unconsolidated clastic ma-
trix, which had an overriding position (accumulated
on top of the subducting plate). This process allowed
episodic emplacement of rising magma into the over-
riding clastic sequence, and amalgmation and piece-
meal growth of juvenile continental crust. Thus, the
peraluminous magmas compensated the ongoing un-
derthrusting (Franz and Kroner 2006; Balintoni et al.
2011a) affecting thermally and spatially (anatexis) the
overriding juvenile crust. Essentially, this process ex-
plains the upwards-directed magma flow and amalga-
mation of voluminous terrigenous detritus previously
transported into a foredeep. This pallet of alterna-
tive crustal growth or encrustation processes yields
a crustal reorganization (“cratonization”) referred to
as the “Cenerian Orogeny”. Though the “Caledonian
North African orogen” was recently proposed
(Balintoni et al. 2011a), the terminology used (e.g.,
“cratonization”, “orogeny”; Zurbriggen 2015) cannot
be accepted, at least not in conventional use (some-
thing also pinpointed by Zurbriggen 2015). Namely,
the investigated Cambro-Ordovician continental crust
is not the nucleus of a continent and it was not stable
because it was reworked and overprinted later on,
during the Variscan and Alpine events. Therefore, in-
stead “cratonized”, we use “newly accreted”. Because
the term “Cenerian orogeny” does not fit perfectly, as
there is no considerable wedging and crustal thicken-
ing reshaping the ancient landscapes, we rather prefer
the use of the term ‘Cenerian event’. These coalesced
peripheral North Gondwana crystalline terranes are
disconnected at the expense of protracted southward
subduction of oceanic crust (Haydoutov et al. 2010;
Nance and Linemann 2008; von Raumer and Stampfli
2008). The terrane detaching scenario offers a back-
arc mechanism for rifting, successor oceanic embay-
ment and eventual drifting off from north Gondwana.
REGIONAL TECTONIC FRAMEWORK AND
PRE-ALPINE CONFIGURATION
The geological configuration of southeast Europe
(SEE) illustrates a complex plate-tectonic interplay
of exotic peri-Gondwanan terranes and intervening
Paleozoic and Mesozoic oceans. The north Gondwana
terranes (Text-fig. 1a) subclassified as Avalonian- or
Cadomian-type are embedded into what is now: (i)
European Variscides (e.g., Franke 2006; Nance et
al. 2008; Jastrzębski et al. 2013; Kroner and Romer
‘Cenerian event’ Strona-Ceneri
zone
Serbo-Macedonian Unit
(for tectonic model and expla-
nation see discussion chapter)
1. Clastic sediment sourcing and formation of “mud pile.” (Paragneisses) documented documented
2. Syntectonic extrusion of mixed magma sources (anatexis, presence of orthogneisses) documented documented
3. Steeply structured pervasive amphibolite facies main schistosity of the orthogneisses
(moderately to steeply oriented subduction-accretion complex) documented documented*
4. Ductile deformation – folding (vicinity of accretionary wedge) documented documented
5. Syntectonic extrusion of mixed magma sources (anatexis, presence of orthogneisses) documented documented
6. Intermittent peraluminous magmatic imprints documented documented
7. No over-thickened crust documented documented
8. Different spatial position (regional scale) of the documented Variscan suture not documented documented
9. Presence of Neoproterozoic–Ordovician oceanic crust (or downgoing plate) not documented documented
10. Absence of stable craton documented documented
Table 1. Comparison between the Strona-Ceneri zone and the Serbo-Macedonian Unit. The numbers on the left indicate the essential features
of the “Cenerian model” from Zurbriggen (2015). Point 3* indicates a high probability that foliation recorded within Serbo-Macedonian Unit
is of Variscan age. In addition to the essential features of the model of Zurbrieggen (2015), the different spatial position (regional scale) of the
documented Variscan suture is highlighted for the Serbo-Macedonian Unit. Moreover, the presence of Neoproterozoic–Ordovician oceanic crust
(or downgoing plate) adjoining the Serbo-Macedonian Unit is documented.
6 DARKO SPAHIĆ ET AL.
2013; Žák and Sláma 2017; Stephan et al. 2018,
2019; Golonka et al. 2019), (ii) south European Eo-
Cimmerian Minoan terranes (Franz et al. 2005;
Zulauf et al. 2007, 2014, 2018; Zlatkin et al. 2014;
Dörr et al. 2015) including (iii) East Mediterranean
basements (e.g., Ustaömer et al. 2011; Koralay et al.
2012). In between, (iv) a few considerably large seg-
ments of these late Pan African to Early Paleozoic ter-
ranes are incorporated in Alpine Europe – its central
domain (e.g., Winchester et al. 2002; Scheiber et al.
2014; Zurbriggen 2015; Siegesmund et al. 2018; Arboit
et al. 2019; Text-fig. 1). Alpine Europe includes the
Southeast European (SEE) Carpathian-Balkan arc.
Despite significant Variscan accretionary incorpora-
tion into the west Moesian (micro)craton (e.g., Plissart
et al. 2017, 2018; Jovanović et al. 2019; Spahić et al.
2019) that was succeeded by the polyphase Alpine
overprint, these SEE inliers host important yet undoc-
umented evidence of a disputed plate-tectonic interval
connecting the Cadomian orogeny in the Ediacaran–
early Cambrian (Linnemann et al. 2007, 2014) with
peculiar Lower Paleozoic events (Meinhold et al. 2 011
and referen ces therein).
The Mesozoic Alpine configuration is comprised
of the following tectonic units/zones: the ALCAPA
(Alps and West Carpathians), Southern Alps, Tisza,
Pelagonides (i.e. External Hellenides) and South
Carpathians/Carpatho-Balkanide terrane amalga-
mation (Supragetic/Getic or Supragetic/”Kučaj”,
Danubian and Moesian Euxinic craton; Text-figs 1c,
2, 3) including the NNW-SSE striking Serbo-Mace-
do nian Unit (Text-fig. 3a). The latter basement inlier
partially belongs to the Inner Hellenides, striking
alongside the western Rhodopean Massif (divided
by the Strymon fault/Kerdylion Detachment; e.g.,
Kydonakis et al. 2015). The opposite western side of
the Serbo-Macedonian Unit occupies the Neotethyan
composite paleosuture (Vardar Zone) and the Dina-
rides of the Adria microplate (e.g., Dimitrijević 1997,
2001; Csonotos and Vörös 2004; Text-fig. 3a). Any
pre-Alpine correlation of the Carpathian-Balkan oro-
gen is hampered as most of these inliers are con-
cealed beneath a cluster of displaced Tethyan assem-
blages and overlain by late Alpine Neogene strata.
Thus, despite a significant effort (Dimitrijević 1997;
Neubauer 2002; Kräutner and Krstić 2003; Schmid et
al. 2008, 2020; Jovanović et al. 2019), there is no com-
prehensive tectonic correlation capable of unambigu-
ously connecting the Alpine units and their basement
inliers between the Romanian South Carpathians, the
Carpatho-Balkanides in eastern Serbia and western
Bulgaria. Even the Alpine tectonic inheritance of
the Serbo-Macedonian Unit remains unconstrained
(for comments see Spahić and Gaudenyi 2018, 2020;
Jovanović et al. 2019).
The Serbo-Macedonian basement inlier is now ex-
posed externally as the upper allochton along strike
of the arcuate Carpathian-Balkan basement amalga-
mation of the Alpine orogenic system (bent around
the Moesian microcontinent once accreted to the
southwestern Baltica margin (Text-figs 1c, 2 and 3a,
b). That exotic Cadomian-type terrane (Antić et al.
2016; Spahić and Gaudenyi 2018), with widespread
Neoproterozoic to Tertiary magmatic and metamor-
phic imprints, connects the South Carpathians in the
north (Romania; e.g., Iancu et al. 2005; Balintoni et
al. 2010a, b, 2014) and the Balkanides in the south-
east (Ograzhden Unit; Bulgaria; e.g., Zagorchev et al.
2012, 2014, 2015; Text-fig. 1c). Its southern segment
strikes across North Macedonia and Greece (Inner
Hellenides; including its analog in the orthometamor-
phic Vertiskos Unit; Himmerkus et al. 2009; Meinhold
et al. 2010; Abbo et al. 2019; Text-figs 1c, 2, 3). The
investigated segment of the Serbo-Macedonian high-
grade metamorphic agglomeration (Serbia; a combi-
nation of para- and orthometamorphics; Text-fig. 4)
is in overprinted tectonic contact with a similar-aged
subordinate greenschist-facies metamorphosed ocean-
floor assembly (ancient olistostroms desposited on the
ocean floor; Haydoutov et al. 2010) referred to as the
Supragetic basement, the former “Vlasina Unit” (sensu
Spahić et al. 2019b). An alternative interpretation of
that unit as a separate terrane (Serbo-Macedonian vs.
Supragetic) was discarded by earlier authors because
of the transitional/gradational (non-tectonic) contact
between the greenschist-facies rocks and gneisses
observed in northeastern North Macedonia, area of
the Kratovo sheet, 1: 100,000 (N-NE section of the
map; Geološki zavod Skopje 1968; see explanation in
Dimitrijević 1997). A similar opinion was reported
much earlier, describing the gradual transition of the
‘Lisina Series’ to higher-grade gneisses near Vlasina,
southern Serbia (Pavlović 1977).
In eastern Serbia and southwestern Romania, an-
cient vestiges of the Alpine basement inliers are clas-
sified as a collage of tectonometamorphic/tectonos-
tratigraphic agglomerations or “terranes” docked
onto the Moesian microplate of Amazonian-Avalo-
nian provenence (Baltican promontory) (Text-fig. 3a).
