CGMW - metamorphic and magmatic maps

Georeferenced version of the tectonic map of Schmid et al. (2020; Plate 1) provided by Jan Pleuger, FU Berlin VERSION 1.0 (8.5.2020) The original map of Schmid et al. (2020) has been slightly modified (“Tectonic_map_Schmid_et_al_20200508.pdf”) in order to achieve a better accuracy for georeferencing. The dataset contains the georeferenced version of the tectonic map of Schmid et al. (2020; Plate 1) as shape files and as a geotiff file. The QGis project and the geotiff files use the WGS84/World Mercator (EPSG:3395) projection. The projection data of the original map of Schmid et al. (2020) and the PDF file, i.e. a Lambert conformal conic projection with a central meridian at 20°E, two standard parallels at 38°N and 48°N, a latitude of origin at 30°N and a scaling factor of 1.2, are contained in the file “Belgrad2020.txt” in the “QGis_project-files” folder. This folder also comprises style files for the different layers that largely match the style of Plate 1 in Schmid et al. (2020). For questions and remarks please contact Jan Pleuger (jan.pleuger@fu-berlin.de) Reference Schmid, S.M., Fügenschuh, B., Kounov, A., Matenco, L., Nievergelt, P., Oberhänsli, R., Pleuger, J., Schefer, S., Schuster, R., Tomljenović, B., Ustaszewski, K. & van Hinsbergen, D.J.J. (2020): Tectonic units of the Alpine collision zone between Eastern Alps and western Turkey. Gondwana Research, 78, 308-374; doi: 10.1016/j.gr.2019.07.005

We present a map that correlates tectonic units between Alps and western Turkey accompanied by a text providing access to literature data, explaining the concepts used for defining the mapped tectonic units, and first-order paleogeographic inferences. Along-strike similarities and differences of the Alpine-Eastern Mediterranean orogenic system are discussed. The map allows (1) for superimposing additional information, such as e.g., post-tectonic sedimentary basins, manifestations of magmatic activity, onto a coherent tectonic framework and (2) for outlining the major features of the Alpine-Eastern Mediterranean orogen. Dinarides-Hellenides, Anatolides and Taurides are orogens of opposite subduction polarity and direction of major transport with respect to Alps and Carpathians, and polarity switches across the Mid-Hungarian fault zone. The Dinarides-Hellenides-Taurides (and Apennines) consist of nappes detached from the Greater Adriatic continental margin during Cretaceous and Cenozoic orogeny. Internal units form composite nappes that passively carry ophiolites obducted in the latest Jurassic–earliest Cretaceous or during the Late Cretaceous on top of the Greater Adriatic margin successions. The ophiolites on top of composite nappes do not represent oceanic sutures zones, but root in the suture zones of Neotethys that formed after obduction. Suturing between Greater Adria and the northern and eastern Neotethys margin occupied by the Tisza and Dacia mega-units and the Pontides occurred in the latest Cretaceous along the Sava-İzmir-Ankara-Erzincan suture zones. The Rhodopian orogen is interpreted as a deep-crustal nappe stack formed in tandem with the Carpatho-Balkanides fold-thrust belt, now exposed in a giant core complex exhumed in late Eocene to Miocene times from below the Carpatho-Balkan orogen and the Circum-Rhodope unit. Its tectonic position is similar to that of the Sakarya unit of the Pontides. We infer that the Rhodope nappe stack formed due to north-directed thrusting. Both Rhodopes and Pontides are suspected to preserve the westernmost relics of the suture zone of Paleotethys.

