
Petrology, geochemistry and 

tectono-magmatic affinity of gabbroic 
olistoliths from the ophiolite mélange 

in the NW Dinaric-Vardar ophiolite zone 
(Mts. Kalnik and Ivanščica, North Croatia)


†Boško Lugović1, Damir Slovenec2, Ralf Schuster3, Winfried H. Schwarz4 
and Marija Horvat2

1  University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Department of Mineralogy, 
Petrology and Mineral Resources, Pierottijeva 6, 10000 Zagreb, Croatia

2  Croatian Geological Survey, Sachsova 2, 10000 Zagreb, Croatia;
(corresponding author e-mail: damir.slovenec@hgi-cgs.hr)

3  Geological Survey of Austria, Neulinggasse 38, 1030 Wienna, Austria
4 Institute of Earth Sciences, Im Neuenheimer Feld 234-236, 69120 Heidelberg, Germany

doi: 10.4154/gc.2015.03

Ab strA ct
Mafic intrusive rocks are subordinately represented fragments of the oceanic crust in the ophiolite mélange exposed 
at Mts. Kalnik and Ivanščica located in the NW Dinaric-Vardar ophiolite zone. This ophiolite mélange  occurs in the 
northern area of the Kalnik Unit and represents the SW surface boundary of the Zagorje-Mid-Transdanubian Shear 
Zone. The mélange, except for mafic intrusive rocks, consists of a chaotic mixture of various extrusive rocks formed 
in different tectonic settings of the Repno Oceanic Domain (ROD). The ROD was the segment of Neo-Tethys that 
connects the Meliata-Maliak and Dinaric-Vardar oceanic systems. Previous study of mafic extrusive sequences sug-
gested an 80 Ma period of tectono-magmatic evolution of the ROD from intra-continental rifting during the Anisian, 
to the formation of proto-arc crust during the Callovian-Oxfordian. The domain exposes ophiolitic rocks in four mé-
lange areas. Isotropic gabbroic rocks that are abundant in two northern areas (Mts. Kalnik and Ivanščica), can be dis-
criminated into three distinct geochemical groups: (A) N-MORB-type gabbro [(Th/Nb)n = 0.99–1.10; (Nb/La)n = 
0.95–0.99], (B) IAT-type amphibole gabbro with clear supra-subduction characteristics [(Th/Nb)n = 6.04–8.16; (Nb/
La)n = 0.32–0.42] and (C) BABB-type amphibole-bearing gabbro [(Th/Nb)n = 2.88–4.02; (Nb/La)n = 0.58–0.69]. 
Representative gabbro samples of each geochemical group were dated by the Ar-Ar and/or the K-Ar dating method. 
The Early Jurassic N-MORB-type gabbros (geochemical group A), ~185 Ma old, signifies a peculiar stage of Palaeo-
Tethyan slab break-off. The Late Jurassic IAT-type gabbros (geochemical group B), ~147 Ma old, is the vestige of a 
nascent intra-oceanic arc, whilst the Early Cretaceous BABB-type gabbros (geochemical group C),  ~100 Ma old, 
provides evidence of magmatism in the back-arc marginal basin. The analyzed gabbroic rocks enable refinement and 
completion of the geodynamic evolution of the ROD, from the opening of an ensialic back-arc basin during the Ladi-
nian and a continuous spreading event until the Bajocian. Intra-oceanic convergence was initiated in the Bathonian, 
with the formation of a nascent island-arc during the Tithonian, leading to formation of a Cretaceous ensimatic back-
arc marginal basin. There are many lines of evidence that correlate the geodynamic evolution of the ROD with the 
Albanide-Hellenide Neo-Tethyan oceanic segment.
Keywords: petrology and geochemistry, N-MORB, IAT, BABB, gabbro, ophiolite mélange, Dinaric-Vardar 
ophiolite zone, Mts. Kalnik and Ivanščica, Croatia

Geologia croatica 68/1 25–49 13 Figs. 6 tabs. Zagreb 2015

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Geologia croatica 68/1Geologia Croatica
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1. INtrODUctION

The oceanic lithosphere may be preserved as large thrust 
sheets of a relatively undisturbed coherent lithostratigraphic 
pile (ophiolite complex) thrust onto a tectono-sedimentary 
unit which represents a chaotic mixture of various (in terms 
of age and lithology), ophiolitic rock fragments, embedded 
in a matrix during accretion, obduction and emplacement onto 
the continental margin (ophiolite mélange). Ophiolite mé-
langes are by consensus understood as chaotic tectono-sedi-
mentary complexes initially deposited by tectonically in-
duced sedimentary processes in the deep ocean trench 
(accretionary wedge) from a fore-arc region over the subduct-
ing plate in front of the leading edge of the overriding plate 
(FESTA et al., 2010). Consequently, the mélange mostly in-
corporates very heterogeneous magmatic material, derived 
from both interfaced oceanic sides of the accretionary wedge, 
representing remnants of different tectonostratigraphic units 
formed during the lengthy evolution of an oceanic system. 
Many mélanges are overlain by slices of coherent fragments 
of the genetically related oceanic lithosphere (ophiolites) 
which may include lithologies not found in the associated mé-
lange and vice versa (eg.WAKABAYASHI & DILEK, 2003). 
Only the systematic petrological and geochemical analyses 
of ophiolite thrust sheets and magmatic rock fragments ar-
chived in the associated mélanges provide the opportunity to 
study the history of an oceanic system in order to understand 
the complete geodynamic evolution of an ancient oceanic do-
main; from intracontinental rifting, onset of oceanization and 
formation of oceanic lithosphere, through spreading and con-
vergence until the closure and final ophiolite emplacement. 
Such systematic studies are particularly useful when regional 
field relationships fail in areas of poorly exposed ophiolitic 
rocks such as the Sava Zone or the Pannonian Basin. 

In the SW segment of the Zagorje-Mid-Transdanubian 
shear Zone (ZMTDZ), i.e. in the northeasternmost border of 
the Sava-Vardar Zone (SVZ) a tectono-sedimentary ophiolite 
mélange is observed in the form of separate areas outcropping 
and forming the slopes of Mts. Kalnik, Ivanščica, Medved-
nica & Samoborska Gora (e.g. PAMIĆ & TOM LJE NOVIĆ, 
1998; with references; Fig. 1A). All these mélange areas are 
integrated as a single tectonostratigraphic unit named by 
HAAS et al. (2000) as the Kalnik Unit (Fig. 1B). On  account 
of similar textural features, all the mélange areas of the Kalnik 
Unit provide strong evidence for a discrete Mesozoic oceanic 
domain called the Repno Oceanic Domain (ROD - sensu 
BABIĆ et al., 2002). The ROD was a part of the Neo-Tehtys 
Oceanic realm and links the Meliata-Maliak and Dinaric-
Vardar oceanic domains (BABIĆ et al., 2002; Fig. 1C). This 
may be understood to represent the key oceanic domain con-
necting the Central Dinaridic ophiolites located to the SW, 
with Meliata-Maliak ophiolites to the NE and the Alpine ophi-
olites to the NW (SLOVENEC & LUGOVIĆ 2008, 2009; 
SLOVENEC et al., 2010, 2011). The ROD is documented 
mainly by isolated bodies of extrusive rocks, whereas coher-
ent fragments of oceanic lithosphere (ophiolite complexes) 
are lacking. It contains four separate ophiolite mélange areas 
in two southern (Mts. Medvednica and Samoborska Gora), 
and two northern parts (Mts. Ivanščica and Kalnik) (Fig. 1A-

B). Extensive studies of extrusive rocks, particularly the pil-
low-basalts associated with radiolarian cherts from all four 
mélange areas (SLOVENEC & LUGOVIĆ, 2009, 2012; 
SLOVENEC et al., 2010, 2011; KISS et al., 2012), and intru-
sive gabbroic rocks from the Mt. Medvednica ophiolite mé-
lange (SLOVENEC & LUGOVIĆ, 2008), provided a high-
resolution view of the geodynamic evolution of the ROD that 
commenced with intra-continental rifting during Anisian time. 
This was followed by the formation of the proto-oceanic crust, 
followed by the onset of spreading and maximum widening 
of the oceanic domain in the Bajocian, until the formation of 
an infant proto-arc crust in the Callovian-Oxfordian.

In many mélange portions, extrusive rock sequences are 
generally the most abundant fragments. However, subordi-
nate blocks of intrusive gabbroic rocks can also be an excel-
lent magmatic indicator of a geotectonic setting. Although 
the hectometre-scale gabbroic blocks are relatively abundant 
in the Kalnik and Ivanščica Mts. mélange areas of the ROD 
(Fig. 2A-B), they have not been previously investigated in 
detail. The gabbroic rocks from the Kalnik and Ivanščica 
Mts. mélange are dated here by Ar-Ar and/or K-Ar dating 
methods and can be geochemically and petrologically cat-
egorized into three distinct groups. Therefore, they can rep-
resent different geotectonic formational settings that were 
not recognized in previous research. 

The aim of this work is to provide an overall petrologi-
cal and geochemical characterization of the Mt. Kalnik and 
Ivanščica gabbroic rocks to determine their petrogenesis and 
to propose a likely geotectonic setting for their formation, 
with the purpose of improving and completing our knowl-
edge of the geodynamic evolution of the ROD as a discrete 
Mesozoic domain that was the corner-stone between the Me-
liata-Maliak and Dinaric-Vardar oceanic systems. The Kalnik 
and Ivanščica Mts. gabbroic rocks are correlated with equiv-
alent rocks from the nearby Mt. Medvednica highlighting 
their potential geotectonic link. With reference to the chro-
nology of particular tectonomagmatic episodes, the inferred 
geodynamic model for the ROD in many respects correlates 
with the model for the Albanide-Hellenide Neo-Tethyan 
ocean segment, as deduced from the study of ophiolites and 
ophiolite mélanges in the latter area (SACCANI et al., 2011).

2. rEGIONAL GEOLOGIcAL sEttING

Geographically the study area is located in the northernmost 
part of the Dinarides, located between the Adriatic Sea and 
the Southern Alps in the southwest and west and the Panno-
nian Basin with some inselbergs in the north and east (Fig. 
1A-B). The Dinarides represent an Alpine fold-thrust belt, 
bordered to the southwest by the Adriatic (Apulian) micro-
plate, the Southalpine and Austroalpine Unit to the north and 
by the Tisza Mega-Unit to the east (HAAS et al., 2000; Fig. 
1B). They are subdivided into the External Dinarides, mainly 
consisting of Mesozoic carbonate platforms (VLAHOVIĆ 
et al., 2005), and the Internal Dinarides which comprise sev-
eral zones: The Bosnian flysch zone is overlain by a zone 
composed of Upper Jurassic to Cretaceous mixed carbonate 
and siliciclastic sedimentary units, derived from a distal 



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
27

Adriatic plate margin, which was involved in the Late Juras-
sic ophiolite obduction. Most internal units comprise the 
Central Dinaridic Ophiolite Zone (CDOZ) and finally the 
Sava-Vardar Suture Zone (SVSZ) sensu PAMIĆ (2002). The 

Dinarides characteristically stretch northwest-southeast and 
were traditionally understood to be bracketed between the 
Zagreb-Zemplin Lineament and the Skutari-Peć transform 
fault (eg. PAMIĆ, 2002; Fig. 1A).

Figure 1: (A) Geotectonic sketch map of the Alps, Dinarides and Hellenides showing the   position of the Periadriatic-Sava-Vardar suture zone (after PAMIĆ, 
2000). Legend: 1 – External units (External Dinarides and Alps); 2 – Internal units [Passive continental margin, Central Dinaride Ophiolite Belt (CDOB), 
Mirdita Zone]; 3 – Periadriatic-Sava-Vardar Zone; 4 – Serbo-Macedonian Massif; 5 – Pelagonides; 6 – Golija Zone; 7 – Zagorje-Mid-Transdanubian Zone; 8 
– Pannonian Basin. Faults: BL – Balaton; DF – Drava; PL – Periadriatic Lineament; SF – Sava Fault; SP – Scutari-Peć; SN – Sava Nape; VF – Vardar; ZZ – Zagreb-
Zemplin. Mountains: I – Ivanščica; K – Kalnik; Ko – Kopaonik; Kz – Kozara; Md – Medvednica; SG – Samoborska Gora; SD – Szarvaskö-Darnó; Bü – Bükk. B 
– Bódva valley; JK – Jaklovce. (b) Sketch map of the structural units and major lineaments (modified after HAAS et al., 2000). Insert map: geographic set-
ting of the area presented in the sketch map. Legend: BL – Balaton Lineament; ZZL – Zagreb-Zemplin Lineament; PL – Periadriatic Lineament. (c) Sketch 
map of hypothetical reconstruction of the oceanic belt consisting of Meliata, Repno and Central Dinaric Ophiolite Zone segments (after BABIĆ et al., 2002). 



Geologia croatica 68/1Geologia Croatica
28

The study area comprises the southwestern part of a 
larger zone, about 100 km wide and 400 km long, sheared 
between two regional fault systems, the Zagreb-Zemplin 
Lineament to the south and the Periadriatic-Balaton Linea-
ment to the north, which was (after PAMIĆ & 
TOMLJENOVIĆ, 1998), recognized as the ZMTDZ (Fig. 
1A-B). This area forms a junction between the Southalpine 
and Austroalpine Unit, the Tisza Mega-Unit and the Internal 
Dinarides. It is also known as the Sava Unit (HAAS et al., 
2000; Fig. 1B). The ZMTDZ includes triangular shaped in-
tra-Pannonian inselbergs: Mts. Kalnik, Ivanščica, Medved-
nica and Samoborska Gora. The inselbergs are composed of 
pre-Neogene heterogeneous and superimposed Dinaric and 
Alpine tectonostratigraphic and tectonometamorphic units, 
(see for example: PAMIĆ & TOMLJENOVIĆ, 1998; TARI 
& PAMIĆ, 1998; HAAS et al., 2000; HAAS & KOVÁCS, 
2001; PAMIĆ, 2002). However, the origin of these units is 
still debated. Structural and palaeomagnetic data indicate 
that the pre-Neogene basement of Mts. Ivanščica, Kalnik and 
Medvednica experienced large, regional-scale tectonic trans-
port from the northwest, and an approximately 130° clock-
wise rotation during the Oligocene to the earliest Miocene 
(TOMLJENOVIĆ et al., 2008), that aligned them almost 
perpendicular to the overall northwest – southeast Dinaric 
structural trend. When reconstructed for this clock-wise ro-
tation, these three mountains continue the main Dinaric trend 
to the northwest. On the basis of their similar tectonostrati-
graphic evolution, SCHMID et al. (2008) considered the 
ZMTDZ to be part of the Western Vardar Ophiolite Unit.

