Benedek, K. and Zupančič,
N. (2002): Periadriatic Intrusive Chain - version 1. In: Dunkl, I., Balintoni,
I., Frisch, W., Hoxha, L., Janák, M., Koroknai, B., Milovanovic, D.,
Pami, J., Székely, B. and Vrabec, M. (Eds.): Metamorphic Map and Database
of Carpatho-Balkan-Dinaride Area. http://www.met-map.uni-goettingen.de
Periadriatic Intrusive Chain (PAI)
Compiled by: K. Benedek and N. Zupančič (2002)
Lithology, Mineralogy, Geochemistry
Geochronology
Structural Evolution
Summary
Bibliography
Links
Definition
Intrusive (mostly tonalite, granodiorite) magmatic bodies of Tertiary formation age along the Periadriatic Lineament (PAL) and its eastern continuation (Žurga, 1926, Faninger, 1970, Faninger 1976, Exner, 1976; Blanckenburg and Davies, 1995).
Geographic position
The unit is exposed in the Karavanke (Karawanken) and Pohorje Mts., but covered by Neogene sediments in the Zala Basin (Western Hungary). The Pohorje forms an approx. 40 km long and up to 8 km broad continuous unit and Karavanke 35 km long and 2 km broad belt which on the west continues to Austria (Mioč and Žnidarčič, 1972, Žnidarčič and Mioč, 1987, Mioč, 1997; Altherr et al., 1995; Pamić and Palinkaš, 2000; Benedek, 2002a).
Maps
Surface exposures: Mioč and Žnidarčič (1972), Žnidarčič and Mioč (1987), Mioč (1997), Germovšek (1954). Subsurface extent: Kőrössy (1988), Benedek (2002a)
Boreholes
Some boreholes penetrating the unit in Hungary:
Balatonfenyves-1 (tonalite): Ravasz-Baranyai and Ravasz (1971), Balogh et al. (1983)
Pu-3, Nab-ÉNY-1, Gel-1 (tonalite, diorite): Kőrössy (1988)
Boundaries
The bordering tectonic elements of the unit in Hungary are strike-slip faults as a consequence of early Miocene lateral escape of the ALCAPA microplate (Fodor et al., 1998; Benedek, 2002a). In the Karavanke unit, the tonalite predominantly occurs in shear lenses (strike-slip duplexes) of the PAL (Fodor et al., 1998), however locally the original intrusive contacts, associated with contact metamorphism are preserved (Mioč and Žnidarčič, 1983). Boundary of the Pohorje unit with the neighbouring rocks is predominantly contact metamorphic (Mioč and Žnidarčič, 1972).
Structural position
The basement of the unit is unknown, the oldest covering sediments are Miocene in age (Kőrössy, 1988). Contact metamorphic alteration of the country rocks is unknown in the Zala Basin (Benedek, 2002b). In the NE Pohorje dacite intrusion caused contact metamorphic changes of Magdalensburg low-grade metamorphic rocks (Faninger, 1973, Zupančič, 1994a, Germovšek 1954, Štrucl and Kluge, 1991).
Subunits
According to the main exposure areas:
-Karavanke Mts. (Austria-Slovenia)
-Pohorje Mts. (Slovenia)
-Zala Basin (Hungary)
Correlation
These intrusive bodies are the easternmost equivalents of other Paleogene intrusives aligned along the PAL (Zupančič, 1994a, Zupančič, 1994b, Pamić and Palinkaš, 2000; Benedek, 2002a). Similar rock outcrops are exposed in Bergell, Adamello, Riesenferner, Monte Alto (Exner, 1976). The intrusive magmatic activity along the PAL is accompanied by abundant dyke swarms (Józsa, 1983; Deutsch, 1984, Zupančič 1994c).
Lithology, mineralogy, geochemistry
In the Zala Basin typical intrusive rocks (tonalite and minor diorite) show hypidiomorphic texture and they consist of plagioclase, potassium feldspar, amphibole, biotite, quartz, rutile, apatite, zircon, opaque minerals and garnet. In the tonalite, rare mafic enclaves (max. size of 20 cm in diameters) occur with identical texture to their host rock. Texture of Pohorje igneous rocks is hypidiomorphic granular with transition to porphyritic in NW direction. Main minerals are plagioclase, metasomatic potassium feldspar, quartz and biotite, accesory hornblende, allanite, apatite, sphene, epidote, zircon and opaque minerals. In NW part hydrothermal alteration to chlorite, calcite and white mica is observed (Zupančič, 1995). Karavanke tonalite consists mainly of plagioclase, quartz, hornblende and biotite (Faninger, 1976).
Close chemical similarity of the Karavanke tonalite and the Zala Basin tonalite can be demonstrated by using MORB normalized trace element distribution diagram (Benedek, 2002b). However, the Pohorje tonalite is enriched in LILE and La, Ce relative to those of the two other intrusives suggesting different melt evolution. Pamić and Palinkaš (2000) suggested that metasomatized garnet peridotite was the source rock and primary melts of the source rock were subjected by AFC process producing the tonalite suites. Zupančič (1994a,b) suggested that partial melting of amphibolite and eclogite can produce melts being similar in composition to the Pohorje tonalite. The primary melt generation was driven by slab-breakoff process (Blanckenburg and Davies, 1995).
