@article{OberhaensliGoffeBousquet1995, author = {Oberh{\"a}nsli, Roland and Goffe, B. and Bousquet, Romain}, title = {Record of a HP-LT metamorphic evolution in the Valais zone : Geodynamics implications}, issn = {0392 - 758X}, year = {1995}, language = {en} } @article{HoferBreyOberhaensli1996, author = {Hofer, H. E. and Brey, G. P. and Oberh{\"a}nsli, Roland}, title = {The determination of the oxidation state of iron in synthetic garnets by X-ray spectroscopy with the electron microprobe}, year = {1996}, language = {en} } @article{RettingerSchorscherOberhaensli1996, author = {Rettinger, Rolf and Schorscher, H. D. and Oberh{\"a}nsli, Roland}, title = {Geothermobarometric correlation of geothermobarometers and petrogenetic modelling in Ne-Quadrilatero Ferrifero, Minas Gerais, Brazil}, year = {1996}, language = {en} } @article{CandanDoraOberhaenslietal.1997, author = {Candan, O. and Dora, O. and Oberh{\"a}nsli, Roland and {\"O}lsner, F. and D{\"u}rr, S.}, title = {Blueschist relics in the Mesozoic cover series of the Menderes Massif and correlations with Samos Island, Cyclades}, year = {1997}, language = {en} } @article{BousquetOberhaensli1997, author = {Bousquet, Romain and Oberh{\"a}nsli, Roland}, title = {Distribution of HP-LT metamorphism and extensional deformation in the "B{\"u}ndnerschiefer" of the Engadine window (eastern Central Alps) : Implication of regional evolution}, year = {1997}, language = {en} } @article{OberhaensliNegendank1997, author = {Oberh{\"a}nsli, Roland and Negendank, J{\"o}rg F. W.}, title = {Natural and anthropogenic influences on the geochemistry of Quaternary lake sediments from Holzmaar, Germany}, year = {1997}, language = {en} } @article{OberhaensliCandanDoraetal.1997, author = {Oberh{\"a}nsli, Roland and Candan, O. and Dora, O. and D{\"u}rr, S.}, title = {Eclogites within the Menderes Massif / western Turkey}, year = {1997}, language = {en} } @article{WenzelMertzOberhaenslietal.1997, author = {Wenzel, T. and Mertz, D. and Oberh{\"a}nsli, Roland and Becker, Thomas and Penne, P.}, title = {Age, geodynamic setting, and mantle enrichment processes of a K-rich intrusion from the Meissen massif (northern Bohemian massif) and implications for related occurrences from the mid-European Hecynian}, year = {1997}, language = {en} } @article{ZakariadzeKarpenkoBazylevetal.1998, author = {Zakariadze, G. S. and Karpenko, S. F. and Bazylev, B. A. and Adamia, S. A. and Oberh{\"a}nsli, Roland and Solov'eva, N. V. and Ljialikov, A. V.}, title = {Fragments of Pan-African paleooceanic complexes in the Dzirula salient of the Transcaucassian crystalline massif (petroloy, geochemistry, Sm-Nd age, problems of origin)}, year = {1998}, language = {en} } @article{KronerOberhaensliMezgeretal.1998, author = {Kroner, Alfred and Oberh{\"a}nsli, Roland and Mezger, Klaus and Teklay, M.}, title = {Geochemistry, Pb-Pb single zircon ages and Nd-Sr isotope composition of Precambrian rocks from southern and eastern Ethiopia: implications for crustal evolution in east Africa}, year = {1998}, language = {en} } @article{ZakariadzeKarpenkoBazylevetal.1998, author = {Zakariadze, G. S. and Karpenko, S. F. and Bazylev, B. A. and Adamia, S. A. and Oberh{\"a}nsli, Roland and Solov'eva, N. A. and Lyalikov, A. V.}, title = {Petrology, geochemistry, and Sm-Nd age of the pre-Late Hercynian paleooceanic complex of the Dzirula salient, Transcaucasian Massif}, year = {1998}, language = {en} } @article{BazylevZakariadzeZhelyazkovaPanayotovaetal.1998, author = {Bazylev, B. A. and Zakariadze, G. S. and Zhelyazkova-Panayotova, M. D. and Solov'eva, N. V. and Oberh{\"a}nsli, Roland}, title = {Genetic diversity of ophiolite ultramafics from the crystalline basement of Rhodope massif}, year = {1998}, language = {en} } @article{JolivetGoffeBousquetetal.1998, author = {Jolivet, L. and Goffe, B. and Bousquet, Romain and Oberh{\"a}nsli, Roland and Michard, Andre}, title = {Detachments in high-pressure mountain belts, Tethyan examples}, year = {1998}, language = {en} } @article{Oberhaensli1998, author = {Oberh{\"a}nsli, Roland}, title = {The age of blueschist metamorphiosm ion the Mesozoic cover series of the Menderes massif}, year = {1998}, language = {en} } @article{BousquetOberhaensli1998, author = {Bousquet, Romain and Oberh{\"a}nsli, Roland}, title = {High-pressure-low-temperature metamorphism and deformation in the "B{\"u}ndnerschiefer" of the Engadine window : implications for the regional evolution of the eastern Central Alps}, year = {1998}, language = {en} } @article{Oberhaensli1998, author = {Oberh{\"a}nsli, Roland}, title = {The tectono-metamorphic signature of detachments in high-pressure mountain belts, Tethyan examples}, year = {1998}, language = {en} } @article{BianchiMartinottiOberhaensli1998, author = {Bianchi, Gianphino Walter and Martinotti, G. and Oberh{\"a}nsli, Roland}, title = {Metasedimentary cover sequences and associated metabasites in the Sabbione Lake zone, Formazza Valley, Italy}, year = {1998}, language = {en} } @article{ArmbrusterBermanceZebecetal.1998, author = {Armbruster, Thomas and Bermance, V. and Zebec, M. and Oberh{\"a}nsli, Roland}, title = {Titanium and iron poor zincoh{\"o}gbomite-16H, Zn14(al,Fe3+,Ti,Mg)8Al24O62(OH)2, from