The Kalnik and Ivanščica Mts. ophiolite mélange (Figs. 
2A and B) form the two separate northern mélange areas of 
the Kalnik Unit (Fig. 1B). The Kalnik Unit consists of the 
lithological remnants of a discrete oceanic domain that con-
nects the Dinaric-Vardar ophiolites, located to the southwest, 
with the Meliata-Maliak ophiolites exposed to the northeast. 
Based on matrix palynomorph assemblages, the accretion-
ary age of the Kalnik Unit, i.e. ophiolite mélange is inferred 
to be Middle Jurassic to Hauterivian (BABIĆ et al., 2002). 
This time interval represents a period of accumulation of 
lithostratigraphically diverse material in the intra-oceanic 
trench (SLOVENEC et al., 2011).

The Kalnik Unit was involved in Aptian to post-Palae-
ocene emplacement onto the eastern continental margin of 
the Adria plate (PAMIĆ & TOMLJENOVIĆ, 1998; PAMIĆ, 
2002). However, the basement rocks of the Kalnik Unit in 
the Ivanščica and Kalnik Mts. are not known. In Mt. Medved-
nica, the Kalnik Unit is thrust onto Aptian low-grade meta-
morphic complexes (Medvednica Unit, HAAS et al., 2000; 
Fig. 1B), generated during the emplacement of the Late 
Jurassic island-arc onto the Adria continental margin 
(LUGOVIĆ et al., 2006). However, the pelitic to silty matrix 
of the Kalnik Unit does not show a metamorphic overprint 
from burial diagenesis (JUDIK et al., 2008).

3. LOcAL GEOLOGY AND DEscrIPtION  
OF tHE stUDY ArEA

A simplified geological map of the Kalnik and Ivanščica 
Mts. is shown in Figures 2A and 2B, respectively. The old-

est rocks in the area are Middle-Upper Triassic limestones 
and dolomites derived from the Adriatic passive continental 
margin (ŠIMUNIĆ et al., 1982; HALAMIĆ, 1998). At Mt. 
Ivanščica, this carbonate succession is intersected by calc-
alkaline extrusives and interlayered with distal pyroclastics, 
interpreted as remnants of a late Anisian-Ladinian Andean-
type volcanic arc, located at the European continental mar-
gin (GORIČAN et al., 2005). Late Jurassic to Early Creta-
ceous limestones unconformably overlie this Middle Triassic 
volcano-sedimentary formation. Both units are in turn over-
thrust onto an ophiolite mélange. 

These Mesozoic rock successions have not been encoun-
tered at Mt. Kalnik. The central ridge of Mt. Kalnik consists 
of Palaeocene carbonate breccias thrust over Neogene sedi-
mentary rocks (ŠIMUNIĆ et al., 1981). The common con-
stituents of these breccias are fragments of Triassic algal and 
stromatolitic limestones and dolomites, as well as Jurassic 
and Upper Cretaceous limestones. Similar breccias are also 
found in nearby Mt. Medvednica (ŠIMUNIĆ et al., 1993), 
and were encountered during drilling in the Drava Depres-
sion (ŠIMUNIĆ & PAMIĆ, 1989) suggesting a wide areal 
extent. 

Several individual fragments of highly serpentinized 
mantle peridotites (lherzolites) were exhumed at the moun-
tain ridge tectonic zone (POLJAK, 1942), together with a 
composite block of serpentinized lherzolite underlain by 
metamorphic sole amphibolites (LUGOVIĆ et al., 2007). 
The amphibolites were dated by K-Ar on amphibole sepa-
rates which yielded an age of 118 ± 8 Ma (IGNJATIĆ, 2007). 
The northern part of the Mt. Kalnik ophiolite mélange is 
thrust onto the Neogene-Pleistocene sedimentary succession 
(ŠIMUNIĆ et al., 1982). All other contacts of the ophiolite 
mélange areas of Mts. Kalnik and Ivanščica exhibit a tec-
tonic-erosional unconformity against the youngest Neogene 
and Pleistocene sedimentary rocks (Fig. 2A-B). 

The ophiolite mélange areas of Mts. Kalnik and Ivanščica 
show similar structural features characterized by a “block-
in-matrix” fabric, typical of chaotic complexes from subduc-
tion-related tectonic mélanges (FESTA et al., 2010). They 
are dominated by magmatic rocks and contain lithostrati-
graphically heterogeneous fragments of sedimentary rocks 
including greywacke, minor shale, red and grey cherts, and 
scarce limestones (ŠIMUNIĆ et al., 1982). The fragments 
range in size from pebbles to hectometre-kilometre sized 
blocks embedded in a predominantly sheared continent-de-
rived pelitic to silty matrix (Figs. 2A-B). Fragments of mafic 
extrusive rocks are the prevailing magmatic lithologies in 
both ophiolite mélange areas. They show various geochem-
ical signatures consistent with their different geotectonic for-
mational settings during an age span from the Illyrian to the 
late Oxfordian (SLOVENEC et al., 2011). Gabbroic rocks 
are relatively abundant in the mélange areas of Mts. Kalnik 
and Ivanščica and occur as hectometre-sized homogeneous 
blocks (CRNKOVIĆ et al., 1974; VRKLJAN, 1989; PAMIĆ, 
1997; VRKLJAN & GARAŠIĆ, 2004; Fig. 2A-B). However, 
an exceptional composite gabbro block, intersected by a me-
tre-wide dacitic dyke was observed in Gotalovec quarry at 
Mt. Ivanščica. In the field, part of these Cretaceous blocks 



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
29

(Fig. 2A, location 3 and Fig. 2B, location 3) appear as fault-
bounded tectonic inclusions subsequently embedded in the 
mélange during the ophiolite emplacement. The locations of 
the all analysed blocks are indicated in Figure 2A for Mt. 
Kalnik and Figure 2B for Mt. Ivanščica.

4. ANALYtIcAL tEcHNIQUEs
The mineral compositions of ten samples were analysed at 
the Mineralogisches Institut der Universität Heidelberg, Ger-
many, using a CAMECA SX51 electron microprobe 
equipped with five wavelength-dispersive spectrometers. 
Measurements were performed using an accelerating volt-

age of 15 kV, a beam current of 20 nA, beam size of ~1 µm 
(for feldspars 10 µm) and 10s counting time for all elements. 
Natural oxides and silicates were used as standards and for 
calibration. Raw data were corrected for matrix effects with 
the PAP algorithm (POUCHOU & PICHOIR, 1984, 1985) 
implemented by CAMECA. Calculations of the structural 
chemical formulae were undertaken using a software pack-
age written by Hans-Peter Meyer (Mineralogisches Institut, 
Heidelberg).

Bulk-rock powders for chemical analyses of 21 samples 
were obtained from vein-free rock chips. The samples were 
analysed by ICP-OES for major elements and ICP-MS for 

Figure 2: (A) Simplified geological map of Mt. Kalnik and (b) of Mt. Ivanščica (modified after ŠIMUNIĆ et al., 1982 and HALAMIĆ, 1998). Legend: 1 – Neo-
gene and Pleistocene sedimentary rocks; 2 – Jurassic-Cretaceous limestones; 3 – ophiolite mélange with blocks of: 3a - basalt, 3b - gabbro, 3c - tectonite 
peridotite and Triassic-Jurassic radiolarites, sandstones and shales (not separated on the maps); 4 – Triassic limestones and dolomites; 5 – reverse or thrust 
faults; 6 – normal faults; 7 – discordance line, tectonic-erosion discordance; 8 – sample location (Mt. Kalnik: 1 = vsk-242/2, vsk-242/4, vsk-242/6; 2 = vsk-
204; 3 = vsk-229/1, vsk-229/7, vsk-229/12; 4 = vsk-228, vsk-228/2, vsk-228/5; 5 = vsk-217/1; Mt. Ivanščica: 1 = be-3; 2 = vsi-5; 3 = vsi-8/1, vsi-8/2; 4 = vsi-7/1; 
5 = gi-2, gi-5, gtc-3, gtc-4, gtc-6); 9–picture break; 10 – quarry.



Geologia croatica 68/1Geologia Croatica
30

all trace elements, utilizing the 4Lithoresearch analytical 
protocol at Activation Laboratories in Ancaster, Canada. Ma-
jor element and trace element concentrations were measured 
with accuracy better than 1% and 5%, respectively.

Isotopic compositions of six bulk rock samples were 
measured in the Centre de Recherches Pétrographiques et 
Géochimiques in Vandoeuvre, France on a Triton Plus mass 
spectrometer. Normalizing ratios of 86Sr/88Sr = 0.1194 and 
146Nd/144Nd = 0.7219 were used. The 87Sr/86Sr ratio for the 
NBS 987 Sr standard based on n = 92 for the period of meas-
urement was 0.710242 ± 0.000030 (2σ). The 143Nd/144Nd 
ratio for the La Jolla standard was 0.511845 ± 0.000010 (2σ) 
(n = 22). Total procedural blanks were ~500 pg and ~ 150 
pg for Sr and Nd, respectively.

40Ar/39Ar analysis was performed at the Institut für Ge-
owissenschaften der Universität Heidelberg, Germany. The 
amphibole separate from the gabbro sample vsk-228 was 
prepared by crushing and sieving the 200-400 μm fraction 
followed by magnetic separation and finally by handpicking 
under a stereomicroscope. For irradiation, the samples were 
wrapped in Al-foil and packed into an evacuated and Cd-
shielded quartz tube. They were irradiated for 15 days with 
2*1018 fast neutrons/cm2. The irradiation was performed in 
the FRG-1 reactor of the Kernforschungszentrum Geesth-
acht, Germany. An apparent age and the flux gradients of the 
reactor were determined by an in-house muscovite standard; 
muscovite BMus/2, 328.5 ± 1.1 Ma, 1s (SCHWARZ & TRI-
ELOFF, 2007). Ar was extracted in a resistance-heated Ta 
furnace in a double-vacuum system up to 1400°C. The gas 
was cleaned using Zr-Al getters and a cooling trap. Ar iso-
tope compositions were measured in a MAT GD-150 gas 
mass spectrometer with no detectable argon background. 
Constants used for age calculations are those recommended 
by STEIGER & JÄGER (1977) - note that suggestions for a 
revised decay constant for Ar-Ar dating (RENNE et al., 2010, 
2011; SCHWARZ et al., 2011) would increase the apparent 
age by 1% in this age range. The argon amounts were cor-
rected for blanks, decay and irradiation interference reac-
tions. 40Ar/39Ar age uncertainties comprise the errors of the 
40Ar/39Ar ratios of the irradiation monitors and age errors of 
the monitor. When two age uncertainties are given, the first 
error is without, while the error in parentheses is with mon-
itor errors. All error assignments of argon isotopic ratios and 
ages given within this paper are within ± 1σ, unless other-
wise stated.

The K-Ar age data are measured on plagioclase sepa-
rated from three gabbros (sample vsk-228/5, vsk-229/7 and 
vsi-8/1). Plagioclase was separated by an electromagnetic 
separator and standard heavy liquid techniques and finally 
was purified by hand picking under a stereomicroscope. The 
K concentration and Ar analysis were determined by ICP-
OES and an isotope dilution procedure on noble gas mass 
spectrometry, respectively. The analyses were performed at 
the Activation Laboratories in Ancaster (Canada). The Ar 
analysis: Aliquot of the sample is weighted into an Al con-
tainer, loaded into the sample system of the extraction unit, 
degassed at ~ 100°C over 2 days to remove the surface gases. 
Argon is extracted from the sample in a double vacuum fur-

nace at 1700°C. The Argon concentration is determined us-
ing isotope dilution with 38Ar spike, which is introduced to 
the sample system prior to each extraction. The extracted 
gases are cleaned up in a two-step purification system. Then 
pure Ar is introduced into the custom built magnetic sector 
mass spectrometer (Reinolds type ) with Varian CH5 mag-
net. The ion source has an axial design (Baur-Signer source), 
which provides more than 90% transmission and extremely 
small isotopic mass-discrimination. Measurement of Ar iso-
tope ratios is corrected for mass-discrimination and then at-
mospheric argon is removed, assuming that 36Ar is only from 
the air. The concentration of 40Ar radiogenic is calculated 
using the 38Ar spike concentration. After each analysis the 
extraction temperature is elevated to 1800°C for few minutes 
and the furnace is prepared for the next analysis. K-analysis: 
Aliquot of the sample is weighted into a graphite crucible 
with lithium metaborate/tetraborate flux and fussed using a 
LECO induction furnace. The fusion bead is dissolved with 
acid. Standards, blanks and sample are analysed by an ICP 
Spectrometer.

5. PEtrOGrAPHY AND MINErAL cHEMIstrY

The studied gabbroic rocks are isotropic with preserved ig-
neous fabric and show a non-cumulus anhedral granular tex-
ture with grain sizes of 1-3 mm and homogene structure. 
They were subdivided on the basis of their petrographic 
characteristics into three groups. The gabbros of group A are 
composed of plagioclase and augite, the gabbros of group B 
additionally contain variable edenitic amphibole, whilst ede-
nite represents a minor phase in group C samples (Figs. 3A, 
B, C). Ilmenite and apatite occur as accessory minerals in all 
groups. Due to the textural relationships of edenite and its 
high content of TiO2, Al2O3 and Na2O (up to 2.5, 8.3 and 2.7 
wt%, respectively; Table 1) it is interpreted as an igneous 
mineral (compare with COOGAN, 2003), cotectic with au-
gite (Table 2). These amphiboles have slightly different com-
positions compared to their Mt. Medvednica analogues 
which are classified as magnesiohornblende (Fig. 4). Some 
of the primary amphibole grains are partly altered to actino-
lite, ferroactinolite or ferro-anthophyllite (Table 1; Fig. 4). 
However, magnesiohornblende in the analysed gabbroic 
rocks may have formed during late crystallization of an 
evolved hydrous magma and may reflect the influence of a 
deep oceanic crustal hydrothermal system. The Gotalovec 
quarry gabbroic rocks (Fig. 2B, location 5; which are in-
cluded in group C based on their geochemical similarities) 
are characterised by coarse grained intergranular textures 
and form a texturally unique group. They contain discrete 
domains of parallel oriented ilmenite plates (up to 35 µm 
wide) exsolved from completely decomposed mineral. A sig-
nificant chemical difference with respect to the Mn-content 
of ilmenite was measured between rocks of groups B and C, 
(7.82-7.96 wt% vs. 3.28-4.67 wt% MnO), respectively. The 
representative gabbro (sample vsk-242/2) from group A con-
tains low-Mn ilmenite (< 1.5 wt% MnO) typical of ocean 
ridge gabbros (HÉBERT et al., 1991). Plagioclase in gabbro 
samples of group A shows a nearly homogenous composi-
tion (An~50-45). However, magmatic plagioclase preserved 



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
31

Figure 3: Microphotography of the Kalnik and Ivanščica Mts. non-cumulus gabbroic rocks subdivided on the basis of petrographic characteristics into 
three groups: (A) group A – composed of plagioclase and augite (sample vsk-242/2). N+, (b) group B – composed of plagioclase, augite and variable ede-
nitic amphibole (sample vsk-228). N– and (c) group C – composed of plagioclase and augite while edenite represents a minor phase (sample vsk-229/12). 
N+. Legend: pl = plagioclase, cpx = clinopyroxene, amp = amphibole, ilm = ilmenite.

in rocks of groups B and C shows continuous normal zoning 
patterns with the widest core to rim compositional range of 
An64.3 to An33.7 measured in samples vsk-228 and vsk-228/5 
and An56.2 to An36.8 measured in samples vsk-229/7 and vsi-
8/2. A smaller portion of the measured feldspar shows an al-
bite (An0.3-2.9) to peristerite (An~6) composition. 