The Serbo-Macedonian Unit represents a high-grade
crystalline unit comprised mainly of gneisses, biotite-
and mica-schists, migmatites along with quartzites,
quartzitic-graphitic schists, amphibolites, marbles,
calc-schists and isolated occurrences of eclogites
(Kalenić 2004; Text-fig. 4). Some recent authors place
the high-grade metamorphic imprint in the Cado mian
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 7
Text-fig. 3. a – Main tectonic units surrounding western Moesia: Carpatho-Balkanides of Serbia/South Carpathians of Romania (Danubian,
Getic/”Kučaj”-Supragetic), Serbo-Macedonian Unit, Vardar Zone, Dinarides, Hellenides, Pannonian basin (modified after Schmid et al. 2008;
inset from Kounov et al. 2011). b – Location map, main outcrops of the Serbo-Macedonian Unit and Supragetic basement in Serbia (inset from
Dimitrijević et al. 1967).
8 DARKO SPAHIĆ ET AL.
framework (Zagorchev et al. 2012), whereas the main
process of migmatitization is placed within the pro-
tracted Variscan orogeny (Antić et al. 2017 and refer-
ences therein).
The Supragetic basement (former “Vlasina Unit”),
a greenschist-facies crystalline unit representing a
mixture of sericite schists, calc-schists, and actinolite
schists as remnants of basic ophiolite-bearing rocks,
is accommodated at the opposite, eastern side (Text-
fig. 3a, b) of the Serbo-Macedonian Unit (Spahić et al.
2019b). The questionable greenschist-facies retrogres-
sion supposedly occurred in the Early Jurassic (Antić
et al. 2017). The contact between the two inliers of
the Serbo-Macedonian Unit and the Supragetic base-
ment is severely overprinted by the Variscan, Alpine
and Neoalpine cycles (Dimitrijević 1997, pp. 114–115;
Haydoutov and Yanev 1997; Erak et al. 2016; Spahić
et al. 2019b and references therein). A Neoproterozoic
(detrital zircons; Antić et al. 2016) to earliest Ordo-
vician age of the Supragetic basement (southeas-
tern segment in Serbia) is documented. Namely, the
youngest documented age of the Supragetic basement
(or “pre-Ordovician Vlasina Unit” of Antić et al.
2016) is Tremadocian, constrained by the remarkable
discovery of an inarticulate colder climate Obolus and
Lingullela brachiopod fauna (‘Lisina Series’; Pavlović
1962; see also in Spahić et al. 2019b). More to the
east, the Bulgarian analog of the Supragetic basement
is the so-called Balkan ter rane or “Morava Nappe”.
The Balkan/Thracian terrane concept describes the
Lower Paleozoic interface zone investigated here as
the “Thracian ophiolite suture”. This suture (topic of
this study) is characterized by an island-arc associa-
tion (Neubauer 2002) comprised of a sedimentary and
volcanic complex (Haydoutov et al. 2010, fig. 1).
To the north, basement units with a similar met-
amorphic overprint (like the Serbo-Macedonian
Unit) exist in themore internal crystalline units of
the Romanian South Carpathians. The Getic unit
carries the Sebeş-Lotru terrane subdivided onto the
Cumpăna and Lotru subunits (Balintoni et al. 2009,
2010b). These agglomerations are characterized by
an Ordovician accretionary event comparable to the
“Cenerian” (Balintoni et al. 2011a). The Danubian
unit of Avalonian inheritance is comprised of much
the older Făgeţel augen gneiss from the Drăgşan
terrane basement of 803.2±4.4 Ma age (Balintoni et
al. 2011b; Spahić and Gaudenyi 2018). These base-
ment inliers continue into the east Serbian Carpatho-
Balkanides (Text-figs 2, 3a). The most external
Serbo-Macedonian crystalline agglomeration ex-
tends farther across western Bulgaria as the analog
known as the Ograzhden unit (e.g., Zagorchev and
Milovanović 2006; Zagorchev et al. 2012). The Serbo-
Macedonian analog or the Ograzden unit/Thracian
terrane of Bulgaria contains abundant anatectic gran-
ites (Zagorchev et al. 2014; for a configuration com-
parison see Spahić and Gaudenyi 2018). The Serbo-
Macedonian Unit stretches further throughout North
Macedonia and terminates in Greece as the Vertiskos
basement (Himmerkus et al. 2009; Meinhold et al.
2010; Text-fig. 3a). In North Macedonia, in addition to
the Serbo-Macedonian Unit, there is another peculiar
Lower Paleozoic gneiss-dominated unit overthrust on
top of the latter (Dimitrijević 1997; Antić et al. 2016;
Šoster et al. 2020). This basement unit often referred
to as the ‘Easter n Veles Series’ is nothing more than
a displaced segment of the Serbo-Macedonian Unit
during the late Alpine convergence (Savezni Geološki
Zavod 1970; Robertson et al. 2013; Antić et al. 2 016;
Spahić et al. 2019a; Text-fig. 3a). The ‘Eastern Veles
Series’ is a “segment” of the ‘Veles Series’ (sensu
Spahić et al. 2019a; Šoster et al. 2020). In Greece,
the age of this gneiss-dominated crystalline belt is
growing younger to become of Upper Ordovician
to Ordovician age (dominant orthogneiss with leu-
cocratic two-mica gneiss; Abbo et al. 2019). This
recently introduced Ordovician age is favorable in
comparison to the previously imposed Silurian age
(Himmerkus et al. 2009; Meinhold et al. 2010). The
aforementioned age bracket has similarities with the
Neoproterozoic–Silurian eastern South Alpine base-
ment (explained by the up-section age variations due
to a temporal change in provenance; Arboit et al.
2019). In the eastern Mediterranean, the rocks of simi-
lar age which include an almost complete pre-Variscan
sedimentary sequence (from Ordovician) are referred
to as the Istanbul terrane, whereas the Zonguldak ter-
rane records a hiatus between Silurian and Devonian
sequences (Ustaömer et al. 2 011) .
RESULTS
This chapter represents a stepwise compilation
of the field structural observations (including litho-
stratigrahy) juxtaposed onto the documented Variscan
paleosuture accommodated within the region. The
outcropping areas of the Serbo-Macedonian Unit
in Serbia expose several complexes of high-grade
crystalline rock units (for a review see Dimitrijević
1997; Kalenić 2004; Spahić and Gaudenyi 2020 and
references therein; Text-fig. 3a, b): (i) the Crni Vrh
and Batočina area with dominant gneiss and mica
schist, marbles, quartzite and amphibolite gneiss
(Kalenić 2004), (ii) the Juhor area with dominant
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 9
two-mica schist, gneiss and a zone of migmatites,
Stalać (investigated area, see further in the text),
(iii) the Crna Čuka and Jastrebac with high-grade
metamorphic gneiss which include mylonites devel-
oped between the two gneiss-dominated segments
of the Serbo-Macedonian Unit (Rakić et al. 1969).
At localities Vidojevica-Pasjača and Jablanica, the
Serbo-Macedonian Unit includes several metamor-
phic zones with migmatites, and the presence of
kyanite-sillimanite with a dominance of fine-grained
gneiss. An orthometamorphic protolith with a U-Pb
age of ~500 Ma is reported in the Vučje gneiss (per-
aluminous granite; south of Leskovac; Zagorchev
and Milovanović 1998; also in Vukanović et al. 1974,
1977; Text-fig. 3b). An overview of the magmatic
episodes is available in Neubauer (2002), Antić et al.
(2016) and a recent summary of Abbo et al. (2019).
In most outcrops in Serbia, the rocks of the Serbo-
Macedonian Unit represent metamorphosed psam-
mitic-pelitic deposits (shallow to deep-water, prob-
ably of turbiditic origin/accretionary wedge). These
mica-rich gneissic rocks ocassionaly record blas-
topsammitic texture (Cvetković 1992; also in Kalenić
2004) and alternate with orthogneisses being of
Neoproterozoic to early Paleozoic age. Biotite gneiss
is recorded with blastopsammitic texture comprised
of poorly rounded granitoid, gneiss and quartz grains
(Batočina area; Text-fig. 3). Accordingly, such texture
marks short material transport within a highly mobile
gneiss-granodiorite system (Cvetković 1992). The or-
thogneisses reveal different geochemical signatures
(e.g., Zagorchev and Milovanović 2006; Antić et al.
2016; see details in chapter 3.2.3). In central Serbia,
the Ediacarian–Cambrian transition is documented
by the stratigraphically lower-positioned graphitic
schists (fossil vesicles of algae Archaeofavosina sim-
plex Naum; Kalenić et al. 1975; Kalenić 2004). The
age of the Serbo-Macedonian Unit covers the earliest
Neoproterozoic to early Cambrian time span (Kalenić
et al. 1975; Deleon et al. 1972; Antić et al. 2016) reach-
ing the Ordovician (documented in southern Serbia,
also in Bulgaria as the Ograzhden unit; Zagorchev et
al. 2015) and the Republic of North Macedonia.
Rock units over a considerably large area (ca.