Figure 1 Chondrite and MORB-normalized trace element pattern of the tonalites from the Zala Basin (pink), Karavanke (red line). and Pohorje Mts. (blue). Trace element data of Karavanke and Pohorje Mts. were taken from Altherr et al. (1995) and Pamić and Palinkaš (2000) and those of the Zala Basin from Benedek (2002b). Normalizing constants of MORB are taken from Sun and McDonough (1989) and that of chondrite from Nakamura (1974).
The K/Ar data measured on mineral separates (amphibole, biotite, plagioclase) from intrusive rocks in the Zala Basin (Western Hungary) yield from 28.6± 1.8 Ma to 33.9± 1.4 Ma (Benedek, 2002b). This range overlaps with that of igneous plutons aligned along the Periadriatic Line (about 30 Ma, e.g. von Blanckenburg and Davies, 1995). Age determination published from the Karavanke Mts. are about 30Ma (Scharbert, 1975). Rb/Sr age from the Pohorje Mts. is 19.5 Ma (Deleon, 1969), but K/Ar ages measured on biotite are 16.5±5 to 18±5 Ma and 15±5 to 16±5 Ma for whole rock (Dolenec, 1994, Márton et al., 2002). K/Ar ages are rejuvenated (Márton et al., 2002).
Zala Basin
|
|
Mean |
Range |
Source |
|
K/Ar plagioclase |
c.a. 29.2 |
26.6-31.9 (2) |
Benedek (2002b) |
|
K/Ar biotite |
c.a. 31 |
26.8-35.3 (2) |
Benedek (2002b) |
|
K/Ar amphibole |
33 |
(1) |
Benedek (2002b) |
|
K/Ar whole rock |
30.7 |
(1) |
Balogh et al. (1987) |
|
FT zircon |
39.0 |
(1) |
I. Dunkl (unpubl.) |
Pohorje Mts.
|
|
Mean |
Range |
Source |
|
Rb/Sr |
19.5 |
(1) |
Deleon (1969) |
|
K/Ar whole rock |
15.5 |
|
Dolenec (1994) |
|
K/Ar biotite |
16.5 |
|
Dolenec (1994) |
|
K/Ar whole rock |
15.5 |
|
Márton et al. (2002) |
|
K/Ar biotite |
17 |
|
Márton et al. (2002) |
|
FT zircon |
16.2 |
15.6-16.9 (2) |
I. Dunkl (unpubl.) |
Karawanke Mts.
|
|
Mean |
Range |
Source |
|
U/Pb zircon |
31.4 ± 0.7 |
(1) |
Elias (1998) |
|
Rb/Sr biotite |
29.5 |
24-35 (2) |
Scharbert (1975) |
|
Ar/Ar hornblende |
30.7 ± 1.1 |
(1) |
Elias (1998) |
|
Ar/Ar biotite |
30.1 ± 0.5 |
(1) |
Elias (1998) |
|
Ar/Ar plagioclase |
26.5 ± 1.1 |
(1) |
Elias (1998) |
|
FT zircon |
27.1 ± 0.9 |
(1) |
Elias (1998) |
|
FT apatite |
13.1 ± 0.4 |
(1) |
Elias (1998) |
The unit, at least its Hungarian part, is strongly sheared (Benedek, 2002b) due to the early Miocene intensive movements along the PAL. Tectonic evolution of the ALCAPA microplate suggests that the Zala Basin tonalite was westward to its recent position at the time of intrusion (Fodor et al., 1998), close to the Karavanke tonalite (Benedek, 2002b).
The magmatism was not related to active subduction (Pamić and Palinkaš, 2000). Experimental data and trace element modelling suggests that also about 30% partial fusion of subducted, metamorphosed oceanic crust can produce melts with similar composition to the tonalites (Benedek, 2002b). In this scenario the main driving factor of the magmatism could be the uprise of geotherms (thermal relaxation) in the subduction channel after collision. This process can be reflected by p-T-t evolution of Penninic units exposed in the Tauern Window. The magmatism took place in compressional tectonic environment.
Balogh, K., Árva Sós, E., Buda, G. (1983): Chronology of granitoid and metamorphic rocks of Transdanubia (Hungary). Ann Inst Geol Geofiz 6, Bucuresti: 359-364.
Benedek, K. (2002a): Paleogene igneous activity at the easternmost segment of the Periadriatic lineament. Acta Geol. Hung. 45/4 359-371.
Benedek, K. (2002b) Petrogenetic and geochemical study on Palaeogene igneous rocks penetrated in the Zala Basin, Western Hungary. PhD Thesis, Eötvös University, Budapest.
Altherr, R., Lugovic, B., Meyer, H.P., Majer, V. (1995): Early Miocene post-collisional calc-alkaline magmatism along the easternmost segment of the Periadriatic fault system (Slovenia and Croatia). Mineral. Petrol., 54, 225-247.