The dacite dyke intersecting gabbroic rocks in the Gota-
lovec quarry (Fig. 2B, location 5) shows a dense aphyric fine-
grained pilotaxitic to intergranular texture. Close to the contact 
with the gabbro it may contain scarce clinopyroxene and al-
bite phenocrysts. Clinopyroxene microphenocrysts are only 
partly replaced or pseudomorphed by ferroedenite/ferrohorn-
blende corresponding to high temperature deuteric alteration, 
whereas chlorite, pumpellyite and titanite probably reflect hy-
drothermal alteration. The groundmass consists of albite laths, 
acicular clinopyroxene, interstitial quartz, ilmenite, chlorite 
and accessory pumpellyite, zircon, apatite and tourmaline. 

Clinopyroxene composition is repeatedly used as an in-
dicator of petrogenesis and geotectonic setting, particularly 
in ophiolites and other ocean-related rocks (BECCALUVA 

et al., 1989). Selected clinopyroxene compositions from the 
analysed rocks are shown in Table 2, plotted in the classifi-
cation diagram in Figure 5, and displayed in geochemical 
geotectonic discrimination diagrams in Figure 6.

The clinopyroxene from the gabbroic rocks of all groups 
is augite (Wo36.5-44.7En29.8-47.7Fs11.0-29.7). In some samples 
augite is partly altered to trioctahedral (Type “I” of ZANE 
& WEISS, 1998) chlorite and belongs to the clinochlore-
chamosite series. In all analysed samples clinopyroxenes show 
normal zoning patterns with continuously decreasing Mg# 
towards the rim of the crystal, the widest range of 85.4 to 
65.7 was measured in the Gotalovec quarry sample gtc-4. 
This type and intensity of zoning is typical for slow cooling in 
a closed magmatic system (STERN, 1979). Dacite clinopyro-
xene has a low-Al ferroaugite composition (Wo39.7-42.9En16.8-26.9 
Fs31.4-41.9). Both populations show a significant Fe-enrich-
ment trend (Fig. 5; Table 2). The dacite clinopyroxene com-
position is typical for a highly evolved acidic magma as seen 
in Figure 6 where it occupies a position with the lowest Ti 
and highest Na-abundance.



Geologia croatica 68/1Geologia Croatica
32

ta
bl

e 
1:

 S
el

ec
te

d 
m

ic
ro

pr
ob

e 
an

al
ys

es
 a

nd
 fo

rm
ul

ae
 o

f a
m

ph
ib

ol
e 

fro
m

 th
e 

ga
bb

ro
ic

 ro
ck

s a
nd

 d
ac

ite
 in

 th
e 

Ka
ln

ik
 (K

A)
 a

nd
 Iv

an
šč

ic
a 

(IV
) M

ts
. o

ph
io

lit
e 

m
él

an
ge

.

G
ro

up
 B

G
ro

up
 C

Sa
m

pl
e

vs
k-

22
8

vs
k-

22
8

vs
k-

22
8

vs
k-

22
8

vs
k-

22
9/

1
vs

k-
22

9/
7

be
-3

vs
i-5

+g
tc

-3
+g

tc
-3

+g
tc

-3
+g

tc
-3

+g
tc

-3
*g

tc
-6

An
al

. n
r.

1
2

26
27

1
12

13
3

3
17

34
40

57
19

Si
te

c
r

c
r

c
r

c
c

r
c

c
c

c
c

M
in

er
al

Ed
Ed

Ed
Ed

Ed
M

hb
l

Fa
th

M
hb

l
Fe

d
Fa

ct
Ed

Fh
bl

Fa
th

Fe
d

Lo
ca

lit
y 

/ S
am

pl
e 

lo
c.

KA
/4

KA
/4

KA
/4

KA
/4

KA
/3

KA
/3

IV
/1

IV
/2

IV
/5

IV
/5

IV
/5

IV
/5

IV
/5

IV
/5

Si
O

2
43

.8
0

46
.3

0
44

.9
9

47
.4

7
45

.6
8

49
.5

2
49

.2
48

.9
1

48
.1

1
47

.8
1

47
.1

8
47

.5
8

49
.9

7
47

.7
0

Ti
O

2
3.

01
2.

15
2.

44
1.

73
2.

25
1.

07
0.

62
0.

70
0.

97
1.

09
1.

28
0.

98
0.

72
0.

17

Al
2O

3
9.

54
7.

42
8.

28
5.

50
7.

29
3.

26
1.

63
5.

24
3.

20
2.

98
5.

33
3.

32
1.

07
2.

92

Cr
2O

3
0.

02
0.

06
0.

04
0.

05
0.

01
0.

10
0.

03
0.

00
0.

00
0.

00
0.

00
0.

03
0.

02
0.

00

Fe
O

16
.1

2
16

.8
1

17
.4

8
19

.4
7

18
.9

2
20

.9
0

33
.1

9
14

.1
4

26
.3

7
28

.6
5

18
.8

7
28

.9
4

33
.6

8
29

.9
4

M
nO

0.
34

0.
27

0.
29

0.
05

0.
33

0.
28

0.
37

0.
34

0.
44

0.
46

0.
43

0.
38

0.
56

1.
03

M
gO

11
.5

6
12

.3
5

11
.4

6
11

.1
0

10
.7

3
10

.2
6

17
.2

9
14

.4
2

8.
23

6.
97

11
.9

5
6.

70
8.

52
5.

08

Ca
O

10
.2

4
10

.3
1

10
.0

7
9.

98
9.

81
9.

80
4.

17
11

.5
5

8.
54

8.
15

9.
60

8.
00

2.
65

7.
78

N
a 2

O
2.

90
2.

24
2.

66
2.

08
2.

53
1.

45
0.

59
0.

89
1.

53
1.

26
2.

04
1.

14
0.

47
1.

87

K 2
O

0.
16

0.
21

0.
19

0.
15

0.
16

0.
30

0.
05

0.
03

0.
35

0.
24

0.
15

0.
25

0.
02

0.
25

H
2O

2.
01

2.
02

2.
01

2.
00

1.
99

1.
98

1.
91

2.
02

1.
94

1.
92

1.
98

1.
91

1.
92

1.
89

To
ta

l
99

.7
0

10
0.

14
99

.9
1

99
.7

7
99

.7
0

99
.9

8
99

.0
2

98
.2

4
99

.6
8

99
.5

3
98

.8
1

99
.2

0
99

.5
8

98
.6

3

Si
6.

61
7

6.
91

4
6.

79
3

7.
18

8
6.

95
1

7.
59

9
7.

76
7

7.
22

1
7.

48
2

7.
50

1
7.

17
3

7.
48

6
7.

81
0

7.
68

6

Ti
0.

34
2

0.
24

2
0.

27
7

0.
19

7
0.

25
8

0.
12

4
0.

07
4

0.
07

8
0.

11
3

0.
12

9
0.

14
6

0.
11

6
0.

08
5

0.
02

1

Al
1.

69
7

1.
30

5
1.

47
2

0.
98

1
1.

30
6

0.
58

9
0.

30
3

0.
91

2
0.

58
6

0.
55

0
0.

95
4

0.
61

5
0.

19
7

0.
55

5

Cr
0.

00
2

0.
00

7
0.

00
5

0.
00

6
0.

00
1

0.
01

2
0.

00
4

0.
00

0
0.

00
0

0.
00

0
0.

00
4

0.
00

4
0.

00
2

0.
00

0

Fe
3+

0.
00

0
0.

00
0

0.
00

0
0.

00
0

0.
00

0
0.

00
0

0.
00

0
0.

23
0

0.
00

0
0.

00
0

0.
00

0
0.

00
0

0.
00

0
0.

00
0

Fe
2+

2.
03

7
2.

09
9

2.
20

7
0.

46
6

2.
40

8
2.

68
2

4.
38

2
1.

51
6

3.
43

0
3.

75
9

2.
39

9
3.

80
8

4.
40

2
4.

03
5

M
n

0.
04

4
0.

03
4

0.
03

7
0.

03
7

0.
04

3
0.

03
6

0.
04

9
0.

04
3

0.
05

8
0.

06
1

0.
05

5
0.

05
1

0.
07

4
0.

14
1

M
g

2.
60

4
2.

74
9

2.
58

0
2.

50
6

2.
43

4
2.

34
7

1.
71

6
3.

17
4

1.
90

8
1.

63
0

2.
70

8
1.

57
2

1.
98

5
1.

22
0

Ca
1.

65
7

1.
65

0
1.

62
9

1.
61

9
1.

59
9

1.
61

1
0.

70
5

1.
87

2
1.

42
3

1.
37

0
1.

56
4

1.
34

9
0.

44
4

1.
34

3

N
a

0.
85

0
0.

64
9

0.
77

9
0.

61
1

0.
74

6
0.

43
1

0.
18

1
0.

25
5

0.
46

1
0.

38
3

0.
60

1
0.

34
8

0.
14

2
0.

58
4

K
0.

03
1

0.
04

0
0.

03
7

0.
02

9
0.

03
1

0.
06

5
0.

01
0

0.
00

6
0.

06
9

0.
04

8
0.

02
9

0.
05

0
0.

00
4

0.
05

1

To
ta

l
15

.8
81

15
.6

89
15

.8
15

15
.6

40
15

.7
78

15
.4

96
15

.1
91

15
.2

60
15

.5
31

15
.4

31
15

.6
30

15
.3

98
15

.1
46

15
.6

36

M
g#

56
.1

56
.7

53
.9

50
.4

50
.3

46
.7

28
.1

64
.5

35
.7

30
.3

53
.0

29
.2

31
.1

23
.2

Fo
rm

ul
ae

 c
al

cu
la

te
d 

on
 th

e 
ba

si
s o

f 2
3 

ox
yg

en
s a

nd
 fi

xe
d 

nu
m

be
r o

f 1
5 

ca
tio

ns
 e

xc
lu

di
ng

 N
a 

an
d 

K.
 E

st
im

at
ed

 H
2O

 c
or

re
sp

on
ds

 2
 (O

H
) p

er
 fo

rm
ul

ar
 u

ni
t. 

c 
= 

co
re

, r
 =

 ri
m

. E
d 

= 
ed

en
ite

, F
ed

 =
 fe

rr
o-

ed
en

ite
, F

hb
l =

 fe
rr

o-
ho

rn
bl

en
de

, 
M

hb
l =

 m
ag

ne
si

o-
ho

rn
bl

en
de

, F
ac

t =
 fe

rr
o-

ac
tin

ol
ite

, F
at

h 
= 

fe
rr

o-
an

th
op

hy
lli

te
. M

g#
 =

 1
00

*(
M

g/
(M

g 
+ 

Fe
2+

)).
 +  =

 d
io

rit
e,

 *
 =

 d
ac

ite
. S

am
pl

e 
lo

ca
tio

n 
nu

m
be

r c
or

re
sp

on
ds

 to
 th

e 
lo

ca
tio

ns
 in

 F
ig

ur
e 

2A
-B

.



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
33

ta
bl

e 
2:

 S
el

ec
te

d 
m

ic
ro

pr
ob

e 
an

al
ys

es
 a

nd
 fo

rm
ul

ae
 o

f c
lin

op
yr

ox
en

e 
fro

m
 th

e 
ga

bb
ro

ic
 ro

ck
s a

nd
 d

ac
ite

 in
 th

e 
Ka

ln
ik

 (K
A)

 a
nd

 Iv
an

šč
ic

a 
(IV

) M
ts

. o
ph

io
lit

e 
m

él
an

ge
.

G
ro

up
 A

G
ro

up
 B

G
ro

up
 C

Sa
m

pl
e

vs
k-

24
2/

2
vs

k-
24

2/
2

vs
k-

22
8

vs
k-

22
8

vs
k-

22
8

vs
k-

21
7/

1
vs

k-
21

7/
1

vs
k-

22
9/

1
vs

k-
22

9/
1

vs
k-

22
9/

7
vs

k-
22

9/
7

be
-3

vs
i-5

vs
i-8

/1
gt

c-
4

gt
c-

4
gt

c-
5

*g
tc

-6

An
al

. n
r.

2
5

13
14

17
19

20
37

38
14

15
3

19
4

3
4

9
9

Si
te

c
c

r
c

c
c

r
c

r
c

r
r

c
c

r
c

c
c

Lo
ca

lit
y 

/ S
am

pl
e 

lo
c.

KA
/1

KA
/1

KA
/4

KA
/4

KA
/4

KA
/5

KA
/5

KA
/3

KA
/3

KA
/3

KA
/3

IV
/1

IV
/2

IV
/3

IV
/5

IV
/5

IV
/5

IV
/5

Si
O

2
50

.7
6

50
.9

2
51

.0
0

51
.9

7
51

.9
8

51
.9

3
51

.3
9

51
.7

5
51

.4
7

50
.9

1
50

.8
4

51
.0

4
50

.6
8

52
.6

7
50

.2
3

50
.1

3
50

.7
3

49
.7

3

Ti
O

2
1.

13
0.

97
0.

93
0.

79
0.

62
0.

65
0.

67
0.

63
0.

88
0.

86
0.

