Schuster, R. and Thöni, M. (2001): Austroalpine basement units - version 1. In: Dunkl, I., Balintoni, I., Frisch, W., Janák, M., Koroknai, B., Milovanovic, D., Pamiæ, J., Székely, B. and Vrabec, M. (Eds.): Metamorphic Map and Database of Carpatho-Balkan-Dinaride Area. http://www.met-map.uni-goettingen.de
Austroalpine basement
units (AAB)
Version 1
compiled: R. Schuster and M. Thöni (2001)
completed:
==== ==== ====
Definition==== ==== ====
The Austroalpine basement units represent a complex nappe pile composed of pre-Variscan metasediments with intrusions of pre-Variscan, Variscan, Permo-Triassic and Tertiary magmatic rocks. They experienced Variscan, Permo-Triassic and Eo-Alpine metamorphism of various grade. Transgressive Permo-Mesozoic metasediments are locally preserved (Tollmann, 1977; Frank et al., 1987; Dallmeyer et al., 1998; Hoinkes et al., 1999; Neubauer et al., 1999; Thöni, 1999; Schuster et al., 2001a).
Geographic Position
The Austroalpine basement units form an E-W oriented belt extending between the Central Alps and the West Carpathians. In the Eastern Alps the Austroalpine basement is about 650 km long, and 50 to 150 km wide. The map covers the easternmost part only.
Maps
Overview maps: Geologische Karte von Österreich 1:1.500.000 (Beck-Mannagetta, 1964).
Maps of the Austrian Geological Survey, scale 1:200.000: Wien und Umgebung, Fuchs & Grill (1984); Steiermark, Flügel & Neubauer (1984)
Maps of the Austrian Geological Survey, scale 1:50.000: 104 Mürzzuschlag, 105 Neunkirchen, 106 Aspang, 107-108, Mattersburg-Deutschkreuz, 134 Passail, 137 Oberwart, 162 Köflach, 187 Bad St. Leonhard, 188 Wolfsberg, 189 Wolfsberg
Additional maps: Wieseneder (1971); Dallmeyer (1998); Tollmann (1977), Schuster et al. (2001b).
Boreholes
Most of the unit is exposed in the central Eastern Alps. However, some boreholes have also proven its existence below the Neogene sediments of the Styrian basin and the Pannonian basin (Frank et al., 1996).
Boundaries
To the north the Austroalpine basement units are bordered by the tectonically overlying Palaeozoic metasediments of the Greywacky Zone. In the northeast and east they are covered by Upper Tertiary sediments of the Vienna and Styrian Basin. In the southern part the border shows a complex pattern to the Penninic Rechnitz Window group and to the (Austroalpine) Graz Paleozoic and the Gurktal Nappe system. The border to the south is formed by the Periadriatic lineament.
Structural Position
Within the Alpine (Tertiary to Cretaceous) orogenic belt the Austroalpine units are in a hanging wall position with respect to the Penninic of the Rechnitz window group (RE-WI). Austroalpine Palaeozoic metasedimentary sequences (Palaeozoic of Graz, Greywacky Zone) and Austroalpine Mesozoic sedimentary piles (Northern Calcareous Alps, Stangalm Mesozoics) are overlying tectonically, mainly with thrust contacts. At several places the present-day contacts are formed by (Tertiary or Cretaceous) normal faults or steely dipping strike slip faults.
Subunits
The Austroalpine basement consists of several subunits which form a complex nappe pile. The individual units are characterised by differences in lithological composition, mineralogy, protolith age and geochemistry, the occurrence of meta-igneous rocks and by different tectonometamorphic evolutions. At present no generally accepted subdivision and nomenclature for the subunits exists. The subdivision used here is based on studies by Faupl (1970), Wieseneder (1971), Becker (1980), Jung (1982), Tollmann (1977), Dallmeyer et al. (1998) and Schuster et al. (2001b) (Fig. 1). In the northeasternmost part the section comprises from north to south and from bottom to top the Wechsel, Waldbach, Semmering, Strallegg and Sieggraben Complex. To the west the succession is formed by the Seckau-Troiseck-Floning, Speik, Wölz, Rappolt, Saualpe-Koralpe and Plankogel Complex. Generally, the contacts between these units are thrust contacts, except the Plankogel Complex, which rests upon the Saualpe-Koralpe Complex with a normal fault contact.
Correlation
The Austroalpine and the Southalpine units are part of the Apulian microplate (Stampfli & Mosar, 1999). Therefore the Southalpine unit shows many similarities with respect to lithology and the pre-Alpine tectonic and metamorphic history.
Fig.1: Tectonic map showing the eastern part of the Austroalpine unit. Show map in bigger size & higher resolution (1 Mb).
Age of Protolith, Geochemistry
As the Austroalpine basement rocks are transgressively overlain by Permo-Triassic and partly also by Palaeozoic sequences, pre-Variscan protolith ages for the metasedimentary crystalline rocks can generally be assumed.
Several cycles of magmatic activity have been recognised: Pre-Variscan magmatic rocks occur in the Seckau-Troiseck-Floning and Speik Complex. They comprise ultramafic bodies composed of serpentinites, dunites, harzburgites and orthopyroxenites which are interpreted as relics of an ophiolitic sequence. Layered amphibolites and hornblende gneisses are interpreted to be of volcanic and of volcanodetritic origin respectively, probably related to an island arc system. The protolithe ages of the ultramafic and the mafic rocks are unknown. However, they have to be pre-Variscan, because they are affected by Variscan metamorphism. In the Seckau-Troiseck-Floning Complex Variscan S-type metagranites and augengneisses occur (Frank et al., 1976; Scharbert, 1981). Huge masses of porphyric granitegneisses ("Grobgneise") are characteristic in the Semmering Complex. Variscan (Scharbert, 1990; Peindl, 1990) and Permian (Pumhösl et al., submitted) age data have been published. Intense magmatism can be recognised in Permo-Triassic times: Permian quartzporphyric volcanic rocks (Roßkogel Formation) occur in the northern part of the Semmering Complex (Gaal, 1965). Gabbros with N-MORB characteristics occur in the Saualpe-Koralpe Complex (Miller & Thöni, 1997), olivine-gabbros derived from a subcontiental mantle are reported from the Semmering Complex (Pumhösl et al, submitted). In the Wölz Complex of the Wolfsberg window an A-Type granite occurs (Morauf, 1980), whereas S-Type granites are typical in the Strallegg Complex (Scharbert, 1990; Schuster et al., 2001b). Pegmatitic mobilisates are characteistic in the Rappold, Strallegg, Sieggraben and Saualpe-Koralpe Complex (Thöni & Miller, 2000; Schuster et al., 2001a). This magmatic event is thought to be related to Permo-Triassic lithospheric extension (Thöni, 1999; Schuster et al., 2001a). Scarce Eo-Alpine pegmatitic mobilisates formed during exhumation of the Eo-Alpine high-pressure rocks in the Saualpe-Koralpe Complex (Heede, 1997). Oligocene magmatic rocks are present along the Periadriatic lineament (Exner, 1976), whereas Miocene volcanics occur at the margins of the Styrian and Pannonian basin.