Nezilovo, Macedonia: occurrence and crystal structure of a new polysome}, year = {1998}, language = {en} } @article{SchmidAltenbergerOberhaensli1998, author = {Schmid, Robert and Altenberger, Uwe and Oberh{\"a}nsli, Roland}, title = {Polyphase tectono-metamorphic evolution of the northwestern Lindas Nappe on Holsnoy, Bergen Arcs, Caledonides, SW-Norway}, year = {1998}, language = {en} } @article{PoupeauSaddiqiMichardetal.1998, author = {Poupeau, G. and Saddiqi, O. and Michard, Andre and Goffe, B. and Oberh{\"a}nsli, Roland}, title = {Late thermal evolution of the oman mountains subophiolitic windows : apatite fission-track thermochronology}, issn = {0091-7613}, year = {1998}, language = {en} } @article{OberhaensliWendtGoffeetal.1999, author = {Oberh{\"a}nsli, Roland and Wendt, A. S. and Goffe, B. and Michard, Andre}, title = {Detrital chromites in metasediments of East-Arabian continental margin in te Saih Hatat area : constraints for the palaeogeographic setting of the Hawasina and Semail basins (Oman Mountains)}, year = {1999}, language = {en} } @article{BazylevZakariadzeZhelyazkovaPanayotovaetal.1999, author = {Bazylev, B. A. and Zakariadze, G. S. and Zhelyazkova-Panayotova, M. D. and Kolcheva, K. and Oberh{\"a}nsli, Roland and Solov'eva, N. V.}, title = {Petrology of ultramafic rocks from the ophiolithe association in the crystalline basement of the Rhodope massif}, year = {1999}, language = {en} } @article{CandanDoraOberhaenslietal.2000, author = {Candan, O. and Dora, O. and Oberh{\"a}nsli, Roland and Cetinkaplan, Mete and Partzsch, Julius and Warkus, Friederike C. and D{\"u}rr, S.}, title = {Pan-African high-pressure metamorphism in the Precambrian basement of the Menderes massif, Western Anatolia, Turkey}, year = {2000}, language = {en} } @article{OberhaensliPartzschCandanetal.2000, author = {Oberh{\"a}nsli, Roland and Partzsch, Julius and Candan, O. and Cetinkaplan, Mete}, title = {First occurrence of Fe-Mg-carpholite documenting a high pressure metamorphism in the metasediments of the Lycian nappes, SW Turkey}, year = {2000}, language = {en} } @article{WenzelOberhaensliMezger2000, author = {Wenzel, T. and Oberh{\"a}nsli, Roland and Mezger, Klaus}, title = {K-rich plutonic rocks and lamprophyres from the Meissen Massif (northern Bohemian Massif) : Geochemical evidence for variably enriched lithospheric mantle sources}, year = {2000}, language = {en} } @article{AltenbergerOberhaensliSteinetal.2001, author = {Altenberger, Uwe and Oberh{\"a}nsli, Roland and Stein, Eckehard and Moghni, Mohsen}, title = {Geochemistry, tectonic setting and geodynamic position of late orogenic dikes in the Melibocus Massiv, Bergstraesser Odenwald}, year = {2001}, language = {en} } @article{WilhelmAltenbergerOberhaensli2001, author = {Wilhelm, Stefan and Altenberger, Uwe and Oberh{\"a}nsli, Roland}, title = {Intrusive marbles in the Ivrea Zone (Italy) : evidence for melting of metacarbonates}, year = {2001}, language = {en} } @article{OberhaensliBousquetGoffe2003, author = {Oberh{\"a}nsli, Roland and Bousquet, Romain and Goffe, B.}, title = {Comment to "Chloritoid composition and formation in the eastern Central Alps : a comparison between Penninic and Helvetic occurrences" by M. Rahn, M. Steinmann and M. Frey}, issn = {0036-7699}, year = {2003}, language = {en} } @article{LiuJahnDongetal.2003, author = {Liu, Xiaochun and Jahn, Bor-Ming and Dong, Shuwen and Li, Huimin and Oberh{\"a}nsli, Roland}, title = {Neoproterozoic granitoid did not record ultrahigh-pressure metamorphism from the Southern Dabieshan of China}, issn = {0022-1376}, year = {2003}, abstract = {It has been often debated whether all granitic gneisses associated with coesite-bearing eclogites in southern Dabieshan, China, have also been subjected to ultrahigh-pressure (UHP) metamorphism. We show here that a metagranitoid adjacent to the Bixiling eclogite-ultramafic complex has preserved primary granitic textures and an igneous mineral assemblage of biotite + plagioclase + microcline + quartz + allanite +/- amphibole. The absence of UPH recrystallization for the metagranitoid is particularly manifested by the conservation of euhedral-zoned plagioclase phenocrysts, the lack of corona garnets around igneous biotite, and the presence of an igneous mineral assemblage in zircons. The only metamorphic overprint was the epidote-amphibolite facies metamorphism characterized by the assemblage of biotite + phengiticmica + epidote + albite + K-feldspar + quartz +/- amphibole Metamorphic conditions are estimated at ca. 550degrees-680degreesC and 6-13 kbar for the metagranitoid and its amphibolitic enclave. Geochemically, the metagranitoid is similar to its country gneiss and shows an affinity to volcanic arc granitoid. Zircon U-Pb dating suggests that the Bixiling metagranitoid was emplaced during the Neoproterozoic (729+/-4 Ma), when most other granitic rocks and the protoliths of eclogite were also formed in Dabieshan. Taking into account the discovery of non-UHP granitic gneisses in other places, we argue that part of Neoproterozoic granitic rocks in the Dabieshan and Sulu terranes have escaped UHP metamorphism during the Triassic deep subduction of the continental crust as a consequence of a lack of penetrative deformation and fluid-rock interaction}, language = {en} } @article{JolivetRimmeleOberhaenslietal.2004, author = {Jolivet, L. and Rimmele, Gaetan and Oberh{\"a}nsli, Roland and Goffe, B. and Candan, O.