30 km in width; Text-fig. 4) in the central segment
of the Serbo-Macedonian Unit have been surveyed
for deformation of Paleozoic i.e. pre-Alpine age. This
area carries the evidence of (1) Neoalpine (Neogene)
extensional episode, (2) Alpine (late Cretaceous–
Paleogene) contractional episode inclusive nappe
stacking, (3) late Paleozoic foliation and (4) a root-
less paleosuture with no ophiolites. Nevertheless, a
late Paleozoic, ophiolite-decorated Variscan suture
is documented to the northeast of the investigated
area (Plissart et al. 2018; Spahić et al. 2019; Text-
fig. 1). In order to isolate the Variscan overprints
from expectedly Cenerian features, the study defines
the essential differences between the two Paleozoic
paleosutures, which includes time-constraints on the
formation of these two essential structural elements:
(i) age of widespread penetrative foliation and (ii)
indications for apparently rare pre-Variscan ductile
deformation. The Variscan age of the former is also
suggested for a more southern segment of the Serbo-
Macedonian Unit in SE Serbia (Antić et al. 2017),
and, in general, is accepted for the whole crystalline
entity (Table 2).
Stalać area: Lithostratigraphy and paleosuture
indicators
The core section of the exposed lower crust is
accommodated toward the Supragetic unit (to the
east). The basement geology is however obscured by
several localized Neogene basins (Dimitrijević 1997)
and a veneer of Quaternary deposits (Rakić et al.
1969; Krstić et al. 1974; see the geological map or
Text-fig. 4 and following mapping units: Miocene
(M), Miocene–Pliocene (M+Pl), and Quternary (Qt).
The investigated central segment of the Serbo-
Macedonian Unit is comprised of gneisses and am-
phibolites, occasional augen gneisses, dominant two-
mica paragneisses, sporadically occurring granite
gneisses and locally exposed spectacular migmatites
(Rakić et al. 1969; Dimitrijević 1997; in older liter-
ature these rocks are referred to as the “ectinites”,
sensu Levinson-Lessing and Struve 1963; Text-fig. 4).
Sporadically, the gneiss-dominated matrix includes
HP/HT eclogite lenses exposed with the associated
structural imprint (Krstić et al. 1974; Text-figs 4, 5a–
d, 6 and 7). The presence of metasedimentary quartz-
ites and carbonates (marbles, calc-schists) documents
the presence of the important parametamorphic se-
quences. On the contrary, the Serbo-Macedonian an-
alog in Greece, referred to as the Vertiskos unit, is
comprised entirely of orthometamorphites (Abbo et
al. 2019). The protolith ages of Serbo-Macedonian
crystalline rocks exposed in the Stalać area (Text-
fig. 5a–d) or the Juhor-Stalać Mts. yield a lowermost
Cambrian to Lower Ordovician age (541 to 475 Ma;
Deleon et al. 1972). The dominantly clastic sequence
probably belongs to an elongated marginal basin
supplied with immense amounts of terrigenous ma-
terial (with late Pan-African Cambrian–Ordovician
sources; e.g., Bahlburg et al. 2009; Meinhold et al.
2013). The clastic material contains minor detrital in-
10 DARKO SPAHIĆ ET AL.
put from the remote cratonic basement (e.g., Saharan
metacraton; Avigad et al. 2017; Text-fig. 1b). The doc-
umented presence of older North African cratonic
elements suggests the northward paleodirection of
sedimentary transport across the junction with the
north Gondwanan realm (North Africa).
The stratigraphically higher marbles are reported
to be of early Cambrian age (primitive marine fossil
algae Zonosphaeridium absolutum Timofeev, Proto-
leiosphaeridium sigillarium Andreeva; Kalenić et
al. 1975). The biostratigraphic age is similar to the
aforementioned Rb-Sr data (Deleon et al. 1972). The
Text-fig. 4. Geological map of a wider area of the Stalać-Kruševac area, slightly modified after Rakić et al. 1969, sheet Kruševac, 1: 100,000;
Krstić et al. 1974, sheet Aleksinac, 1:100,000). The position in the regional-scale shown in Text-Fig. 3b. The map exhibits an outcropping
segment of the gneiss-dominated Serbo-Macedonian Unit surrounded by a Mio-Pliocene veneer. Explanation is in the text.
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 11
metamorphic event occurred at temperatures ranging
between 550 and 600°C and a pressure of ca. 6 kb
(Batočina area; 488 Ma; Balogh et al. 1994). Another,
similar age early Paleozoic metamorphic imprint is
recorded within the Ograzhden unit, southwestern
Bulgaria (Zagorchev et al. 2014). The P-T values in
rocks of the Batočina segment are characterized by a
garnet-staurolite-kyanite assemblage in gneisses and
mica schists and by epidote-hornblende-garnet in
amphibolites. According to the mineral assemblages,
this part belongs to the deeper crust (garnet-kyanite
level, Zurbriggen 2015).
Eclogites (E; Text-fig. 4) are locally distributed
in lenses that crosscut local gneiss and migmatites
(Rakić et al. 1969; Krstić et al. 1974; Text-fig. 4).
Migmatites (Mi; Text-fig. 4) occur as bodies and
tectonic zones and as lenses. Their position inter-
fingered with eclogite (the eastern edge towards the
Supragetic unit) indicates that the highest pressure
zone was later cut off by a principal Alpine fault
(Kalenić et al. 1975). The migmatites are comprised
of microcline-plagioclase gneiss. According to some
authors, the migmatites of the Serbo-Macedonian
Unit exhibit a retrogressive phase inferred from
the emplacement of garnet-oligoclase-quartz veins
and low-temperature quartz veins (Zagorchev and
Milovanović 2006).
Gneisses (G; Text-fig. 4) are fine- to coarse-
grained including spectacular augen gneisses (Text-
fig. 5a). The former is more abundant and developed
during the first phase of migmatitization (Krstić et
al. 1974). Beside oval or lenticular feldspar porphy-
roblasts (also in Buriánek et al. 2009), the gneisses
are composed of quartz, plagioclase (oligoclase to an-
desine), microcline and biotite. Feldspars are often
albitized, sericitized and kaolinitized. In the Batočina
area, augen gneisses are usually interlayered with host
metasediments with occasional occurrences of bodies
Sampling entitles Lithology Age
Ternary
geotectonic
discrimination
εHf values A/CNK vs. A/NK
classification plot
Golemo selo/Sijarinjska banja
(SM250-2 and SM250-2-019) paragneiss 562 Ma −3.3 inherited core of 3.049 Ga
indicates presence of Archean crust
Doganica metagranitoid
(Supragetic) (SM600-1) granite 562 Ma convergent
setting
(+3.7 to +2.8) higher presence of
crustal material
Lisina gabbro (Supragetic)
(SM352) gabbro 550 Ma within-plate (+3.7 to +2.8) higher presence of
crustal material
Vlajna granitoid
(SM02)
calc-alcaline gran-
itoid 558 Ma volcanic arc juvenile magma source (+12.6 and
−2.8) peraluminous
Bosilegrad (Supragetic/Struma
Unit) (SM236-1) monzonite 522 Ma volcanic arc (+12.6 to +4.2) juvenile magma
source
Božica magmatic complex
(Supragetic) (SM272-1) granite and diorite 521 Ma within-plate (+12.6 to +4.2) juvenile magma
source peraluminous
Delčevo (Supragetic/Struma
Unit) (SM140-1) granite 536 Ma magmatic arc (+12.6 to +4.2) juvenile magma
source peraluminous
Vinica*
(SM173-3) leucocratic gneiss 490 Ma volcanic arc
(granites) (+18. to +6.9) new crust peraluminous
Maleševski Mts. (Ograzhden
i.e. Serbo-Macedonian Unit)
(SM184-1)
orthogniess (acidic
and intermediate) 472 Ma within-plate (+4.3 to −6.2) juvenile
magma source peraluminous
Kukavica granites at Vrvi
Kobila area (Sm01)
granodiorite (acidic
and intermediate) 478 Ma within-plate (+4.3 to −6.2) juvenile magma
source peraluminous
bujanovac granite
(SM377-2) s-type granite 439 Ma within-plate (+4.3 to −6.2) mixed juvenile and
continental crust peraluminous
Štip magmatic complex
(SM195-1) 304 Ma late and
post-collisional
(+4.3 to −6.2) mixed juvenile and
continental crust signature of the
melt
peraluminous
Novo Brdo schists
(KOS02) Micaschists
Maximum
deposition
at 255 Ma
For peak ca. 560 Ma: +3.7 to −2.8;
higher presence of crustal material
Table 2. Summary of the main peraluminous magmatic rocks of Cenerian relevance emplaced into the Serbo-Macedonian Unit (older vs. juve-
nile crust). Numeric data taken from Antić et al. (2016), reinterpreted. Color code indicates magmatism associated with each phase: light red
(Neoproterozoic-lowermost Cambrian), blue-green (uppermost Cambrian–Ordovician), green (Silurian), light green (uppermost Carboniferous
= Pennsylvanian).
12 DARKO SPAHIĆ ET AL.
separated by sharp contacts (Balogh et al. 1992). The
paragneiss sequence is characterized by a linear fab-
ric on the foliation, defined by parallel quartz-feldspar
rods set in a dominantly mica-rich matrix (Text-fig.
5d). The biotite content decreases in the gneiss bodies
or gneiss-granites (Text-fig. 4, mapping unit ¥Pz2;
Krstić et al. 1974). The main gneiss-dominating ma-
trix is, however, crosscut by gneiss-granites of early
Carboniferous age (ca. 350 Ma; Deleon et al. 1972;
Text-figs 4, 5c). These Variscan gneiss-granites attest
the Variscan interference in almost the entire Serbo-
Macedonian Unit. Importantly, in a comparison with
the main Serbo-Macedonian high-grade assembly,
these Variscan gneiss-granites exhibit no developed
foliation fabric (Text-fig. 4).