Lithology, Mineralogy, Metamorphic grade
The lowermost Wechsel Complex consists of polyphase greenschist facies metamorphic gneisses which are overlain by prograde metamorphic phyllites. Medium-grade hornblende gneisses, augengneisses and phyllitic micaschists with a greenschist facies overprint are dominating the Waldbach Complex. The Semmering Complex is composed of granitegneisses, micaschists and phyllitic micaschists. Leucophyllites composed of white mica + leuchtenbergite + quartz developed from orthogneisses by metasomatic processes (Huber, 1994). In the Seckau-Troiseck-Floning Complex hornblende gneisses and biotite plagioclase gneisses are widespread. The Speik Complex comprises ultramafic bodies overlain by amphibolites. The Wölz Complex mainly consists of prograde metamorphosed garnet-micaschists with intercalated layers of amphibolites, paragonite-bearing amphibolites and marbles. Staurolite-garnet micaschists of the Rappold Complex exhibit a polyphase metamorphic evolution. They are associated with marbles, amphibolites and pegmatitic mobilisates. Polyphase alumosilicate-bearing gneisses, associated with pegmatitic mobilisates are characteristic lithologies of the Strallegg, Saualpe-Koralpe and Sieggraben Complexes. Based on the microfabrics an older HT/Lp assemblage, including andalusite and sillimanite, can be recognised, which in turn is transformed into kyanite-bearing gneisses during a later Hp/LT event. Mylonitic gneisses up to several hundred meters thick ("Plattengneis") and eclogite lenses occur in the Sieggraben and Saualpe-Koralpe Complex. The Plankogel Complex consists of polyphase garnet-micaschists characteristic associated with Mn-quarzites, serpentinite slices and marbles. It is interpreted as a remnant of a pre-Alpine suture zone (Frisch et al., 1989).
Three metamorphic events can be recognised in the Austroalpine basement units:
In the Wechsel, Waldbach, Seckau-Troiseck-Floning, and Speik Complexes a Variscan metamorphic imprint reached greenschist to amphibolite facies conditions at medium to high pressures. Eclogite facies rocks have been preserved in the Hochgrössen massif in the northwesternmost part of the Speik Complex (Faryad et al., 2001).
A Permo-Triassic HT/Lp event with a geothermal field gradient of more than 45°C/km shows increasing conditions from the north to structurally higher units in the south. In parts of the Wölz and Plankogel Complexes almandine-rich garnet was formed at greenschist facies conditions (Lichem et al., 1997; Schuster & Frank, 2000). In the Rappold, Saualpe-Koralpe, Strallegg and Sieggraben Complexes amphibolite to ganulite facies conditions with local anatexis have been reached (Habler & Thöni, 2001; Schuster et al., 2001a; Schuster et al, 2001b). Typical assemblages are characterised by andalusite, sillimanite and K-feldspar.
The Eo-alpine event exhibits increasing conditions from north to south (Hoinkes et al., 1999). In the Wechsel and Waldbach Complex lowermost greenschist facies conditions have been reached. The Semmering and Seckau-Troiseck-Floning Complex exhibit greenschist facies metamorphism, whereas amphibolite facies conditions are indicated by staurolite in the Wölz and Strallegg Complex. In the Saualpe-Koralpe and Sieggraben Complex an eclogite facies event is overprinted by upper amphibolite facies conditions during exhumation (Thöni & Miller, 1996; Stüwe & Powell, 1995). The uppermost Plankogel Complex experienced lower amphibolite facies metamorphism.
Thermobarometry
1) Variscan collisional event: Variscan eclogites (T = 700 °C, p = 18 kbar) of the Hochgrössen massif (Speik Complex) are characterised by mineral parageneses consisting of clinopyroxene (Jd£
39), garnet (Py15-19) and hornblende (Faryad et al., 2001).
2) Permo-Triassic extensional event:
The metamorphic evolution of the Strallegg complex during the HT/LP event is estimated by a characteristic succsession of reactions: paragonite + quartz = sillimanite + albite + H2O (T = 550 °C, p = 3.2-4.8 kbar), staurolite + muscovite + quartz = andalusite + biotite + H2O, muscovite + quartz = sillimanite + K-feldspar + H2O (T = 640-710 °C, p = 2.2-3.8 kbar (Draganits, 1998; Török, 1999)
Calculations from the assemblage garnet + biotite + plagioclase + muscovite + sillimanite yielded peak metamorphic conditions of 600 °C at 4 kbar for the Saualpe-Koralpe Complex (Habler & Thöni, 2001).
3) Eo-Alpine collisional event:
3a) Eo-Alpine subduction-related HP/LT metamorphism:
For the eclogites of the Sieggraben Complex conditions of T = 670-750 °C at p = 14-15 kbar have been determined, based on assemblages of clinopyroxene (Jd£ 30), garnet and hornblende (Neubauer et al., 1999; Putis et al., 2000).
Eclogites of the Saualpe-Koralpe Complex are composed of garnet + omphacite (Jd40) + kyanite + quartz + rutile + phengite ± amphibole (Miller, 1990; Miller & Thöni, 1997; Habler, 1999). Metamorphic conditions of T = 580-650 °C and p = 18-20 kbar have been calculated. For eclogites from the southern part of the Koralpe conditions of T = 700-750 °C and p ³ 16-17 kbar are reported (Lichem et al., 1997).