}, title = {Correlation of syn-orogenic tectonic and metamorphic events in the Cyclades, the Lycian nappes and the Menderes massif : Geodynamic implications}, issn = {0037-9409}, year = {2004}, abstract = {The recent discovery of HP-LT parageneses in the basal unit of the Lycian nappes and in the Mesozoic cover of the Menderes massif leads us to reconsider and discuss the correlation of this region with the nearby collapsed Hellenides in the Aegean domain. Although similarities have long been pointed Out by various authors, a clear correlation has not yet been proposed and most authors insist more on differences than similarities. The Menderes massif is the eastern extension of the Aegean region but it has been less severely affected by the Aegean extension during the Oligo-Miocene. It would thus be useful to use the structure of the Menderes massif as an image of the Aegean region before a significant extension has considerably reduced its crustal thickness. But the lack of correlation between the two regions has so far hampered Such comparisons. We describe the main tectonic units and metamorphic events in the two regions and propose a correlation. We then show possible sections of the two regions before the Aegean extension and discuss the involvement of continental basement in the Hellenic accretionary complex. In our interpretation the Hellenic- Tauric accretionary complex was composed of stacked basement and cover units which underwent variable P-T histories. Those which were not exhumed early enough later followed a high-T evolution which led to partial melting in the Cyclades during post-orogenic extension. Although the Menderes massif contains a larger volume of basement units it does not show significant evidence for the Oligo-Miocene migmatites observed in the center of the Cyclades suggesting that crustal partial melting is strictly related to post-orogenic extension in this case}, language = {en} } @article{WeberAbuAyyashAbueladasetal.2004, author = {Weber, Michael H. and Abu-Ayyash, Khalil and Abueladas, Abdel-Rahman and Agnon, Amotz and Al-Amoush, H. and Babeyko, Andrey and Bartov, Yosef and Baumann, M. and Ben-Avraham, Zvi and Bock, G{\"u}nter and Bribach, Jens and El-Kelani, R. and Forster, A. and F{\"o}rster, Hans-J{\"u}rgen and Frieslander, U. and Garfunkel, Zvi and Grunewald, Steffen and Gotze, Hans-J{\"u}rgen and Haak, Volker and Haberland, Christian and Hassouneh, Mohammed and Helwig, S. and Hofstetter, Alfons and Jackel, K. H. and Kesten, Dagmar and Kind, Rainer and Maercklin, Nils and Mechie, James and Mohsen, Amjad and Neubauer, F. M. and Oberh{\"a}nsli, Roland and Qabbani, I. and Ritter, O. and Rumpker, G. and Rybakov, M. and Ryberg, Trond and Scherbaum, Frank and Schmidt, J. and Schulze, A. and Sobolev, Stephan Vladimir and Stiller, M. and Th,}, title = {The crustal structure of the Dead Sea Transform}, year = {2004}, abstract = {To address one of the central questions of plate tectonics-How do large transform systems work and what are their typical features?-seismic investigations across the Dead Sea Transform (DST), the boundary between the African and Arabian plates in the Middle East, were conducted for the first time. A major component of these investigations was a combined reflection/ refraction survey across the territories of Palestine, Israel and Jordan. The main results of this study are: (1) The seismic basement is offset by 3-5 km under the DST, (2) The DST cuts through the entire crust, broadening in the lower crust, (3) Strong lower crustal reflectors are imaged only on one side of the DST, (4) The seismic velocity sections show a steady increase in the depth of the crust-mantle transition (Moho) from 26 km at the Mediterranean to 39 km under the Jordan highlands, with only a small but visible, asymmetric topography of the Moho under the DST. These observations can be linked to the left-lateral movement of 105 km of the two plates in the last 17 Myr, accompanied by strong deformation within a narrow zone cutting through the entire crust. Comparing the DST and the San Andreas Fault (SAF) system, a strong asymmetry in subhorizontal lower crustal reflectors and a deep reaching deformation zone both occur around the DST and the SAF. The fact that such lower crustal reflectors and deep deformation zones are observed in such different transform systems suggests that these structures are possibly fundamental features of large transform plate boundaries}, language = {en} } @article{CandanCetinkaplanOberhaenslietal.2005, author = {Candan, O. and Cetinkaplan, Mete and Oberh{\"a}nsli, Roland and Rimmele, Gaetan and Akal, Cemal B.