Blanckenburg, F., Davies, J.H. (1995): Slab breakoff: A model for syncollisional magmatism and tectonics in the Alps. Tectonics, 14/1, 120-131.
Deleon, G. (1969): Pregled rezultata obredivanja apsolutne geološke starosti granitoidnih stena u Jugoslaviji. Rad Inst geol rud istraž ispit nukl drug min sirov, 6, 165-182.
Deutsch, A. (1984): Young Alpine dykes south of the Tauern Window (Austria): a K-Ar and Sr isotope study. Contrib. Mineral. Petrol., 85, 45-57.
Dolenec, T. (1994) Novi izotopski in radiometrični podatki o pohorskih magmatskih kamninah. RMZ, 41, 147-152
Elias, J. (1998): The thermal history of the Ötztal-Stubai complex (Tyrol, Austria/Italy) in the light of the lateral extrusion model. Tübinger Geowissenschaftliche Arbeiten, Reihe A, 36, 172 p.
Exner, P. (1976): Die geologische Position der Magmatite des periadriatischen Lineamentes. Verh Geol Bundesanstalt Wien, 2, 3-64.
Faninger, E. (1970): Pohorski tonalit in njegovi diferenciati. Geologija, 13, 35-104.
Faninger, E. (1976): Karavanški tonalit. Geologija, 19, 153-210.
Fodor, L., Jelen, B., Márton, E., Skaberne, D., Čar, J., Vrabec, M. (1998): Miocene-Pliocene tectonic evolution of the Slovenian Periadriatic fault: implications for Alpine-Carpathian extrusion models. Tectonics, 17, 690-709.
Germovšek C (1954), Petrografske preiskave na Pohorju v letu 1952. Geologija, 2, 191-210.
Józsa, S. (1983): Petrographic and geochemical study of andesite from the Velence Mts., Hungary. M.S. Thesis, Department of Petrology and Geochemistry, Eötvös University, Budapest, pp 107.
Kőrössy, L. (1988): Hydrocarbon geology of the Zala basin in Hungary. Ált Földt Szemle, 23, 3-162.
Márton, E., Zupančič, N., Pécskay, Z., Trajanova, M., Jelen, B. (2002) Paleomagnetism and new K-Ar ages of the Pohorje igneous rocks. Geol. Carpat. (in press).
Mioč, P. and Žnidarčič, M. (1972): Osnovna geološka karta SFRJ Slovenj Gradec 1 : 100000. Zvezni geol. zavod Beograd.
Mioč, P. and Žnidarčič, M. (1983): Osnovna geološka karta SFRJ. Tolmač za list Ravne na Koroškem. Zvezni geol. zavod Beograd.
Mioč, P. (1997): Tectonic structures along the Periadriatic Lineament in Slovenia. Geol Croat ,50/2, 251-260.
Nakamura, N. (1974): Determination of REE, Ba, Fe, Mg, Na and K in carboniceous and ordinary chondrites. Geochim Cosmochim Acta, 38, 757-773.
Pamić, J. and Palinkaš, L. (2000): Petrology and geochemistry of Palaeogene tonalities from the easternmost parts of the Periadriatic Zone. Contrib Mineral Petrol, 70, 121-141.
Ravasz-Baranyai, L., Ravasz, Cs. (1971): Quartz diorite from water-exploratory drilling at Balatonfenyves. Acta Mineral Petrograph, XX/1, 133-139.
Scharbert, S. (1975): Radiometrische altersdaten von intrusivegesteinen im raum Eisenkappel (Karawanken, Kärnten). Verh. Geol. B.A., 4, 301-304.
Sun, S., McDonough, W.F. (1989): Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Magmatism in the ocean basins, Saunders, A.D., Norry, M.J. (Eds.), Geol Soc Spec Publ, 42, 313-345.
Štrucl, I. and Kluge, R. (1991): Metalogenetska problematika železovih nahajališč v staropaleozoiskih metamorfnih kameninah. Geologija, 34, 305-335.
Zupančič, N. (1994a): Petrološke in geokemične značilnosti pohorskih magmatskih kamnin. PhD Thesis, Ljubljana University, Ljubljana.
Zupančič, N. (1994b): Geokemične značilnosti in nastanek pohorskih magmatskih kamnin. RMZ, 41, 113-128.
Zupančič, N. (1994c): Petrografske značilnosti in klasifikacija pohorskih magmatskih kamnin. RMZ, 41, 101-112.
Zupančič, N. (1995): Minerali pohorskega magmatskega masiva. Geologija, 37,38, 271-303.
Žurga, J. (1926): Starost granita na Pohorju. Geog. vest., 35-37.
Žnidarčič, M. and Mioč, P. (1987): Osnovna geološka karta SFRJ Maribor in Laibnitz 1 : 100000. Zvezni geol. zavod Beograd.
Descriptions of the neighbouring Units:
Austroalpine Basement Unit (AAB)
Transdanubian Central Range (TCR)
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