81
0.

50
0.

80
0.

46
1.

07
1.

01
0.

32
0.

19

Al
2O

3
2.

91
2.

95
2.

77
2.

76
2.

84
2.

15
1.

55
2.

74
2.

26
3.

13
2.

31
1.

38
1.

88
1.

22
2.

86
3.

25
0.

64
0.

42

Cr
2O

3
0.

01
0.

00
0.

04
0.

03
0.

31
0.

07
0.

00
0.

62
0.

00
0.

08
0.

00
0.

00
0.

00
0.

06
0.

04
0.

06
0.

03
0.

00

Fe
O

12
.1

9
10

.6
3

9.
76

8.
20

6.
87

8.
43

11
.6

7
7.

28
10

.9
2

8.
04

11
.4

4
15

.4
5

11
.1

9
11

.5
5

9.
69

7.
98

19
.0

1
22

.7
8

M
nO

0.
34

0.
28

0.
28

0.
25

0.
22

0.
27

0.
38

0.
29

0.
43

0.
23

0.
37

0.
57

0.
33

0.
34

0.
23

0.
12

0.
63

0.
71

M
gO

15
.0

3
15

.7
8

14
.5

8
15

.3
6

15
.9

4
15

.8
3

14
.4

4
15

.2
5

13
.5

6
15

.4
5

13
.7

5
11

.6
8

13
.7

8
13

.8
4

14
.0

0
14

.4
8

8.
75

6.
21

Ca
O

17
.2

9
17

.7
3

19
.5

4
20

.3
0

20
.6

8
19

.9
7

18
.5

3
20

.9
4

20
.0

3
20

.3
3

19
.6

6
18

.1
3

19
.7

4
19

.7
3

20
.9

6
21

.3
8

19
.4

0
18

.9
6

N
a 2

O
0.

30
0.

30
0.

40
0.

31
0.

30
0.

28
0.

25
0.

25
0.

31
0.

38
0.

29
0.

24
0.

24
0.

30
0.

30
0.

32
0.

25
0.

31

To
ta

l
99

.9
5

99
.5

6
99

.3
0

99
.9

7
99

.7
6

99
.5

8
98

.8
8

99
.7

5
99

.8
6

99
.4

1
99

.4
7

98
.9

9
98

.6
4

99
.4

2
99

.3
8

98
.7

3
99

.7
6

99
.3

1

Si
1.

89
7

1.
89

7
1.

90
9

1.
92

2
1.

91
7

1.
92

6
1.

94
5

1.
91

7
1.

93
2

1.
88

9
1.

91
5

1.
96

8
1.

92
5

1.
95

8
1.

88
4

1.
88

0
1.

98
0

1.
98

5

Ti
0.

03
2

0.
02

7
0.

02
6

0.
02

2
0.

01
7

0.
01

8
0.

01
9

0.
01

8
0.

02
5

0.
02

4
0.

02
5

0.
01

5
0.

02
3

0.
01

3
0.

03
0

0.
02

8
0.

00
9

0.
00

6

Al
IV

0.
10

3
0.

10
3

0.
09

1
0.

07
8

0.
08

3
0.

07
4

0.
05

5
0.

08
3

0.
06

8
0.

11
1

0.
08

5
0.

03
2

0.
07

5
0.

04
2

0.
11

6
0.

12
0

0.
02

0
0.

01
5

Al
VI

0.
02

5
0.

02
7

0.
03

2
0.

04
2

0.
04

0
0.

02
0

0.
01

4
0.

03
7

0.
03

2
0.

02
6

0.
01

8
0.

03
1

0.
00

9
0.

01
3

0.
01

0
0.

02
4

0.
00

9
0.

00
5

Cr
0.

00
0

0.
00

0
0.

00
1

0.
00

1
0.

00
9

0.
00

2
0.

00
0

0.
01

8
0.

00
0

0.
00

2
0.

00
0

0.
00

0
0.

00
0

0.
00

2
0.

00
1

0.
00

2
0.

00
1

0.
00

0

Fe
3+

0.
03

7
0.

04
3

0.
03

4
0.

01
3

0.
02

1
0.

03
6

0.
02

0
0.

01
1

0.
00

9
0.

06
3

0.
04

2
0.

00
3

0.
03

7
0.

02
3

0.
06

5
0.

06
0

0.
01

0
0.

02
2

Fe
2+

0.
34

4
0.

28
9

0.
27

1
0.

24
1

0.
19

2
0.

22
6

0.
34

9
0.

21
5

0.
33

4
0.

18
7

0.
31

8
0.

49
6

0.
31

8
0.

34
1

0.
23

9
0.

19
0

0.
61

0
0.

73
9

M
n

0.
01

1
0.

00
9

0.
00

9
0.

00
8

0.
00

7
0.

00
8

0.
01

2
0.

00
9

0.
01

4
0.

00
7

0.
01

0
0.

01
9

0.
01

1
0.

01
1

0.
00

7
0.

00
4

0.
02

1
0.

02
4

M
g

0.
83

7
0.

87
7

0.
81

4
0.

84
7

0.
87

6
0.

87
5

0.
81

5
0.

84
2

0.
75

9
0.

85
5

0.
77

2
0.

67
1

0.
78

0
0.

77
8

0.
78

3
0.

81
0

0.
50

9
0.

37
0

Ca
0.

69
2

0.
70

8
0.

78
4

0.
80

4
0.

81
7

0.
79

4
0.

75
2

0.
83

1
0.

80
6

0.
80

8
0.

79
4

0.
74

9
0.

80
3

0.
79

7
0.

84
2

0.
85

9
0.

81
1

0.
81

1

N
a

0.
02

2
0.

02
2

0.
02

9
0.

02
2

0.
02

1
0.

02
0

0.
01

8
0.

01
8

0.
02

3
0.

02
7

0.
02

1
0.

01
8

0.
01

8
0.

02
2

0.
02

2
0.

02
3

0.
01

9
0.

02
4

M
g#

70
.9

75
.2

75
.0

77
.9

82
.0

2
79

.5
70

.0
79

.7
69

.4
82

.1
70

.8
75

.7
71

.0
69

.5
76

.6
81

.0
45

.5
33

.4

Al
VI

/A
lIV

0.
24

0.
26

0.
36

0.
54

0.
48

0.
27

0.
25

0.
46

0.
45

0.
23

0.
21

0.
97

0.
12

0.
31

0.
09

0.
20

0.
45

0.
33

W
o

36
.0

36
.8

41
.0

42
.1

42
.7

40
.9

38
.6

43
.6

41
.9

42
.1

40
.9

38
.7

41
.2

41
.3

43
.5

44
.7

41
.4

41
.3

En
43

.6
45

.6
42

.6
44

.3
45

.8
45

.2
41

.8
44

.1
39

.5
44

.5
39

.8
34

.7
40

.0
47

.7
40

.4
42

.1
25

.9
18

.8

Fs
20

.4
17

.7
16

.5
13

.7
11

.4
13

.9
19

.6
12

.3
18

.6
13

.4
19

.2
26

.7
18

.8
11

.0
16

.1
13

.2
32

.7
39

.9

Fo
rm

ul
ae

 c
al

cu
la

te
d 

on
 th

e 
ba

si
s o

f 4
 c

at
io

ns
 a

nd
 6

 o
xy

ge
ns

. c
 =

 c
or

e,
 r 

= 
rim

. M
g#

 =
 1

00
*(

M
g/

(M
g 

+ 
Fe

2+
)).

 *
 =

 d
ac

ite
. S

am
pl

e 
lo

ca
tio

n 
nu

m
be

r c
or

re
sp

on
ds

 to
 th

e 
lo

ca
tio

ns
 in

 F
ig

ur
e 

2A
-B

.



Geologia croatica 68/1Geologia Croatica
34

Figure 4: AlIV – (Na + K)A plot of amphiboles from the Kalnik and Ivanščica 
Mts. gabbroic rocks with the nomenclature fields of LEAKE et al. (1997). 
Fields of amphiboles from the Mt. Medvednica Middle- to Late Jurassic 
gabbros and ultramafic cumulates (LUGOVIĆ et al., 2007; SLOVENEC & 
LUGOVIĆ, 2008) are shown for comparison.

Figure 5: Plot of clinopyroxene compositions in the En – Wo – Fs (Mg2Si2O6 – Ca2Si2O6 – Fe2Si2O6) diagram with the nomenclature fields of MORIMOTO 
(1988) for gabbroic rocks and dacite from the Kalnik and Ivanščica Mts. ophiolite mélange. Field for clinopyroxene compositions from Middle- to Late 
Jurassic isotropic gabbros in the Mt. Medvednica ophiolite mélange (SLOVENEC & LUGOVIĆ, 2008) are plotted for correlation constraints.

Clinopyroxenes from the gabbroic group A, show the 
lowest Wo- and higher Fs-content (Fig. 5) and have signifi-
cantly higher Ti-abundance than clinopyroxene populations 
hosted in the gabbroic rocks of groups B and C (Fig. 6; Ta-
ble 2). The clinopyroxenes from group B show compositions 
similar to clinopyroxenes hosted in amphibole gabbros from 

nearby Mt. Medvednica (Fig. 5) that are related to late Mid-
dle Jurassic intra-oceanic subduction in the ROD (SLO-
VENEC & LUGOVIĆ, 2008). In the same figure, the clinopy-
roxene populations from group A show a wide span of 
Fs-content and overlap with clinopyroxene compositions 
from rocks of group C.

6. bULK rOcK cHEMIcAL cOMPOsItION

Table 3 displays the results of 20 analyses of gabbroic rocks 
and 1 dacite from the Ivanščica and Kalnik Mts. tectono-
sedimentary ophiolite mélange. Nd and Sr isotopic compo-
sition of 6 gabbroic samples are shown in Table 4.

The analysed gabbroic rocks were subdivided on the ba-
sis of geochemical criteria into three geochemical groups (see 
Section 6 below) which were isotopically dated to three dis-
tinct geological times (see Section 7 below). The geochemical 
group A is represented by the Early Jurassic sample vsk-242/2 
(Fig. 2A, location 1), group B by the Late Jurassic samples 
vsk-228 and 228/5 (Fig. 2A, location 4) and geochemical 
group C by Early Cretaceous samples vsk-229/7 (Fig. 2A, lo-
cation 3) and sample vsi-8/1 (Fig. 2B, location 3).

The analysed gabbroic rocks partly underwent deuteric 
and sea-floor hydrothermal alteration which resulted in a mi-
nor increase in the loss on ignition (LOI £ 3.08 wt%) and 
minor chemical modification of the major elements. In ad-
dition, the TiO2 vs. Al2O3 diagram (COLOMBI, 1989) 
clearly shows that all analysed gabbros reflect basaltic liquid 
composition (Fig. 7A). This indicates that our gabbroic rocks 
may be considered to reflect original magmatic composition. 



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
35

Figure 6: (A) Ti – AlIV and (b) SiO2/100 – Na2O – TiO2 discriminant diagram (simplified after BECCALUVA et al., 1989) for clinopyroxene from gabbroic rocks 
and dacite of the Kalnik and Ivanščica Mts. ophiolite mélange. IAT = island-arc tholeiites, MORB = mid-ocean ridge basalts, BABB = back-arc basin basalts. 
Fields for clinopyroxene compositions from Middle- to Late Jurassic isotropic gabbros in the Mt. Medvednica ophiolite mélange (SLOVENEC & LUGOVIĆ, 
2008) are plotted for correlation constraints.

Figure 7:  (A) Al2O3 – TiO2 discrimination diagram (adopted from COLOMBI, 1989) and (b) TAS classification diagram with the nomenclature fields of in-
trusive rocks after COX et al. (1979) for the gabbroic rocks from the Kalnik and Ivanščica Mts. ophiolite mélange.

In the (Na2O + K2O) vs. SiO2 classification diagram for in-
trusive rocks (COX et al., 1979), all rocks plot in the subal-
kaline field (Fig. 7B). The majority of the mafic samples plot 
in the gabbro field and only sample gtc-3 from Gotalovec 
quarry represents a true diorite composition, pointing to the 
relative immobility of Na and K. In the same type of diagram 

for volcanic rocks, the felsic dyke (sample gtc-6) intersect-
ing the Gotalovec quarry intrusives, plots in the dacite field 
(not shown). Samples from Gotalovec quarry represent the 
fractionated rocks, whereby sample gtc-4 is the least frac-
tionated specimen. On the basis of co-variation of TiO2 and 
Mg# following the classification scheme for ophiolitic gab-



Geologia croatica 68/1Geologia Croatica
36

ta
bl

e 
3:

 C
he

m
ic

al
 a

na
ly

se
s o

f g
ab

br
oi

c 
ro

ck
s a

nd
 d

ac
ite

 in
 th

e 
Ka

ln
ik

 (K
A)

 a
nd

 Iv
an

šč
ic

a 
(IV

) M
ts

. o
ph

io
lit

e 
m

él
an

ge
.

G
ro

up
 A

G
ro

up
 B

G
ro

up
 C

Sa
m

pl
e

vs
k-

24
2/

2
vs

k-
24

2/
4

vs
k-

24
2/

6
vs

k-
20

4
vs

k-
22

8
vs

k-
22

8/
2

vs
k-

22
8/

5
vs

k-
21

7/
1

vs
k-

22
9/

1
vs

k-
22

9/
7

vs
k-

22
9/

12
be

-3
vs

i-5
vs

i-7
/1

vs
i-8

/1
vs

i-8
/2

gi
-2

gi
-5

+g
tc

-3
gt

c-
4

*g
tc

-6

Lo
ca

lit
y 

/  
Sa

m
pl

e 
lo

c.
KA

/1
KA

/1
KA

/1
KA

/2
KA

/4
KA

/4
KA

/4
KA

/5
KA

/3
KA

/3
KA

/3
IV

/1
IV

/2
IV

/4
IV

/3
IV

/3
IV

/5
IV

/5
IV

/5
IV

/5
IV

/5

Si
O

2 
49

.1
0

48
.5

3
49

.8
4

51
.9

1
50

.4
9

49
.9

9
49

.4
2

49
.6

5
49

.0
3

49
.7

6
49

.2
2

50
.9

9
50

.8
5

48
.9

3
49

.4
8

49
.6

7
51

.4
5

51
.2

6
55

.9
9

50
.7

0
64

.5
8

Ti
O

2 
2.

06
2.

25
2.

14
1.

03
0.

97
0.

99
0.

91
1.

35
1.

66
1.

74
1.

50
2.

13
2.

29
2.

19
1.