Calculations for metapelite assemblages of garnet + kyanite + muscovite + biotite + plagioclase + quartz from the Saualpe-Koralpe Complex yielded T = 700 °C, p = 14-15 kbar for the Koralpe (Stüwe & Powell, 1995; Gregurek, 1995) and T = 680-690 °C at 20 kbar for the Saualpe (Thöni & Miller, 1996; Habler, 1999).
3b) Eo-Alpine regional metamorphism:
Metamorphic conditions for the gabbros of the Strallegg Complex yielded T = 530–568 °C at p = 8-11 kbar, calculated from garnet + amphibole + plagioclase + quartz and garnet + paragonite + amphibole assemblages (Pumhösl et al., submitted).
A typical feature in the coarse grained micaschists of the Rappold Complex is the breakdown of staurolite by the reaction staurolite + muscovite = kyanite + garnet + biotite + H2O. Conditions based on this reaction are T = 650-700 °C, p = 10.5 kbar (Lichem et al., 1997).
Equilibrium parageneses of garnet + staurolite + kyanite + chloritoid + chlorite + paragonite + muscovite + quartz from the Plankogel Complex gave T = 550-600 °C, p = 8-11 kbar (Gregurek, 1995)).
Numerous age data for rocks and minerals of metamorphic as well as meta-igneous origin have been published, mainly over the past 20 years, based on the K-Ar, Rb-Sr, Sm-Nd and U-Th-Pb systems. Additionally, few FT-data are also available (Thöni, 1999). The data are compiled in Tab. 1.
|
Wechsel
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Rb-Sr
phengitic Ms WR |
gneisses |
360±30 |
331-386
(6) |
Müller
et al. (1999) |
|
Ar-Ar
phengitic Ms |
gneisses |
326±20 |
303-339
(3) |
Müller
et al. (1999) |
|
Rb-Sr
paragonitic Ms-WR |
phyllites |
260±20 |
240-271
(3) |
Müller
et al. (1999) |
|
Ar-Ar
paragonitic Ms |
phyllites |
248±1 |
(1) |
Müller
et al. (1999) |
|
Ar-Ar
muscovite-WR |
mylonite |
86±12 |
(1) |
Müller
et al. (1999) |
|
FT
apatite |
|
|
6-15
(6) |
Dunkl
(1992) |
|
Waldbach
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Ar-Ar
muscovite |
Permo-Triassic
cover |
82±1 |
(1) |
Dallmeyer
et al. (1998) |
|
Semmering
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Rb-Sr
WR errorchron |
orthogneisses
(6) |
338±12 |
(1) |
Scharbert
(1990) |
|
Rb-Sr
WR errorchron |
orthogneisses
(13) |
253±19 |
(1) |
Schuster
et al. (2001a) |
|
U-Pb
zircon |
orthogneisses |
270±10 |
270-275 |
Pumhösl
et al. (submitted) |
|
Sm-Nd
Cpx-Pl-WR |
olivine-gabbro |
264±8 |
(1) |
Pumhösl
et al. (submitted) |
|
U-Th-Pb
EMP xenotime |
lazulithe-quartz
vein |
246±23 |
(1) |
Bernhard
et al. (1998) |
|
Rb-Sr
muscovite-WR |
orthogneisses |
203±80 |
111-277
(9) |
Scharbert
(1990), Müller (1994) |
|
Ar-Ar
muscovite |
phyllitic
micaschists |
140±20 |
132-164
(2) |
Berka
(1998), Müller et al. (1999) |
|
Rb-Sr
muscovite-WR |
Permo-Triassic
cover |
86±3 |
84-88
(2) |
Müller
et al. (1999) |
|
K-Ar,
Ar-Ar muscovite |
orthogneisses |
85±15 |
77-148
(10) |
Scharbert
(1981), Huber (1994), Dallmeyer et al. (1998), |
|
|
|
|
|
Müller
et al. (1999), Pumhösl et al. (2001) |
|
K-Ar
biotite |
orthogneisses |
83±2 |
82-84
(2) |
Scharbert
(1981) |
|
Ar-Ar
muscovite |
leucophyllites |
80±5 |
71-94
(10) |
Huber
(1994) |
|
Ar-Ar
muscovite |
Permo-Triassic
cover |
81±3 |
79-84
(6) |
Schmidt
(1998), Berka (1998), Müller et al. (1999) |
|
Rb-Sr
biotite-WR |
orthogneisses |
71±10 |
59-83
(7) |
Scharbert
(1990), Müller et al. (1999) |
|
FT
zircon |
|
|
70-80
(3) |
Dunkl
(1992) |
|
FT
apatite |
|
56±15 |
40-70
(18) |
Balogh
& Dunkl (pers. comm.) |
|
Strallegg
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Sm-Nd
garnet-WR |
pegmatite-granite |
286±4 |
(1) |
Schuster
et al. (2001b) |
|
Sm-Nd
garnet-WR |
metapelite |
270±7 |
263-276
(2) |
Schuster
et al. (2001b) |
|
Rb-Sr
muscovite-WR |
metapelite |
290±7 |
283-296
(2) |
Berka
(1998), Schuster et al. (2001b) |
|
Rb-Sr
WR errorchron |
granitgneisses
(9) |
240±10 |
(1) |
Scharbert
(1990) |
|
Rb-Sr
muscovite-WR |
pegmatite |
230±15 |
214-244
(3) |
Scharbert
(1990), Draganits (1996), Berka (1998) |
|
Ar-Ar
muscovite |
pegmatite |
240±2 |
(1) |
Berka
(1998) |
|
Ar-Ar
muscovite |
gneisses |
90±20 |
94-124
(4) |
Berka
(1998), Schuster et al. (2001b) |
|
Rb-Sr
biotite-WR |
gneisses
(N' part) |
133±70 |
53-209
(6) |
Draganits
(1996), Berka (1998) |
|
Rb-Sr
biotite-WR |
gneisses
(S' part) |
66±4 |
66
(2) |
Scharbert
(1990) |
|
Sieggraben
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
U/Pb
zircon, monazite |
granitic
dyke |
313±8 |
(1) |
Putis
et al. (2000) |
|
U/Pb
zircon, monazite |
granitic
dyke |
103±14 |
(1) |
Putis
et al. (2000) |
|