The 12 Ma old Cordillera del Paine laccolith (CPL) is located in the southernmost Andes of Chile. The CPL is composed of a basal layer of gabbroic rocks. A fine to medium grained biotite granite (I type) forms the majority of the pluton. The 8x12x12 km big laccolith intruded mudstones, sandstones and con-glomerates of the Cretaceous Cerro Torre and Punta Barrosa formation [1] creating a well defined, but small contact aureole of 200-400 m width. The CPL contains abundant textural evidence of fluid exsolution and eutectic crystallisation. It hence represents a good example for the transport of large quantities of mag-matic aqueous fluids to the uppermost level of the crust. Textural observations, oxygen isotope data, phase petrological constraints and fluid inclusion data are presented to discuss mechanism of fluid and heat transport in the intrusion and its contact aureole. The CPL is remarkable for its abundance of mia-rolitic cavities. Locally, at the margins of the pluton, a microgranitic phase is found with up to 15% of cavities. While some miaroles are isolated, others are interconnected , forming tube-like structures. Open miaroles contain euhedral crystals of quartz and feldspar. Other important phases are biotite, tourmaline, fayalite and late chlorite and carbonate. Individual crystals are typically between < 1cm up to a few cm in length. Some miaroles are completely filled with coarse quartz forming pods of up to one meter resembling pegmatites. Miaroles are surrounded by a fine-grained groundmass characterized by an eutectic (micrographic) quartz-feldspar intergrowth. Oxygen isotope data for granites range from 9.1-9.9 per mil for quartz and 5.1-6.0 per mil for biotite. The miaroles show a wider range in their quartz values of 8.8-11.1 per mil. Yet, the similarity of miarolitic and granitic quartzes suggests they formed from a common fluid. Oxygen isotope thermometry of quartz-fayalite pairs from miaroles yield a temperature of 750±30°C. Comparison of fluid inclusions in phenoc-ryst and miarolitic quartz reinforce the suggestion, that the two occurrences of quartz trapped the same mag-matic fluid. Contact-metamorphic assemblages yield valuable information on the intrusion temperature and em-placement depth of the laccolith. Exceptional is the presence of prograde prehnite-bearing assemblages in calcareous marls. The assemblage prehnite + anorthite is particularly diagnostic. Its upper temperature stability is limited to T < 425 °C and low X(CO2) < 0.06. The presence of prograde prehnite a few meters away from the contact indicates that peak metamorphic temperatures were between 400-450°C. This in good agreement with simple thermal models and estimated intrusion temperatures. The prehnite-anorthite assemblage further indicates a pressure < 1 kbar, suggesting a shallow intrusion level of 2-4 km depth. This is consistent with the abundance of miarolitic cavities [2] and with preliminary results of fluid inclusion work. [1] Michael P.

Metagabbros in the core series of the Menderes Massif, for some time considered as post orogenic Miocene intrusives, revealed a strong poly-metamorphic history. The metagabbro bodies exhibit a pronounced zonation. Within their cores, igneous minerals are still preserved. Coronitic textures are interpreted as results of a high temperature, possibly granulitic overprint. The outer parts of the metagabbro bodies mostly consist of strongly to completely retrograded garnet-amphibolites, but occasionally contain relics of eclogites. Petrologic investigations confirmed a high pressure overprint and allowed preliminary P, T estimates (650°C, ≥ 1.3 GPa). The intensity of the HP metamorphism seems to rise from south to north within the Menderes basement, thus pointing to a northward subduction as the cause. The age of the high pressure event still awaits clarification. However, its very existence reanimates the question, how close the relationship between Menderes and the Cyclades evolution might have been.

 In Oman, the convergence between Arabia and Eurasia resulted in the Late Cretaceous overthrusting of oceanic crust and mantle lithosphere onto the Arabian continental margin. During this compressional event, a part of the continental plate was subducted to a depth of more than 60 km (0.5 GPa, 250–350  °C to more than 2.0 GPa, 550  °C) resulting in progressive metamorphism of the continental margin sediments, well exposed in the Saih Hatat tectonic window, northeastern Oman Mountains. We attempt to constrain the possibility of one continuous history of extension (starting along the east Arabian continental margin in the Permian) that was followed by one continuous history of convergence starting at 90 Ma near a dead oceanic ridge. This compression resulted in the observed progressive metamorphism by ophiolite overthrusting onto the continental margin. Constraining arguments are the palaeogeographic setting before ophiolite obduction of the As Sifah units and the Hawasina Complex near Ghurba. Detrital chromites in the Triassic–Cretaceous metasediments of the Hawasina Complex are compared with magmatic Semail chromites, and the whole-rock chemistry of these metasediments and associated metabasites are investigated. In contrast to former hypotheses, differences in the chemical composition between detrital and magmatic chromites, and the probable origin of all detrital chromites in the Hawasina Basin from Permian age oceanic rocks, suggest that the high-pressure metamorphic sediments of As Sifah can be considered as part of the basal deposits of the Hawasina Basin.