}, title = {Alpine high-P/low-T metamorphism of the Afyon Zone and implications for the metamorphic evolution of Western Anatolia, Turkey}, issn = {0024-4937}, year = {2005}, abstract = {Carpholite+chloritoid+pyrophyllite association occurs widely in the Triassic metaclastic rocks of the Afyon Zone in west-central Turkey. Fe-Mg-carpholite is associated with rare aragonite pseudomorphs and glaucophane in marbles and metabasites, respectively. The Afyon Zone consists stratigraphically of a Pan-African basement and an overlying Mesozoic cover sequence. The Pan-African basement, which shows Barrovian-type amphibolite-facies metamorphism, comprises garnet-mica schists, intruded by sodic amphibole-bearing metagabbros and leucocratic metagranites. It is unconformably overlain by a continuous metasedimentary sequence extending from Triassic to early Palaeocene. This cover sequence begins with metaconglomerates, which pass upwards into phyllites. Fe-Mg-carpholite occurs within this metaclastic sequence as rosette-like crystals in metapelites and fibres in quartz segregations. The metaclastic rocks are succeeded by metamorphosed platform carbonates, grading into Latest Mesozoic metamorphosed pelagic limestones, which in turn progress up to a Late Mesozoic-Early Tertiary olistostrome. This sequence is tectonically overlain by the blueschists of the Tavsanh Zone. Fe-Mg-carpholite-bearing assemblages imply temperatures of about 350 degrees C and minimum pressures of 6-9 kbar, corresponding to burial depths of about 30 km for the Mesozoic passive continental margin sediments and the underlying Pan-African supracrustal metasediments and metaintrusives. The metamorphic rocks of the Afyon Zone are unconformably overlain by Upper Palaeocene-Lower Eocene sedimentary rocks, indicating a Paleocene age for the regional HP/LT metamorphism. This implies continuous younging of HP/LT metamorphism in the Anatolides related to northward subduction of the Anatolide-Tauride platform beneath the Sakarya Zone. From north to south this involved the Tavsanh Zone (Campanian, 80 +/- 5 Ma), the Afyon Zone (Palaeocene?), the Menderes Massif (Middle Eocene) and the Lycian Nappes (Late Cretaceous-Eocene?), all of which were probably derived from the frontal part of the Anatolide-Tauride platform. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{RimmeleParraGoffeetal.2005, author = {Rimmele, Gaetan and Parra, T. and Goffe, B. and Oberh{\"a}nsli, Roland and Jolivet, L. and Candan, O.}, title = {Exhumation paths of high-pressure-low-temperature metamorphic rocks from the Lycian Nappes and the Menderes Massif (SW Turkey) : a multi-equilibrium approach}, issn = {0022-3530}, year = {2005}, abstract = {The Menderes Massif and the overlying Lycian Nappes occupy an extensive area of SW Turkey where high-pressure- low-temperature metamorphic rocks occur. Precise retrograde P-T paths reflecting the tectonic mechanisms responsible for the exhumation of these high-pressure-low-temperature rocks can be constrained with multi-equilibrium P-T estimates relying on local equilibria. Whereas a simple isothermal decompression is documented for the exhumation of high-pressure parageneses from the southern Menderes Massif, various P-T paths are observed in the overlying Karaova Formation of the Lycian Nappes. In the uppermost levels of this unit, far from the contact with the Menderes Massif, all P-T estimates depict cooling decompression paths. These high-pressure cooling paths are associated with top-to-the-NNE movements related to the Akcakaya shear zone, located at the top of the Karaova Formation. This zone of strain localization is a local intra-nappe contact that was active in the early stages of exhumation of the high-pressure rocks. In contrast, at the base of the Karaova Formation, along the contact with the Menderes Massif, P-T calculations show decompressional heating exhumation paths. These paths are associated with severe deformation characterized by top-to-the-east shearing related to a major shear zone (the Gerit shear zone) that reflects late exhumation of high-pressure parageneses under warmer conditions}, language = {en} } @article{WawrzenitzRomerOberhaenslietal.2006, author = {Wawrzenitz, Nicole and Romer, Rolf L. and Oberh{\"a}nsli, Roland and Dong, Shuwen}, title = {Dating of subduction and differential exhumation of UHP rocks from the Central Dabie Complex (E-China) : constraints from microfabrics, Rb-Sr and U-Pb isotope systems}, doi = {10.1016/j.lithos.2005.12.001}, year = {2006}, abstract = {The correlation of deformation fabrics and metamorphic reactions with geochronologic data of UHP metamorphic rocks demonstrate that the multistage subduction and exhumation history of the Central Dabie Complex requires rapid subduction and rapid initial exhumation. Moreover, these data show that volume diffusion is not the major resetting mechanism of radiogenic isotope systems. Thus, our age data do not simply reflect a thermal/cooling history. In the investigated section, the maximum age for UHP is given by the 244 +/- 3 Ma (2 sigma) U-Pb age of a pre-UHP titanite phenocryst that survived UHP metamorphism and subsequent tectonometamorphic events. A minimum age for UHP is set by the 238 +/- 1 Ma (2 sigma) U-238-Pb-206 mineral isochron age of titanite and cogenetic epidote. These minerals formed from local partial melts during ascent and their age suggests fast exhumation and emplacement in the middle crust. In the period of ca. 238-218 Ma, the UHP terrain records HT metamorphism, local partial melting, and extensive pervasive strain below the eclogite (jd+grt) stability field. Exhumation was polyphase with a first phase of fast exhumation, succeeded by episodes of HT metamorphism and concomitant deformation at deep/mid crustal level between 238 and 218 Ma. Slow exhumation related to the final emplacement of tectonic units along greenschist facies shear zones did not cease before ca. 209-204 Ma. The resetting and homogenization of radiogenic isotope systems were aided by dissolution precipitation creep, which was the dominant deformation mechanism in quartz-feldspar rocks, in combination with fluid influx. