GMPV10.1 | Magmatism, metamorphism and geodynamics of the Variscan orogeny in Europe
Magmatism, metamorphism and geodynamics of the Variscan orogeny in Europe
Co-organized by GD9
Convener: Urs Schaltegger | Co-conveners: Pavlina Hasalová, Anna Pietranik, Pavla Stipska
| Tue, 25 Apr, 14:00–15:45 (CEST)
Room 0.96/97
Posters on site
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
Hall X2
Orals |
Tue, 14:00
Tue, 10:45
The crystalline areas of Europe are formed predominantly by rocks of Variscan age (370-300 Ma), or older rocks that underwent a Variscan metamorphic overprint. The interest in this continent-scale orogeny is sourced in the fact that the reconstruction of Variscan geodynamics requires the development and reconsideration of fundamental concepts of orogenic cycling. We need to explain the evolution of Variscan cycle via the existence of multiple, partly opposing subduction zones, as well as periods of lithospheric thinning and ultrarapid exhumation during extensional stages, or oroclinal bending. These orogenic processes are reconstructed based on information from transcrustal magmatic systems that established during pre-, syn and post-collisional stages as well as from understanding of P-T-t evolution in the different metamorphic units. Especially linking geochronological, isotopic and petrological records led to significant advances in understanding the evolution of both magmatic and metamorphic rocks. We invite contributions from all fields that investigate the nature, conditions and the timing of orogenic processes, crustal melting, or the structure of the lithosphere, through analytical or numerical approaches. Recent advances linking geochronological and petrological records are welcomed.

Orals: Tue, 25 Apr | Room 0.96/97

Chairpersons: Pavlina Hasalová, Anna Pietranik
On-site presentation
Piotr Wojtulek, Bernhard Schulz, Reiner Klemd, Grzegorz Gil, Michał Dajek, and Katarzyna Delura

The Central-Sudetic Ophiolites (CSO) are located in the Sudetes constituting the NE fragment of the Bohemian Massif, one of Variscan basement outcrops in Central Europe. The CSO involve the Ślęża, Braszowice-Brzeźnica, Szklary and Nowa Ruda massifs that are dated at 404.8 ± 0.3 – 401.2 ± 0.3 Ma (Awdankiewicz et al., 2020). These massifs display highly depleted, harzburgite mantle sections containing gabbroic dykes and local occurrences of mostly isotropic, large gabbroic bodies as well as volcanic rocks. The ultramafic rocks locally show melt percolation-derived clinopyroxene-olivine aggregates and chromitites. The low REE composition and depletion in LREE relative to HREE of the clinopyroxene as well as the chromite Cr# and Mg# values point to phases formed from refractory melts occurring in the supra-subduction zone environment. The gabbroic bodies consist of differently evolved, mostly cumulate rocks, while the volcanic rocks form a relatively monotonous basalt sequence. The trace element compositions of both the plutonic and volcanic rocks display depleted N-MORB affinities, their derivation from a refractory mantle source is further reflected by depleted mantle-like Sr-Nd isotopic compositions. The ultramafic and mafic members of the CSO show greenschist- to lower amphibolite facies metamorphic overprints.

The CSO represent an ancient supra-subduction-type oceanic lithosphere that formed in a slow- to intermediate spreading regime. The lithosphere of the CSO is heterogeneous and lacks the structure of a typical layered ophiolitic complex, but rather resembles that of slow spreading oceanic complexes with gabbroic bodies formed due to local magma injections. Melt percolation phases in ultramafic member as well as plutonic and volcanic rocks of the CSO display geochemical signatures accounting for their derivation from a refractory mantle source, typical of N-MORB-type melts depleted in supra-subduction zone settings but lacking subduction-related enrichment. These rocks of the CSO are believed to have formed in a mature, intra-oceanic back-arc basin. Chemical affinities between the CSO and other Devonian ophiolites belonging to the Middle Allochthon (for instance Careón ophiolite in the NW Iberian Massif, Spain or Tisoviţa Iuţi ophiolitic massif in Romania) confirm that a typical MORB-type lithosphere is absent in the European Variscides. Therefore, these ophiolites are thought to constitute fragments of lithosphere that were generated in supra-subduction-zone domains during the amalgamation of Pangea.


Awdankiewicz, M., Kryza, R., Turniak, K., Ovtcharova, M., Schaltegger, U., 2020. The Central Sudetic Ophiolite (European Variscan Belt): precise U-Pb zircon dating and geotectonic implications. Geological Magazine 158, 555–556.

How to cite: Wojtulek, P., Schulz, B., Klemd, R., Gil, G., Dajek, M., and Delura, K.: The Central-Sudetic ophiolites (NE Bohemian Massif) and their geodynamic setting compared with Devonian ophiolites of the Variscan suture in Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16962,, 2023.

On-site presentation
Charlotte Connop, Andrew Smye, and Joshua Garber`

The thermal budget of metamorphic terranes with evidence for kilometric-scale partial melting in the shallow crust (< 15 km depth) cannot be solely explained by conductive relaxation of thickened crust. Such high temperature-low pressure (HT-LP) metamorphism demands a prodigious heat supply to overcome the cooling effect of heat loss from the Earth’s surface. In this study, we present results from a systematic monazite and zircon petrochronological investigation of a classic HT-LP terrane: the Variscan-aged Trois Seigneurs Massif, French Pyrenees.

The massif is composed of a progressive metamorphic sequence from chlorite-bearing phyllites to sillimanite-bearing migmatites, culminating in an S-type granitoid body that occupies over one-third of the massif’s area. Phase equilibrium modelling refines established pressure-temperature (PT) conditions of melting and granite formation to 4-6 kbar and >685 °C. Monazite from five metapelitic samples spanning the structural thickness of the massif records an extended period of metamorphism from 330-290 Ma, with only the low-grade andalusite schists recording a significant population of U/Th-Pb dates older than 310 Ma. Higher-grade schists and migmatites preserve dates from 310-295 Ma, constraining the duration of peak metamorphism, which overlaps zircon U-Pb dates obtained from the S-type granitoid (305.1 ± 1.9 Ma). Peak metamorphic conditions and granitoid emplacement dates at the Trois Seigneurs massif overlap with other published dates for HT-LP metamorphism and granitoid emplacement across the entire Variscan Pyrenees. Combining these PT estimates with those derived from proximal Variscan Pyrenean massifs defines a composite ‘dogleg’ geotherm with elevated dT/dz through the shallow crust (>50 °C/km, <12 km) but near-isothermal conditions through the mid-crust (12-25 km).

A simple thermal model is used to show that this ‘dogleg’ thermal structure can be attained in <15 Myr by advection of magmatic heat between the lower and shallow crust. For such a mechanism to operate on orogenic length scales, however, requires a critical combination of: i) a fertile lower crust buffering the deep crust at the wet solidus, ii) attenuated mantle lithosphere during the waning stages of orogenesis, and ii) significant focusing of melt through the crustal column. We speculate that melt-driven HT-LP metamorphism should be present in other orogenic belts where these conditions are met.

How to cite: Connop, C., Smye, A., and Garber`, J.: Heat sources for Variscan high temperature-low pressure metamorphism: constraints from a petrochronological investigation of the Trois Seigneurs Massif, French Pyrenees, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4504,, 2023.

On-site presentation
Luc de Hoÿm de Marien, Pavel Pitra, Marc Poujol, Nathan Cogné, Florence Cagnard, and Benjamin Le Bayon

The P–T–t evolution of eclogite samples from a locality of the French Massif Central where a Silurian age for the high-pressure metamorphism is commonly accepted is reinvestigated. Petrology combined with LA-ICP-MS U-Pb dating and trace-element analysis in zircon and apatite discard the Silurian age and rather reveal an Ordovician (c. 490 Ma) rifting, a Devonian (c. 370 to 360 Ma) subduction and a Carboniferous (c. 350 Ma) exhumation in this part of the French Massif Central.

The petrological study using pseudosection document a prograde evolution in the eclogite facies marked by an increase of pressure above 20 kbar associated with a strong temperature increase from 650 to 850 °C. Peak-temperature and incipient decompression to the high-pressure granulite facies (19-20 kbar and 875°C) were accompanied by partial melting of the eclogite. Further decompression resulted in partial equilibration in the high-temperature amphibolite facies (<9 kbar, 750-850°C). Local fractures filled by analcite and thomsonite testify to late interaction with alkaline fluids. Metamorphic zircon with eclogitic REE patterns (no Eu anomaly, flat HREE) and inclusions (garnet, rutile and probably omphacite) shows concordant apparent ages that spread from c. 370 down to c. 310 Ma. A c. 350 Ma age of apatite attributed to cooling following decompression from the eclogite facies indicates that zircons younger than 350 Ma, were rejuvenated but preserved an apparent eclogitic signature. It is suggested that interaction with alkaline fluids at low temperatures would lead to the recrystallisation of zircon while leaving apatite unaffected.