Ar-Ar
hornblende |
eclogite |
122±14 |
108-136
(3) |
Neubauer
et al. (1999) |
|
Ar-Ar
muscovite |
gneisses |
80±3 |
78-82
(2) |
Dallmeyer
et al. (1998) |
|
K-Ar
muscovite |
pegmatite |
103±8 |
102-104
(2) |
Milota
(1983) |
|
K-Ar
muscovite |
gneisses |
86±10 |
76-95
(3) |
Milota
(1983), Putis et al. (2000) |
|
K-Ar
biotite |
gneisses |
78±6 |
(1) |
Putis
et al. (2000) |
|
FT
apatite |
|
|
10-80
(3) |
Dunkl
(1992) |
|
Troiseck-Floning
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Ar-Ar
hornblende |
amphibolites |
358±100 |
458-260
(3) |
Handler
(1994), Schmidt (1998) |
|
Ar-Ar
muscovite |
metapelites |
310±10 |
314-265
(4) |
Handler
(1994), Schmidt (1998) |
|
Ar-Ar
muscovite |
pegmatites |
275±20 |
255-295
(2) |
Schmidt
(1998) |
|
Ar-Ar
muscovite |
diaphthoritic
micaschists |
260±25 |
314-265
(2) |
Handler
(1994), Schmidt (1998) |
|
Ar-Ar
muscovite |
metapelites |
145±25 |
119-170
(2) |
Schmidt
(1998) |
|
Ar-Ar
muscovite |
Permo-Triassic
cover |
89±3 |
87-93
(4) |
Handler
(1994) |
|
Ar-Ar
muscovite |
pegmatite
mylonite |
81±1 |
(1) |
Dallmeyer
et al. (1998) |
|
Rb-Sr
muscovite-WR |
pegmatites |
253±30 |
219-284
(3) |
Handler
(1994), Schmidt (1998) |
|
Rb-Sr
muscovite-WR |
metapelites |
305±25 |
273-332
(4) |
Handler
(1994), Schmidt (1998) |
|
Rb-Sr
biotite-WR |
metapelites |
89±15 |
75-134
(7) |
Handler
(1994), Schmidt (1998) |
|
Seckau
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Rb-Sr
WR-errorchrone |
metavolcanic
gneisses (5) |
500±45 |
(1) |
Frank
et al. (1976) |
|
Rb-Sr
muscovite |
pegmatite |
329±12 |
(1) |
Scharbert
(1981) |
|
Rb-Sr
muscovite |
granite |
331±7 |
(1) |
Scharbert
(1981) |
|
K-Ar
muscovite |
orthogneiss |
105±4 |
(1) |
Scharbert
(1981) |
|
Rb-Sr
muscovite-WR |
paragneiss |
84±9 |
(1) |
Frank
et al. (1976) |
|
Ar-Ar
biotite |
paragneisses |
91±2 |
(3) |
Kolenprat
(1997) |
|
K-Ar
biotite |
orthogneiss |
91±2 |
(1) |
Scharbert
(1981) |
|
Ar-Ar
muscovite |
Permo-Triassic
cover |
89±3 |
(3) |
Kolenprat
(1997) |
|
Rb-Sr
biotite-WR |
orthogneisses |
74±4 |
70-77
(3) |
Scharbert
(1981) |
|
Rb-Sr
biotite-WR |
paragneiss |
77±3 |
72-80
(4) |
Frank
et al. (1976), Kolenprat (1997) |
|
FT-apatite |
|
52±10 |
44-60
(2) |
Hejl
(1997) |
|
Speik
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Ar-Ar
hornblende |
eclogite |
397±8 |
(1) |
Faryad
et al. (2001) |
|
Ar-Ar
hornblende |
amphibolites |
101±8 |
96-109
(6) |
Neubauer
et al. (1995), Schuster et al. (1999) |
|
Ar-Ar
muscovite |
augengneisses |
86±2 |
84-87
(2) |
Frank
(unpubl. data) |
|
Ar-Ar
muscovite |
paragneiss |
84±1 |
(1) |
Neubauer
et al. (1995) |
|
Ar-Ar
biotite |
augengneisses,
gneisses |
89±5 |
84-93
(3) |
Kolenprat
(1997), Frank (unpubl. data) |
|
Rb-Sr
biotite-WR |
paragneiss |
80±1 |
(1) |
Kolenprat
(1997) |
|
FT
sphene |
amphibolite |
70±9 |
(1) |
Neubauer
et al. (1995) |
|
FT
zircon |
amphibolite |
61±6 |
(1) |
Neubauer
et al. (1995) |
|
FT
apatite |
amphibolite |
34±6 |
(1) |
Neubauer
et al. (1995) |
|
Wölz
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Rb-Sr
WR errorchron |
orthogneisses
(6) |
258±11 |
(1) |
Morauf
(1980) |
|
Sm-Nd
garnet(core)-WR |
micaschists |
269±4 |
(1) |
Schuster
& Frank (2000) |
|
Sm-Nd
garnet-WR |
micaschists |
90±10 |
84-95
(2) |
Schuster
& Frank (2000) |
|
Ar-Ar
muscovite |
micaschists |
88±10 |
81-115
(3) |
Frank
(unpubl. data) |
|
K-Ar
muscovite |
micaschists,
orthogneisses |
87±5 |
75-95
(18) |
Morauf
(1980), Hejl (1984), Schuster & Frank (2000) |
|
K-Ar
biotite |
micaschists,
orthogneisses |
92±20 |
76-131
(8) |
Morauf
(1980), Hejl (1984), Schuster (1994) |
|
Rb-Sr
muscovite-WR |
orthogneisses |
79±3 |
79-80
(7) |
Morauf
(1980) |
|
Rb-Sr
biotite-WR |
micaschists,
orthogneisses |
76±2 |
74-78
(7) |
Morauf
(1980); Schuster & Frank (2000) |
|
FT
apatite |
|
17±3 |
14-20
(5) |
Hejl
(1997) |
|
Rappold
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Sm-Nd
garnet-WR |
pegmatite |
276±12 |
264-288
(2) |
Schuster
& Frank (2000), Schuster et al. (2001a) |
|
Rb-Sr
muscovite-WR |
pegmatite |
235±30 |
205-248
(5) |
Frank
et al. (1983), Schuster et al. (2001a) |
|
Sm-Nd
garnet-WR |
micaschist |
286±3 |
(1) |
Schuster
et al. (2001) |
|
Ar-Ar
muscovite |
pegmatite |
86±3 |
84-88
(4) |
Frank
(unpubl. data) |
|
Ar-Ar
muscovite |
metapelites |
86±2 |
84-87
(3) |
Frank
(unpubl. data) |
|
FT
apatite |
|
33±4 |
(1) |
Hejl
(1997) |
|
Saualpe-Koralpe
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Sm-Nd
Cpx-Pl |
gabbro |
257±15 |
247-275
(4) |
Thöni