36
1.

35
1.

64
1.

55
2.

04
1.

74
0.

51
Al

2O
3 

14
.6

8
14

.2
8

14
.3

0
13

.0
1

15
.0

1
15

.0
5

15
.9

5
14

.1
0

14
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7
14

.2
1

14
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2
14

.6
2

12
.6

3
11

.8
9

13
.2

7
13

.3
3

15
.9

0
16

.9
6

14
.6

1
16

.4
9

16
.1

3
Fe

2O
3t

ot
al

 
10

.0
2

10
.5

4
10

.5
3

9.
84

9.
81

8.
58

9.
12

8.
89

10
.2

4
10

.3
0

9.
69

9.
81

12
.4

2
14

.0
5

10
.2

7
9.

92
10

.1
6

9.
14

10
.7

8
10

.0
8

6.
38

M
nO

0.
67

0.
17

0.
19

0.
18

0.
33

0.
25

0.
29

0.
17

0.
19

0.
20

0.
17

0.
24

0.
25

0.
27

0.
18

0.
18

0.
17

0.
17

0.
23

0.
19

0.
13

M
gO

5.
75

6.
45

6.
93

8.
30

9.
99

9.
76

9.
37

7.
61

8.
33

8.
36

7.
84

6.
25

6.
37

8.
19

9.
14

9.
50

5.
99

5.
52

3.
42

5.
73

0.
84

Ca
O

10
.4

4
10

.0
6

9.
09

7.
97

6.
70

8.
02

8.
32

10
.1

5
8.

62
6.

95
9.

10
7.

72
6.

52
6.

83
7.

85
8.

61
6.

45
6.

62
4.

47
7.

21
1.

74
N

a 2
O

3.
28

3.
78

3.
72

4.
46

3.
90

3.
15

3.
43

4.
30

3.
97

4.
31

3.
93

4.
01

4.
75

4.
26

4.
11

3.
76

5.
30

5.
52

5.
04

5.
37

8.
49

K 2
O

0.
04

0.
08

0.
05

0.
73

0.
49

0.
19

0.
47

0.
03

0.
18

0.
80

0.
37

0.
19

0.
16

0.
08

0.
24

0.
01

0.
07

0.
01

0.
47

0.
02

0.
23

P 2
O

5 
0.

22
0.

23
0.

20
0.

10
0.

08
0.

09
0.

07
0.

17
0.

16
0.

18
0.

15
0.

28
0.

21
0.

23
0.

15
0.

12
0.

18
0.

23
0.

36
0.

17
0.

10
LO

I
3.

05
2.

95
3.

05
2.

31
2.

62
3.

03
2.

26
3.

08
3.

06
2.

75
2.

93
3.

05
3.

04
2.

07
3.

01
3.

03
2.

99
2.

92
3.

04
0.

24
1.

61

To
ta

l
99

.3
1

10
0.

32
10

0.
04

99
.8

4
10

0.
39

99
.1

0
99

.6
1

99
.5

0
99

.8
1

99
.8

4
99

.2
2

99
.2

9
99

.4
9

99
.9

9
99

.0
6

99
.4

8
10

0.
30

99
.9

0
10

0.
45

10
0.

90
10

0.
74

M
g#

53
.2

4
56

.0
8

57
.8

4
64

.9
0

68
.9

9
71

.3
0

67
.6

1
62

.9
0

62
.2

5
62

.3
4

63
.5

9
58

.2
0

50
.7

9
54

.8
8

64
.4

1
67

.9
1

54
.2

5
55

.1
5

40
.3

8
56

.0
7

23
.0

4

Cs
0.

2
0.

1
0.

1
2.

9
1.

2
1.

4
0.

8
1.

0
2.

6
3.

8
2.

3
1.

6
1.

0
0.

2
0.

3
0.

6
2.

0
0.

2
1.

2
1.

3
0.

8
Rb

1
1

2
10

15
8

16
1

8
7

11
8

13
3

2
3

1
1

11
1

5
Ba

54
79

67
33

0
31

4
20

8
35

5
78

16
4

34
1

17
2

60
8

65
7

74
18

8
17

4
11

4
75

23
7

47
12

5
Th

0.
50

0.
32

0.
28

0.
28

0.
25

0.
29

0.
21

0.
43

0.
43

0.
50

0.
43

1.
27

0.
92

0.
78

0.
42

0.
35

0.
44

0.
56

1.
28

0.
43

1.
81

Ta
0.

31
0.

36
0.

34
0.

05
0.

04
0.

04
0.

03
0.

14
0.

17
0.

19
0.

16
0.

38
0.

33
0.

25
0.

13
0.

12
0.

15
0.

22
0.

43
0.

18
0.

47
N

b
4.

9
5.

8
5.

3
0.

9
0.

7
0.

7
0.

5
2.

3
2.

8
3.

1
2.

6
6.

1
5.

5
4.

1
2.

1
2.

0
2.

5
3.

6
6.

9
2.

9
7.

6
Sr

89
72

11
5

28
9

23
3

13
5

20
2

17
5

30
3

34
0

26
4

18
7

24
6

91
16

6
15

7
14

1
87

21
0

78
13

8
Zr

11
7

12
9

12
4

70
57

63
49

11
1

11
3

12
9

11
6

18
7

18
0

16
5

93
85

87
12

3
22

4
10

3
35

0
H

f
3.

4
3.

8
3.

6
2.

0
1.

7
1.

8
1.

4
2.

8
3.

1
3.

8
3.

0
5.

9
5.

5
4.

8
2.

7
2.

4
2.

6
3.

6
6.

9
3.

1
9.

1
Y

39
.7

42
.5

43
.1

27
.6

25
.0

27
.2

21
.8

34
.2

33
.4

35
.8

33
.7

58
.7

58
.5

51
.4

32
.4

29
.8

30
.3

45
75

.9
35

.4
90

.7
Sc

41
40

37
42

38
36

36
37

40
37

38
27

37
38

40
42

35
28

22
35

11
V

33
3

38
0

34
6

34
4

33
8

35
7

32
1

28
9

31
8

31
8

30
0

32
8

41
1

37
5

27
9

27
9

31
9

28
5

32
2

30
5

27
3

Cr
11

0
12

5
13

0
23

0
26

0
25

2
24

4
20

0
29

0
25

0
16

0
19

19
20

40
0

45
0

40
30

18
34

20
N

i
40

39
41

40
<2

0
<2

0
<2

0
<2

0
<2

0
<2

0
<2

0
<2

0
<2

0
<2

0
60

40
40

30
30

31
<2

0
La

5.
97

6.
57

6.
25

2.
31

1.
81

2.
06

1.
69

3.
98

4.
58

5.
33

4.
37

9.
43

8.
62

7.
59

3.
76

3.
40

3.
95

5.
66

12
.1

0
4.

77
15

.0
0

Ce
16

.7
9

18
.6

4
17

.8
5

7.
28

5.
55

6.
25

5.
01

12
.6

0
13

.7
3

15
.8

0
13

.1
1

28
.7

1
24

.9
3

22
.0

1
11

.7
0

10
.4

0
12

.3
16

.8
0

34
.3

13
.7

0
44

.3
0

Pr
2.

71
2.

92
2.

80
1.

30
1.

07
1.

27
0.

86
1.

97
2.

14
2.

45
2.

06
4.

29
3.

82
3.

36
1.

83
1.

68
1.

92
2.

59
5.

36
2.

24
6.

53
N

d
14

.1
0

15
.1

4
14

.7
0

7.
07

6.
41

6.
34

5.
16

11
.1

0
11

.8
5

13
.3

0
11

.4
0

22
.3

0
20

.2
0

18
.0

0
10

.3
0

9.
38

10
.3

0
14

.1
0

27
.4

0
11

.8
0

32
.3

0
Sm

4.
74

5.
18

4.
94

2.
63

2.
34

2.
59

2.
16

3.
38

3.
65

4.
33

3.
53

6.
53

5.
95

5.
32

3.
23

2.
90

3.
29

4.
34

8.
58

3.
67

9.
91

Eu
1.

55
1.

86
1.

71
0.

93
0.

81
0.

97
0.

65
1.

25
1.

45
1.

50
1.

34
2.

28
2.

25
1.

86
1.

17
1.

12
1.

36
1.

60
2.

77
1.

44
3.

11
G

d
6.

05
6.

59
6.

45
3.

57
3.

27
3.

68
3.

09
4.

70
5.

11
5.

46
4.

90
8.

32
8.

07
7.

24
4.

49
4.

11
4.

45
5.

95
10

.9
0

5.
09

12
.0

0
Tb

1.
17

1.
29

1.
21

0.
63

0.
58

0.
65

0.
52

0.
86

0.
94

1.
00

0.
89

1.
56

1.
51

1.
31

0.
84

0.
74

0.
85

1.
12

2.
08

0.
98

2.
44

D
y

7.
12

7.
58

7.
42

4.
04

3.
83

4.
36

3.
34

5.
49

5.
97

6.
37

5.
69

10
.4

0
9.

77
8.

53
5.

49
4.

91
5.

45
7.

10
12

.9
0

6.
20

15
.2

0
H

o
1.

56
1.

71
1.

61
0.

87
0.

84
1.

01
0.

74
1.

19
1.

30
1.

38
1.

23
2.

29
2.

11
1.

83
1.

18
1.

06
1.

09
1.

43
2.

75
1.

33
3.

36
Er

4.
59

4.
81

4.
09

2.
78

2.
69

2.
85

2.
37

3.
63

3.
95

4.
23

3.
69

6.
99

6.
40

5.
60

3.
58

3.
24

3.
27

4.
31

8.
03

3.
82

10
.1

0
Tm

0.
67

2
0.

70
1

0.
68

3
0.

43
3

0.
39

6
0.

44
5

0.
35

3
0.

51
4

0.
55

8
0.

59
8

0.
52

5
1.

00
1

0.
90

5
0.

79
6

0.
50

4
0.

44
8

0.
47

8
0.

62
6

1.
19

1
0.

55
7

1.
61

0
Yb

4.
48

4.
74

4.
54

3.
08

2.
92

3.
11

2.
37

3.
31

3.
51

3.
84

3.
42

6.
46

5.
90

5.
20

3.
18

2.
92

3.
13

4.
13

7.
71

3.
62

10
.1

0
Lu

0.
68

2
0.

71
8

0.
70

1
0.

44
2

0.
40

2
0.

45
5

0.
33

4
0.

48
3

0.
50

9
0.

57
0

0.
49

3
0.

92
6

0.
88

4
0.

76
0

0.
46

8
0.

43
0

0.
46

3
0.

63
2

1.
25

0
0.

57
3

1.
62

0

M
aj

or
 e

le
m

en
ts

 in
 w

t.%
, t

ra
ce

 e
le

m
en

ts
 in

 p
pm

. L
O

I =
 lo

ss
 o

n 
ig

ni
tio

n 
at

 1
10

0o C.
 M

g#
 =

 1
00

*m
ol

ar
 (M

gO
/(

M
gO

+F
eO

to
ta

l))
. +  =

 d
io

rit
e,

 *
 =

 d
ac

ite
. S

am
pl

e 
lo

ca
tio

n 
nu

m
be

r c
or

re
sp

on
ds

 to
 th

e 
lo

ca
tio

ns
 in

 F
ig

ur
e 

2A
-B

.



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
37

ta
bl

e 
4:

 N
d 

an
d 

Sr
 is

ot
op

ic
 d

at
a 

of
 g

ab
br

os
 fr

om
 th

e 
Ka

ln
ik

 (K
A)

 a
nd

 Iv
an

šč
ic

a 
(IV

) M
ts

. o
ph

io
lit

e 
m

él
an

ge
.

Sa
m

pl
e 

   
   

   
   

 L
oc

al
ity

/  
   

   
   

G
ro

up
   

   
   

14
7 Sm

/14
4 N

d 
   

   
   

   
  14

3 N
d/

14
4 N

da     
   

   
   

   
   

  87
Rb

/86
Sr

a     
   

   
   

   
   

   
  87

Sr
/86

Sr
a    

   
   

   
   

   
   

   
  S

m
   

   
   

   
   

   
N

d 
   

   
   

   
   

 R
b 

   
   

   
   

   
   

 S
r  

   
   

   
   

   
   

e N
d(

t)b    
   

   
   

  87
Sr

/86
Sr

(t)
c    

   
   

   
   

   
 A

ge
 (t

)*
   

   
   

   
   

   
   

   
  S

am
pl

e 
lo

c.

vs
k-

24
2/

2 
 

KA
/1

  
A

 
0.

20
32

5 
 

0.
51

29
23

  (
 9

) 
0.

03
25

06
 

 
0.

70
32

08
 (1

0)
 

4.
74

 
14

.1
0 

1 
89

 
+5

.4
1 

0.
70

31
22

 
18

5 
M

a

vs
k-

22
8 

 
KA

/4
 

B 
0.

22
07

2 
 

0.
51

29
42

  (
 8

) 
0.

15
89

75
 

 
0.

70
43

16
 ( 

9)
 

2.
34

 
6.

41
 

15
 

27
3 

+5
.4

7 
0.

70
39

77
 

14
7 

M
a

vs
k-

22
9/

7 
 

KA
/3

 
C 

0.
19

68
4 

 
0.

51
29

23
  (

 7
) 

0.
05

95
65

 
 

0.
70

37
62

 ( 
5)

  
4.

33
 

13
.3

0 
7 

34
0 

+5
.5

6 
0.

70
36

73
 

10
5 

M
a

vs
k-

22
9/

12
 

KA
/3

  
C 

0.
19

54
9 

 
0.

51
29

55
  (

 3
) 

0.
12

05
51

 
 

0.
70

38
58

 ( 
4)

 
3.

88
 

12
.0

0 
11

 
26

4 
+6

.2
0 

0.
70

36
87

 
10

5 
M

a

gi
-2

 
 

IV
/5

 
C 

0.
19

31
3 

 
0.

51
29

64
 (1

5)
 

0.
02

05
18

 
 

0.
70

34
33

 (1
4)

 
3.

29
 

10
.3

0 
1 

14
1 

+6
.4

3 
0.

70
34

04
 

10
5 

M
a

vs
i-8

/1
 

 
IV

/2
 

C 
0.

18
96

0 
 

0.
51

29
50

 (1
2)

 
0.

03
48

57
 

 
0.