Comparison with available P–T–t data from eclogites in Western Europe shows that Devono-Carboniferous high-temperature eclogites are also recognized in the Saxo-Thuringian and Moldanubian zones of the Bohemian Massif suggesting they belonged to the same subducting bloc. Devono-Carboniferous trench/arc and arc/back-arc relationships recognized in the Bohemian Massif and the French Massif Central respectively point to a southward subduction in both areas. This comparison challenges the historical interpretation of a northward subduction in France and brings an overall more coherent picture of the Variscan belt.

How to cite: de Hoÿm de Marien, L., Pitra, P., Poujol, M., Cogné, N., Cagnard, F., and Le Bayon, B.: Using petrochronology to re-investigate the age of the HP metamorphism in the French Massif Central, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5275,, 2023.

On-site presentation
Stylianos Karastergios, Simona Ferrando, and Maria Luce Frezzotti

In the Italian Alps, the Ivrea-Verbano Zone (IVZ) is known as one of the best preserved, i.e., not re-equilibrated during Alpine metamorphism, Variscan Units and, from SW to NE, it extends from Ivrea to Locarno. The sub-units constituting the IVZ are the Kinzigite Formation (supracrustal metapelites intercalated with marbles and metamafic rocks), the Peridotitic Massifs (Baldissero, Balmuccia and Finero) and the gabbroic Mafic Complex. The well-studied lithologies from Val Strona di Omegna and Val Sesia provide evidence of a nearly completed section from the lower crust (e.g., mafic granulites, metamafic migmatites, migmatitic metapelites) to the middle crust (e.g., amphibolites, marbles, calc-silicates and minor quartzites). In the present work, we focus on the less-studied area around Ivrea town to provide further insights into the P-T-X evolution of the IVZ.

Our field work shows that the main attribute of the Ivrea outcrops is the presence of metamafic rocks intercalated with enderbitic granulites and minor high-grade metapelites (stronalites). The lithologies and their field relationships are compatible with the metamafic septa intercalated with migmatitic meta-sediments of pelitic to psammitic composition and calc-silicates of the Kinzigite Formation described in the Val Strona di Omegna and Val Sesia areas.

The metabasites (orthopyroxene + clinopyroxene + plagioclase + amphibole + spinel + magnetite + ilmenite) are two-pyroxene granulites devoid of garnet. They are characterized by the widespread presence of brown amphibole, whose volume may locally exceed 20% of the rock (point-counting data). The enderbitic granulites consist of orthopyroxene + plagioclase + ilmenite + magnetite, relict calcic plagioclase + K-feldspar ± quartz, and minor retrograde amphibole and biotite. The stronalites are metapelites consisting of garnet + plagioclase + sillimanite + quartz + rutile + relict biotite. Despite the very simple mineralogy, more than one generations of the same mineral assemblage have been identified in the studied rocks by both textural relationships and mineral chemistry. These data suggest a complex metamorphic evolution of the studied area.

Preliminary P-T estimates (winTWQ software) have been obtained for each mineral assemblage of the two-pyroxene granulites. The results suggest a prograde-to-peak evolution under amphibolite- to granulite-facies conditions. Pressure is not higher than 5,5 – 6,5 kbar, in agreement with the absence of garnet. The temperature varies depending on the considered mineral assemblage.

Our data suggest that the Ivrea area belongs to the Kinzigite Formation and corresponds to a lower crust at the transition with a middle crust. The peculiar presence of the enderbitic granulites suggests a more complex evolution of this area with respect to the Val Strona di Omegna and Val Sesia areas.

How to cite: Karastergios, S., Ferrando, S., and Frezzotti, M. L.: Metamorphic evolution of the south-western Ivrea-Verbano Zone (Ivrea Town area, NW Italy): metamorphic textures, mineral assemblages and P-T evolution., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9350,, 2023.

On-site presentation
José R. Martínez Catalán, Karel Schulmann, Puy Ayarza, and Jean-Bernard Edel

Arcuate trace of large structures characterizes many mountain chains. The Variscan Belt is not an exception, and depicts one of the tightest oroclines in the world, the Ibero-Armorican Arc. In addition, the belt features a few more open arcs in the Eastern Moroccan Meseta, Central Iberia, the French Massif Central and the Bohemian Massif. All Variscan arcs are considered oroclines or secondary oroclines according to definitions by Weil and Sussman (2004) and Johnston et al. (2013) respectively. They are also essentially late orogenic features, but their timing and deformation mechanisms differ. Models explaining their origin have been proposed for some individual arcs, and are generally controversial.

This contribution aims at interpreting the ensemble of Variscan arcs paying attention to their age relative to previous orogenic features as well as to those associated with arc development. Such features include first order structures, metamorphism and plutonism, as well as magnetic and gravimetric anomalies. Development of the arcs is viewed as somehow related with late Variscan dextral transpression provoked by the relative displacement of Laurussia to the East relatively to Gondwana during the Pennsylvanian and early Permian (325-290 Ma; Arthaud and Matte, 1977; Shelley and Bossière, 2000; Martínez Catalán et al., 2021). But several mechanisms operated to form the arcs, the most important of them being ductile transcurrent shearing, indentation and shortening perpendicular and parallel to the orogenic trend. These mechanisms acted at different time intervals and their participation or relative importance varies for each arc, as well as their involvement in the development of the structural, metamorphic and igneous features and in the geophysical characteristics.


Arthaud, F. and Matte, P. 1977. Late Paleozoic strike-slip faulting in southern Europe and northern Africa: result of a right-lateral shear zone between the Appalachians and the Urals. Geological Society of America Bulletin, 88, 1305-1320.

Johnston, S.T., Weil, A.B. and Gutiérrez-Alonso, G. 2013. Oroclines: Thick and thin. Geological Society of America Bulletin, 125 (5-6), 643-663.

Martínez Catalán, J.R., Schulmann, K. and Ghienne, J.F. 2021. The Mid-Variscan Allochthon: Keys from correlation, partial retrodeformation and plate-tectonic reconstruction to unlock the geometry of a non-cylindrical belt. Earth-Science Reviews, 220, 103700, 1-65.

Shelley, D. and Bossière, G. 2000. A new model for the Hercynian Orogen of Gondwanan France and Iberia. Journal of Structural Geology, 22 (6), 757-776.

Acknowledgement: Spanish Ministry of Science and Innovation, project PID2020-117332GB-C21.

How to cite: Martínez Catalán, J. R., Schulmann, K., Ayarza, P., and Edel, J.-B.: Oroclinal arcs of the Variscan Belt: features and mechanisms, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7611,, 2023.

On-site presentation
Karel Schulmann, Jean Bernard Edel, José Ramón Martínez Catalán, Stanislaw Mazur, Alexandra Guy, Jean Marc Lardeaux, Puy Ayarza, and Imma Palomeras

Comprehensive set of seismic and potential field data from the whole European Variscan belt is used to interpret the structure and evolution of the European Variscides as defined by Martínez Catalán et al. (2021). The gravity data show the presence of high amplitude, short-wavelength gravity anomalies correlated with the outcrops of eclogites, ultramafic rocks and ophiolites delineating the main body of the Mid-Variscan Allochthon (MVA) and the Devonian Mid-Variscan suture (MVS). The medium amplitude and elongated long-wavelength gravity highs, aligned parallel to the Variscan structural grain, correspond to the low-grade Proterozoic rocks of the MVA and Devonian arc – back-arc system. On the other hand, the short wavelength negative gravity anomalies developed in the central part of the belt coincide with Carboniferous (330–310 Ma) per- to meta-aluminous magmatic bodies. The magnetic data show two belts correlated with Carboniferous Rhenohercynian and Devonian Mid-Variscan magmatic arc granitoids. The Rhenohercynian and Mid-Variscan subduction systems are also well-imaged by moderately dipping primary reflectors in reflection seismic lines. Younger moderately dipping reflectors in the upper-middle crust coincide with outcrops of Carboniferous detachments, limiting granite plutons and core complexes along-strike the core of the Variscan orogeny. Deep crustal reflectors are considered as an expression of lower crustal flow resulting from extensional re-equilibration of the previously thickened Variscan crust. A P-wave velocity logs synthesis shows a high-velocity cratonic crust surrounding a thin Variscan orogenic crust defined by low-velocity lower and middle crusts. The latter crustal type coincides with regional outcrops of 330–310 Ma per- to meta- aluminous granitoids and associated gravity lows along-strike the belt. All these data are used to define the primary polarity of Devonian subduction systems defining the European Variscan belt (Schulmann et al., 2022) and discuss the Carboniferous extension forming specific structure of the Variscan crust. This geodynamic evolution is integrated into a paleomagnetically constrained model of the movements of continental plates and intervening oceans (Edel et al., 2018; Martínez Catalán et al., 2021).