& Jagoutz (1992), Miller & Thöni (1997) |
|
U-Pb
Zircon |
spodumene
pegmatite |
240±1.5 |
(1) |
Heede
(1997) |
|
Rb-Sr
spodumene-WR |
spodumene
pegmatite |
241±5 |
239-243
(2) |
Thöni
& Miller (2000) |
|
Sm-Nd
garnet-WR |
pegmatites |
245±20 |
225-264
(3) |
Thöni
& Miller (2000) |
|
Sm-Nd
garnet(core)-WR |
micaschist |
267±17 |
(1) |
Schuster
et al. (2001a) |
|
Sm-Nd
Grt-Cpx-WR |
eclogites |
98±10 |
91-109
(6) |
Thöni
& Jagoutz (1992), Miller & Thöni (1997), |
|
|
|
|
|
Lichem
et al. (1997) |
|
Sm-Nd
garnet-WR |
metapelites |
90±4 |
86-94
(9) |
Thöni
& Miller (1996), Miller & Thöni (1997) |
|
Rb-Sr
muscovite-WR |
pegmatites
(corse gr.) |
294±120 |
232-428
(7) |
Frank
et al. (1983) |
|
Rb-Sr
muscovite-WR |
pegmatites
(fine grained) |
152±50 |
117-205
(4) |
Frank
et al. (1983) |
|
Rb-Sr
phengite-WR |
pegmatiodes
in eclogites |
92±10 |
84-102
(4) |
Thöni
& Jagoutz (1992), Heede (1995) |
|
K-Ar,
Ar-Ar hornblende |
eclogites |
301±150 |
163-536
(9) |
Rittmann
(1984) |
|
K-Ar,
Ar-Ar hornblende |
pegmatiodes
in eclogites |
150±40 |
109-190 |
Rittmann
(1984) |
|
Ar-Ar
phengite |
pegmatiodes
in eclogites |
85±3 |
83-88
(2) |
Rittmann
(1984) |
|
K-Ar
muscovite |
pegmatites |
90±15 |
79-116
(14) |
Morauf
(1980), Morauf (1981) |
|
K-Ar
muscovite |
metapelites |
85±3 |
82-88
(5) |
Morauf
(1980) |
|
K-Ar
biotite |
metapelites |
87±9 |
79-109
(6) |
Morauf
(1980) |
|
Rb-Sr
biotite-WR |
metapelites |
87±9 |
79-109
(6) |
Morauf
(1980) |
|
FT
apatite |
|
42±15 |
26-53
(5) |
Hejl
(1997) |
|
Plankogel
Complex |
Lithology |
Mean
(±Ma) |
Range(n)
(±Ma) |
Source |
|
Sm-Nd
garnet-WR |
micaschist |
275±10 |
264-285
(2) |
Lichem
et al. (1997), Thöni (2002) |
Table1: Geochronological age data from the Austroalpine basement units.
In Eoalpine times the Austroalpine basement units were affected by several deformation events (Ratschbacher, 1986; Ratschbacher et al., 1989; Genser & Neubauer, 1989). The collisional event prior to 100 Ma is characterised by W-WNW directed thrust tectonics. It is responsible for the decoupling of the sedimentary cover series and burial of the crystalline rocks. Exhumation of the high pressure rocks started at about 90± 3 Ma (Thöni, 1999). In the eastern part of the basement units it is characteried by a first period of northwest to north directed thrusting and south directed normal faulting (Frank et al., 1983; Krohe, 1987), followed by southeast directed extension (Habler, 1999). It started close to the thermal peak of metamorphism by ductile deformation and continued into the regime of brittle deformation in the lower grade metamorphic units. In Miocene times lateral extrusion of the orogen caused block faulting (Ratschbacher et al., 1989; Genser & Neubauer, 1989; Peresson & Decker, 1997).
The Austroalpine represents a part of the northern Apulian microplate. Prior to the Variscan collisional event it held an island arc environment position, and magmatic rocks developed. During the Variscan collisional event parts of the Unit experienced a Lower Carboniferous HP/LP metamorphism (390-350 Ma) and a subsequent thermal overprint in Upper Carboniferous times (340-300 Ma). In Permian time an extensional regime developed. Lithospheric extension caused a HT/Lp metamorphic imprint and related magmatic activity. Peak metamorphic conditions were reached at about 260 Ma. Subsequently, the lithosphere cooled down and huge Triassic sedimentary piles were deposited on top (245-200 Ma). Since the Jurassic the Austroalpine realm was affected by strike slip faulting and compressional tectonics. In Cretaceous times the Austroalpine acted as the tectonic lower plate during the closure of the Meliata-Hallstatt Ocean. The peak of the suduction-related HP/LT metamorphism occurred at about 100± 10 Ma, followed by a medium-pressure thermal overprint during exhumation (90-65 Ma).
According to Stampfli et al. (1998) the Austroalpine was a part of the Hun Superterrane in early Palaeozoic times. Due to subduction processes the Austroalpine stayed in an island arc environment and pre-Variscan intrusives and volcanic rocks developed (Neubauer et al., 1999).
In late Palaeozoic time the Austroalpine was affected by the Variscan event, induced by the collision of Africa, Baltica, Laurentia and the intervening microplates (Tait et al., 1997). Parts of the Unit experienced a Lower Carboniferous HP/LP event (390-350 Ma) and a subsequent thermal overprint in Upper Carboniferous times (340-300 Ma) (Thöni, 1999; Faryad et al. 2001,).