In the basal thrust sheets of the Lycian nappes fresh Fe-Mg-carpholite documents low-grade, high-pressure (HP) metamorphism. Here we describe the first occurrences of this HP indicator mineral in Turkey, its regional distribution and geodynamic consequences. Carpholite and its breakdown products, such as chloritiod and pyrophyllite, occur in the Lycian nappes s.s. Relics of Fe-Mg-carpholite were also found in klippen of Lycian nappe material located on top of the Menderes crystalline massif. The distribution of the Fe-Mg-carpholite and its relics traces an extensive area of HP metamorphism in the sediments of a passive continental margin.

High-pressure metamorphic terranes in the Anatolide - Taurid belt document the complex distribution of paleo-sutures in the Tethyan realm. Field based petrologic studies of metapelites in the Anatolide-Taurid realm allow to trace HP-LT metamorphism not only in the well known ophiolitic Tavsanli Zone (2.4 GPa/500 °C) but also in the Afyon Zone (0.9 GPa/350 °C), the Menderes Massif (1.2 Gpa/500 °C;) and in the Lycian Nappes (1.0 Gpa/400 °C) - all situated north of the so called Taurid Platform. While the HP metamorphism is dated to 90-80 Ma (Rb/Sr; Ar/Ar) in the Tavsanli Zone, it ranges from 60-70 Ma (Ar/Ar) in the Afyon Zone and its tectonic equivalent, the Lycian Nappes. The Afyon Zone s.l. is closely related to the glaucophane- lawsonite-bearing rocks of the Tavsanli Zone and its eastward extension. Blueschist-facies metamorphism is documented by Fe,Mg-carpholite in regionally distributed metapelites and glaucophane in sparse mafic rocks (Afyon, Menderes, Lycia). Since observations of HP are based on Fe,Mg-carpholite bearing metasediments and not on mafic blueschists new thermodynamic data and petrologic modelling was elaborated to match P-T data and field-based observations. Moreover, newly formed phengitic mica allows precise dating. Both, Tavsanli and Afyon Zones can be followed along strike over more than 600 km and around the southern edge of the Central Anatolian Crystalline Complex. The two zones are situated north of the Taurid Platform and correlate with the Amasia Zone in Armenia. To the extreme East the Bitlis Complex underwent a LT - HP metamorphic blueschist evolution (1,1 GPa/ 350 °C; glaucophane, Fe,Mg-carpholite) in its sedimentary cover while the basement is eclogitic. Depending on the structural position and mineral association of phengitic mica metamorphic ages of the Bitlis blueschists scatter around 70-80 Ma. Eclogites from the basement are slightly older. These LT-HP units cannot be correlated with the Tavsanli - Afyon blueschist belts since they occur south of the Taurid Platform. Thus the Bitlis Complex represents a terrane detached from the Arabian Platform that subsequently collided with the Taurus Platform during closure of the Neo-Tethys. In SW Anatolia, south of the Taurus Platform, the Alanya Zone documents a Late Cretaceous HP evolution with blueschists and eclogites. Together with the Bitlis Complex the two Late Cretaceous HP-LT regions represent a suture south of the Taurid Platform but still north of the Hatay - Güleyman - Zagros ophiolites separating the Arabian Platform from the Anatolide-Taurid realm. The dissection of the Anatolide-Taurid realm into several paleo-subduction zones of Late Cretaceous age impacts on the lithospheric structure and has consequences for the Tertiary plateau formation in Central and Eastern Anatolia. Geophysical data and observations from the East Anatolian Plateau can be explained with petrologic modelling when hydration of the lithospheric lids above subduction zones is considered.