Catalan, J.R.M., Schulmann, K. and Ghienne, J.F., 2021. The Mid-Variscan Allochthon: Keys from correlation, partial retrodeformation and plate-tectonic reconstruction to unlock the geometry of a non-cylindrical belt. Earth-Science Reviews, 220, 1–65.

Edel, J.B., Schulmann, K., Lexa, O. and Lardeaux, J.M., 2018. Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt. Earth-science reviews, 177, 589-612.

Schulmann, K., Edel, J.B., Catalán, J.R.M., Mazur, S., Guy, A., Lardeaux, J.M., Ayarza, P. and Palomeras, I., 2022. Tectonic evolution and global crustal architecture of the European Variscan belt constrained by geophysical data. Earth-Science Reviews, 234,  p.104195.

How to cite: Schulmann, K., Edel, J. B., Martínez Catalán, J. R., Mazur, S., Guy, A., Lardeaux, J. M., Ayarza, P., and Palomeras, I.: Tectonic evolution and global crustal architecture of the Variscan crust of the European Variscan belt constrained by geophysical data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5364,, 2023.

On-site presentation
Jean-Marc Lardeaux

In mountain belts, one the one hand, the method to restore the paleopositions of landmasses, and thus oceanic domains, is paleomagnetism, combined with high-resolution geochronological data. As far as the Palaeozoic is concerned, we are fortunate to benefit of the so-called unified full plates reconstruction models (i.e. paleomagnetic databases consistent with coherent plate boundaries kinematics, mantle dynamics and geologic features, see for example Domeier and Torsvik, 2017 for a general discussion).

On the other hand, deciphering orogenic polarity requires the combination of different geophysical methods. Regarding the European Variscan belt, a synthetic overview of results and interpretations of various methods of geophysical imagery is now available ( Edel et al, 2018; Schulmann et al., 2022).

These two types of data constitute robust points of reference that any orogenic evolution model must respect at least in the first order.

In the last decade, in the French Variscan belt, significant advances linking petrological and geochronological records have been performed, especially on high to ultra-high pressure metamorphic rocks. In addition, new observations have confirmed the occurrence and extension of magmatic arcs and back-arcs systems active during Devonian and Carboniferous times.

We present and discuss a review of all these new data and their confrontation with the available robust paleomagnetic and geophysical crustal-scale constraints. This analysis leads us to a revision, and sometimes a radical re-evaluation, of the orogenic evolution models hitherto proposed to interpret the evolution of the French part of the European Variscan belt.


Edel JB, Schulmann K, Lexa O, Lardeaux JM. 2018. Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt. Earth Sciences Review, 177:589−612

Domeier M, Torsvik TH. 2017. Full-plate modelling in pre-Jurassic time. Geological Magazine, 156(2): 261−280.

Schulmann, K., Edel, J.B., Martinez-Catalàn, J.R., Mazur, S., Guy, A., Lardeaux, J.M., Lexa, O., Ayarza, P., Palomeras, I. 2022. Tectonic evolution and global architecture of the European Variscan belt constrained by geophysical data. Earth Sciences Review, 234, 104195.

How to cite: Lardeaux, J.-M.: Orogenic polarity, paleo-magnetic constraints and updated geochronology of high to ultra high-pressure metamorphism: towards a re-interpretation of the evolution of the French Variscan belt?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2583,, 2023.

On-site presentation
Manuela Durán Oreja, Pablo Calvín, Juan José Villalaín, Puy Ayarza, and José R. Martínez Catalán

As a result of the collision of Gondwana, peri-Gondwanan terranes, and Laurussia in the Upper Devonian to early Permian, various Paleozoic oceans are thought to have closed, leading to the formation of the Variscan belt. The belt experienced oroclinal bending in the latter phases of the orogeny, a process that became significant in the Iberian Massif, the westernmost part of the European Variscan belt. There, the belt acquired an S-shaped attitude defined by the Central Iberian Arc (CIA) to the south and the Ibero-Armorican Arc (IAA) to the north. The early Variscan structures, the magnetic anomalies, and the tectonostratigraphic zonation of the Iberian Massif are all bent by both arcs.

The IAA is extensively studied, but the tectonic evolution of the CIA is not well resolved because a large part of it is covered by sediments of the Paleogene Duero basin. Paleomagnetism is a very useful tool used to identify possible vertical axis rotations. Therefore, we carefully searched for outcrops that may record paleomagnetic directions that could shed some light on the development of the CIA.

Weakly metamorphic Cambrian limestones from the southern limb of the CIA were subjected to magnetic and paleomagnetic investigations. 32 sites in 5 outcropping structures in the Urda-Los Navalucillos Formation of Montes de Toledo (Central Iberian Zone, Spain), close to the CIA hinge zone, yielded more than 270 cores. These outcrops were affected by two regional-scale Variscan folding phases, namely C1 and C3, which developed interference patterns. A characteristic paleomagnetic component was found at 19 sites in 4 of the structures. This component reveals different temporal correlations with C3 folds, from syn-folding to certainly post-folding. The resulting mean directions of the magnetic vector, in geographic coordinates, consistently display northward to north-western declinations and negative, low inclinations, indicating that they have been acquired before the geomagnetic reverse polarity Kiaman superchron when Iberia was in the southern hemisphere. Although the inclination of the paleomagnetic mean directions is consistent amongst structures, the declination varies from N to NW, suggesting a vertical axis rotation synkinematic to C3 folding previous to 318 Ma. These directions indicate that the early evolution of the southern limb of the CIA was differentially recorded by the paleomagnetic directions of the different structures and underwent a 42º clockwise rotation during the late Carboniferous. The later development of the IAA was associated with a significant counterclockwise rotation that affected the entire paleomagnetic record. (Research support: SA084P20, PID2020-117332GB-C21, PID2019-108753GB-C21, AEI/10.13039/501100011033, FPU16/00980, PTA2017-14779-I and FJC2019-041058-I)

How to cite: Durán Oreja, M., Calvín, P., Villalaín, J. J., Ayarza, P., and Martínez Catalán, J. R.: Insights for late-Variscan kinematics and oroclinal bending in the Central Iberian Zone from the paleomagnetic characterization of the Cambrian Urda-Los Navalucillos Limestone (Montes de Toledo, Spain)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8958,, 2023.

Virtual presentation
António Oliveira, Helena Martins, and Helena Sant'Ovaia

The Permo-Carboniferous magmatism, recorded throughout NW and SW Europe, is related to the late to post-tectonic stages of the Variscan orogeny and constitutes an important period of reorganization of the stress field due to the transition from a compressive/transpressive to extensional/transtensive setting. In northern Portugal, this event manifested through the presence of numerous dykes, sills, and masses of subvolcanic lithologies such as granite porphyries, lamprophyres, and dolerites. The present study is focused on the geochronological results acquired from zircon U-Pb dating of selected dykes, namely the Póvoa de Agrações (PA) and Vila Nova de Foz Côa (VNFC) granite porphyries, the Lamas de Olo (LO) lamprophyre, and the Bolideira quartzdiorite porphyry, and the interpretation of these results from a geodynamic perspective.

Attending only to the most concordant analytical spots (discordance < 5 to 10%) with appropriate ages, corrected for common Pb, weighted means of the 206Pb/238U age yield the following crystallization values: (i) 286 ± 1.5 Ma (MSWD = 0.3) (PA); (ii) 290 ± 6 Ma (MSWD = 2.5) (VNFC); (iii) 295 ± 2 Ma (MSWD = 2.5) (LO); and (iv) 291 ± 5 Ma (MSWD = 3.8) (Bolideira). The porphyries also exhibit two sets of inherited zircon cores, an older one (broadly Paleoproterozoic to Mesoproterozoic) and a younger counterpart (Neoproterozoic (Cryogenian) to Early Silurian), while in the LO lamprophyre, the composing inherited cores are Neoproterozoic (Ediacaran) to Early Ordovician (Floian). For the PA and VNFC dykes, the existence of two inherited core components is possibly associated with the distinct protolith contributions (i.e., metapelites and metagreywacke/orthogneiss) involved in the petrogenesis of these lithotypes, as deduced from the whole-rock geochemistry, whereas the presence of inherited cores in the Bolideira porphyry is most likely related to crustal contamination. Moreover, the inherited cores of the LO lamprophyre are interpreted to have resulted from sediment-induced, metasomatic enrichment of its lithospheric mantle source during subduction.