70
35

64
 (1

3)
 

3.
23

 
10

.3
0 

2 
16

6 
+6

.2
3 

0.
70

35
14

 
10

5 
M

a

Sa
m

pl
e 

lo
ca

tio
n 

nu
m

be
r c

or
re

sp
on

ds
 to

 th
e 

lo
ca

tio
ns

 in
 F

ig
ur

e 
2A

-B
.  a 

Er
ro

rs
 in

 b
ra

ck
et

s f
or

 N
d 

an
d 

Sr
 is

ot
op

ic
 ra

tio
s a

re
 g

iv
en

 a
t t

he
 2

s-
le

ve
l. T

he
 14

7 Sm
/14

4 N
d 

ra
tio

s c
al

cu
la

te
d 

fro
m

 S
m

 a
nd

 N
d 

IC
P-

M
S 

co
nc

en
tr

at
io

ns
 (d

is
pl

ay
ed

 in
 

pp
m

) f
ol

lo
w

in
g 

th
e 

eq
ua

tio
n:

 14
7 Sm

/14
4 N

d 
= 

(S
m

/N
d)

 *
 [0

.5
31

51
 +

 0
.1

42
52

 *
 14

3 Sm
/14

4 N
d]

. T
he

 87
Rb

/86
Sr

 ra
tio

s c
al

cu
la

te
d 

fro
m

 R
b 

an
d 

Sr
 IC

P-
M

S 
co

nc
en

tr
at

io
ns

 (d
is

pl
ay

ed
 in

 p
pm

) f
ol

lo
w

in
g 

th
e 

eq
ua

tio
n:

 87
Rb

/86
Sr

 =
 (R

b/
Sr

) *
 [2

.6
93

9 
+ 

0.
28

32
 *

 87
Sr

/86
Sr

]. 
 b In

iti
al

 e
N

d(
t) 

ca
lc

ul
at

ed
 a

ss
um

in
g 

Io CH
U

R =
 0

.5
12

63
8,

 (14
7 Sm

/14
4 N

d)
o CH

U
R =

 0
.1

96
6,

 a
nd

 l
Sm

 =
 6

.5
4 *

10
-1

2  a
-1

. c 
 In

iti
al

 87
Sr

/86
Sr

(t)
 c

al
cu

la
te

d 
as

su
m

in
g 

l R
b =

 1
.4

2 *
10

-1
1  a

-1
. *

Co
re

sp
on

di
ng

 a
rb

itr
ar

y 
ag

e 
fo

r t
he

 in
iti

al
 e

N
d 

an
d 

in
iti

al
 S

r i
so

to
pi

c 
ra

tio
s.

ta
bl

e 
5:

 K
–A

r a
ge

s o
f g

ab
br

oi
c 

ro
ck

s i
n 

th
e 

Ka
ln

ik
 (K

A)
 a

nd
 Iv

an
šč

ic
a 

(IV
) M

ts
. o

ph
io

lit
e 

m
él

an
ge

.

Sa
m

pl
e 

Lo
ca

lit
y/

 
G

ro
up

 
An

al
is

ed
 

K 
[%

] 
40

Ar
 (r

ad
) 

40
Ar

 (a
ir)

 
Ag

e 
 

Sa
m

pl
e 

lo
c.

 
 

m
at

er
ia

l 
 

nl
/g

 
[%

 ] 
M

a 
± 

1s

vs
k-

22
8/

5 
KA

/4
 

B 
pl

ag
io

cl
as

e 
0.

39
5 

1.
11

6 
55

.6
0 

14
6.

4 
± 

3.
4

vs
k-

22
9/

7 
KA

/3
 

C 
pl

ag
io

cl
as

e 
0.

70
9 

3.
06

7 
68

.4
1 

10
7.

6 
± 

4.
2

vs
i-8

/1
 

IV
/2

 
C 

pl
ag

io
cl

as
e 

0.
12

9 
4.

50
1 

41
.5

0 
10

3.
4 

± 
3.

6

Sa
m

pl
e 

lo
ca

tio
n 

nu
m

be
r c

or
re

sp
on

ds
 to

 th
e 

lo
ca

tio
ns

 in
 F

ig
ur

e 
2A

-B
.

ta
bl

e 
6:

 40
Ar

/39
Ar

 d
at

a 
of

 a
m

ph
ib

ol
e 

fro
m

 g
ab

br
o 

sa
m

pl
e 

vs
k-

22
8 

(g
eo

ch
em

ic
al

 g
ro

up
 B

) f
ro

m
 th

e 
M

t. 
Ka

ln
ik

 o
ph

io
lit

e 
m

él
an

ge
.

St
ep

   
   

   
   

   
   

   
   

   
   

   
   

   T
em

p.
   

   
   

   
   

   
   

  T
im

e 
   

   
   

   
   

   
   

   
   

 40
Ar

*/
39

Ar
   

   
   

   
   

   
   

   
   

38
Ar

/39
Ar

   
   

   
   

   
   

   
   

   
   

 37
Ar

/39
Ar

   
   

   
   

   
   

   
   

   
  36

Ar
/39

Ar
   

   
   

   
   

   
   

   
   

   
Cu

m
.   

   
   

   
   

   
   

   
   

   
   

 R
ad

.   
   

   
   

   
   

   
   

   
  A

pp
ar

en
t a

ge
 

 
 

 
 

    
   

   
   

   
   

   
   

   
   

   
   

   
  x

 1
0–2

    
   

   
   

   
   

   
   

   
   

   
39

Ar
   

   
   

   
   

   
   

   
   

   
   

  40
Ar

   
   

   
   

   
   

   
   

   
   

   
  ±

1 
s 

s.d
.

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

  (
o C)

   
   

   
   

   
   

   
   

  (
m

in
.) 

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
   

   
(%

)  
   

   
   

   
   

   
   

   
   

   
   

 (%
)  

   
   

   
   

   
   

   
   

   
   

   
   

  (
M

a)

  1
 

60
0 

10
 

5 
± 

18
.0

 
0.

68
 ±

 0
.0

9 
19

.9
 ±

 1
.7

0 
25

2 
± 

23
 

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.



Geologia croatica 68/1Geologia Croatica
38

broic rocks (SERRI, 1981), the analysed samples of groups 
A and C correspond to a high-Ti gabbro (typical for a MORB/
BABB setting) and samples of group B match to the low-Ti 
suite (typical for a SSZ setting).

Successive alteration may also mobilize trace elements 
that are very important indicators of petrogenetic processes 
and for the geotectonic formational setting of the rock. A test 
of trace element mobility in our samples was applied by plot-
ting their concentration against Zr (not shown). High-field 
strength elements Ti, P, Ta, Nb, Y and Th (HFSE) as well as 
all rare earth elements (REE) appeared to be relatively im-
mobile during alteration. In contrast, almost all large ion 
lithophile elements (LILE) showed selective, but generally 
high intensities of mobility and consequently will not be uti-
lized for petrogenetic and geotectonic constraints. On multi-
element abundance patterns normalized to N-type MORB, 
the analysed gabbros reveal a broad variety of compositions 
(Fig. 8A,B), suggesting different sources and/or fractional 
spans. Neglecting the LILE, which are selectively enriched 
due to alterations, the relative concentration profile is char-
acterized by smooth patterns at 0.6 to 9.8 times relative to 
N-MORB. However, all samples of geochemical groups B 
and C display a negative anomaly for Nb, Ta and Ti, which 
is atypical for N-MORB, and indicates an input of a subduc-

tion component. These compositional patterns designated as 
N-MORB-type with arc signatures (SHERVAIS, 2001) are 
very common in mafic rocks of the Dinaric ophiolites 
(LUGOVIĆ et al., 1991; TRUBELJA et al., 1995). The ab-
sence of a subduction component input [(Nb/La)n = 0.95-
0.99; (Ti/Gd)n = 0.97-1.00] is only observed in the gabbro 
samples of the group A that are generated during the Early 
Jurassic (Fig. 8A1). The highest input of subduction related 
components [(Nb/La)n = 0.32-0.42; (Ti/Gd)n = 0.78-0.85] is 
recorded in the Late Jurassic edenite gabbro samples of 
group B and suggests generation in an upper plate during 
intra-oceanic convergence. In these respects, they are very 
similar to the amphibole gabbros from the nearby Mt. 
Medvednica ophiolite mélange (Fig. 8A1). However, the 
Early Cretaceous gabbros of group C, show intermediate 
values [(Nb/La)n = 0.58-0.69; (Ti/Gd)n = 0.74-1.07; Fig. 
8A2] between the gabbros of the former groups. 

The analysed gabbros display similar chondrite normal-
ized REE profiles at very different relative concentration 
levels which are characterized by flat patterns with a slight 
depletion in the LREE (Figs. 8B1 and 8B2). The intensity of 
LREE depletion expressed as (La/Sm)cn increases from the 
representative Early Jurassic (group A) via the Early Creta-
ceous (group C) to the Late Jurassic (group B) gabbroic rocks 

Figure 8: (A1, A2) N-MORB normalised multi-element diagram and (b1, b2) REE patterns for the Kalnik and Ivanščica Mts. gabbroic rocks and dacite. 
Normalisation values are from SUN and MCDONOUGH (1989). Patterns for Middle- to Late Jurassic isotropic gabbros in the Mt. Medvednica ophiolite 
mélange (SLOVENEC & LUGOVIĆ, 2008) are plotted for correlation constraints.



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
39

(0.79, 0.73-0.77 and 0.48-0.49, respectively). This is consist-
ent with overall depletion of the samples shown by the con-
centration levels of their REE patterns (Figs. 8B1 and 8B2). 
The dacite dyke and host diorite from the Gotalovec quarry 
show MREE to HREE profiles 40-46 times relative to chon-
drite and represent highly fractionated compositions. The 
calculated range of Eu anomalies (0.77-1.09) is typical for 
fractionation and minor accumulation of plagioclase in the 
individual samples, respectively.

The measured 143Nd/144Nd ratios of gabbroic rocks are 
similar and vary from 0.512923 to 0.512964 which corre-
sponds to respective initial εNd(T) values ranging from +5.41 
to +6.43 (Table 4). The 87Sr/86Sr ratios range from 0.703208 
to 0.704316 and correspond to respective initial ratios of 
0.703122 to 0.703977. The initial εNd and 87Sr/86Sr ratios of 
the representative Early Jurassic (group A) gabbroic rock 
plot in the MORB field, while the all other representative 
Late Jurassic (group B) and Early Cretaceous (group C) gab-
bro samples plot in the field of recent island-arc and back-
arc analogues (Fig. 9). 

7. PrEVOUsLY PUbLIsHED AND NEW IsOtOPIc 
DAtING

7.1. K-Ar dating 
Previously published K-Ar dating of the MORB-type gab-
bro south from of the Hruškovec quarry revealed an Early 
Jurassic (Pliensbachian) age of 185 ± 6 Ma (PAMIĆ, 1997). 
Here, a gabbro from the same block [sample vsk-242/2 (Fig. 
2A, location 1)] is geochemically characterized and used as 
a representative for geochemical rock group A.

New K-Ar age data, presented here, are measured on 
plagioclase separated from gabbro [sample vsk-228/5 (Fig. 
2A, location 4)] of geochemical rock group B, and two gab-
bros [sample vsk-229/7 (Fig. 2A, location 3) and vsi-8/1 
(Fig. 2B, location 3)] of geochemical rock group C. The re-
sults are presented in Table 5. 

We interpreted the ages as the ages of rock consolida-
tion. The time of rock consolidation (146.4 ± 3.4 Ma) for 
gabbro which is used as a representative for geochemical 
rock group B in geological terms matches the Late Jurassic 
(Tithonian). 

However, the other two ages (107.6 ± 4.2 Ma and 103.4 
± 3.6 Ma) obtained for BABB-type gabbros which are used 
as representatives for geochemical rock group C in geologi-
cal terms correspond to the latest Early Cretaceous (Albian). 

7.2. 40Ar-39Ar dating 
The results of the 40Ar-39Ar measurements on a magmatic 
amphibole (edenite - Table 1, Fig. 4) separate of sample vsk-
228 (Fig. 2A, location 4) are displayed in Table 6 and Figure 
10. The initial heating steps indicate variable ages, steps 4-7 
(with 70% of the released gas) suggest an apparent age of 
147 ± 7 Ma. The last step of the spectrum is higher than the 
mean age, indicating inherited argon (e.g. from high-temper-
ature minerals like apatite). The Ca/K spectrum (Fig. 10B) 
is increasing, suggesting some contamination of the mea-

sured sample by a mineral degassing at lower temperatures 
than amphibole and containing more potassium rather than 
calcium.

The plateau age of 147 ± 7 Ma from sample vsk-228 
seems to be geologically significant, especially considering 
the similar age (146.4 ± 3.4 Ma) of sample vsk-228/5 from 
the same block obtained using K-Ar dating. We interpreted 
this plateau age as the age of gabbro crystallisation. Further-
more, it is (significantly) different in age from the gabbro 
south of the Hruškovec quarry of 185 ± 6 Ma. Therefore, this 
Late Jurassic gabbro is also used as a representative for geo-
chemical rock group B.

8. DIscUssION AND cONcLUsIONs

Besides the dominant extrusive oceanic rock fragments, the 
Kalnik Unit also contains blocks of deep crustal sequences 
represented by ultramafic cumulates (LUGOVIĆ et al., 
2007), as well as mafic cumulate and isotropic plutonic rocks 
(SLOVENEC & LUGOVIĆ, 2008). The latter sequence, 
which was studied at the nearby Mt. Medvednica ophiolite 
mélange, comprises gabbro and predominant amphibole 
gabbro compositions, including a gabbro-pegmatite dated to 
161.1 ± 2.1 Ma (Callovian-Oxfordian) (SLOVENEC & 
LUGOVIĆ, 2008). It was suggested that the Mt. Medved-
nica mafic-ultramafic crustal sequence represents remnants 
of a proto-arc–forearc system that was initiated in the ROD 
in Bathonian times (SLOVENEC et al., 2011). Isotropic gab-
broic fragments are more abundant in the northern areas of 
the Kalnik Unit, in the Kalnik and Ivanščica Mts. ophiolite 
mélange. In this work, the analysed gabbroic rocks are sub-
divided on the basis of petrographic and geochemical crite-
ria into three groups (group A, B and C) which were isoto-
pically dated to three distinct geological times. These 
gabbroic rocks show a similar overall bulk rock chemistry 
(Fig. 8), isotopic compositions (Fig. 9) and clinopyroxene 
compositions (Fig. 5), that compare well with the analogues 
from the MORB, IAT and BABB geotectonic environments, 
respectively. This particularly holds true for the Early Juras-
sic and Early Cretaceous representative gabbros, whereas 
the Late Jurassic gabbros, follow an IAT trend also inferred 
for the Middle-Late Jurassic isotropic gabbros from the 
nearby Mt. Medvednica ophiolite mélange, as analysed by 
SLOVENEC & LUGOVIĆ (2008).