Major discoveries in metamorphic petrology, as well as other geological disciplines, have been made in the Alps. The regional distribution of Late Cretaceous–Tertiary metamorphic conditions, documented in post-Hercynian metasediments across the entire Alpine belt from Corsica–Tuscany in the west to Vienna in the east, is presented in this paper. In view of the uneven distribution of information, we concentrate on type and grade of metamorphism; and we elected to distinguish between metamorphic paths where either pressure and temperature peaked simultaneously, or where the maximum temperature was reached at lower pressures, after a significant temperature increase on the decompression path. The results show which types of process caused the main metamorphic imprint: a subduction process in the western Alps, a collision process in the central Alps, and complex metamorphic structures in the eastern Alps, owing to a complex geodynamic and metamorphic history involving the succession of the two types of process. The western Alps clearly show a relatively simple picture, with an internal (high-pressure dominated) part thrust over an external greenschist to low-grade domain, although both metamorphic domains are structurally very complex. Such a metamorphic pattern is generally produced by subduction followed by exhumation along a cool decompression path. In contrast, the central Alps document conditions typical of subduction (and partial accretion), followed by an intensely evolved collision process, often resulting in a heating event during the decompression path of the early-subducted units. Subduction-related relics and (collisional/decompressional) heating phenomena in different tectonic edifices charac-terize the Tertiary evolution of the Eastern Alps. The Tuscan and Corsica terrains show two differ-ent kinds of evolution, with Corsica resembling the western Alps, whereas the metamorphic history in the Tuscan domain is complex owing to the late evolution of the Apennines. This study confirms that careful analysis of the metamorphic evolution of metasediments at the scale of an entire orogen may change the geodynamic interpretation of mountain belts. After more than a century of investigations, the Alps still represent an outstanding natural labora-tory for the study of geodynamic processes linked to the evolution of mountain belts in general. The integration of regional geology and meta-morphic evolution provides highly needed con-straints for increasingly complex quantitative models (e.g. Escher & Beaumont 1996; Henry et al. 1997; Pfiffner et al. 2000). Major discoveries in metamorphic petrology, as well as other geological disciplines, have been and are still made in the Alps. For example, eclogites were described for the first time in the eastern Alps (Koralpe, Saualpe massifs) by Haüy (1822). More recently, the discovery of coesite in the Dora Maira unit (Chopin 1984, 1987) proved that continental crust went into subduction, contrary to a still widely held opinion, and returned from *This paper is dedicated to Martin Burkhard who tragically died during work in the Alps.

Numerous (meta-)gabbroic dikes or stocks occur within the latest Neoproterozoic- early Cambrian series of the Menderes Massif (Anatolide-Tauride Block, western Turkey). These well-preserved rocks were locally converted into eclogitic metagabbros and garnet amphibolites along the contacts or shear zones. Both bulk-rock composition and compositions of igneous clinopyroxenes suggest continental tholeiitic affinity. U-Pb dating of igneous zircons from gabbroic rocks yielded a mean age of 563±1 Ma (2σ), indicating emplacement during the latest Neoproterozoic (Ediacaran). On the other hand, rims of zircons from eclogitic metagabbro gave 535±3 Ma (2σ), (early Cambrian), in addition to 558±3 Ma (2σ) obtained from the igneous core of zircons. These ages are interpreted as the time of high-P metamorphism and crystallization age of gabbroic protolith, respectively. Given the estimated paleogeographic position of the Anatolide-Tauride Block during the late Neoproterozoic and early Cambrian, this orogenic event can be spatially and temporally related to the northward continuity of 600 – 500 Ma orogenic event (Malagasy / Kuunga orogeny) extending from western margin of India, Madagascar, via Arabia up to northern margin of Gondwana beneath thick Phanerozoic cover series in Arabian Peninsula. Therefore, the high-P evolution of the basement of the Menderes Massif and associated basic intrusions can be interpreted to mark the latest stages of consumption of the basin/oceanic branches and final amalgamation of the Gondwana during the late Neoproterozoic – early Cambrian around the Arabian region.