Based on the aforementioned geochronological constraints, the acid, intermediate and mafic subvolcanic rocks analyzed within the scope of this work are, in fact, late to post-Variscan and, most importantly, (sub)contemporaneous. The prior observation is possibly valid for several other hypabyssal dykes in northern Portugal that have yet to be dated, considering their general orientations and similarities concerning the bulk-rock composition. Therefore, assuming that the regional felsic, intermediate, and mafic (lithosphere-derived and asthenosphere-derived) subvolcanic specimens are roughly coetaneous, the geodynamic evolution of the Central Iberian Zone during the post-Variscan stages is implied to have progressed more rapidly than previously thought, due to the presumed coeval emplacement of distinct mafic melts generated from both lithospheric and asthenospheric sources.

This work was supported by national funding awarded by FCT – Foundation for Science and Technology, I.P., projects UIDB/04683/2020 and UIDP/04683/2020. The main author is financially supported by FCT through an individual Ph.D. grant (reference SFRH/BD/138818/2018). We also acknowledge Professor Pilar Montero (IBERSIMS, University of Granada) for performing the geochronological analyses.

How to cite: Oliveira, A., Martins, H., and Sant'Ovaia, H.: Geochronological constraints on the late to post-Variscan hypabyssal dykes from northern Portugal and their geodynamic implications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9470,, 2023.


Posters on site: Tue, 25 Apr, 10:45–12:30 | Hall X2

Chairpersons: Pavla Stipska, Urs Schaltegger
Irakli Gamkrelidze, David Shengelia, Tamara Tsutsunava, Tamara Gavtadze, Giorgi Chichinadze, Kakhaber Koiava, Giorgi Beridze, and Irakli Javakhishvili

The Loki crystalline massif and adjacent territories are exposed in South Georgia within the northern marginal part of the Beiburt-Sevan terrane. It is part of the Loki-Karabakh tectonic zone. The Loki massif is a large anticlinal structure with a pre-Alpine crystalline basement exposed in the core surrounded by a Mesozoic-Cenozoic sedimentary cover. According to the complex study of the massif, it was established that it is composed of autochthonous Upper Devonian gneissose quartz-diorites, allochthonous pre-Late Paleozoic Moshevani and Sapharlo-Lok-Jandari overthrust sheets of metasediments, Precambrian Lower Gorastskali ofiolite sheet and Upper Gorastskali mélange sheet. All these rocks are cut by Late Paleozoic, Jurassic and Cretaceous intrusions. All sheets, except for ophiolite one, were metamorphosed during the Caledonian orogeny and then were overthrust during Bretonian and Early Cimmerian orogenies. The Loki massif is a part of the northern active continental margin of the Paleotethys oceanic basin, where supra-subduction regional metamorphism and granite formation occurred during Variscan orogeny. During the Late Bretonian orogeny, the obduction of Precambrian ophiolite rocks and the overthrusting of Paleozoic metamorphic sheets onto the continental margin took place. Later they were intruded by granites. Along the entire perimeter, the crystalline basement and granites are transgressively covered by Mesozoic-Cenozoic deposits. On the basis of detailed studies of terrigenous deposits in the section of the r. Gorastskali gorge on nanoplankton new age data have been obtained. Based on these data, for three lithostratigraphic units – Moshevani (conglomerates and quartz sandstones), Lokchay (mica sandstones) and Jandari (argillites) suites, the following ages were established: Norian - Rhaetian, Hettangian - Low Pliensbachian and Upper Pliensbachian - Aalenian, respectively. Triassic deposits were discovered in this area for the first time. With the accumulation of new data on the Loki massif and surrounding area, a new corrected digital geological map, lithostratigraphic column and 3D section were compiled.

How to cite: Gamkrelidze, I., Shengelia, D., Tsutsunava, T., Gavtadze, T., Chichinadze, G., Koiava, K., Beridze, G., and Javakhishvili, I.: New geological map and 3D section of the Loki crystalline massif and surrounding area (the Caucasus), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2790,, 2023.

Máté Szemerédi, Zoltán Kovács, István Dunkl, Réka Lukács, Marija Horvat, Barnabás Jákri, and Elemér Pál-Molnár

Two-mica leucogranites and/or granodiorites, often affected by various degrees of post-emplacement deformation and/or metamorphism (i.e., sheared granites, metagranites or orthogneisses), occur in several parts of the Tisza Mega-unit (Carpathian–Pannonian region), including the Apuseni Mts. (Romania), the Papuk Mt. (Croatia), and basement highs of the Pannonian Basin (Battonya–Pusztaföldvár and Algyő–Ferencszállás areas, SE Hungary). Despite the similar petrological characteristics (e.g., mineralogical composition, texture), these formations have not been compared to each other yet for correlational purposes and the scarce geochemical and almost completely lacking geochronological records also demanded further petrological investigations and datings.

Petrographically, granitoids from all the studied areas (SW Apuseni Mts., Papuk Mt. and the previously mentioned basement highs) proved to be similar, medium to coarse-grained monzogranites or granodiorites, containing quartz, plagioclase, K-feldspar, biotite, and muscovite. In some quarries or rarely in drill cores aplites and pegmatites were also found. As accessory components most commonly apatite, zircon, monazite, and xenotime, occasionally garnet were identified. As secondary phases sericite, albite, chlorite, epidote, kaolinite, and calcite appear frequently. Whole-rock geochemistry revealed that despite the various post-magmatic alterations (deformation/metamorphism/fluid effects etc.), the majority of the granitoids preserved their primary major and trace element compositions. All of them proved to be subalkaline, peraluminous, alkali-calcic or calc-alkalic with basically magnesian and S-type (rarely S/I-type) character. Major and trace element distributions, chondrite-normalized REE patterns (with slight negative Eu anomalies) and other relatively immobile trace element (HFSEs) concentrations showed significant similarities among the studied samples suggesting their common origin and local correlation possibilities within the Tisza Mega-unit. Interestingly, samples from the Papuk Mt. geochemically differ from the others as well as the aplites and pegmatites associated with the Codru granitoids (Apuseni Mts.). The former might represent a different source and igneous episode; however, the geochemical distinction of the latter (with more pronounced negative Eu anomaly and lower concentrations in REEs and HFSEs) is rather odd. Trace element-based discrimination diagrams (e.g., Yb vs. Ta, Yb+Ta vs. Rb) suggested that most of the studied rocks are volcanic-arc granites and only a few of them (basically aplites and pegmatites) are syn-collisional despite their typical S-type mineralogy (e.g., muscovite, monazite, garnet) that unequivocally referred to continental crustal sources.

Considering another means of geotectonic discrimination (e.g., Sr/Y and La/Yb ratios) and the ascertainment of Broska et al. (2022) in case of Western Carpathians granitoids, it is feasible that the studied granites bear the geochemical signature of a slab break-off, being crust- and mantle-derived, too, while shallower level melts (aplites and pegmatites) represent purely crustal sources in the Variscan orogeny. The latter corresponds to the calculated zircon saturation temperatures, as well (granites: 740–780 °C, aplites/pegmatites: 580–600 °C).

Preliminary datings (Battonya granitoids, SE Hungary) suggested that the main zircon crystallization period occurred in the Early Carboniferous (356 Ma) that fits well into the regional geological framework of the European Variscides.

This study was financed by NRDIF (K131690).

Broska, I., Janák, M., Svojtka, M., Yi, K., Konečný, P., Kubiš, M., Kurylo, S., Hrdlička, M., Maraszewska, M. (2022). Lithos 412–413:106589

How to cite: Szemerédi, M., Kovács, Z., Dunkl, I., Lukács, R., Horvat, M., Jákri, B., and Pál-Molnár, E.: Variscan S-type granitoids in the Tisza Mega-unit (Carpathian–Pannonian region): petrology, geochronology, geotectonic implications, and correlation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1201,, 2023.