8.1. tectonomagmatic and petrogenetic significance
a) Geochemical group A – Early Jurassic gabbroic suite  
The amphibole-free gabbroic block [sample vsk-242/2 (Fig. 
2A, location 1)], from Mt. Kalnik, dated by PAMIĆ (1997) to 
185 ± 6 (Pliensbachian) has been assigned as the representa-
tive of the Early Jurassic geochemical group of rocks. Its geo-
chemical characteristics are the most akin to slightly evolved 
N-MORB of all the analysed gabbro samples. This is evident 
from the normalized bulk rock chemistry (eg. multi-element 
abundance patterns normalized to N-type MORB; Fig. 8A1), 
initial Nd-Sr isotopic composition (Fig. 9) as well as the high-
est clinopyroxene Ti-abundances (Fig. 6) and position of the 
rocks in the selected geotectonic discrimination diagrams 



Geologia croatica 68/1Geologia Croatica
40

(Fig. 11). The absence of the subduction component input ex-
pressed by the ratio (Nb/La)n of 0.95-0.99, strongly suggests 
formation of the gabbroic rocks of group A at a ridge, spread-
ing over a subducting slab at the terminal stage of the Palaeo-
Tethyan slab break-off, which was previously dated to the 
Bajocian (SLOVENEC et al., 2011). The amphibole-free gab-
bro represents a plutonic sequence of crust formed during the 
Early Jurassic onset of ocean-floor spreading in the ROD.

The residual mantle where these Early Jurassic gabbros 
were fractionated from should have extracted around 5% of 
partial melt (Fig. 12). However, a very high fertile mantle 
residuum (lherzolite) that is abundant in the CDOB ophiolite 
complexes (LUGOVIĆ et al., 1991; BAZYLEV et al., 2008) 
has not been previously observed in the ROD mélanges.

b) Geochemical group B – Late Jurassic gabbroic suite
A gabbroic crystallization sequence with magmatic amphi-
bole, in this case edenite (Table 1, Fig. 4) represented in Late 
Jurassic samples vsk-228 and vsk-228/5 (Fig. 2A, location 
4), in the context of ophiolites, is typical for the fractionation 
of tholeiitic basalts, under low to medium pressures in supra-
subduction settings (SERRI & SAITTA, 1980). It is atypical 
for mafic rocks from an ocean ridge (PEARCE et al., 1984). 
However, accessory amphibole may crystallize at the ocean 
floor near to transform faults (CONSTANTIN, 1999) and 
mid-ocean ridges, where formation of Ti-pargasite-tscher-
makite is confined to the late-magmatic evolution of an in-
trusive sequence as an interstitial phase with low abundance 
(TRIBUZIO et al., 2000; COOGAN et al., 2001).

Figure 9: Initial 143Nd/144Nd – 87Sr/86Sr isotope ratios 
diagram for the Kalnik and Ivanščica Mts. gabbroic 
rocks showing the main oceanic mantle reservoirs of 
ZINDLER & HART (1986). Fields for Middle- to Late 
Jurassic isotropic gabbros in the Mt. Medvednica 
ophiolite mélange (SLOVENEC & LUGOVIĆ, 2008) are 
plotted for correlation constraints. DM – depleted 
mantle, BSE – bulk silicate Earth, EMI and EMI II – en-
riched mantle, HIMU – mantle with high U/Pb ratio, 
PREMA – PREvalent MAntle composition. The mantle 
array is defined by many oceanic basalts and a bulk 
Earth value for 87Sr/86Sr can be obtained from this 
trend. Data for back-arc basin basalts - BABB (shaded 
field) compiled from WILSON (1989) and references 
therein, COUSENS et al. (1994) and references therein, 
PEARCE et al. (1995), GRIBBLE et al. (1998) and EWART 
et al. (1998). Data for mid-ocean ridge basalts - MORB 
(solid line) compiled from WILSON (1989) and refer-
ences therein and COUSENS et al. (1994), references 
therein and PEATE et al. (1997). Data for oceanic island 
arcs and active continental margins - IAB (broken line) 
compiled from WILSON (1989) and references therein, 
COUSENS et al. (1994) and references therein, PEARCE 
et al. (1995) and PEATE et al. (1997). The field for 
87Sr/86Sr values affected by syn- or post-magmatic al-
teration in contact with seawater (light-grey shading) 
is from USTASZEWSKI et al. (2009).

Figure 10: (A) 40Ar/39Ar step heating diagram of Late Jurassic gabbro amphibole (sample vsk-228) from the Mt. Kalnik ophiolite mélange. (b) Ca/K spec-
trum.



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
41

In contrast, abundant magmatic amphibole is typical for 
rocks related to true subduction magmatism, sensu STERN 
(2004) that is, for the rocks crystallized from melt derived 

from the mantle wedge, metasomatized by a flux of fluids re-
leased from the subducting slab. These volatile-rich magmas 
produced by hydrous melting of the mantle wedge (TATSUMI 

Figure 11: Discrimination diagrams for the gabbroic rocks from the Kalnik and Ivanščica Mts. ophiolite mélange. (A) V – Ti/1000 diagram (SHERVAIS, 1982). 
IAT = island-arc tholeiites, MORB = mid-ocean ridge basalts, BABB = back-arc basin basalts, CAB = calc-alkaline basalts, CFB = continental flood basalts, 
OIB = ocean-island basalts and AB = alkali basalts. (b) Th – Hf/3 – Nb/16 diagram (WOOD, 1980). N-MORB = normal mid-ocean ridge basalts, E-MORB = 
enriched MORB, WPT = within plate tholeiites, WPB = alkaline within plate basalts, CAB = calc-alkaline basalts and IAT = island-arc tholeiites. 1 - crustal 
contamination; 2 - SSZ ophiolites trend; 3 - MORB ophiolites trend. (c) Ta/Yb – Th/Yb diagram (PEARCE, 1983). S - subduction zone enrichment; C - crustal 
contamination; W - within-plate enrichment. N-MORB, E-MORB and OIB are from SUN & MCDONOUGH (1989). T-MORB is from GESHI et al. (2007). Data 
for back-arc basin basalts (BABB) fields are from PEARCE et al. (1984), EWART et al. (1994) and LEAT et al. (2000). (D) NbN – ThN diagram. Seven marked 
fields of different basaltic rock-type of Albanide-Hellenide ophiolites are from SACCANI et al. (2011). N-MORB, E-MORB and OIB are from SUN and MC-
DONOUGH (1989). T-MORB is from GESHI et al. (2007). Fields for Middle- to Late Jurassic isotropic gabbros in the Mt. Medvednica ophiolite mélange 
(SLOVENEC & LUGOVIĆ, 2008) are plotted for correlation constraints.



Geologia croatica 68/1Geologia Croatica
42

Figure 12: Petrogenic model for gabbroic rocks from the Kalnik and Ivanščica Mts. ophiolite mélange. Highly differentiated rock samples vsi-5 and vsi-
7/1 from Mt. Ivanščica are omitted. Partial melting lines: DM – depleted mantle source, PM – primitive mantle source (KOSTOPOULOS & JAMES, 1992), OIB 
– enriched mantle source (CLAGUE & FREY, 1982). Model parameters = spinel-lherzolite source (ol57-opx25.5-cpx15-sp2.5), melting proportion = ol1.21-opx8.06-
cpx76.37-sp14.36, distribution coefficients are from KOSTOPOULOS & JAMES (1992). Fractional crystallization lines: initial magma = 10% melting of DM and 
PM mantle source, respectively, fractionated mineral assemblage = ol30-cpx40-pl30, distribution coefficients are from CHEN et al. (1990). Data for N-MORB, 
E-MORB are from SUN & MCDONOUGH (1989). Field for Middle- to Late Jurassic isotropic gabbros in the Mt. Medvednica ophiolite mélange (SLOVENEC 
& LUGOVIĆ, 2008) are plotted for correlation constraints.

larly in La (LUGOVIĆ et al., 1991; BAZYLEV et al., 2008). 
Subsequent subduction related enrichment of these peridotites 
in the mantle wedge will never increase La (as well as other 
LREE) concentration to an extent capable of producing a typ-
ical IAT REE pattern of partial melts (SLOVENEC & 
LUGOVIĆ, 2009). The Late Jurassic IAT-type amphibole gab-
bro is derived from the plutonic sequences of crust formed in 
the upper plate during initial subduction in the ROD. Accord-
ing to the La/Yb vs. La diagram (Fig. 12), the analyzed Late 
Jurassic gabbros from Mt. Kalnik, represent crust derived from 
a depleted mantle wedge that suffered around 13-17% partial 
melting. Amphibole-bearing transitional harzburgites inserted 
within the Campanian-Maastrichtian rudist limestones from 
Gornje Orešje in nearby Mt. Medvednica (LUGOVIĆ et al., 
2007) with U-shaped REE patterns and slightly depleted spi-
nel compositions (Mg# ~ 0.67; Cr# ~ 0.41) consistent with ~ 
15% partial melting, perfectly matches the residual mantle af-
ter extraction of the parental melt. Another transitional harz-
burgite slice from Gornje Orešje showing a more depleted 
spinel composition (Mg# ~ 0.56; Cr# ~ 0.45) which is consist-
ent with ~ 20% partial melting, may represent vestiges of the 
residual mantle from where the Mt. Medvednica gabbros were 
derived.

The geochemical signatures of the gabbro samples vsk-
228 and vsk-228/5 indicate magmatism at around ~ 147 Ma 
(Tithonian) related to a nascent island-arc setting. Since this 
age is younger than those obtained on island-arc basalt from 

& EGGINS, 1995) crystallize amphibole-bearing mafic-ultra-
mafic rock associations, either in island-arcs or continental 
margins (CONRAD & KAY, 1984; DEBARI & COLEMAN, 
1989; CLAESON & MEURER, 2004; KOCAK et. al., 2005). 
Based on their strong mineralogical and geochemical simi-
larities with recent or ancient lithological analogues, most of 
the blocks representing the oceanic plutonic succession ar-
chived in the Kalnik and Medvednica Mts. ophiolite mélange, 
must have formed in a supra-subduction setting. Samples vsk-
204, vsk-228, vsk-228/2 and vsk-228/5 from Mt Kalnik (Fig. 
2A, location 2 and 5), systematically plot in the field of island-
arc tholeiites (Fig. 6 and 11). They show a strong subduction-
related signature expressed as negative HFSE anomalies (Fig. 
8A1). Initial εNd and 87Sr/86Sr ratio (Fig. 9) also indicates their 
supra-subduction origin. At the same time, the sample shows 
significant depletion of LREE (Fig. 8B1), which is a peculiar 
geochemical feature of late Middle- to Late Jurassic supra-
subduction magmatism, recorded by the extrusive blocks in 
the Kalnik and Ivanščica Mts. ophiolite mélange (SLOV-
ENEC et al., 2011). The amphibole gabbros from the nearby 
Mt. Medvednica ophiolite mélange (Fig. 1A-B), although ap-
parently older (~ 161 Ma; SLOVENEC & LUGOVIĆ, 2008), 
are more influenced by subduction related components (Fig. 
6, 8 and 11). This suggests that the mantle wedge had been 
previously depleted in LREE by very small increments of melt 
removal, possibly similar to that for the mantle lherzolites in 
the CDOB, which are extremely depleted in LREE, particu-



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
43

Ivanščica Mt. (154 ± 8.7 Ma; see SLOVENEC et al., 2011), 
this is the youngest measured age concerning the Late 
Jurassic intra-oceanic subduction related crust in the ROD.

c) Geochemical group C – Early Cretaceous gabbroic suite
The gabbroic blocks represented by samples vsk-229/7 from 
Mt. Kalnik and vsi-8/1 from Mt. Ivanščica, dated to the latest 
Early Cretaceous (Albian) have been adopted as the represen-
tative samples of group C. This group also includes undated 
isotropic gabbro samples with the same or very similar geo-
chemical and mineralogical compositions and characteristics 
(Table 1-3, Fig. 4-9 and 11). Gabbros from this block contain 
minor amounts of edenite (Table 1; Fig. 4), suggesting crys-
tallization from a volatile-bearing magma. Given the bulk 
rock chemistry, (Table 3; Fig. 8) and host clinopyroxene com-
position (Table 2; Fig. 6), the gabbros show transitional geo-
chemical signatures between the Early Jurassic N-MORB-
type gabbros of group A and the Late Jurassic IAT-type 
gabbros of group B. Geochemical features compiled from se-
lected discrimination diagrams (Fig. 11) as well as  initial εNd 
and 87Sr/86Sr ratios (Fig. 9) indicate the BABB-type affinity 
of this gabbroic group that clearly forms a discrete trend (Fig. 
11B and 11D). This suggests that the rock suite of group C 
may represent cogenetic crustal fragments derived from a sim-
ilar mantle source. These Early Cretaceous gabbros are formed 
in an ensimatic back-arc marginal basin of the ROD. Since 
those gabbros reflect basaltic liquids (Fig. 7A), their compo-
sitions may be used for petrogenetic modelling. The represen-
tative gabbro samples and other members of the group, except 
Gotalovec quarry samples, show ~ 7-9% total partial melting 
(Fig. 12). However, the Gotalovec quarry sample gtc-4, albeit 
being slightly fractionated, may reflect melts derived from a 
comparatively slightly more depleted mantle source. The 
other three Gotalovec quarry gabbros are moderately fraction-
ated (Fig. 12).  The highly serpentinized lherzolite from the 
Mt. Kalnik metamorphic sole, that has undergone 7% of par-
tial melting (LUGOVIĆ et al., 2007), perhaps could be com-
positionally reminiscent of the mantle residue of these repre-
sentative gabbros. The Kalnik lherzolite is LREE depleted due 
to very small increments of melt removal and in this respect 
closely resembles Jurassic mantle lherzolites from the CDOB 
ophiolite complexes (LUGOVIĆ et al., 1991; BAZYLEV et 
al., 2008).