Pegmatite intrusions of early Paleozoic age (Text-
fig. 4, mapping unit øPz1; Krstić et al. 1974) are abun-
dant at the wester n realm of greater migmatitic bodies
probably documenting progressively formed diatex-
ites. A set of intruded pegmatite bodies illustrates
rather steeply inclined syn-magmatic structures.
Amphibolites (A; Text-fig. 4) are not widespread.
These rocks occur as elongated bands in the eastern
segment of the Stalać complex, near the eclogites,
and in the form of isolated ribbons. The protolith
appears to be magmatic mafic rocks (Zagorchev
and Milovanović 2006) set in a sandy-clayey ma-
trix (Krstić et al. 1974). According to the SiO2 and
(K2O+Na2O) content in amphibolites of the Batočina
area, these rocks were alkaline basalts (prior expo-
sure to the metamorphic event) and correspond to
subalkaline within-plate tholeiites (Cvetkovic 1992).
The upper crustal level rocks represented by a mix-
ture of quartzites, biotite gneisses, marbles and gra-
phitic gneisses, were overprinted by low-pressure/
high-temperature amphibolite facies metamorphism,
very similar to that recognized in the much older
Lainici-Păiuş Group (Lower Danubian; Liégeois et
al. 1996 and references therein).
Plate boundaries late in the early Paleozoic
and in late Paleozoic (Variscan) times
To specify and distinguish the imprints of the
Variscan and the alternative lower Paleozoic paleosu-
ture, a detailed comparison of the structures associ-
ated with late Paleozoic Variscan and early Paleozoic
terrane amalgamations is provided. The paleogeogra-
Text-fig. 5. Example of rock formations within the investigated area: a, b – Augen gneiss. c – Granit-gneiss. d – Mica-rich gneiss with a pen-
etrative foliation.
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 13
phy and pre-Alpine (dominantly Variscan) provenance
of these terranes (e.g., Krstić et al. 1996; Winchester
et al. 2006; Himmerkus et al. 2009; Haydoutov et al.
2010; Oczlon et al. 2010) were inferred from detailed
petrology/geochemistry, biostratigraphic, structural
and occasional radiometric age data (Aleksić 1977;
Liégeois et al. 1996; Krstić et al. 2005; Iancu et al.
2005 and references therein; Haydoutov et al. 2010
and references therein; Jovanović et al. 2019; Antić
et al. 2017; Plissart et al. 2018). Late Paleozoic re-
constructions were also based on the occasionally
discussed sedimentary provenance (Balintoni et
al. 2009, 2010, 2013, 2014; Himmerkus et al. 2009;
Antić et al. 2016; Abbo et al. 2019). The scarce paleo-
magnetic data of these stacked pre-Variscan exotic
low- to high-grade Pan-African basement terranes
show higher early Paleozoic Southern Hemisphere
latitudes and lower latitudes during Carboniferous
amalgamation (Milićević 1996; Ebner et al. 2010; for
details see table 1 in Spahić et al. 2019).
A reconstruction of Paleozoic active margins
in the Balkans is hindered by significant Alpine
interference and nappe stacking. Nevertheless, the
amalgamated Carpathian-Balkan basement terranes
expose the position of the pr incipal Variscan paleosu-
ture (Liégeois et al. 1996; Haydoutov and Yanev 1997;
Seghedi et al. 2005; Gerdjikov et al. 2010; Kounov et
al. 2012; Iancu and Seghedi 2017; Plissart et al. 2018;
Spahić et al. 2019b; Text-fig. 2). Moreover, the data
indicate that prior to the well-documented Variscan
amalgamation of the Carpathian-Balkan basement
terranes, an older Ordovician thermometamorphic
event occurred. Of particular importance are imprints
recorded within the Neoproterozoic to Ordovician
Sebeş-Lotru unit (South Carpathians; Balintoni
et al. 2010b; U/Pb Concordia age of 550.7±1.7 Ma
by Balintoni and Balica 2013; Text-figs 2 and 3a),
Serbo-Macedonian Unit (Central Serbia; magmatic
and detrital zircons including the numeric age by
Antić et al. 2016; Text-fig. 3b), analog Ograzhden
unit (south-western Bulgaria, Zagorchev et al. 2014)
and a segment in Greece (magmatic and detrital zir-
cons including numeric age by Meinhold et al. 2010;
Abbo et al. 2019).
Variscan paleosuture
The evidence of HP-HT records in the SEE base-
ment inliers may provide an insight into the deeper
levels of the Variscan orogenic belt and its suture.
Such data can also provide vital differences relative
to the ‘Cenerian event’. Vestiges of the dominant
Variscan paleosuture are marked by (meta)mafic rocks
scattered across (1) the peri-Moesian Variscan realm
(Text-figs 2, 8b), (2) the west Moesian paleosuture or
“Carpathian segment” (Kounov et al. 2012; Plissar t
et al. 2017, 2018; Spahić et al. 2019b and references
therein) and (3) the Moesian microplate or “Balkan
segment” that abuts against the Rhodopean Massif
further south (e.g., Arkadakskiy et al. 2003; Carrigan
et al. 2005; Plissart et al. 2018 and references therein).
In Serbia, records of regional thermal imprint,
sampled from the central part of the Serbo-Mace-
donian Unit (apatite fission track), indicate a rapid
cooling through the zircon and apatite partial anneal-
ing zones during the late early Cretaceous and early
late Cretaceous (Antić et al. 2015). In the area of Vrvi
Kobila (Text-fig. 3b), 40Ar/39Ar thermochronology on
mus cov ite yield s early Carbo nife rous (350.73±1.22 Ma)
and Permian ages (250.913±1.07 Ma; numeric age by
Antić et al. 2017). These exhumation data coupled
with the st ructural observations constrain the Variscan
involvement of the subordinate Supragetic basement
and Serbo-Macedonian Unit. Importantly, the inves-
tigated ‘Cenerian’ paleosuture is positioned remotely
relative to the Variscan front (Text-figs 2, 3a, 8b).
This configuration of Variscan event implies a
paleo-northwards subducting plate beneath Moesia
and closure of the Paleozoic ocean(s) (e.g., Haydoutov
et al. 2010; Franke et al. 2017; Spahić et al. 2019a).
The protracted Variscan suturing ultimately pro-
duced voluminous acidic syn- and post-orogenic im-
prints (Cherneva and Georgieva 2005; Haydoutov et
al. 2010; Jovanović et al. 2019; Deleon et al. 1972;
Antić et al. 2016; Text-fig. 8b). The Moscovian/
Kasimovian latitude is 5°N (flora analyses by
Pantić and Dulić 1991; paleo-latitudes by Milićević
1996). The Variscan paleosuture is ophiolite-deco-
rated (Text-figs 1d, 2) associated with the Danubian
Unit (Devonian ophiolites; Plissart et al. 2017). The
nearby Osogovo-Lisets magmatic arc amalgamation
(560–540 Ma; Kounov et al. 2012; Text-fig. 3a) is
significantly older and consists of amphibolite, mica
schists, muscovite-biotite and amphibole-biotite
gneiss with ophiolitic protoliths (Frolosh Formation
or “Diabase-Phyllitoid Complex”). The Osogovo-
Lisets is intruded by gabbrodiorites and younger leu-
cogranites belonging to the Strouma unit.
Lower Paleozoic subduction-accretion complex:
The reactivated interface between the Serbo-
Macedonian and Supragetic basement
Apart from the Stalać crystalline Serbo-Mace do-
nian block investigated, another rare exposure of the
contact between the Serbo-Macedonian Unit with the
14 DARKO SPAHIĆ ET AL.
subordinate Supragetic basement is in the Jastrebac
Mts. (Central Serbia). The reactivated disjunctive
zone, composed of chloritic schists, mica schists, in-
cluding quartzites, actinolitic schists, amphibolites
and gneisses, was obliterated by a late Cretaceous
extensional detachment (Erak et al. 2016). Severe
Variscan and Alpine overprints elevated this ancient
interface, which fits with the initially interpreted
boundary between the ‘Thracian’ and ‘Balkan’ ter-
ranes (Haydoutov 1989; Haydoutov and Yanev 1997;
Yanev et al. 2005; Haydoutov et al. 2010).
North of the Danube River (the administrative
boundary between Serbia and Romania; Text-fig. 2),
in more external segments of the South Carpathians,
there is a continuation of this unconstrained pa-
leosuture (Iancu and Seghedi 2017). The nearby
Cumpăna unit (a segment of the Sebeş-Lotru terrane;
Text-fig. 3a; sensu Iancu et al. 2005) consists of or-
thogneisses characterized by distinctive migmatitic
structures, paragneisses, metabasites and meta-ultra-
basic layers, including rare eclogites. The eclogites
are of Variscan age (Medaris et al. 2003; Balintoni et
al. 2010b and references therein). Two samples of or-
thogneiss from the Cumpăna unit yielded U-Pb zircon
crystallization ages of 458.9±3.5 Ma and 466.0±4.2
Ma (Balintoni et al. 2010b). Migmatitic structures, au-
gen gneisses and rodded gneisses are found together
with eclogites that were derived from metabasic pro-
toliths of unknown age (Medaris et al. 2003). High-
pressure granulites and amphibolites may represent
the overprinted eclogites. The relative depletion of Nb
and Zr suggests a craton-proximate tectonic setting
(Drăguşanu et al. 1997), similar to that proposed for
the Cenerian system.