Ludwik de Doliwa Zieliński, Michał Bukała, Jakub Bazarnik, Mateusz Mikołajczak, Karolina Kośmińska, and Jarosław Majka

The crystalline basement of the Tatra Mountains belongs to the northernmost part of the Tatric unit of the Western Carpathians and is composed of pre-Mesozoic crystalline rocks, overlain by Mesozoic and Cenozoic sedimentary cover and nappes. Metamorphic rocks are the most abundant in the Western Tatra Mts. and display an inverted metamorphic sequence with high-grade rocks in the hanging wall (Upper Unit; peak conditions: 1.6 GPa, 750-800°C; Janák et al. 1996) and lower-grade rocks in the footwall (Lower Unit; peak conditions: 0.6-0.8 GPa, 640-660°C; Janák et al. 1996) separated by mid-crustal thrust fault. Those two basement units of contrasting pressure-temperature evolution are well documented in southern part of basement (i.e. in Slovakia). However, a presence of the Lower Unit in the northern part of the Western Tatras (i.e. in Poland) is highly debated.

To tackle this problem several field campaigns were carried out targeting an inferred thrust fault allegedly separating both basement units in the north. The field studies coupled with the structural analysis revealed presence of a wide high-strain zone, but no significant lithological difference across the zone on question. A set of three metasedimentary and one metaigneous rocks were collected along the profile cross-cutting the high-strain zone (from the bottom to the top: MB21-71, -82, -03, -32), and display a gradual increase in migmatization. The provenance study of detrital zircon shows no significant differences between the samples. The metasediments MB21-71, -82, -32 define prominent peaks at ca. 570-530 Ma, whereas MB21-32 shows additional younger peak at 520-500 Ma. Additionally, minor Palaeozoic (490-460 Ma;not in MB21-71), Proterozoic (ca. 680 Ma, 1500-1400 Ma, 2000 Ma), and Archean peaks (ca. 2800-2500 Ma) are present. The samples exhibit a metamorphic signature around 360-340 Ma too. The metaigneous rock MB21-03 yields U/Pb zircon age of ca. 490-480 Ma with only few Precambrian grains.

Our preliminary results coupled with a similar study from the southern side of the Western Tatras (Kohút et al. 2022) suggest that the observed similarities in the detrital zircon populations could indicate a similar protolith, thereof all samples could represent only one basement unit . This dataset helps to reconcile the nature of the Variscan basement assembly in the Western Tatra Mts. It also shows that the local tectonostratigraphy of the Tatra Mts. needs to be re-visited and re-evaluated.

Research funded by the National Science Centre, Poland, project no. 2021/43/B/ST10/02312 and supported by the Foundation for Polish Science stipend (M. Bukała). We also acknowledge the Tatra National Park for help and permission to conduct fieldwork.


Janák, M., O'Brien, J.P., Hurai, V., & Reutel, C. (1996). Metamorphic evolution and fluid composition of the garnet-clinopyroxene amphibolites from the Tatras Mountains, Western Carpathians. Lithos, 39, 57-79.

Kohút M., Linnemann U., Hofmann M., Gärtner A., Zieger J. (2022) Provenance and detrital zircon study of the Tatric Unit basement (Western Carpathians, Slovakia). International Journal of Earth Sciences 111:2149-2168.

How to cite: de Doliwa Zieliński, L., Bukała, M., Bazarnik, J., Mikołajczak, M., Kośmińska, K., and Majka, J.: On the track of thrust faults within the Variscan basement of the Western Tatras: structural and geochronological approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6470,, 2023.

Anna Pietranik, Elżbieta Słodczyk, and Arkadiusz Przybyło

The Halle Volcanic Complex is composed of rhyolites interpreted as intrusive-extrusive complexes that pierced host sedimentary cover during their vertical growth. Zircon ages from several units vary from 291.7 ± 1.8 Ma to 301 ± 3 Ma suggesting the prolonged evolution of this subvolcanic-volcanic system. In this study, we sampled the Landsberg (301 ± 3 Ma) and the Petersberg (292 ± 3 Ma) laccoliths to better identify the magmatic processes involved in silicic magma formation and their duration.  Altogether seven depths have been analyzed from these two laccoliths including electron microprobe analyses of zircon and apatite and U-Pb SHRIMP dating of zircon. At the first sight, zircon is chemically similar within and between laccoliths. Additionally, SHRIMP ages are scattered over 30 Ma for each sample in Landsberg. These ages overlap with two Concordia ages obtained for the uppermost horizon (289.7±2.8 Ma) and the lowermost horizon (297.1±1.7 Ma) in the Petersberg laccolith. The ages suggest that the volcanic system was active for at least 10 Ma and similar age range is recorded in both laccoliths. The scatter of ages seems to indicate the formation of the laccoliths over a prolonged period of time with periodic reactivation of the magma chamber, but the lead loss cannot be excluded. Also, prolonged formation may indicate either younger pulses reactivating previously formed parts of the magma chamber or multiple unrelated  magma injections amalgamated separately within the system.

The processes involved in the prolonged evolution of the magmatic system in Halle are evident from petrographic analyses of thin sections, where zircon can be imagined in association with other phases. Both zircon and apatite occur almost exclusively within complex glomerocrysts, an assemblage of major phases (variably altered biotite, feldspar, pyroxene). Such glomerocrysts were described in the literature and interpreted as remnants of crystal mush, probably re-mobilized at the final stage (heating episode) before laccoliths emplacement. The glomerocrysts in Petersberg and Landsberg laccoliths are similar leftovers of previous magmatic episodes, but they are special in that they contain abundant zircon and apatite. Such a picture is consistent with the evolution of magma in a long-lived magmatic system that underwent at least one reactivation. The major implication is that in some systems large proportion of zircon may represent the early stages of magma evolution, this context may be missed without detailed textural observations of zircon occurrence and associations.

Acknowledgements: Christoph Breitkreuz is thanked for his constant help with our rhyolitic research. The research has been funded by the NCN research project to AP no. UMO-2017/25/B/ST10/00180

How to cite: Pietranik, A., Słodczyk, E., and Przybyło, A.: Re-heating of rhyolitic leftovers in the Halle Volcanic Complex: an insight from zircon ages and composition., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5532,, 2023.

Stephen Collett

The Devonian to early Carboniferous geodynamic evolution of the Bohemian Massif is largely controlled by a “diffuse cryptic suture zone” (Schulmann et al., 2014), which crops out between the Saxothuringian Zone (forming the lower plate) in the north and the Teplá-Barrandian and Moldanubian Zones (collectively the upper plate) in the south. Oceanic passing to continental subduction within this suture zone has been linked to at least three discrete episodes of high-pressure to ultra-high-pressure metamorphism; the formation and obduction of Devonian age ophiolites; the up to 50 myr building of a continental magmatic arc; and potentially, the large-scale relamination of continental crust beneath the upper plate and its exhumation into the upper plate in the form of trans-lithsopheric diapirs.

Taken together, this would appear to require long-lasting subduction of a vast oceanic domain likely including old and dense oceanic lithosphere. Yet, significant separation between the lower and upper plates during the Early Paleozoic is not consistent with litho-stratigraphic, paleontological, or paleomagnetic data, which indicate a shared peri-Gondwanan shelf derivation of these units. Nonetheless, within the high-grade rocks of the suture zone itself, an exotic assemblage of Cambrian age volcanic-arc related rocks are identified. These rocks have been variably metamorphosed up to eclogite- and granulite-facies conditions during an early phase of the Variscan Orogen, but, also include lower-grade segments that experienced only lower amphibolite- or greenschist-facies conditions. A compilation of whole-rock geochemical, isotopic and zircon U-Pb and Lu-Hf data from this Cambrian arc assemblage is presented to argue for the exotic nature of this terrane including its possible derivation from the Baltica paleo-continent and for an association with old oceanic lithosphere (Stenian-Tonian age) likely captured from the circum-Rodinia Mirovoi Ocean.

Thus, it is proposed that the geodynamic evolution of the Bohemian Massif cannot be reconciled with a single-phase of oceanic passing to continental subduction. Instead, a three stage evolution is proposed involving: (1) initial subduction of an old oceanic crust and extinct Cambrian age arc terrane derived from the Baltica paleo-continent beneath the peri-Gondwanan margin; (2) transcurrent displacement of a strip of peri-Gondwanan crust behind the initial subduction zone; (3) a second phase of oceanic passing to continental subduction of this displaced peri-Gondwanan crust beneath the initial subduction zone.