After a period of orogenic collapse and erosion, an extensional regime developed between the European and the Apulian plate. As an element in between the Austroalpine unit was affected by a HT/LP metamorphic imprint and magmatic activity, due to lithospheric extension. Peak metamorphic conditions were reached at about 260 Ma. Ongoing extension resulted in the opening of the Triassic Meliata-Hallstatt Ocean to the south. The Austroalpine lithosphere cooled down and huge Triassic sedimentary piles were deposited on top (245-200 Ma) (Schuster et al. 2001a) .
Opening of the Atlantic and Penninic Ocean in Jurassic time leads to sinistral strike slip faults in Europe and a reorganisation of the westernmost part of the Tethyan realm. The Austroalpine realm was also affected by strike slip faulting and compressional tectonics (Gawlik, et al., 1999).
The change of motion between the African and Eurasian Plate since lower Cretaceous time caused shortening in the area resulting in the complex scenario of the Eo-Alpine and Neo-Alpine orogeny. In Cretaceous times the Austroalpine acted as the tectonic lower plate during the closure of the Meliata-Hallstatt Ocean. The peak of the suduction related HP/LT metamorphism occurred at about 100± 10 Ma, followed by a medium-pressure thermal overprint during exhumation (90-65 Ma) (Thöni, 1999). During the following subduction of the Peninnic ocean the Austroalpine formed the tectonic upper plate and suffered only minor thermal influence.
Becker, L.P. (1980): Erläuterungen zur Geologischen Karte der Republick Österreich 1:50000, Blatt Köflach (162). Geol. B.-A. Wien, Wien.
Beck-Mannagetta, P. (1964): Geologische Übersichtskarte der Republik Österreich mit tektonischer Gliederung 1:1.500.000 (revidierter Nachdruck 1986). Geol. B.-A. Wien, Wien.
Berka, R. (2000): Die Stellung der Traibachschiefer im Semmering-Wechsel System. Unpubl. Diploma Thesis Formal- Natwiss. Fak. Univ. Wien, 133pp, Wien.
Bernhard, F., Finger, F., Schitter, F., Berka, R. & Schuster, R.: Electron microprobe ages of monazite and xenotime from the austroalpine basement units of the Fischbacher Alpen, Styria, Austria.- Mitt. Österr. Miner. Ges., 143 (1998), 246-248, Wien.
Dallmeyer, R.D., Handler, R., Neubauer, F. & Fritz, H. (1998): Sequence of Thrusting within a Thick-Skinned Tectonic Wedge: Evidence from 40Ar/39Ar and Rb-Sr Ages from the Austroalpine Nappe Complex of the Estern Alps. J. Geol., 106, 71-86.
Draganits, E. (1996): Kristallingeologische Neubearbeitung des südlichen Ödenburger Gebirges, Burgenland (Österreich). Unpubl. Diploma Thesis Formal- Naturwiss. Fak. Univ. Wien, 150pp., Wien.
Draganits, E. (1998): Seriengliederung im Kristallin des südlichen Ödenburger Gebirges (Burgenland) und deren Stellung zum Unterostalpin am Alpenostrand. Jb. Geol. B.-A. Wien, 141, 113-146, Wien.
Dunkl, I. (1992): Final episodes of the cooling history of eastern termination of the Alps. In: Neubauer, F. (ed.): ALCAPA Field Guide - The Eastern Central Alps of Austria.- (IGP/KFU) Graz, 137-139, Graz.
Exner, Ch. (1976): Die geologische Position der Magmatite des periadriatischen Lineamentes. Verh. Geol. B.- A. Wien, 1976/2, 3-64, Wien.
Faryad, S.W., Hoinkes, G. & Ivan, P. (2001): Pre-Alpine eclogites and garnet-pyroxene-bearing metabasites in the Austroalpine units of the Eastern Alps and the Western Carpathians. Mitt. Österr. Miner.Ges., 146, 82-83.
Faupl, P. (1970): Zur Geologie und Petrographie des südlichen Wechselgebietes. Mitt. Geol. Ges. Wien, 63, 22-51, Wien.
Flügel, H.W. & Neubauer, F. (1984): Steiermark, Geologie der Österreichischen Bundesländer in Kurzgefaßten Einzeldarstellungen. - Geol. B.-A. Wien, 127pp.
Frank, W. (1981): Geochronologische Datierung Frühalpiner Metamorphosevorgänge in den Ostalpen (Jahresbericht 1980 des Geochronologischen Labors). Jber. 1980 Hochschulschwerpunkt S15, 9-43, Graz.
Frank, W., Esterlus, M., Frey, J., Jung, G., Krohe, A. & Weber, J. (1983): Die Entwicklungsgeschichte von Stub- und Koralpenkristallin und die Beziehung zum Grazer Paläozoikum. Jber. 1982 Hochschulschwerpkt S 15, 1983, 263-293, Graz.
Frank, W., Kralik, M., Scharbert, S. & Thöni, M. (1987): Geochronological data from the Eastern Alps. In: FLÜGEL, H. W. & FAUPL, P. (Hrsg.): Geodynamics of the Eastern Alps. - 272-281, Deuticke, Wien.
Frank, W., Klein, P., Nowy, W. & Scharbert, S. (1976): Die Datierung geologischer Ereignisse im Altkristallin der Gleinalpe (Steiermark) mit der Rb/Sr-Methode. Tschermaks Min. Petr. Mitt., 23, 191-203.
Frank, W., Lelkes-Felvàri, G & Dunkl, I. (1996): Thermal history of Austroalpine rocks of the borehole Fertöràkos-1004, Western Hungary. – In: Dudich, E. & Lobitzer, H. (Eds.): Advances in Austrian-Hungarian Joint Geological Research. – Occas. Papers Geol. Inst. Hung. (Budapest), 189, 177-195, Budapest.
Frisch, W., Schmerold, R. & Neubauer, F. (1989): Die Plankogelserie eine ophiolithische Sutur. - Arbeitstagung Geol. B.-A. Wien 1989, 34-41, Wien.
Fuchs, W. & Grill, R. (1984): Geologische Karte von Wien und Umgebung 1:200.000. Geol. B.-A. Wien, Wien.