The existence of Early Cretaceous oceanic crust in the 
ROD may be inferred from protoliths of the almandine am-
phibolite facies metamorphic sole, welded beneath the Mt. 
Kalnik lherzolite (LUGOVIĆ et al., 2007). The metamorphic 
sole includes BABB-type protoliths from plutonic and ex-
trusive sequences that were metamorphosed at 118 ± 8 Ma 
(IGNJATIĆ, 2007). The formation of a metamorphic sole 
bears witness to the termination of spreading and indicates 
the initial stages of convergence in an oceanic basin, wherein 
the youngest oceanic crust and parental mantle are involved 
in a contact dynamo-thermal interaction (e.g. INSERGUEIX-
FILIPPI et al., 2000; WAKABAYASHI & DILEK, 2000, 
2003). The amphibolite-lherzolite composite slice from Mt. 
Kalnik is tectonically emplaced into Palaeocene carbonate 
breccias and represents the remnant that provides the crucial 

key to understanding the tectonomagmatic evolution in the 
final oceanic stage of the ROD.

Unfractionated and least fractionated samples of group 
C from Figure 12 resemble the geochemical characteristics 
of the Aptian metamorphic sole protoliths (Fig. 11B and 
11D), and may be interpreted as crust formed in an Early 
Cretaceous back-arc basin. Alternatively, a similar rock suite 
may have formed during the subduction of an active ridge 
(e.g. BORTOLLOTTI et al., 2002), when an enormous vol-
ume of magma generated in a relatively short period of time, 
creates incipient crust in the leading edge of the upper (over-
riding) plate (e.g. STERN & BLOOMER, 1992). From this 
standpoint, the same rock suite should be relatively younger 
than in the model that assumes its formation at a back arc 
basin spreading ridge. However, a full time range of crust 
formation in the Cretaceous back-arc basin of the ROD re-
quires extensive dating.

The composite gabbroic megablock from the Gotalovec 
quarry (Fig. 2B, location 5) shows a high level of magma frac-
tionation resulting in minor diorite, and finally in the intersect-
ing tholeiitic dacite. These petrogenetic characteristics of the 
rocks reflect pressure release melting, fractionation and for-
mation of felsic compositions which is analogous with crust 
formation during the early stage of widening in the modern 
back-arc basin (SINTON et al., 2003). Continuous normal 
zoning observed in edenite suggests fractional crystallization 
in a closed, deep-seated magma system (STERN, 1979). The 
edenite Al- and Ti-content thermobarometer (ERNST & LIU, 
1998) suggests the crystallization pressures and temperatures 
for the Gotalovec megablock were 0.6 GPa at 860 °C. Their 
petrological characteristics suggest formation at a slow-rate 
spreading ridge of a marginal basin. However, the alteration 
pattern of the Gotalovec quarry gabbroic plutonic rocks is, ac-
cording to the evidence, in many ways similar to that of ac-
creted island-arc terrains reported by MAHLBURG & KAY 
(1983), particularly concerning exsolved Mn-rich ilmenite. 
Assuming the type of alterations atypical for ridge crust, Gota-
lovec quarry deep crustal rocks must have acted as the leading 
edge of a back-arc upper plate.

The Cretaceous back-arc basin mantle from the ROD is 
comparable in most mineralogical and geochemical features 
to mantle peridotites from the Early Jurassic CDOB ophio-
lites. This may suggest that it was not affected by the sub-
duction that commenced in the ROD in the Middle Jurassic 
(Bathonian). If these assumptions concerning gabbroic rocks 
are generally correct, then rifting and formation of the back-
arc spreading centre must have initiated in the Early Jurassic 
(or older ?) lithosphere behind the island-arc. The mode of 
back-arc opening in the ROD is apparently different to that 
proposed for most modern back-arc basins (see MARTINEZ 
et al., 2007).

8.2. Improved geodynamic model for the rOD
In geotectonic modelling of the Neo-Tethyan realm, the 
ROD ophiolites belong to its easternmost segment (BOR-
TOLOTTI & PRINCIPI, 2005). Disagreement exists as to 
whether the fragmented ROD oceanic lithosphere, including 
lithosphere related to the advanced stage rifting has a Di-



Geologia croatica 68/1Geologia Croatica
44

Figure 13: Improved schematic geodynamic model for the evolution the Repno oceanic domain as a corner domain connecting the Meliata-Maliak and 
Dinaric-Vardar oceanic systems. (A) The first spreading stage and formation of ensialic back-arc basin. (b) The early stage of the first subduction in the ROD 
with formation of an infant proto-arc. (c) The evolved subduction stage with initiation of an island arc and formation of the subsequent ensimatic marginal 
(back-arc) basin. (D) Ongoing spreading in the back-arc basin – the second spreading stage in the ROD. (E) Subduction in the back-arc basin – the second 
subduction stage in the ROD with the formation of a proto-arc (?) in the overriding plate. (F) The closure stage of the ROD. 1 – mantle diapir, 2 – oceanic crust 
with radiolarian cherts, 3 – raising of the mantle diapir, 4 – melting zone; AP = accretionary prism BAB = back-arc basin, PA = Cretaceous proto-arc.

2005; SLOVENEC & LUGOVIĆ, 2008, 2009; SLOVENEC 
et al., 2010, 2011). However, the ROD indeed represents a 
corner stone domain between these two oceanic systems 

naric-Vardar oceanic provenance (e.g. PAMIĆ, 1997; HAAS 
& KOVÁCS, 2001; KISS et al., 2012), or is a segment of 
the Meliata-Maliak oceanic system (e.g.GORIČAN et al., 



† Lugović et al.: Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ... Geologia Croatica
45

(Fig. 1C), which for example after BABIĆ et al., (2002) and 
SCHMID et al. (2008), are assumed to be integral parts of 
one and the same ocean basin. In general, all parts of the 
oceanic domain shared a common tectonomagmatic evolu-
tion throughout the Mesozoic, although some events might 
be locally specific and diachronous. 

The data presented here chronologically defines the late 
stage of Early Jurassic spreading, a nascent stage of island-arc 
formation in the Late Jurassic, and may suggest the existence 
of a Cretaceous back-arc marginal basin from the Sava-Vardar 
Suture Zone (PAMIĆ, 2002) or, in other words, from the in-
ner part of the Western Vardar Ophiolite Unit (SCHMID et 
al., 2008). Therefore, the results presented in this work only 
complement the previously proposed segmental model of the 
geodynamic evolution of the ROD. The proposed model of 
the geodynamic evolution of the ROD presented in this paper 
represents a comprehensive model based on all the up to date 
published research results (see SLOVENEC & LUGOVIĆ 
2009, 2012; SLOVENEC et al., 2010, 2011).

In the framework of the Dinaric-Vardar oceanic prove-
nance, the ROD probably commenced its geodynamic evolu-
tion as an ensialic back-arc basin formed behind a peri-con-
tinental volcanic arc, related to Andean-type subduction of 
the Palaeo-Tethyan lithosphere beneath the European conti-
nental margin (STAMPFLI & BOREL, 2002, 2004; 
GORIČAN et al., 2005). Alternatively, it may have formed 
as a westward prograding embayment of the Neo-Tethys 
Ocean (see discussion in PAMIĆ et al., 2002; ROBERTSON 
et al., 2009).

The oldest record of rifting of the intra-continental litho-
sphere behind the peri-continental volcanic arc was dated as 
late Anisian, specifically as Illyrian (SLOVENEC et al., 
2010). The advanced stage rifting is characterized by pelagic 
carbonate peperites (HALAMIĆ et al., 1998; PALINKAŠ et 
al., 2000, 2008). The onset of rifting created a rift basin with 
pelagic sediments and within plate alkali basalt - type crust 
(SLOVENEC et al., 2010, 2011; KISS et al., 2012). This ba-
sin was located between the future Adriatic microplate and 
the continental edge of south Laurussia (represented by 
pieces of the recent ALCAPA, Dacia and Tisza Mega-Unit; 
Fig. 1A-B), at least in the early Ladinian. The oldest spread-
ing ridge oceanic crust related to the proto-oceanic stage 
(first spreading stage in the ROD) is represented by enriched 
E-MORB-type extrusive rocks formed in the early Ladinian, 
particularly the late Fassanian, and was followed by depleted 
E-MORB-type crust in the late Ladinian, T-MORB-type 
crust in the middle Carnian and the first appearance of N-
MORB-type crust in the late Carnian (SLOVENEC et al., 
2011; Fig. 13A). Such a regular chemostratigraphic succes-
sion of ridge crust formation through the opening of an ocean 
reflects a slow spreading rate (eg. WILSON, 1989).

The T-MORB-type and N-MORB-type crust formed 
during spreading from the middle to late Carnian, displays 
slight supra-subduction characteristics inherited from the 
Middle Triassic subduction of the Palaeo-Tethys (or an ear-
lier subduction?). The inherited SSZ characteristics system-
atically diminished through the onset of spreading after the 
late Carnian and completely disappeared until the Bajocian 

oceanic crust due to the subducting slab-break-off (SLOV-
ENEC & LUGOVIĆ, 2009). Therefore the Bajocian crust is 
assumed to represent the maximum evolved stage of spread-
ing in the ROD (SLOVENEC & LUGOVIĆ, 2012). How-
ever, this work suggests that the sinking slab should have 
already broken-off in the Pliensbachian (Fig. 13A).

Intra-oceanic convergence (the first stage of subduction 
in the ROD) commenced in the late Middle Jurassic (late 
Bathonian) as recorded by subduction of an active oceanic 
ridge and production of “N-MORB with arc signature” crust 
in the overriding plate (SLOVENEC & LUGOVIĆ, 2009; 
Fig. 13B). At this stage magmatism was not related to a sig-
nificantly metasomatized mantle wedge (sensu STERN 
(2004) and WHATAM & STERN (2011)), and does not rep-
resent true subduction derived igneous activity. Due to the 
onset of spreading accompanied by progressive metasoma-
tism of the mantle wedge during the Callovian-Oxfordian, 
the IAT-type crust was produced in an infant proto-arc ex-
tensional setting (SLOVENEC et al., 2011; Fig. 13B). The 
youngest IAT-type edenite gabbro dated here as Tithonian 
represents the youngest crust related to the first subduction 
event in the ROD that reflects the nascent stage of formation 
of an intra-oceanic volcanic arc. Although the amphibole-
bearing gabbroic rocks from the nearby Mt. Medvednica 
ophiolite mélange (SLOVENEC & LUGOVIĆ, 2008) are 
more influenced by subduction related components, they 
show older formational ages (~ 161 Ma vs. ~ 147 Ma). This 
inverse chemostratigraphic evolution suggests that true SSZ 
magmatism might have been delayed and/or was diachronous 
during the onset of the first subduction event in the ROD. 
Moreover, it indicates specific metasomatically induced ther-
mal regimes of hydrous partial melting along the subduction 
front (Fig. 13C).

A modern fore-arc progressed over a period of about 15 
Ma to a mature island arc, accompanied by a coeval and cog-
nate back-arc basin (STERN et al., 1996; BLOOMER et al., 
1995). Rocks typical for a mature island-arc, such as calc-
alkaline extrusives, have not yet been reported for the ROD 
and represent a missing link needed to complete the geody-
namic model.

The back-arc marginal basin in the ROD must have 
formed during the Early Cretaceous, but it is not clear when 
the spreading (second spreading stage in the ROD) com-
menced (Fig. 13D). The Early Cretaceous BABB-type lower 
crust and related mantle peridotites from the ROD show ev-
idence against island-arc involvement in the rifting. There-
fore the rifting must have initiated behind the island-arc and 
led to formation of the extensional back-arc basin. The meta-
morphic sole derived from BABB-type crust dated to 118 ± 
8 Ma (IGNJATIĆ, 2007) indicates termination of back-arc 
spreading in the basin during the Aptian. Simultaneously, a 
thick island-arc crust was emplaced onto the continental mar-
gin of the Adriatic plate, forming the Mt. Medvednica lower 
greenschist facies metamorphic complex, and consists of 
rocks of both pericontinental and oceanic provenance 
(LUGOVIĆ et al., 2006, with references). Since the green-
schists derived from IAT-protoliths dated to 119 ± 5 Ma (BE-
LAK et al., 1995), the formation of the metamorphic sole in 



Geologia croatica 68/1Geologia Croatica
46

the back-arc basin, and the emplacement of the island-arc 
onto the Adriatic continental margin, did not appear as se-
quential events. Formation of oceanic crust in the ROD must 
have continued after the Aptian, and obviously in the upper 
plate (second subduction stage in the ROD; Fig. 13E). This 
is indicated by the youngest Early Cretaceous (Albian) ophi-
olites back-arc affinity of rock group C. The back-arc basins 
or marginal basins located in front of the Tisza-Dacia Mega-
Units, where the oceanic crust was formed during the latest 
Early Cretaceous to early Campanian (e.g.USTASZEWSKI 
et al., 2009 with references therein), (referred to as ophiolites 
of rock group C), are included in the Sava-Vardar Zone 
(PAMIĆ, 2002; Fig. 1A), or simply the Sava Zone (SCHMID 
et al., 2008). This Sava-Vardar zone is thought to be a suture 
zone between the Dinarides and fragments of the European 
continental margin (Fig. 1A). Following this model, the ROD 
back-arc basin from the Aptian (formation of metamorphic 
sole) onwards, may be interpreted as one of several discrete 
marginal basins stretching along the Sava-Vardar-Izmir-An-
kara-Erzinam Suture Zone. The next Cretaceous marginal 
basin domain of this suture zone may be envisaged in North 
Kozara in the southeast (Fig. 1A) where Campanian bimodal 
magmatic succession reflects its stage of closure (USTASZE-
WSKI et al., 2009; model b2).

The ROD back-arc basin closed to a great extent during 
the latest Late Cretaceous (Fig. 13F) as deduced from peri-
dotite clasts in Campanian basal conglomerates (HALAMIĆ, 
1998), subaerial weathering of peridotites into Ni-lateritic 
crust (PALINKAŠ et al., 2006) and composite peridotite-
amphibolite slices tectonically emplaced into Palaeocene 
breccias (LUGOVIĆ et al. 2007).

AcKNOWLEDGEMENt

This work is the contribution to the scientific projects: Me-
sozoic magmatic, mantle and pyroclastic rocks of northwest-
ern Croatia (grant no. 181-1951126-1141 to Da. S.) and Tec-
tonomagmatic correlation of fragmented oceanic lithosphere 
in the Dinarides (grant no. 195-1951126-3205 to B. L.), car-
ried out under the support of the Croatian Ministry of Sci-
ence, Education and Sport. Critical comments by Vesnica 
GARAŠIĆ and an Anonymous Reviewer greatly helped to 
achieve final version of the manuscript.

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Manuscript received July 24, 2014 
Revised manuscript accepted January 23, 2015 

Available online February 27, 2015