The investigated interface between the Serbo-
Macedonian unit and the Supragetic basement steeply
bends towards the southeast (Bulgaria), further
striking to the east (Kraishte) and having the form
of the aforementioned “Thracian ophiolite suture”
(sensu Haydoutov et al. 2010). This suture is char-
acterized by a mixture of sedimentary and volcanic
complexes and illustrates the “Ordovician orogeny”
(Haydoutov et al. 2010). In the Vertiskos terrane in
northern Greece, early Silurian crystallization ages
of the basement granites, based on the magmatic in-
ternal structure of the zircon grains coupled with
trace-element and isotope geochemistry, show either
a magmatic-arc setting with the presence of pre-ex-
isting Silurian continental crust (Himmerkus et al.
2009) or the grains were more recently introduced as
a segment of Ordovician crust (zircon U-Pb LA-SF-
ICP-MS zircon geochronology; Meinhold et al. 2010;
U-Pb-Hf and rutile U\Pb data, Abbo et al. 2019). The
presence of or the trace of Early Paleozoic welding
in the Hellenic part of the Inner Hellenides (if any)
remains unknown (and should not be expected).
*
The essential difference between the two dif-
ferent paleosutures is their modern-day locations.
The one more internal is the peri-Moesian Variscan
suture (with abundant Paleozoic ophiolite vestiges;
Plissart et al. 2017, 2018), whereas the ‘Cenerian’
rootless lithospheric scale boundary is positioned
within the external flank of this Carpathian-Balkan
nappe stack (Text-fig. 8b; see also Haydoutov et al.
2010). The modern-day distance between the two
principal Paleozoic tectonic entities is ca. 100 km
(Text-fig. 2). Despite the important Alpine interfer-
ence in the Variscan configuration, there is no evi-
dence of any “Caledonian” interference (unlike the
situation within the Penninic pre-Alpine basement,
sensu Scheiber et al. 2014).
Recycled continental crust of the Cenerian
relevance
The more recent paleogeographic and deep
crustal lithotectonic reconstructions are based on the
Lu/Hf isotopic signatures from basement units and
on ages and possible sources of detrital zircons in
Neoproterozoic–Lower Paleozoic metamorphic rocks
(e.g., Balintoni et al. 2010b; Antić et al. 2016; Abbo
et al. 2019). The presence of late Neoproterozoic in-
herited zircon cores, detrital grains and xenocrysts
with εHf values between +7.5 and −18.3 (694–580
Ma) within the Serbo-Macedonian Unit has been de-
scribed as originating in a basement comprised of
magmatic and sedimentary rocks comparable with
a Neoproterozoic magmatic arc distributed along
the length of the northeastern margin of Gondwana
(Neubauer 2002; Antić et al. 2016). The transi-
tion into the postdated Ordovician juvenile crust
is marked by the negative εHf values (εHf(t) = -3)
from granitic augen gneiss and mylonitic granite
gneiss (εHf(t) = (−7.9)-(−2.8) of ca. 460 Ma peak
documented within the Greek segment of the Serbo-
Macedonian Unit; Abbo et al. 2019). A moderate el-
evation in εHf(t) values is observed in the igneous
basement rocks. The Serbo-Macedonian high-grade
agglomeration car ries a geochemical f ingerprint
marking reworked crust and depleted mantle-derived
magmas. A mixed juvenile and continental crust sig-
nature of the melt is marked by the lower εHf values
for the zircons, whose age range revolves around the
Lower Ordovician (numeric values by Antić et al.
2016; Table 2). The Kukavica granite (478 Ma), the
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 15
coarse-grained Bujanovac Qz-monzonite (439 Ma),
and the Maleševski Mts. orthogneiss have lower εHf
values (+4.3 to distributed within the fine-grained
Bujanovac granite, the granite associated with the
Štip magmatic complex; North Macedonia) includ-
ing amphibolite from the Vinica area. However, the
entire set of the latter markers is of Variscan and
tentative Eocimmerian importance (sensu Zulauf et
al. 2007, 2014, 2018). A recent study documented the
repeated recycling of the Cadomian crust interfered
with a minor juvenile crustal involvement (Serbo-
Macedonian Unit in Greece; Abbo et al. 2019).
Structural record: distinguishing Variscan
and Early Paleozoic imprints
Working in the highly complex Dinaric and Car-
patho-Balkan orogenic areas which experienced mul-
tiple overprinting (orogenic) episodes, a pioneering
geologist measured the folded and often transposed
foliation fabric (i.e. its b- or fold axis as markers of
the Variscan episode; Đoković 1985). Such pioneering
work contributed to the deciphering of an overprinted
structural style that included Alpine orogenic inter-
ference (Geological map of SFRY; 1:100.000). The
Variscan (Đoković 1985; Antić et al. 2017; Plissart et
al. 2018) and Alpine cycles are succeeded by Neogene
or Neoalpine overprinting (see Table 3 for details).
The Neoalpine stage is additionally marked by
strike-slip tectonics (Fügenschuh and Schmid 2005;
Marović et al. 2007; Burchfiel and Nakov 2015; Antić
et al. 2017). Unfor tunately, the possible imprints of the
Cadomian Pan African event well-documented across
the Eastern Mediterranean (e.g., Koralay et al. 2012
and references therein) and postdating the ‘Cenerian’
event have not been distinguished.
For the reconstruction of important pre-Variscan
developments, it is of vital importance to emphasize
Deforma-
tion age /
Tectonic
unit
Alpine and Neoalpine
(Late Cretaceous–
Paleogene and Early
Miocene–today)
Variscan event
(Early–Middle Carboniferous)
‘Cenerian event’
(Lower Paleozoic to Ordovician)
Serbo-Macedonian Unit
(medium- to high-grade gneiss)
Dimitrijević 1997: Extensional faults
Antić et al. (2017):
(1) The main foliation and migma-
ti zation are of Variscan age;
D1 Initial Variscan imprint is related
to isoclinal folding commonly
pre served as up to decimeter-scale
quartz-feldspar rootless fold hinges.
D2 is associated with general
south-eastward tectonic transport
and refolding of earlier structures
into recumbent meter- to kilometer-
scale tight to isoclinal folds.Stages
D1 and occurred in close sequence.
The age of these two ductile
deformation stages was constrained
to the Variscan orogeny based on
indirect geological evidence (ca.
408–ca. 328 Ma).
Spahić et al. this paper:
(1) Foliation is of probably Variscan age (as by Antić et al. 2017).
The pre-Variscan age of the main Cenerian-type matrix (ortho- and
paragneiss) is attested by the emplacement of the Early Paleozoic
pegmatites and gneiss-granites of Variscan age (Text-fig. 4);
(2) Orthogneiss may have been sheared/mylonitized and then
folded and migmatized; The foliation-parallel shear band, should be
formed prior the foliation;
(3) Documented presence of the “Cenerian” upper crust:
Paragneiss, amphibolites, with the rare occurrence of the preserved
ductile folds, shear zones. The vergence of the “Z-type” folds fits
with the statistical b2 (Text-fig. 6c). The shear zone (Text-fig. 7a)
is folded that might indicate the development prior the penetrative
foliation;
(4) Presence of large-sale folding (similar to Strone-Ceneri zone)
can be attested by the documented sub-horizontal fold axis of
“Z-type folds” or presence of sub-horizontal displaced shear zones;
Supragetic basement
(greenschist-facies
rocks)
(2) Dimitrijević 1997: Irregular foliation dips in all
directions, presuming triclinic fabric. (we presume the
Alpine rearrangement of the foliative fabric);
Krstekanić et al. (2018): Foliation underwent Alpine
restructuring in Lower Cretaceous;
Dimitrijević 1997: Transposition of S-surfaces, folded axial
cleavage, preserved remnants of fold hinge;
(5) Haydoutov et al. 2010: Within the “Thracian suture” (more
internal segment of Carpathian-Balkan belt) explaining that the
subduction zone was inclined to the SW under the Gondwana edge.
This scenario is validated by the proposed Serbo-Macedonian Unit
/ Supragetic model). The volcanic rocks of the arc were formed at
the onset of the Ordovician (490 Ma), while its earliest intrusions
were in the beginning of the Cambrian (550–540 Ma). The results
are fitting into the Cenerian interval.
Concluding
remarks
Strong evidence of
significant Alpine
overprint of the
Supragetic basement
Mild Alpine overprint of Serbo-
Macedonian Unit (formation of
large antiforms and synforms).
Foliative fabric is of Variscan age.
Ductile imprint (shear zone / poorly preserved shear bends) precede
dominant Variscan foliation within the Serbo-Macedonian Unit.
The structural parameters (vergence of “Z-type folds) apparently
favor the Variscan style.
Table 3. Summary of the three principal orogenic and imprinted deformations documented hitherto. Ductile imprint (shear zone / poorly pre-
served shear bends) precede the dominant Variscan foliation within the Serbo-Macedonian Unit. The structural parameters (vergence of “Z-type
folds) apparently favor the Variscan style.
16 DARKO SPAHIĆ ET AL.
the tectonic origin of the principal penetrative folia-
tion embedded within the gneiss matrix. The base-
ment units adjoining the Variscan suture (near the
tip of western Moesia) are characterized by a dom-
inant mylonitic foliation (Plissart et al. 2018). More
externally from the Moesian Variscan front (Text-
fig. 1c), in the Serbo-Macedonian Unit, folds in the
foliation planes are reported to have a SW-vergence
(Kalenić et al. 1975). Such a structural pattern with
overprinted dominant foliation fits to the Alpine
shortening framework. Variscan developments are
suggested for a more southern segment of the Serbo-
Macedonian Unit in SE Serbia, near Vrvi Kobila
(Antić et al. 2017; Text-fig. 3b). In the vicinity of
Leskovac, nevertheless, (Text-fig. 3b), there is locally
documented evidence of two generations of foliation
fabrics. The principal gneiss-dominated matrix is in-
truded by a ca. 500 Ma old peraluminous magmatic
body (according to the protolith) exhibiting two gen-
erations of metamorphic foliations (Zagorchev and
Milovanović 2006). The second, most likely younger
foliation pattern (Variscan or Ordovician?) obliquely
intersected the older system (Vučje gneiss).