During the last decade, numerous tectonic models were proposed for the closure of the Neotethys Ocean in Western Anatolia that led to the collision of the Anatolide–Tauride and the Pontide continents during the Palaeogene. These models disagree on some fundamental aspects as the pre-subduction palaeogeography (from one to multiple oceanic strands), number of contemporaneous subduction zones (from one to three), and post-collision slab dynamics (frontal break-off, roll-back, tearing). We compiled, reviewed the most recent of these tectonic models, and pinpointed fundamental controversies that we tentatively resolved based on a multidisciplinary constraints. Among our favoured interpretations, the Neotethys closure features the collision of two continental domains (Tav¸anlı – Afyon, and Menderes–Tauride micro-continents) and the successive consumption of two oceanic domains during the continuous subduction of a single lithospheric slab from ∼95 Ma to ∼40 Ma. Although frontal break-off during the Eocene cannot be univocally excluded, we suggest that the rupture of this slab intervened only during the Miocene, as a tear fault along the highly curved eastern limb of the Hellenic slab. Besides, other aspects such as the timing and locus of subduction initiation, and the transition from subduction-to collision-related tectonics remain ambiguous and should trigger further investigations, especially of the sub-ophiolitic metamorphic soles and the metamorphic evolution of the Menderes Massif.

Modern Eastern Anatolia is a high-plateau region characterized by active N-S crustal shortening, mostly accommodated along strike-slip faults, and recent, abundant volcanism. Due to the extensive Cenozoic marine and Quaternary volcano-sedimentary covers, Tetyhan palaeogeography and related tectonic settings, and thence their impact on modern strain partitioning, in this region are particularly difficult to unravel, and therefore remains strongly debated. According to recent works in Armenia and northernmost Eastern Anatolia, blueschists dated to middle Cretaceous times record the accretion of the South-Armenian Block to the southern Eurasian margin, now separated by the Sevan-Akera Suture. Further south, we recently documented Late Cretaceous HP-LT metamorphism in the Bitlis Complex, which belongs to a micro-continental block isolated between the South-Armenian Block and the Arabian Platform. In order to gain further insights into Eastern Anatolia's tectonic architecture, and its continuation into the better-established Central and Western Anatolian tectonic domains, we collected petrologic data from slightly- to strongly metamorphosed sedimentary and crustal lithologies of scattered localities of SE Anatolia, west and north of the Bitlis Complex. From our field observations, we report only low-grade metamorphic assemblages in metasedimentary rocks of the Pütürge Massif, which was commonly considered as the western equivalent of the Bitlis Massif, but obviously did, in contrast to the latter, not experienced HP-LT metamorphism. Nevertheless, glaucophane-bearing rocks were found farther west, north of Adıyaman, might represent the west continuation of the Bitlis HP Complex. From near Malatya, north of the Pütürge Massif and south of the Eastern Tauride non-metamorphosed carbonate platform, eastwards via Elazig and Bingöl, to Aǧrı, between the Bitlis Massif and the South-Armenian Block, we found numerous, scattered occurrences of HT metamorphic assemblages in metasedimentary rocks, likely belonging to the South-Armenian Block. These findings outline a HT metamorphic belt continuous over ca. 500 km. Assuming that amphibolites recently reported from near Malatya are part of the same belt, we envisage that HT metamorphism might have taken place during the Late Cretaceous. No hint for a westward continuation of the HT metamorphic belt was found, but it might correlate eastwards with the Sirjan-Sanandaj magmatic belt in NW Iran. The Malatya-Aǧrı HT belt might record the same back-arc rifting event as the one responsible for the genesis of oceanic material obducted as the Khoy Ophiolites in NW Iran. We take this as a strong indication that, before collision, the Bitlis Block, the South-Armenian Block and, to the west, the Anatolide-Tauride Block might have been separated micro-continents. Compiling the petrologic record points to the successive accretion of several micro-continental blocks during the middle Cretaceous to the early Eocene, and to a highly-segmented East-Anatolian lithosphere prior to the Neogene.