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @inproceedings{RiedelZiemannOberhaensli2006, author = {Riedel, Michael R. and Ziemann, Martin Andreas and Oberh{\"a}nsli, Roland}, title = {Pattern dynamics applied to the kinetics of mineral phase transformations}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7316}, year = {2006}, abstract = {Interdisziplin{\"a}res Zentrum f{\"u}r Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006}, language = {en} } @article{MoazzenOberhaensliHajialioghlietal.2009, author = {Moazzen, Mohssen and Oberh{\"a}nsli, Roland and Hajialioghli, Robab and Moeller, Andreas and Bousquet, Romain and Droop, Giles and Jahangiri, Ahmad}, title = {Peak and post-peak P-T conditions and fluid composition for scapolite-clinopyroxene-garnet calc-silicate rocks from the Takab area, NW Iran}, issn = {0935-1221}, doi = {10.1127/0935-1221/2009/0021-1887}, year = {2009}, abstract = {The Takab calcareous rocks of northwest Iran crop out in association with a variety of metamorphic rocks including mafic granulites, amphibolites, granitic gneisses, pelitic schists and meta-ultramafic rocks. They can be divided into marbles and calc-silicate rocks on the basis of the dominance of calcite/dolomite and silicate minerals. Dominant peak metamorphic granulite facies assemblage of calc-silicate rocks is Scp + Grt(I) + Cpx + Cal + Qtz +/- Hbl(I). The decrease of temperature and pressure during exhumation produced post-peak metamorphic assemblages. Coronal garnet (Grt II) in the calc-silicate rocks was produced by retrograde reactions consuming plagioclase and clinopyroxene, while peak metamorphic garnet (Grt I) occurs as preserved xenoblastic grains in calcite and/or plagioclase (Pl II). Regional metamorphism took place at 740 degrees C and X-CO2 similar to 0.9. Garnet-clinopyroxene-plagioclase-quartz (GADS) barometry yields a pressure of 8-9 kbar, corresponding to a depth of ca. 24-27 km. This was followed by decompression and hydration during exhumation of the crustal rocks up to the surface. Secondary phases such as garnet (II) hornblende (II), plagioclase (II), zoisite and titanite (II) constrain the temperature and pressure of post-peak metamorphism as similar to 600 degrees C and similar to 6 kbar respectively and a fluid with XCO2 as low as 0.4. Halogens were near-absent during the peak metamorphic stage. The scapolite and hornblende crystallized underpeak metamorphic conditions contain very low fluorine and chlorine, whereas relatively high fluorine (similar to 0.8 wt\%) in the titanite (II) and hornblende (II) suggests a possible infiltration of F-rich fluids into the calc-silicate rocks during retrogression. It is interpreted to be related to external fluids released during crystallisation of granitoid magmas and/or leucosome patches in the adjacent migmatites.}, language = {en} } @article{ToksoyKoeksalOberhaensliGoencueoglu2009, author = {Toksoy-Koeksal, Fatma and Oberh{\"a}nsli, Roland and Goencueoglu, M. Cemal}, title = {Hydrous aluminosilicate metasomatism in an intra-oceanic subduction zone : implications from the Kurancali (Turkey) ultramafic-mafic cumulates within the Alpine Neotethys Ocean}, issn = {0930-0708}, doi = {10.1007/s00710-009-0044-7}, year = {2009}, abstract = {The Kurancali ultramafic-mafic cumulate body, an allochthonous ophiolitic sliver in central Anatolia, is characterized by the presence of abundant hydrous phases (phlogopite, pargasite) besides augitic diopside, plagioclase, and accessory amounts of rutile, sphene, apatite, zircon, and calcite. Based on modes of the essential minerals, the olivine-orthopyroxene-free cumulates are grouped as clinopyroxenite, hydrous clinopyroxenite, phlogopitite, hornblendite, layered gabbro, and diorite. Petrographical, mineralogical and geochemical features of the rocks infer crystallization from a hydrous magma having high-K calcalkaline affinity with slightly alkaline character, and point to metasomatised mantle as the magma source. Our evidence implies that the metasomatising component, which modified the composition of the mantle wedge source rock in an intraoceanic subduction zone, was a H2O, alkali and carbonate-rich aluminosilicate fluid and/or melt, probably derived from a subducted slab. We suggest that the metasomatic agents in the subarc mantle led to the generation of a hydrous magma, which produced the Kurancali cumulates in an island-arc basement in a supra-subduction-zone setting during the closure of the Izmir-Ankara-Erzincan branch of the Alpine Neotethys Ocean.