Schulmann, K., Lexa, O., Janoušek, V., Lardeaux, J.M. and Edel, J.B., 2014. Anatomy of a diffuse cryptic suture zone: an example from the Bohemian Massif, European Variscides. Geology 42, 275–278.

How to cite: Collett, S.: Reconstructing Devonian-Carboniferous subduction in the Northern Bohemian Massif, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5263,, 2023.

Urs Schaltegger, Jürgen Abrecht, Alfons Berger, Richard Spikings, and Michael Wiederkehr

The pre-Alpine evolution of the Central Alpine basement is dominated by magmatic and metamorphic events that occurred during an Ordovician orogenic cycle (ca. 480-440 Ma) and the Variscan orogenic cycle (ca. 350-300 Ma). A detailed zircon U-Pb data and Hf-isotope study of a large set of magmatic and meta-magmatic rocks revealed four magmatic pulses (Ruiz et al. 2022): at 340-350 Ma (calc-alkaline diorite and tonalite from the Surselva Group), 330-335 Ma (shoshonitic diorites, monzonites, granites and syenites of the Rötifirn Group), 307-310 Ma (calc-alkaline diorites, ranging from cumulate-like hornblende gabbros to hornblende-diorites and hornblende- or biotite quartz- monzonite, granodiorites and metaluminous weakly peraluminous I-type granites of the Fruttstock Group), and 297-300 Ma (late-orogenic, calc-alkaline I-type granites of the Haslital Group). High precision U-Pb dates from meta-magmatic rocks indicate a minor, but variable impact of Alpine metamorphism on the U-Pb dates (Gaynor et al. 2022, Ruiz et al. 2022). However, given the poly-cyclic metamorphic record of the country rocks, the relative contributions of the Alpine, Variscan and an earlier Ordovician orogenic cycle are difficult to quantify. More specifically, the physical conditions of the Variscan metamorphic overprint are only weakly constrained, and available radio-isotopic ages are not reliable. However, monazite, rutile, titanite and zircon ages of 329-317 Ma in high-grade metapelites and calcsilicate gneiss indicate a major high grade Variscan metamorphism along the northern rim of the massif (Schaltegger et al., 2003). In addition, frequently found U-Pb dates between 478 and 445 Ma on gabbros, metapelitic to metapsammitic gneisses in the northern part of the Aar massif (Schaltegger et al., 2003) show relics of an older metamorphism in these polycyclic basement units

In order to understand better the temperature-time evolution of this poly-cyclic basement, we will apply detailed U-Pb geochronology on different minerals together with mineralogical, chemical and textural characterization. Combining the mineralogical data with microstructures and petrological data should give better insights in the link of metamorphism and magmatism for the Variscan orogenic cycle. These data will allow placing the Aar massif evolution in a wider framework of the European Variscan orogen. Moreover, they will reveal the existence of one or several pulses of earlier, Ordovician-age high-grade metamorphism, anatexis and magmatism.

References: Gaynor S.P., Ruiz M., & Schaltegger U. (2022) Chem. Geol., 603, 120913; Ruiz M., Schaltegger U., Gaynor S.P., Chiaradia M., Abrecht J., Gisler C., Giovanoli F. & Wiederkehr M. (2022) Swiss J. Geosci., 115, 20; Schaltegger. U., Abrecht J. & Corfu F. (2003) Schweiz. Mineral. Petrogr. Mitt. 83, 183-195


How to cite: Schaltegger, U., Abrecht, J., Berger, A., Spikings, R., and Wiederkehr, M.: Re-assessing the magmatic and metamorphic evolution of the Aar Massif, Central Alpine basement, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10890,, 2023.

Błażej Cieślik, Anna Pietranik, and Jakub Kierczak

The northeastern part of Bohemian Massif is composed of various lithotectonic domains interpreted as microplates, sedimentary basins, and fragments of ancient oceanic lithosphere, which have been amalgamated during the Late Devonian multistage collision. Fragments of the Variscan Central-Sudetic Ophiolite (CSO) preserve information on the nature of the mantle at the onset of Variscan orogeny. They are mainly composed of ultramafic-mafic rocks (UMR) dated at 400 Ma, but these are not the only components. Other lithologies include (a) carbonate veins crosscutting the UMR, (b) dolomite-rich domains associated with clinopyroxenites, and (c) silicic dyke of diorite composition also crosscutting the UMR. The origin of these lithologies may be contemporaneous with UMR or later (Variscan or Cenozoic) and obtaining the ages is the first step to understanding which events they record. Zircons from the diorite yield a concordia age of 378.0 ± 5.0 Ma (SHRIMP) consistent with the diorite representing an early Variscan magmatic episode. The obtained age of the intrusion suggests an affinity with a located nearby outcrop of ultrapotassic syenites (from 378.2 ± 2.4 to 354.7 ± 4.3 Ma). A striking relationship between the two rocks is evident; if certain elements are strongly enriched in one rock they are equally impoverished in the other. Such unusual chemical fractionation can be achieved during the formation of alkaline and carbonatite melts. Also, dolomite domains recently found in clinopyroxenites or puzzling anhydrite inclusions in Ca-amphiboles may support this hypothesis suggesting an enriched mantle as a common source of dioritic, syenitic, and dolomitic lithologies. On the other hand, carbonate veins record another episode. Recently, the U-Pb radiometric dating of calcite sampled from one of the CSO massifs yielded an isochrone age of 15.4 ± 19.7 Ma that generally suits Paleogene and Neogene tropical weathering events, moreover, some parts of CSO contain abundant carbonates mineralization accompanied by plenty of quartz zonal clusters. The co-occurrence of these phases may suggest hydrothermal origin and becomes a foothold for further studies on the carbonation of obducted oceanic lithosphere.
Altogether, it is important to bear in mind CSO’s 400 Ma-long evolution. It seems that Central-Sudetic Ophiolite and associated younger lithologies still have more to tell us about the orogenic and post-orogenic history of the northeastern Bohemian Massif.

Funding: The research is funded by NCN grant PRELUDIUM no. UMO-2022/45/N/ST10/00879 awarded to Błażej Cieślik.

How to cite: Cieślik, B., Pietranik, A., and Kierczak, J.: Variscan and post-Variscan processes in the Central-Sudetic Ophiolite: records from carbonate and silicate rocks., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5732,, 2023.

Puy Ayarza, José Ramón Martínez Catalán, Juan Gómez Barreiro, Imma Palomeras Torres, Yolanda Sánchez Sánchez, and Mercedes Rivero Montero

The Iberian Massif presents a geometry characterized by two oroclines: the conspicuous and tight Ibero-armorican arc to the north and the older and less pronounced Central Iberian Arc (CIA) to the south. The latter is clearly depicted by low amplitude, short wavelength magnetic anomalies in its external part and long wavelength, higher amplitude magnetic anomalies in its internal part. The origin of these is under study as they seem to be indicators of the deep evolution of this orogen in the Iberian Peninsula.

Three magnetic anomalies stand out in the internal part of the CIA. To the north, the Eastern Galicia Magnetic Anomaly overlaps the Lugo Gneiss Dome, a structure delineated by extensional detachments. Here, the exhumation at high temperatures during late Variscan gravitational collapse triggered the formation of magnetite in metasediments, migmatites and S-type syn-orogenic granites, thus stablishing a clear relationship between tectonics and magnetization. To the west, the Porto-Viseu-Guarda Magnetic Anomaly has still an unclear origin, but it also overlaps an area characterized by extensional tectonics, gneiss domes development and granite intrusion. However, the most magnetic outcropping rocks are late Variscan I-type granites (Lavadores granite) and the Mindelo Migmatitic Complex. None of them shows a relationship between magnetization and extension. Contrarily, magnetic minerals seem to be related to the composition of the resisters in migmatites and to the formation of the Lavadores granite itself. Finally, the Spanish Central System Magnetic Anomaly, at the core of the CIA, also overlaps the exhumed products of late Variscan extension (granites and migmatites). The magnetic anomaly associated to this part of the arc has been studied in the Castellanos Antiform, a discrete extensional dome located in its northern part, where the interaction between high degree metasediments, extension, and migmatization can be revised. New high resolution magnetic and gravity data indicate that the magnetic anomaly coincides with a high Bouguer gravity anomaly, and overlaps an outcrop of granitoids with tonalitic xenoliths and gabbros. The relationship between gravity and magnetic anomalies, together with the lack of outcropping magnetic granitoids and/or migmatites in the Central System, and the high amount of heterogeneous xenoliths, including basic rocks, suggest that in central Iberia, late Variscan extension might have involved deeper levels of the crust and maybe the mantle. Considering the location of this area, in the core of the CIA, and the simultaneity between late Variscan extension and the CIA formation, we suggest that the development of the latter might have played an important role in the supply of mantle material.