Gaal, G. (1965): Geologie des Roßkogelgebietes W Mürzzuschlag (Steiermark). Mitt. Ges. Geol. Berbaustud., 16 (1965), 105-148, Wien.
Gawlik, H.-J., Frisch, W., Vecsei, A., Steiger, T. & Böhm, F. (1999): The change from rifting to thrusting in the Northern Calcareous Alps as recorded in Jurassic sediments. Geol. Rundschau, 87, 644-657.
Genser, J. & Neubauer, F. (1989): Architektur und Kinematik der östlichen Zentralalpen - eine Übersicht. – Mitt. Naturwiss. Vereins Steiermark, 120, 203 – 219, Graz.
Gregurek, D. (1995): Geothermobarometrische Untersuchungen an den Gesteinen der südlichen Koralpe.- Unpubl. Diploma Thesis Naturwiss. Fak. Karl-Franzens-Univ. Graz, 224 pp., Graz.
Habler, G. (1999): Die polyphase Metamorphose- und Strukturprägung der Eklogit-führenden ostalpinen Kristallineinheiten im Raum Knappenberg (NW Saualpe, Kärnten). Unpublished Diploma Thesis Formal- u. Naturwiss. Fak. Univ. Wien, 150pp., Wien.
Habler, G., Thöni, M. (2001): Preservation of Permo-Triassic low-pressure assemblages in the Cretaceous high-pressure metamorphic Saualpe crystalline basement (Eastern Alps, Austria). J. metamorphic Geol., 19, 679-697.
Handler, R.(1994): 40Ar/39Ar and Rb-Sr mineral dating within a complex polymetamorphic terrain: the northeastern Alps, Austria. Unpubl. PhD Thesis Naturwiss. Fak. Karl-Franzens-Universität Graz, 143pp, Graz.
Heede, H.-U. (1997): Isotopengeologische Untersuchungen an Gesteinen des ostalpinen Saualpenkristallins, Kärnten-Österreich. Münster. Forsch. Geol. Paläont., 81, 168pp.
Hejl, E. (1997): "Cold spots" during the Cenocoic evolution of the Eastern Alps: thermochronological interpretation of apatite fission-track data. Tectonophysics, 272, 159-173.
Hoinkes, G., Koller, F., Rantisch, G., Dachs, E., Höck, V., Neubauer, F. and Schuster, R. (1999): Alpine metamorphism of the Eastern Alps. Schweiz. Mineralog. Petrogr. Mitt., 79, 155-181.
Huber, M. (1994): Bildung und geotektonische Bedeutung von Scherzonen (Leukophylliten) am Alpenostrand.- Unpubl. PhD Thesis Univ. Leoben, 136pp, Leoben.
Jung, G. (1982): Geologische und geochronologische Untersuchungen des Metamorphoseablaufes in Glein-, Stub- und Koralpe. Unpubl. PhD. Thesis Formal- Naturwiss. Fak. Univ. Wien, 180pp, Wien.
Kolenprat, B. (1997): Strukturgeologische Untersuchungen am Südrand des Bösensteinkristallins. Unpubl. Diploma Thesis Formal- Naturwiss. Fak. Univ. Wien, 121pp, Wien.
Krohe, A. (1987): Kinematics of Cretaceous nappe tectonics in the Austroalpine basement of the Koralpe region (eastern Austria). Tectonophysics, 136, 171-196.
Lichem, Ch., Gregurek, D. & Hoinkes, G. (1996): Alpidische Metamorphosegradienten im Koralmkristallin. Abstract vol. 6. TSK, 253-254, Facultas-Universitätsverlag, Salzburg.
Manby, G.M. & Thiedig, F. (1988): Petrology of eclogites from the Saualpe, Austria. Schweiz Mineral. Petrogr. Mitt., 68, 441-466.
Miller, Ch. (1990): Petrology of the type locality eclogites from the Koralpe and Saualpe (Eastern Alps), Austria. Schweiz. Mineral. Petrogr. Mitt., 70, 287-300.
Miller, Ch. (1990): Petrology of the type locality eclogites from the Koralpe and Saualpe (Eastern Alps), Austria. Schweiz. Mineral. Petrogr. Mitt., 70, 287-300.
Miller. Ch. & Thöni, M. (1997): Eo-Alpine eclogitisation of Permian MORB-type gabbros in the Koralpe (Eastern Alps, Austria): new geochronological, geochemical and petrological data. Chem. Geol., 13, 283-310.
Morauf, W. (1980): Die permische Differentation und die alpidische Metamorphose des Granitgneises von Wolfsberg, Koralpe, SE-Ostalpen, mit Rb/Sr- und K/Ar-Isotopenbestimmungen. Tschermaks Mineral. Petrogr. Mitt., 27, 169-185.
Morauf, W. (1981): Rb-Sr und K-Ar-Isotopenalter an Pegmatiten aus der Kor- und Saualpe. SE-Ostalpen, Österreich. Tschermaks Mineral. Petrogr. Mitt., 28, 113-129.
Müller, W., Dallmeyer, R.D., Neubauer, F. & Thöni, M. (1999): Deformation-induced resetting of Rb/Sr and 40Ar/39Ar mineral systems in a low-grade, polymetamorphic terrane (Eastern Alps, Austria). J. Geol. Soc., 156/3, 261-278, London.
Neubauer, F., Dallmeyer, R. D., Dunkl, I. & Schirnik, D. (1995): Late Cretaceous exhumation of the metamorphic Gleinalm dome, Eastern Alps: kinematics, cooling history and sedimentary response in a sinistral wrench corridor. Tectonophysics, 242, 79-98.
Neubauer, F., Dallmeyer, R.D. & Takasu, A. (1999): Conditions of eclogite formation and age of retrogression within the Sieggraben unit, Eastern Alps: implications for Alpine-Carpathian tectonics. Schweiz. Mineral. Petrogr. Mitt., 79/2, 297-307.
Neubauer, F., Hoinkes, G., Sassi, F., Handler, R., Höck, V., Koller, F. & Frank, W. (1999): Pre-Alpine metamorphism of the eastern Alps. Schweiz. Mineral. Petrogr. Mitt., 79/2, 41-62.