Foliation
As mentioned earlier, the dominant structural
record within the investigated gneiss-dominated
succession is a well-developed penetrative foliation
(Text-figs 4, 5, 6 and 7). The investigated area has
a dominant penetrative foliation (S2; Text-fig. 6) of
the preferred ca. 90° dip-direction (in particular
within its eastern flank; Text-figs 4, 6a). Analyses
of Schmidt’s diagram equal-area lower hemisphere
projection exhibits a statistical gently plunging tight
asymmetrical fold with differently oriented limbs,
(Text-fig. 6a, b). Unlike the neighboring crystalline
blocks (with an NNW-directed Alpine fabric), folds
in the vicinity of Stalać exhibit the E-vergence thus
fitting into the Variscan style. The observed foli-
ation S2 exposes scarce cm-scale folds including
foliation-parallel shear bands (Text-fig. 7e, f, h).
Presumably, the shearing (disrupted shear bands) pre-
ceded the foliation, whereas both structural elements
were subsequently overprinted (likely in transitional
brittle-ductile conditions; Text-fig. 7h, rC’).
This presence of a large overturned fold (Limb1
and Limb2; Text-fig. 6c) with the pole maximum of F1/
Sf1 (266/40) indicates a moderate inclination towards
the E-NE (Limb1 86/60). Another maximum can be
connected to a shallow-dipping inclination of one of
the limbs 226/69 or Limb2 46/31. The statistical fold
axis (13/26) has a shallow-to-moderate dip angle, di-
rected towards NNE (fits with the Variscan pattern).
Such low-angle fold axis attests the presence of larg-
er-scale regional folds. It should be noted that such a
folding fabric is in line with the measurements across
the southern realm of the Serbo-Macedonian Unit in-
terpreted as an early Variscan involvement (Antić et al.
2017). However, the interpreted age of the deformation
Text-fig. 6. Schmidt’s diagram lower hemisphere projection of
the foliative fabric and b-axis of minor folds, segment of Serbo-
Macedonian Units (locations of data collected in Text-Fig. 4). a –
Diagram exibits the two major peaks of foliation poles indicating
the presence of folds (area in the vicinity of eclogites). b – Diagram
exibits the three major peaks of foliation poles indicating probable
Alpine interference. c – Diagram of the b-axis of the observed over-
turned folds. Rotation between the Variscan and Cenerian b-axes
goes over 90°. Further explanation within the text.
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 17
i.e. the penetrative foliation recorded within the Serbo-
Macedonian Unit is tentative (Antić et al. 2017).
The third maximum (Sf3; Text-fig. 6b) illustrates
a dissipation towards E-SE, indicating a probable ro-
tation at the expense of subsequent brittle deforma-
tion events of Alpine age.
Shear zone and evidence of ductile folding
The crystalline rocks of the Serbo-Macedonian
Unit in the Stalać area contain very rare evidence
of folding in ductile conditions (f lank towards the
Supragetic unit). The position of the investigated duc-
tile structures is remote relative to the Vrvi Kobila
shear zone (Vrvi Kobila shear zone is of tentatative
Variscan age; Antić et al. 2017; Text-fig. 3b). These
folds (e.g., fold axis b1 = 164/12) represent exposed
“Z-type” open folds, rootless hinges of parasitic folds
(Text-fig. 7a, b). Apparently, these folds seem to be
tectonically coupled with the folded shear zones. The
rocks also include the presence of a naturally sec-
tioned hinge area exposing folded leucocratic laminae
within orthogneiss (Text-fig. 7c, d). The interpreted
vergence of the “Z-type” folds is towards the ENE.
The “Z-type” subhorizontal fold axis corroborates the
presence of larger folds spatially rearranged during
the subsequent deformational stage. Importantly, at
the same outcrop (Text-fig. 4; point# mRIF), com-
plete small-scale open folds are observed (Text-fig.
7e, f). These features are embedded into and within
the gneiss-dominated matrix i.e. the foliation (Text-
fig. 7h). The fold axes of these small-scale overturned
folds are moderately inclined towards the SSE (Text-
fig. 6c). The observed spatial arrangement seems to
be a result of two compressional (folding) events.
Alternatively, two single-stage compressional pat-
terns were generated in ductile and near brittle-ductile
transitional conditions (the fractures observed as in
Text-fig. 7c indicate brittle-ductile conditions).
The shear zone(s) are observed along with small-
scale “Z-type” parasitic folds which further include
the presence of overturned folds. The tectonic condi-
tions produced the foliation fabric that superimposes
the small-scale shear bands. A narrow shear zone is
marked by the opposite orientation of the limbs of the
small-scale folds (green and yellow points or fold axes
positioned inside small-scale overturned folds; Text-
fig. 7a, b). Thus, these two ductile features could be
regarded as precursory to the e.g. Variscan foliation,
marking a tentative (initial) layering-parallel shearing
associated with two discrete shortening episodes.
The regional shortening evident corroborates a
compressional setting during the early Paleozoic (as
suggested by Balintoni et al. 2011a; Zurbriggen 2015,
2017a; Stephan et al. 2019). The early Paleozoic age
of the main Serbo-Macedonian matrix is well docu-
mented, hence comparable compressional configura-
tion could also be interpreted as post-early Paleozoic
orogen-parallel shearing (in both the Variscan and
Alpine configurations; e.g. Antić et al. 2017; Table 3).
To moderate uncertainty, the age of the local mag-
mato-tectonic developments and its spatial relation-
ship (crosscutting nature of pegmatites and Variscan
gneiss-granites; Text-fig. 4) is further emphasized.
Lower Paleozoic pegmatites and upper Paleozoic
(Variscan) granite gneisses
Despite ambiguous age of the investigated scarce
ductile features, the emplacement of granite proto-
liths of gneisses (numeric age ca. 350 Ma by Deleon
et al. 1972) attests to the pre-Variscan age of the main
Serbo-Macedonian Unit. The best preserved intrusive
contact relationships (Text-fig. 3) is within the inves-
tigated Stalać segment (Text-fig. 4). Another import-
ant analogy with the Cenerian subduction-accretion
model is the well-documented early Paleozoic ana-
texis in the form of pegmatite intrusions (¥Pz1; Text-
fig. 4). Magmatic foliation being concordant with the
intrusive contacts and main schistosity (Zagorchev
and Milovanović 2006) is the third reliable argument
for a syntectonic intrusion. Nevertheless, further
study of structural elements is highly recommended.
DISCUSSION
The following reconstruction is aimed at showing
that lithospheric-scale models during the ‘Cenerian’
early Paleozoic interval can be tested against geo-
logical records preserved far from their original
continental margins (Serbo-Macedonian Unit and
Supragetic basement). To qualify the early Paleozoic
paleogeographic and tectonic model that involved the
‘Cenerian event’, we integrated the rare local (i) Rb-Sr
geochronological determinations (Deleon et al. 1972)
with (ii) records of regional-scale Ordovician im-
prints (e.g., as in the Sebeş-Lotru metamorphic unit;
Balintoni et al. 2010b). The study incorporated (iii)
the already documented peraluminous character of
some of the Neoproterozoic–Lower Paleozoic S-type
granites (Antić et al. 2016). The reconstructed early
Paleozoic paleosuture outlines a flanking peri-Gond-
wanan configuration of welded oceanic lithosphere
(Supragetic basement) beneath newly “cratonized”
crust (Serbo-Macedonian Unit; Text-fig. 1a).
18 DARKO SPAHIĆ ET AL.
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 19
‘Cenerian’ North Gondwanan tectonic and
paleogeographic framework
The ongoing debate considering an “intra-Or-
dovician orogeny” revolves around the so-called
Cenerian or “Sardic” plate-tectonic event in North
Gondwana. The ‘Cenerian event’ overlapped with
the formation of the nearby Hirnantian ice sheet
(ca. 443 Ma; Stephan et al. 2019). In addition to
the Cadomian orogen (Neoproterozoic) and cratonic
sources, erosion beneath the Hirnantian ice sheet ap-
parently enabled another episode of voluminous sup-
ply of terrigenous detritus. The ‘Cenerian event’ has
been interpreted as the result of: (1) a far-field effect
due to the coeval collision of Baltica with Avalonia;
(2) the “Cenerian Orogeny” (with Alaskan-type sub-
duction-accretion as a modern analogue) or as (3)
a localized compressional expression due to strain
partitioning during the Cambro-Ordovician exten-
sion. Thus, the paleogeographic framework and
mechanism of growth of these, later dislodged Peri-
Gondwanan Avalonian- and Cadomian-type crustal
fragments is validated (see Balintoni et al. 2011a, for
a discussion; Text-fig. 1a). As presented, the mag-
matic and sedimentological, geochemical and age
data (very similar to the Strona-Ceneri zone), rare
field structural measurements, including the differ-
ence in position with regards the SEE segment of
the Variscan paleosuture, show a strong fit with the
‘Cenerian event’.
The formation of the Serbo-Macedonian
(continental) crust: Reconstruction of
the ‘Cenerian event’
The following early Paleozoic (Cambro-Ordo vi-
cian reference frame) paleotectonic and stratigraphic
sections are tested by a stepwise comparison with
the archetype model proposed by Zurbriggen (2015).