Funding:  grant PID2020-117332GB-C21 and projects SA084P20,  MCIN/AEI/10.13039/501100011033 and TED2021-130440B-I00

How to cite: Ayarza, P., Martínez Catalán, J. R., Gómez Barreiro, J., Palomeras Torres, I., Sánchez Sánchez, Y., and Rivero Montero, M.: Heterogeneous origin of the magnetic anomalies of the Central-Iberian Arc. Constraints on the source of the Central System Magnetic Anomaly, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6391,, 2023.

Irene Pérez Cáceres, Irene DeFelipe, Puy Ayarza, Juan Gómez Barreiro, Helena Sant’Ovaia, Cláudia Cruz, Maria dos Anjos Ribeiro, Juan José Villalaín, Manuela Durán Oreja, and José Ramón Martínez Catalán

The Iberian Massif presents a complex Late Paleozoic evolution, with intense compressional tectonics followed by gravitational collapse of the thickened crust and orocline development. In NW Iberia, extensional detachments and associated shear zones developed during high temperature-low pressure metamorphism in relation to partial melting in gneiss domes. These structures also feature a conspicuous relationship with magnetic anomalies that define a curvature, delineating the geometry of the internal part of the Central Iberian Arc. Regardless of the geometry of these anomalies and their relationship to extensional tectonics, their source probably differs from northern to central and western Iberia. While in northern Iberia extensional tectonics triggered oxidation and development of magnetite in migmatites and S-type granites, in central Iberia basic rocks associated with I-type granites seem to be the carriers of the magnetization. This study aims to describe the western branch of the Central Iberian Arc magnetic anomaly: the Porto-Viseu-Guarda Magnetic Anomaly (PVGMA) and its metallogenetic potential previously related with magnetite-type granites.

Polyphase deformation within the Porto-Viseu metamorphic belt later affected by the Douro-Beira shear zone and Porto-Tomar fault presents syn-tectonic staurolite and sillimanite-bearing schists and migmatites (Mindelo Migmatite Complex), great abundance of syn and late S-type two mica-granites, and a post-orogenic porphyritic biotite I-type granite with uncommon high values of magnetic susceptibility (Lavadores granite). These rocks crop out at the northwestern tip of the PVGMA and are thought to be related to it. We sampled migmatites, calc-silicate resisters embedded on them and Lavadores granite for its mineralogical and magnetic characterization.

Anisotropy of the magnetic susceptibility sometimes show stable N-S to N90°E, 0°-20° E to NE plunge magnetic lineations and a WNW-ESE magnetic foliation subparallel to the shearing in the area. In migmatites, thin sections feature the expected high temperature metamorphism manifested by sillimanite and ptygmatic folding. Here, rock magnetism studies show Curie temperatures (Tc) around 300°C and low coercivities indicative of titanomagnetite or some sort of multidomain pyrrhotite. Low to moderate magnetic susceptibilities contrast with very high magnetic remanences leading to Königsberger ratios (Qn) of up to 22 in resisters and 10 in the migmatites. Contrarily, the Lavadores granite has high magnetic susceptibilities and moderate Qn (0.1-2). These rocks feature higher Tc=550° and low coercivities indicative of magnetite. Paleomagnetic results show heterogenous directions for both lithologies implying complicated thermal evolutions and possibly late tilting. Despite their proximity, no relationship seems to exist between the Lavadores granite and the Mindelo Migmatite complex protolith. Contrarily to what it is found in northern Iberia, no relationship has been found between extensional features and magnetic mineralization, so if these rocks are the source of the PVGMA, it is most probably related to the characteristics of the protoliths.

Despite the PVGMA lies on top of the Sn belt across Portugal, geochemical results do not support Lavadores as a potential Sn metallogenetic granite, further indicating the lack of relationship between the formation of magnetite and that of Sn mineralizations.

Acknowledgements: Project SA084P20 (regional CYL government); Grants PID2020-117332GB-C21 funded by MCIN/AEI/10.13039/501100011033 and TED2021-130440B-I00; Projects UIDB/04683/2020 and UIDP/04683/2020 (Portugal).

How to cite: Pérez Cáceres, I., DeFelipe, I., Ayarza, P., Gómez Barreiro, J., Sant’Ovaia, H., Cruz, C., Ribeiro, M. D. A., Villalaín, J. J., Durán Oreja, M., and Martínez Catalán, J. R.: Variscan tectonic evolution, magnetic anomalies and metallogenetic potential in the western Central Iberian Zone (Iberian Massif), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9797,, 2023.

Imma Palomeras, Juan Gomez-Barreiro, Puy Ayarza, José R. Martínez-Catalán, David Martí, Mario Ruiz, Santos Barrios, Kelvin Dos Santos, Yolanda Sanchez-Sanchez, Javier Elez, Mariano Yenes, Irene DeFelipe, Irene Pérez-Cáceres, Elena Crespo, and Pedro Castiñeiras

The late Variscan gravitational collapse and coeval magmatism are getting the attention of the community due to their role in the generation of strategic mineral resources. In this regard, the GOLDFINGER project’s main scope is to study how the Variscan orogenic architecture controls the generation of strategic ore deposits (i.e. Sn, W, Nb, Ta, Sc, Au, Sb). With this goal, a 3D model of a gneissic dome with several mineral deposits will be constructed based on high-resolution geophysics (Seismic/Gravity/Magnetism), and regional geology. The study area encompasses the Martinamor gneiss dome which represents a Late-Variscan syn-collisional extensional system with a well-preserved architecture. This gneiss dome structure presents low topography, relatively flat structural geometry in-depth, and contrasting lithotypes regarding seismic, gravity, and magnetic properties. As part of the project, in spring 2022 the area was covered by 30 low-period seismic recorders with 2Hz sensors in a regular grid. The 35x40 km grid consisted of 60 nodes, separated by approximately 4.5 km. To achieve the final node number, the stations were deployed twice, first in a regular grid with nodes each 6 km, and then the grid was moved 3 km to the west and to the south for a second deployment. The seismic stations were continuously recording in the field for up to 40 days in each deployment. We are using a state-of-the-art technique to retrieve high-resolution seismic images of the Martinamor gneiss dome using seismic interferometry applied to seismic background noise (SBN). The preliminary results show that SBN interferometry allows us to 1) detect and track discontinuities that can be related to the structures that control the ore deposits, and 2) identify the location of deep intrusions that are inferred as sources of metallogenic fluids. In this contribution, we present the GOLDFINGER geophysical experiment and the preliminary results.

Funding: grant PID2020-117332GB-C21 funded by MCIN/ AEI /10.13039/501100011033; EIT-Raw Materials project 17024 (SIT4ME: Seismic Imaging Techniques for Mineral Exploration); SA085P20 from the JCYL government, and TED2021-130440B-I00 by MCIN. IP is funded by MCIU and USal (BEAGAL18/00090).

How to cite: Palomeras, I., Gomez-Barreiro, J., Ayarza, P., Martínez-Catalán, J. R., Martí, D., Ruiz, M., Barrios, S., Dos Santos, K., Sanchez-Sanchez, Y., Elez, J., Yenes, M., DeFelipe, I., Pérez-Cáceres, I., Crespo, E., and Castiñeiras, P.: The GOLDFINGER Project: Imaging a Late-Variscan gneissic dome. Preliminary results., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15192,, 2023.

Jérémie Malecki, Stephen Collett, José R. Martínez Catalán, Juan Gómez Barreiro, and Karel Schulmann

The allochthonous complexes of the Galicia-Trás-os-Montes Zone (GTMZ) of the NW Iberian Massif consist of an ensemble of peri-Gondwanan terranes and ophiolitic units stacked during the Variscan orogeny. The Middle Allochthon also known as the ophiolitic complex represents the variscan suture of one or more peri-Gondwanan oceans, and includes Cambro-Ordovician to Lower Devonian units. In the allochthonous Morais Complex (Trás-os-Montes, Portugal), the ophiolitic complex comprises four structural units, which from bottom to top are Macedo de Cavaleiros, Pombais, Izeda-Remondes and Morais-Talhinhas.

The two first units are quite similar to each other and consist of greenschists and metapelites, with metabasites dominating in Pombais and metapelites in Macedo de Cavaleiros. No age data are available for these two units. Their structural position is comparable to that of the Cambro-Ordovician Vila de Cruces Unit in the Órdenes Complex, but also to that of the Lower Devonian Moeche Unit in the Cabo Ortegal Complex, both in Galicia.