Peindl, P. (1990): Variszische und alpidische Entwicklungsgeschichte des südöstlichen Raabalpenkristallins (Steiermark). Unpubl. Diss. Natwiss. Fak. Univ. Graz, 252pp, Graz.
Peresson, H., & Decker, K. (1997): The Tertiary dynamics of the northern Eastern Alps (Austria): Changing Paleostresses in a collisional plate boundary. Tectonophysics, 272, 125-158.
Pumhösl, H., Koller, F., Thöni, M., Faryad, S.W., Seifert-Falkner, C., Frank, W., Miller, C., & Satir, M. (submitted): Origin and evolution of Permian gabbroic intrusions within the Lower Austroalpine Grobgneiss Unit (Eastern Alps). Chem. Geology.
Putis, M., Korikovsky, S.P.; Pushkarev, Y.D. (2000): Petrotectonics of an Austroalpine Eclogite-Bearing Complex (Sieggraben, Eastern Alps) and U-Pb Dating of Exhumation. Jb. Geol. B.-A. Wien, 142, 73-93, Wien.
Ratschbacher, L. (1986): Kinematics of Austro-Alpine cover nappes: changing translation path due to transpression. Tectonophysics, 125, 335-356.
Ratschbacher, L., Frisch, W., Neubauer, F., Schmid, S. M. and Neugebauer, J. (1989): Extension in compressional orogenic belts: The Eastern Alps. Geology, 17: 404-407.
Rittmann, K.-L. (1984): Argon in Hornblende, Biotit und Muskovit bei der geologischen Abkühlung - 40Ar-39Ar-Untersuchungen. Unpubl. PhD Thesis. Univ. Heidelberg, 278pp, Heidelberg.
Scharbert, S. (1981): Untersuchungen zum Alter des Seckauer Kristallins. Mitt. Ges. Geol. Bergbaustud Österr., 27, 173-188, Wien.
Scharbert, S. (1990): Rb-Sr Daten aus dem Raabalpenkristallin. - In: Peindl, P., Neubauer, F., Moyschewitz, G., Reindl, H. & Wallbrecher, E.: Die geologische Entwicklung des südlichen Raabalpen- und Wechselkristallins.- Excursion guide TSK III Exkursion "Raabalpen- und Wechselkristallin" 24. April 1990. Geol. Inst. Univ. Graz, 22-25, Graz.
Schuster, K., Berka, R., Draganits, E., Frank, W. & Schuster, R. (2001b): Lithologien, metamorphosegeschichte und tektonischer Bau der kristallinen Einheiten am Alpenostrand. Arbeitstagung Geol. B.-A. Wien 2001 - Neuberg a.d. Mürz, 29-56, Wien.
Schuster, R. (1994): Die Alpine Großüberschiebung an der Basis des Bundschuhkristallins (Steiermark/Kärnten/Salzburg). Unpubl. Diploma Thesis Formal- Naturwiss. Fak. Univ. Wien, 120pp, Wien.
Schuster, R. & Frank, W. (2000): Metamorphic evolution of the Austroalpine units east of the Tauern Window: indications for Jurassic strike slip tectonics. Mitt. Geol. Bergbau Stud. Österr., 42, 37-58, Wien.
Schuster, R., Scharbert, S., Abart, R. & Frank, W. (2001a): Permo-Triassic extension and related HT/LP metamorphism in the Austroalpine - South Alpine realm. Mitt. Geol. Bergbau Stud. Österr., 44, 111-141, Wien.
Stampfli, G.M. & Mosar, J. (1999): The making and becoming of Apulia. Memorie di Scienze Gelogiche, 51/1, 141-154, Padova.
Stampfli, G.M., Mosar, J., De Bono, A. & Vavasis, I. (1998): Late Paleozoic, early Mesozoic plate tectonics of the Western Tethys. Bulletin of the Geologic Society of Greece, (8. Internat. Congress Geol. Soc. Greece, Patra 1998), 32/1,113-120.
Stüwe, K. & Powell, R. (1995): PT-paths from modal portions. Application to the Koralm complex, Eastern Alps. Contributions to Mineralogy and Petrology, 119, 83-93.
Tait, J.A., Bachtadse,V., Franke,W. & Soffel,H.C. (1997): Geodynamic evolution of the European Variscian Fold Beld: Paleomagmatic and geological constraints. Geologische Rundschau, 86, 585-598.
Thöni, M. (1999): A review of geochronological data from the Eastern Alps. Schweiz. Mineral. Petrogr. Mitt., 79/1, 209-230.
Thöni, M. (2002): Sm-Nd isotope systematics in garnet from different lithologies (Eastern Alps): age results, and an evaluation of potential problems for Sm-Nd garnet chronometry. Chem. Geol. 182/1 (Isotope Geosci. Sect.) (in print).
Thöni, M. & Jagoutz, E. (1992): Some new aspects of dating eclogites in orogenetic belts: Sm-Nd, Rb-Sr, and Pb-Pb isotopic results from the Austroalpine Saualpe and Koralpe type-locality (Carinthia/Styria, southern Austria). Geochemica et Acta, 56, 347-368.
Thöni, M. & Miller, Ch. (1996): Garnet Sm-Nd data from the Saualpe and the Koralpe (Eastern Alps, Austria): chronological and P-T constraints on the thermal and tectonic history. J. metamorphic Geol., 14, 453-466.
Thöni, M. & Miller, Ch. (2000): Permo-Triassic pegmatites in the eo-Alpine eclogite-facies Koralpe complex, Austria: age and magma source constraints from mineral chemical, Rb-Sr and Sm-Nd isotopic data. Schweiz. Mineralog. Petrogr. Mitt., 80, 169-186.
Tollmann, A. (1977): Geologie von Österreich. Band 1. Die Zentralalpen. Deuticke, Wien, 766pp, Wien.
Török, K. (1999): Pre-Alpine development of the andalusite-sillimanite-biotite-schists from the Sopron Mountains, Eastern Alps, Western Hungary. Acta Geologica Hungarica, 42, 127-160, Budapest.
Wieseneder, H. (1971): Gesteinsserien und Metamorphose im Ostabschnitt der Österreichischen Zentralalpen. Verh. Geol. B.-A. Wien, 1971, 344-357, Wien.
Descriptions of the neighbouring Units:
Paleozoic of Graz (PZG)