}, language = {en} } @article{FoersterFoersterOberhaenslietal.2010, author = {F{\"o}rster, Hans-J{\"u}rgen and F{\"o}rster, Andrea and Oberh{\"a}nsli, Roland and Stromeyer, Dietrich}, title = {Lithospheric composition and thermal structure of the Arabian Shield in Jordan}, issn = {0040-1951}, doi = {10.1016/j.tecto.2008.11.014}, year = {2010}, abstract = {In this paper, a unique set of samples from the uppermost crust down to the lithospheric mantle of Jordan is analyzed for composition and petrophysical properties (density. thermal conductivity, radiogenic heat production) These data, covering a vertical section of almost 65 km. are used in conjunction with surface heat flow to generate a detailed and comprehensive lithospheric thermal model that reflects the conditions of the Arabian Shield (AS) prior to the post- Oligocene onset of lithosphere thinning and Voluminous basaltic volcanism. The pre-Miocene model geotherms, based on conductive surface heat flows of 55 and 60 mW m(-2). (a) meet the range of lithosphere-asthenosphere boundary depths of 110-160 km known from seismology, (b) conform to results of thermomechanical models on the on.-in of the Dead Sea basin that started in Miocene time. and (c) are consistent with typical xenolith-derived geotherms for terranes of similar age and lithospheric thickness. Moho temperatures (at depths between 35 and 40 km) of the AS in pre-Miocene times were most likely in the order of 530-650 degrees C, with mantle heat flows averaging between 24 and 29 mW m(-2) Results contradict former views of the late Proterozoic/early Cambrian-stabilized AS being an anomalously cold terrane A "cold" thermal structure inferred from previously measured low surface heat flows (generally <= 45 mW m(-2)) is inconsistent with the thickness, composition, and petrophysical properties of the stable lithosphere of the shield.}, language = {en} } @article{WichuraBousquetOberhaenslietal.2010, author = {Wichura, Henry and Bousquet, Romain and Oberh{\"a}nsli, Roland and Strecker, Manfred and Trauth, Martin H.}, title = {Evidence for middleUocene uplift of the East African Plateau}, issn = {0091-7613}, doi = {10.1130/G31022.1}, year = {2010}, abstract = {Cenozoic uplift of the East African Plateau has been associated with fundamental climatic and environmental changes in East Africa and adjacent regions. While this influence is widely accepted, the timing and the magnitude of plateau uplift have remained unclear. This uncertainty stems from the lack of datable, geomorphically meaningful reference horizons that could record surface uplift. Here, we document the existence of significant relief along the East African Plateau prior to rifting, as inferred from modeling the emplacement history of one of the longest terrestrial lava flows, the similar to 300-km-long Yatta phonolite flow in Kenya. This 13.5 Ma lava flow originated on the present-day eastern Kenya Rift flank, and utilized a riverbed that once routed runoff from the eastern rim of the plateau. Combining an empirical viscosity model with subsequent cooling and using the Yatta lava flow geometry and underlying paleotopography (slope angle), we found that the prerift slope was at least 0.2 degrees, suggesting that the lava flow originated at a minimum elevation of 1400 m. Hence, high paleotopography in the Kenya Rift region must have existed by at least 13.5 Ma. We infer from this that middle Miocene uplift occurred, which coincides with the two-step expansion of grasslands, as well as important radiation and speciation events in tropical Africa.}, language = {en} } @article{HajialioghliMoazzenJahangirietal.2011, author = {Hajialioghli, Robab and Moazzen, Mohssen and Jahangiri, Ahmad and Oberh{\"a}nsli, Roland and Mocek, Beate and Altenberger, Uwe}, title = {Petrogenesis and tectonic evolution of metaluminous sub-alkaline granitoids from the Takab Complex, NW Iran}, series = {Geological magazine}, volume = {148}, journal = {Geological magazine}, number = {2}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0016-7568}, doi = {10.1017/S0016756810000683}, pages = {250 -- 268}, year = {2011}, abstract = {The Takab complex is composed of a variety of metamorphic rocks including amphibolites, metapelites, mafic granulites, migmatites and meta-ultramafics, which are intruded by the granitoid. The granitoid magmatic activity occurred in relation to the subduction of the Neo-Tethys oceanic crust beneath the Iranian crust during Tertiary times. The granitoids are mainly granodiorite, quartz monzodiorite, monzonite and quartz diorite. Chemically, the magmatic rocks are characterized by ASI < 1.04, AI < 0.87 and high contents of CaO (up to similar to 14.5 wt \%), which are consistent with the I-type magmatic series. Low FeO(t)/(FeO(t)+MgO) values (< 0.75) as well as low Nb, Y and K(2)O contents of the investigated rocks resemble the calc-alkaline series. Low SiO(2), K(2)O/Na(2)O and Al(2)O(3) accompanied by high CaO and FeO contents indicate melting of metabasites as an appropriate source for the intrusions. Negative Ti and Nb anomalies verify a metaluminous crustal origin for the protoliths of the