The Izeda-Remondes and Morais-Talhinhas units mostly consist of fine grained amphibolites associated with deformed gabbros, mafic cumulates and serpentinized ultramafics. The Izeda-Remondes Unit is structurally the lower and the older of the two, dated by Pin et al. (2006) around 447 ± 24 Ma (Sm-Nd whole rock isochron). The upper ophiolitic Morais-Talhinhas Unit was also dated by Pin et al. (2006) giving U-Pb ages of 405 ± 1 Ma and 396 ± 1 Ma.

This contribution brings new geochronological and geochemical data from the Middle Allochthon providing new understanding of the history of the suture of the Morais allochthonous complex. Zircons have been collected for LA-MC-ICP-MS U–Pb analyses in two felsic intrusions in the Izeda-Remondes Unit giving concordant ages ranging from 422 ± 4 Ma to 432 ± 4 Ma. These ages together with new and previous whole rock geochemical data obtained from basic and felsic igneous samples from the ophiolitic complex are interpreted to date and reflect the formation of igneous protoliths in an oceanic ridge setting forming part of the Rheic oceanic realm, during Silurian to Devonian. The mantle source for the basic rocks of all four units is similar to that of N-MORB with some influence from a subduction zone.


Pin, C., Paquette, J. L., Ábalos, B., Santos, F. J., & Gil Ibarguchi, J. I. (2006). Composite origin of an early Variscan transported suture: Ophiolitic units of the Morais Nappe Complex (north Portugal). Tectonics, 25(5).

Acknowledgements: Spanish Ministry of Science and Innovation, project PID2020-117332GB-C21.

How to cite: Malecki, J., Collett, S., Martínez Catalán, J. R., Gómez Barreiro, J., and Schulmann, K.: New age and geochemistry data from the Middle Allochthon ophiolitic units of the Morais Complex (Portugal)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8080,, 2023.

Kevin Karner-Ruehl, Christoph A. Hauzenberger, Etienne Skrzypek, and Harald Fritz

The Eastern Greywacke Zone is composed of three Alpine nappes. From bottom to top these are (1) the Veitsch nappe (Early Carboniferous to Permian molasse), (2) the Silbersberg nappe with intercalated slivers of the Kaintaleck Metamorphic Complex and Permian phyllites and conglomerates as cover, and (3) the Noric nappe (mainly Ordovician to Devonian shelf sediments and Permian cover). All units experienced Eo-Alpine lower greenschist facies metamorphism. Due to the development of ductile shear zones during Alpine nappe stacking, the Kaintaleck Complex was dismembered and emplaced as lens-shaped bodies of 10-100m thickness that stretch from West (Kalwang, Upper Styria) to East (Gloggnitz, Lower Austria) below the Noric nappe of the Eastern Greywacke Zone. Lithologically, the Kaintaleck Complex is represented by a mafic suite, comprising amphibolite, garnet-amphibolite, greenschist and serpentinite, and a felsic suite that consists mostly of gneiss and mica-schist (some of them garnet-bearing). The felsic suite corresponds to metamorphosed clastic sediments and granitoids, whereas the mafic suite represents most likely a former oceanic crust. This work tries to constrain the P-T-t path of the Kaintaleck Metamorphic Complex by applying U-Th/Pb monazite and zircon dating and geothermobarometry. Based on whole rock geochemistry, amphibolites from the locality of Frauenberg represent tholeiitic basalts with an E-MORB affinity, whereas garnet-amphibolites, amphibolites and greenschists from the localities of Prieselbauer, Oberdorf, Unteraich, Kalwang, Arzbach and Schlöglmühl show a T-MORB signature. Samples from the localities of Stübminggraben and Utschgraben have a N-MORB affinity. Garnet-amphibolite samples show distinct plagioclase-epidote-rich symplectitic coronae, which are indicative of decompression from former eclogite-facies conditions. P-T estimations based on Zr-in-rutile thermometry and phengite barometry yield up to 720°C and 19 kbar for the felsic suite, and 700°C and 21 kbar for the mafic suite, both interpreted as peak metamorphic conditions. Monazite dating by EPMA in garnet-mica-schist from the localities of Prieselbauer, Arzbach, Schlöglmühl and Oberdorf, revealed weighted average U-Th-total Pb dates of 351 ± 4 Ma, 358 ± 16 Ma, 349 ± 3 Ma and 362 ± 6 Ma, which are interpreted as reflecting peak Variscan metamorphism. Monazite in these samples is partly replaced by an apatite-allanite-corona, related to monazite-breakdown due to Alpine lower grade metamorphic overprint. Preliminary LA-MC-ICP-MS U/Pb age dating results of zircon grains from a garnet-amphibolite from the Prieselbauer locality yield a Devonian mean date of 400 ± 4 Ma ascribed to the protolith formation.

How to cite: Karner-Ruehl, K., Hauzenberger, C. A., Skrzypek, E., and Fritz, H.: P-T-t-EVOLUTION OF VARISCAN REMNANTS IN THE EASTERN ALPS: THE KAINTALECK METAMORPHIC COMPLEX, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6575,, 2023.

Franz Neubauer, Yongjiang Liu, Ruihong Chang, Christoph Hauzenberger, Sihua Yuan, Shengyao Yu, Johann Genser, and Qingbin Guan

The Waldbach Complex is an amphibolite-grade basement unit within the Lower Austroalpine nappes of Eastern Alps, which differs from other Alpine basement units and which represents a magmatic arc-related tectonic setting. For the first time, twenty samples of magmatic and metasedimentary rocks were studied by the LA-ICP U-Pb zircon dating method supplemented by a geochemical survey. Two units are distinguished: (1) The western structurally Lower Waldbach Unit includes phyllonitic micaschist, paragneiss, and quartzites associated with various orthogneisses including augengneisses. Metasedimentary rocks contain mainly Late Ediacaran (550 Ma) detrital zircon populations. Older zircons are rare and include populations at 2.6 Ga (Late Archean) and 700 Ma (Cryogenian). Youngest ages are at ca. 510 Ma constraining the maximum depositional age. Six granitic orthogneisses from distinct lenses were studied and yield ages between 463.4 ± 3.7 Ma and 492.9 ± 3.1 Ma. Abundant inherited Neoproterozoic zircons suggest their S-type origin by remelting of Neoproterozoic crust. A further, granitic, biotite-gneiss intruded at 340 Ma (Early Carboniferous). All data together suggest a late Cambrian metasedimentary succession subsequently intruded by late Cambrian to Middle Ordovician porphyric granites. (2) The Upper Waldbach Unit  is dominated by various types of amphibolites, hornblende-gneisses, coarse-grained garnet-micaschists and sulphidic micaschists. Associated stratiform massive sulphides are exposed as up to two meter thick synsedimentary layers together with black, carbon-rich micaschists. A hornblende-gneiss is interpreted as a tuff and contains a pronounced population at 455 Ma. Coarse-grained garnet-micaschists include zircon populations with ages at 455 Ma and 505 Ma, and youngest ages at 430 and 410 Ma, respectively. Amphibolites vary in their U-Pb zircon ages between 450 and 340 Ma. Both amphibolites and metasedimentary rocks contain zircons with low Th/U ratios between 330 and 315 Ma supported by a chemical  monazite age  at 304.4 ± 7.8 Ma constraining together the age of amphibolite facies metamorphism of the Upper Waldbach Unit. We interpret the Upper Waldbach Unit as a Late Ordovician to Devonian arc system, which was deposited in an anoxic depositional environment with extensive hydrothermal activity leading to stratiform massive sulphides.

Paleogeographically, the Waldbach Complex was located close to Austroalpine-Penninic interface within the Alpine basement and can be likely traced to Carpathians. Tectonically, it is interpreted as the Late Ordovician to Devonian arc system formed during subduction of oceanic lithosphere as also constrained by Devonian eclogites in adjacent Western Carpathians and Devonian blueschists in Southern Carpathians. Consequently, elements of subduction-related settings allow trace a hitherto unknown subduction zone within the Alpine-Carpathian basement, which is potentially part of the Protogonos arc was recently proposed by A. M. Celal Sengör.

How to cite: Neubauer, F., Liu, Y., Chang, R., Hauzenberger, C., Yuan, S., Yu, S., Genser, J., and Guan, Q.: The Waldbach Complex of Eastern Alps: An early Paleozoic arc system and its significance for Variscan geodynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16923,, 2023.