The alternative Serbo-Macedonian encrustation
model incorporates the important geochronological
and geochemical data. The following early Paleozoic
reconstruction further includes the scarce database of
paleocontinental detrital sources. To facilitate track-
ing of the stepwise Cambro-Ordovician subduction
setting proposed here, we suggest to use the location
map or Text-fig. 3a, b of this paper, and fig. 2 of Antić
et al. (2016 ).
Voluminous peri-Gondwanan clastic sediment
sourcing (point#1, Zurbriggen 2015) is reflected by
protoliths of Neoproterozoic–Cambrian meta sedi-
men tary rocks. The sedimentation age of 550–480 Ma
proposed for the Strona-Ceneri zone (Zurbriggen
2017a) is also reported from the Serbo-Macedonian
Unit (maximum depositional age of ca. 560 Ma with
a prominent early Paleozoic peak at ca. 460 Ma). The
presence of blastopsammitic structure with preserved
poorly rounded grains (including gneiss grains them-
selves) indicates two important findings (Batočina
series dated by Archaeofavosina simplex Naum;
position in Text-fig. 3b). The pre-metamorphic sed-
iment-sourcing event (protolith of the main gneiss-
dominated matrix) unambigously occurred prior to
the formation of the presumably Variscan foliation.
Moreover, short sediment transport (Cvetkovic 1992;
also in Kalenić 2004) from proximate Neoproterozoic
sources can also be depicted. Abundant olistostroms
(Haydoutov et al. 2010), including the postdated
‘Lisina Series’, piled up on the top of the Supragetic
basement document the infill age of the subordi-
nate Tremadocian trench (biostratigraphic age of the
‘Lisina Series’; Pavlović 1962, 1977). The Cumpăna
metamorphic sequence (northern analog unit; parag-
neisses) exhibits approximately the same depositional
maximum (Balintoni et al. 2010b). In the paleogeo-
graphic context, the peri-Gondwanan affinity is ad-
ditionally documented by paleomagnetic data that re-
vealed high latitudes in the early Paleozoic (Milićević
1996). Indeed, the cyclic sourcing of terrigeneous
material restarted in the early Ordovician supply-
ing tidal-controlled shallow Tremadocian deposition
(metaconglomerates, metasandstones, metagrey-
wacke, subgreywacke, all documented within the
neighboring “Supragetic/Kučaj unit” or Supragetic/
Getic; Banjac 2004; see Spahić et al. 2019b). Ongoing
sourcing of clastic material shifted into very shallow
Text-fig. 7. Rare ductile structural fabric of the investigated segment of the Serbo-Macedonian Unit. a, b – Examples of the first discovery
of open small-scale “Z-type” folds in outcrop scale (point colors differentiate the opposite curvature around a shear zone. Dashed sense line
implies that the observed shear zone possibly extends further towards the root of the outcrop and deeper. The subhorizontal axial planes ad-
ditionally indicate the presence of larger-scale folding. The shear zone (between the green and yellow dots) underwent folding. The process
of deformation of the orthogneiss (Text-fig. 4 a, b, position in Text-fig. 3) towards sheared/mylonitized and then folded and migmatized rock
depicted on Text-fig. 6. c – An example of densely folded migmatitic gneiss exposing the hinge area in a leucocratic lamina. Red lines designate
abundant “Z-type” folds, whereas pale red lines represent localized brittle-ductle fractures. d – An example of the foliation in gneiss-matrix. e, f,
h – An example of the outcrop scale asymmetric small-scale open folds. The spatial elements of the axial plane fit with the heavily overprinted
C-fabric (shear bend): The irregular foliation somewhat follows the S-fabric. The schematic diagram (to the left of h) indicates the shortening
episode, i.e. the reactivation of the precursory shear zone (shear bend). The reactivated rC’’ fabric is in agreement with the syn-compressional
development of the foliation. g – Transition of the penetrative foliation into the quartz augen and the presence of a quartz-bearing boudinage.
→
20 DARKO SPAHIĆ ET AL.
shore sedimentation, with a documented prograda-
tion to become fine-grained in the late Ordovician
(effect of the Hirnatian inland ice). However, the
Serbo-Macedonian segment records no lower to mid-
dle Ordovician rocks (unconformity; Spahić et al.
2019b; Text-fig. 4). The Upper Ordovician with its
fine-grained deposition occupied deeper sections of
the continental margin positioned in the present-day
eastern Serbo-Macedonian Unit (Kučaj and Homolje,
East Serbia; Krstić and Maslarević 1998; Banjac 2004
and references therein). Voluminous sourcing of ster-
ile, non-fossiliferous clastites (in particular those of
middle Ordovician age; age by Đajić 1996) may indi-
cate an onset of high-latitude Ordovican glaciation in
the hinterland (Text-fig. 8a). Likewise, the presence of
1.1–0.95 Ga detrital zircons in the Golemo Selo parag-
neisses and Izvor micaschists (North Macedonia;
Antić et al. 2016) in the ‘Eastern Veles Series’ (an
analog of Serbo-Macedonian Unit, Text-fig. 3a) marks
the vicinity of Northeast African Gondwana sources
(sensu Meinhold et al. 2013; Avigad et al. 2017) .
As mentioned earlier, the first evidence of ac-
cretion underneath this steeply structured composite
terrane (Serbo-Macedonian hanging wall) or defor-
mation D1 proposed by Zurbriggen (2015; Point #2)
could somewhat be documented by the occurrence
of rather scarce ductile imprints. The foliation planes
in the vicinity of the amphibolite lenses dip steeply
(Text-fig. 4). However, according to our opinion, the
spatio-temporal relationship of the foliation and its
origin recorded with the main gneiss matrix needs
further investigation in both cases, the Strona-Ceneri
zone and the Serbo-Macedonian Unit. Nevertheless,
the overriding position (hanging wall) of the Serbo-
Macedonian Unit can be documented by the addi-
tional HP/HT imprints: (i) the scarce ductile shear
zones, overprinted relics of shear bends and (ii) the
underthrusting position of the Supragetic ocean-floor
assembly (see later in the text).
The Lu-Hf isotopic composition of Neoproterozoic
to Cambrian zircons depicts a mixture of crustal-
(Doganica granite and Lisina gabbro; Struma unit)
and more juvenile Neoproterozoic–Lower Paleozoic
magma sources (Vlajna, Bosilegrad, Božica, Del-
čevo; Text-fig. 3b). This combination marks the
important fore-arc setting proposed by Zurbriggen
(2015; Point #3; Ustaömer et al. 2005). Such bimodal
magma sourcing can be associated with a segment of
the late Cadomian active margin (earliest Cambrian).
Mixing of basalts and crustal rocks in a volcanic sys-
tem has been also documented within the Cumpăna
sequence (Sebeş-Lotru terrane; sensu Drăguşanu et
al. 1997).
The phase of dominant (latest Cambrian) peri-
cratonic synorogenic sediment sourcing (Zurbriggen
2015; phase#4) is corroborated by a detrital zir-
con peak of ca. 488 Ma. Such timing corresponds
to the tectonometamorphic episode and the initial
metamorphic imprint (Serbo-Macedonian gneiss in
the Batočina area; 488 Ma numeric age by Balogh
et al. 1994). A second imprint occurred in the late
Ordovician (454.2±2.1 Ma; numeric age by Zagorchev
et al. 2014). The proposed “synorogenic magmatic
activity” (meaning the peak of magmatism piercing
newly amalgamated continental crust) is documented
by the emplacement of within-plate tholeiitic basalts
in middle–early late Ordovician times (Golemo Selo
in Serbia, and the Vinica and Vlajna granite-gneiss;
450 Ma, Dimitrijević 1997). Importantly, similar crys-
tallization ages of 458.9±3.5 Ma and 466.0±4.2 Ma
are documented within the Cumpăna metamorphic
unit (Balintoni et al. 2010b). Emplacement of mafic
magmas preserved in the scarce amphibolites (in
particular those located in the more southern Serbo-
Macedonian segment) exhibits the involvement of
intermediate magmatic rocks, gabbro diorites, with-
in-plate tholeiites and within-plate alkali-basalts. The
mixing of downgoing sedimentary/clastic material,
protracted magmatic activity and anatexis contributed
to the amalgamation of the new (peri)cratonic crust
(sensu Zurbriggen 2015). The investigated Serbo-
Macedonian block contains ribbons of amphibo-
lite-facies metamorphic rocks and eclogite (similar to
the Strona-Ceneri zone in the Swiss Alps). However,
eclogites are not necessarily markers of the ‘Cenerian
event’, but they are very likely good Variscan markers
(as documented across the Balkans).
Because the suggested “cratonization processes”
or the production of new continental crust do not
form an over-thickened crust (no nappe-stacking of
displaced crustal slices), there is no late- to post-
oro genic exhumation of deeper crustal levels (Zur-
brig gen 2015; Point#5). Back-arc extension or in the
Cenerian case extension of juvenile crust (Text-fig. 8a)
eventually truncated, and finally dislodged a Serbo-
Macedonian/Supragetic crustal accretionary assem-
blage from north Gondwana. A felsic early Silurian
within-plate magmatic episode (quartz monzonite in
the southwestern periphery of the Bujanovac, posi-
tion in Text-fig. 3a) could represent the marker of the
separation of the investigated subduction-accretion
complex from the craton itself (North Gondwanan
promontory). This event is probably connected with a
late opening of the eastern Rheic Ocean (Stampfli and
Borel 2002; Nance et al. 2010; Nance and Linemann
2012) or Paleotethys (Kroner and Romer 2013).