investigated igneous rocks. These are comparable with compositions of the associated mafic migmatites, in the Takab metamorphic complex, which originated from the partial melting of amphibolites. Therefore, crustal melting and a collision-related origin for the Takab calc-alkaline intrusions are proposed here on the basis of mineralogy and geochemical characteristics. The P-T evolution during magmatic crystallization and subsolidus cooling stages is determined by the study of mineral chemistry of the granodiorite and the quartz diorite. Magmatic crystallization pressure and temperature for the quartz-diorite and the granodiorite are estimated to be P similar to 7.8 +/- 2.5 kbar, T similar to 760 +/- 75 degrees C and P similar to 5 +/- 1 kbar, T similar to 700 degrees C, respectively. Subsolidus conditions are consistent with temperatures of similar to 620 degrees C and similar to 600 degrees C, and pressures of similar to 5 kbar and similar to 3.5 kbar for the quartz-diorite and the granodiorite, respectively.}, language = {en} } @article{AkalKoralayCandanetal.2011, author = {Akal, Cuneyt and Koralay, O. Ersin and Candan, Osman and Oberh{\"a}nsli, Roland and Chen, Fukun}, title = {Geodynamic significance of the early triassic karaburun granitoid (Western Turkey) for the opening history of Neo-Tethys}, series = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, volume = {20}, journal = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, number = {3}, publisher = {T{\"u}bitak}, address = {Ankara}, issn = {1300-0985}, doi = {10.3906/yer-1008-1}, pages = {255 -- 271}, year = {2011}, abstract = {The Karaburun Peninsula, which is considered part of the Anatolide-Tauride Block of Turkey, contains clastic and carbonate sequences deposited on the northern margin of Gondwana. The Palaeozoic clastic sequence, which is intruded by the Early Triassic granitoid and tectonically overlies a Mesozoic melange sequence, can be divided into three subunits: a lower clastic subunit consisting of a sandstone-shale alternation, an upper clastic subunit consisting of black chert-bearing shales, sandstone and conglomerate, and a Permo-Carboniferous carbonate subunit. The lower Triassic Karaburun I-type granitoid has a high initial Sr-87/Sr-86 ratio (0.709021-0.709168), and low Nd-143/Nd-144 ratio (0.512004-0.512023) and epsilon Nd (-5.34 to -5.70) isotopic values. Geochronological data indicate a crystallization (intrusion) age of 247.1 +/- 2.0 Ma (Scythian). Geochemically, the acidic magmatism reflects a subduction-related continental-arc basin tectonic setting, which can be linked to the opening of the northern branch of Neo-Tethys as a continental back-arc rifting basin on the northern margin of Gondwana. This can be related to the closure through southward subduction of the Palaeotethys Ocean beneath Gondwana.}, language = {en} } @article{SakiMoazzenOberhaensli2011, author = {Saki, A. and Moazzen, Mohssen and Oberh{\"a}nsli, Roland}, title = {P-T evolution of the precambrian metamorphic complex, NW Iran a study of metapelitic rocks}, series = {Geological journal}, volume = {46}, journal = {Geological journal}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0072-1050}, doi = {10.1002/gj.1236}, pages = {10 -- 25}, year = {2011}, abstract = {The Mahneshan Metamorphic Complex (MMC) is one of the Precambrian terrains exposed in the northwest of Iran. The MMC underwent two main phases of deformation (D-1 and D-2) and at least two metamorphic events (M-1 and M-2). Critical metamorphic mineral assemblages in the metapelitic rocks testify to regional metamorphism under amphibolite-facies conditions. The dominant metamorphic mineral assemblage in metapelitic rocks (M-1) is muscovite, biotite I, Garnet I, staurolite, Andalusite I and sillimanite. Peak metamorphism took place at 600-620 degrees C and similar to 7 kbar, corresponding to a depth of ca. 24 km. This was followed by decompression during exhumation of the crustal rocks up to the surface. The decrease of temperature and pressure during exhumation produced retrograde metamorphic assemblages (M-2). Secondary phases such as garnet II biotite It. Andalusite II constrain the temperature and pressure of M, retrograde metamorphism to 520-560 degrees C and 2.5-3.5 kbar, respectively. The geothermal gradient obtained for the peak of metamorphism is 33 degrees C km(-1), which indicates that peak metamorphism was of Barrovian type and occurred under medium-pressure conditions. The MMC followed a 'clockwise' P T path during metamorphism, consistent with thermal relaxation following tectonic thickening. The bulk chemistry of the MMC metapelites shows that their protoliths were deposited at an active continental margin. Together with the presence of palaeo-suture zones and ophiolitic rocks around the high-grade metamorphic rocks of the MMC, these features suggest that the Iranian Precambrian basement formed by an island-arc type cratonization.}, language = {en} } @article{CandanKoralayAkaletal.2011, author = {Candan, Osman and Koralay, O. E. and Akal, Cemal B. and Kaya, O. and Oberh{\"a}nsli, Roland and Dora, O. O. and Konak, N. and Chen, F.