North of Naran in the Kaghan Valley (NE Pakistan), the metabasites of the mélange units lying below the Kohistan Arc, contain glaucophane. Typically they reflect blueschist-metamorphic conditions (0.7 GPa, 400°C). Associated graphite-rich metapelites with quartz veins underwent upper greenschist to amphibolite conditions. Near Naran we observed in quartz grains of type 3 veins first minute relics of Fe-Mg carpholite indicating earlier blueschist metamorphic conditions. P-T estimates indicate 1.2-1.6 GPa at 380-410 °C, pressure and temperature values typical for blueschist metamorphic conditions. Changes in mineral assemblages and abundant sudoite component in associated chlorite point to a pressure drop after peak I conditions. We assign the observed changes to peak I conditions occurring during a Cretaceous subduction event. Temperatures estimated with Raman graphite-thermometry clearly indicate a significant subsequent rise of post-peak I temperatures up to 500°C. This is compatible with the amphibolite peak II assigned to the Tertiary continental collision that leads to subduction of the Indian Plate and ultra-highpressure metamorphism. During subduction the blueschist metamorphic metapelites underwent dehydration, which caused alteration in the overlying lithospheric mantle. In a hydrated lithospheric mantle density is significantly reduced which enhanced subduction of continental crust in the Higher Himalaya. This P-T evolution is typical for a collision orogen with a high plateau but remarkably contrasting findings from Eastern Anatolia, where plateau building is in "statu nascendi" (e.g., Oberhänsli et al., 2010).

A new occurrence of eclogites was found in the Kesandere valley in the eastern most part of the Bitlis complex, SE Anatolia. These high-pressure (HP) relics were preserved in calc-arenitic metasediments within the high-grade metamorphic basement of the Bitlis complex. The eclogitic parageneses were strongly overprinted during decompression and heating. These new eclogites locality complements the evidence of blueschist-facies metamorphism documented recently in the meta-sedimentary cover sequence of this part of the Bitlis complex. Thermodynamic calculations suggest peak conditions of ca. 480–540 °C/1.9–2.4 GPa. New U/Pb dates of 84.4 ± .9 and 82.4 ± .9 Ma were obtained on zircons from two Kesandere eclogite samples. On the basis of geochemical criteria, these dates are interpreted to represent zircon crystallization during the eclogitic peak stage. Kesandere eclogites differ from those previously described in the western Bitlis complex (Mt. Gablor locality) in terms of lithologic association, protolithic origin, and peak P–T conditions (600–650 °C/1.0–2.0 GPa, respectively). On the other hand, eclogitic metamorphism of Kesandere metasediments occurred shortly before blueschist-facies metamorphism of the sedimentary cover (79–74 Ma 40Ar/39Ar white mica). Therefore, the exhumation of Kesandere eclogites started between ca. 82 and 79 Ma, while the meta-sedimentary cover was being buried. During this short time span, Kesandere eclogite were likely uplifted from ~65 to 35 km depth, indicating a syn-subduction exhumation rate of ~4.3 mm/a. Subsequently, eclogite- and blueschist-facies rocks were likely retrogressed contemporarily during collision-type metamorphism (around 72–69 Ma). The Bitlis HP rocks thus sample a subduction zone that separated the Bitlis–Pütürge (Bistun?) block from the South-Armenian block, further north. To the south, Eocene metasediments of the Urse formation are imbricated below the Bitlis complex. They contain (post Eocene) blueschists, testifying separation from the Arabian plate and southward migration of the subduction zone. The HT overprint of Kesandere eclogites can be related to the asthenospheric flow provoked by subducting slab retreator break off.