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 21
Text-fig. 8. a – Lower Paleozoic tectonic model of the Serbo-Macedonian Unit and Supragetic basement during the ‘Cenerian event’ (inset from
Zurbriggen 2014, modified). The subduction-accretion setting was followed by separation from north Gondwana in the latest Ordovician-early
Silurian. Further explanation within the text. b – The position of the ‘Cenerian continental crust’ (Serbo-Macedonian Unit) and its Ordovician
suture (inset from Kounov et al. 2012, modified).
22 DARKO SPAHIĆ ET AL.
The proposed scenario is in accord with both the
the “Cenerian Orogeny concept” or the option #2 (the
Alaskan-type subduction-accretion model) and the
regional geological configuration of the Carpatho-
Balkanides. The fit of the regional configuration is
further supported by the distant position (in pres-
ent-day reference) of the documented Variscan suture
front (Text-figs 2, 8b). The reliable paleotectonic/pa-
leogeographic/sedimentary/magmatic markers of the
recently constrained ‘Cenerian event’ are:
(i) The date of the culmination of lithospheric
accretional growth (encrustation) is bracketed for
the Cambrian–early to early middle Ordovician.
The documented Tremadocian crustal-scale entan-
glement with the Supragetic basement (in addition
to a widespread olistrome; Haydoutov et al. 2010)
provides another piece of evidence for the proposed
accretionary agglomeration/crustal configuration
(Text-fig. 8b). The ‘Cenerian-type’ crustal growth
process continued probably throughout the early
middle and tentatively upper Ordovician. The Serbo-
Macedonian/Supragetic early Paleozoic crustal ag-
glomeration was eventually interrupted by the early
Silurian separation from the back-arc position (rel-
ative to the Gondwanan hinterland). The proposed
events and timing have a good fit with the ‘Cenerian’
Ordovician event (470 Ma; Balintoni et al. 2011a);
(ii) Dispersal (from the back-arc position) is ad-
ditionally documented by a transgressive (Spahić et
al. 2019b) deep-marine, continuous succession of
latest Ordovician–Devonian age, deposited on the
top the adjoining Supragetic/”Kučaj” (or Supragetic/
Getic) crystalline basement (sensu Spahić et al. 2019b
and references therein; also in Boncheva et al. 2010).
Importantly, a Supragetic/”Kučaj” sedimentary pile
unconformably overlies the Lower Ordovician Supra -
getic basement segment. Thus, the absence of the
middle Ordovician is documented. Another impor tant
fact is that the U/Pb LA-ICP-MS zircon crystalliza-
tion age (similar to the detrital age data from Greece;
Abbo et al. 2019) yielded the middle–late Ordovician
age (Darriwilian) of the Cumpăna metamorphic unit
(Sebeş-Lotru terrane; numeric age by Balintoni et al.
2010 b).
(iii) The disputed effect of the coeval early Paleo-
zoic collision of Baltica with Avalonia can be ruled
out on the ground of at least two following factors.
As East Avalonia was in a drifting stage along with
West Avalonia prior to 420 Ma (Keppie and Keppie
2014), there was no collision that would effect any
developments along the North Gondwanan prom-
ontory. In addition, the slab-pull tectonic forces
of the remote Laurentian southern margin could
not profoundly affect the ongoing southwards-di-
rected Cambrian–early Ordovician underplating
and Cenerian-type lithospheric growth. Secondly,
the effect of the remote collision of Baltica with
(East) Avalonia at 420 Ma had no significance for
the Cenerian lithosphere because the main compres-
sional stage terminated there around 470 Ma. On the
other hand, the precursory back-arc extension and
ongoing spreading of the Rheic Ocean (ridge-push;
Murphy et al. 2008; Keppie and Keppie 2014 and
references therein) was likely to be affected by the
‘Cenerian event’ (the eastern Rheic aborted around
470 Ma; von Raumer et al. 2002; see Balintoni et al.
2011a, for a discussion).
(iv) The alternative interpretation that proposes
localized compressional expression due to strain par-
titioning during the Cambro-Ordovician extension is
not in agreement with the observed data in the Serbo-
Macedonian Unit. Namely, the proposed model pro-
vides no explanation of the multiple early Paleozoic
high-grade metamorphism (latest Cambrian–intra-
Ordovician accretionary wedging) which occurred
within this particular framework. It explains neither
why the Cenerian-type terranes are deficient with
oceanic crust, nor why there was no late early to mid-
dle Ordovician burial (which is expected to account
for the proposed back-arc extension).
CONCLUSIONS
The stepwise in-depth comparison between the
Serbo-Macedonian basement unit relative to the doc-
umented Cenerian imprints described in the Alps in-
dicates affinities of the Car pathian-Balkan basement
segment with the early Paleozoic ‘Cenerian’ orogeny.
These are as follows:
– the Serbo-Macedonian Unit originated from the
Early Paleozoic peri-cratonic segment of North
Gondwana,
– protoliths of a variety of Neoproterozoic to lower
Paleozoic metasedimentary clastic rocks reveal
initial transport from North Gondwana sources
(Cadomian orogeny and continental interior),
– the Serbo-Macedonian Unit is in tight connec-
tion with the wedged slices of Neoproterozoic–
Ordovician oceanic lithosphere (Supragetic base-
ment),
– the Serbo-Macedonian Unit is a carrier of volumi-
nous syntectonic Neoproterozoic–Lower Paleozoic
magmatism with a dominant continental crust
component,
– mobilized diatexites, which rose as plutons and in-
CENERIAN EVENT AND THE CENTRAL SERBO-MACEDONIAN UNIT 23
truded metasediments, are common in the investi-
gated Stalać region (dominant migmatites, gneisses
and locally pegmatites) and all over the Supragetic
basement (Haydoutov et al. 2 010),
– the Serbo-Macedonian Unit contains no evidence
of fragments of Precambrian cratons,
– the observed structures have moderately plunging
fold axes and
– there is no exhumation of the lower crust until the
Variscan event.
Our study enabled the distinguishing of the fol-
lowing early Paleozoic plate-tectonic processes re-
vealed in the Serbo-Macedonian Unit:
• The superposition of the lithologies of the Strona-
Ceneri zone (Zurbriggen 2015, table 1) vs. the
Serbo- Macedonian Unit (Text-fig. 4) have an al-
most identical lithological input: the percentage of
these sedimentary derived rocks is ca. 97% in area
vs. mantle-derived occupying ca. 3% in area;
• The ‘Cenerian event’ connects the ongoing sub-
duction of the Proto-Tethyan oceanic crust (Supra-
getic basement) underneath the newly accreted
continental crust (Serbo-Macedonian Unit). Both
lithospheric domains were distributed along the
length of the North Gondwanan margin (Text-fig.
8). A comparable paleogeographic configuration
is suggested by Abbo et al. (2019 and references
therein);
• The age of the ‘Cenerian event’ in this part of south-
eastern Europe most likely spanned ca. the earliest
Cambrian–middle Ordovician interval (similar as
proposed Haydoutov et al. 2010; Balintoni et al.
2011a). In the case of the Serbo-Macedonian Unit
(segment in Serbia), this mechanism connects a late
Cadomian magmatic arc stage with the produc-
tion of juvenile crust lasting during the Cambrian
up to the Ordovician (the age of protolith ranging
from 541 to 475 Ma; sensu Deleon et al. 1972). The
maximum production of juvenile crust could have
been associated with the widespread Ordovician
magmatism and anatexis (similar to the proposition
of Balintoni et al. 2011a; Zagorchev et al. 2 014).
According to the aforementioned arguments, the
Cenerian setting has often been misinter preted as
being a magmatic arc tectonic inheritance (an intu-
itive continuation of the Cadomian arc);
• The distinction of the Serbo-Macedonian Unit as
the pre-Mesozoic basement offers a unique oppor-
tunity to explore scarce, occasionally preserved
Lower Paleozoic high-grade structures marking
the lower crust. Despite the intense efforts pre-
sented by this paper, due to the significant subse-
quent Variscan and Alpine overprints, we would
recommend further search for and investigation of
rare and difficult-to-find records of pre-Variscan
ductile features;
• The age of the metamorphic overprint (ca. 459 Ma)
reported from the Sebeş-Lotru terrane (Getic;
Text-fig. 3a) illustrates a possible involvement of
the Cumpăna metamorphic unit in the suggested
‘Cenerian event’;
• The documentation of the ‘Cenerian event’ typifies
an ea s tern bi partit e shelf of North Gondwa n a (s ensu
Stephan et al. 2019). The results place (paleogeo-
graphically) the Serbo-Macedonian Unit along the
length of its eastern shelf area. Such a position
increases the likelihood of discovering Cenerian
imprints over Cadomian tectonic elements;
• The geology of the investigated Carpathian-Bal-
kan area (in particular of the Serbian segment) is
of extreme complexity as it comprises the vestiges
of at least three major Phanerozoic sutures (Text-
fig. 8b).
• The “Caledonian North African orogen” (Balin-
toni et al. 2011a) is not a convenient term, instead
we recommend to use the term ‘Cenerian event’.
Acknowledgements
This research did not receive any specific grant from fund-
ing agencies in the public, commercial or not-for-profit sec-
tors. The paper benefited from the constructive reviews of Prof.
Dr Franz Neubauer from the University of Graz and Prof. Dr.
Andrzej Zelaźniewicz, Institute of Geological Sciences, Polish
Academy of Sciences. Special thanks go to Prof. Dr. Andrzej
Zelazniewicz for detailed remarks on the manuscript content, as
well as on the important continuous improvements of the early
manuscript versions. The authors thank Editor-in-chief Piotr
Łuczyński for impeccable guidance throughout the manuscript
review process.
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Manuscript submitted: 9th April 2020
Revised version accepted: 13th November 2020