}, title = {Supra-Pan-African unconformity between core and cover series of the Menderes Massif/Turkey and its geological implications}, series = {Precambrian research}, volume = {184}, journal = {Precambrian research}, number = {1-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-9268}, doi = {10.1016/j.precamres.2010.09.010}, pages = {1 -- 23}, year = {2011}, abstract = {Well-preserved primary contact relationships between a Late Proterozoic metasedimentary and the metagranitic core and Palaeozoic cover series of the Menderes Massif have been recognized in the eastern part of the Cine submassif on a regional-scale. Metaconglomerates occur as laterally discontinuous channel-fill bodies close the base of the metaquartzarenite directly above the basement. The pebbles in the metaconglomerates consist mainly of different types of tourmaline-rich leucocratic granitoids, tourmalinite and schist in a sandy matrix. Petrographic features, geochemical compositions and zircon radiometric ages (549.6 +/- 3.7-552.3 +/- 3.1 Ma) of the diagnostic clasts of the metaconglomerates (e.g. leucocratic granitoids and tourmalinites) show excellent agreement with their in situ equivalents (549.0 +/- 5.4 Ma) occurring in the Pan-African basement as stocks and veins. The correlation between clasts in the metaconglomerates and granitoids of the basement suggests that the primary contact between the basement and cover series is a regional unconformity (supra-Pan-African Unconformity) representing deep erosion of the Pan-African basement followed by the deposition of the cover series. Hence the usage of 'core-cover' terminology in the Menderes Massif is valid. Consequently, these new data preclude the views that the granitic precursors of the leucocratic orthogneisses are Tertiary intrusions.}, language = {en} } @article{AltenbergerMejiaJimenezGuenteretal.2012, author = {Altenberger, Uwe and Mejia Jimenez, D. M. and G{\"u}nter, C. and Sierra Rodriguez, G. I. and Scheffler, F. and Oberh{\"a}nsli, Roland}, title = {The Garzn Massif, Colombia-a new ultrahigh-temperature metamorphic complex in the early Neoproterozoic of northern South America}, series = {Mineralogy and petrology}, volume = {105}, journal = {Mineralogy and petrology}, number = {3-4}, publisher = {Springer}, address = {Wien}, issn = {0930-0708}, doi = {10.1007/s00710-012-0202-1}, pages = {171 -- 185}, year = {2012}, abstract = {The Garzn Complex of the Garzn Massif in SW Colombia is composed of the Vergel Granulite Unit (VG) and the Las Margaritas Migmatite Unit (LMM). Previous studies reveal peak temperature conditions for the VG of about 740 A degrees C. The present study considers the remarkable exsolution phenomena in feldspars and pyroxenes and titanium-in-quartz thermometry. Recalculated ternary feldspar compositions indicate temperatures around 900-1,000 A degrees C just at or above the ultra-high temperature-metamorphism (UHTM) boundary of granulites. The calculated temperatures range of exsolved ortho- and clinopyroxenes also supports the existence of an UHTM event. In addition, titanium-in-quartz thermometry points towards ultra-high temperatures. It is the first known UHTM crustal segment in the northern part of South America. Although a mean geothermal gradient of ca 38 A degrees C km(-1) could imply additional heat supply in the lower crust controlling this extreme of peak metamorphism, an alternative model is suggested. The formation of the Vergel Granulite Unit is supposed to be formed in a continental back-arc environment with a thinned and weakened crust behind a magmatic arc (Guapotn-Mancagua Gneiss) followed by collision. In contrast, rocks of the adjacent Las Margaritas Migmatite Unit display "normal" granulite facies temperatures and are formed in a colder lower crust outside the arc, preserved by the Guapotn-Mancagu Gneiss. Back-arc formation was followed by inversion and thickening of the basin. The three units that form the modern-day Garzn Massif, were juxtaposed upon each other during collision (at ca. 1,000 Ma) and exhumation. The collision leading to the deformation of the studied area is part of the Grenville orogeny leading to the amalgamation of Rodinia.}, language = {en} } @article{SakiMoazzenOberhaensli2012, author = {Saki, Adel and Moazzen, Mohssen and Oberh{\"a}nsli, Roland}, title = {Mineral chemistry and thermobarometry of the staurolite-chloritoid schists from Poshtuk, NW Iran}, series = {Geological magazine}, volume = {149}, journal = {Geological magazine}, number = {6}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0016-7568}, doi = {10.1017/S0016756812000209}, pages = {1077 -- 1088}, year = {2012}, abstract = {The Poshtuk metapelitic rocks in northwestern Iran underwent two main phases of regional and contact metamorphism. Microstructures, textural features and field relations indicate that these rocks underwent a polymetamorphic history. The dominant metamorphic assemblage of the metapelites is garnet, staurolite, chloritoid, chlorite, muscovite and quartz, which grew mainly syntectonically during the later contact metamorphic event. Peak metamorphic conditions of this event took place at 580 degrees C and similar to 3-4 kbar, indicating that this event occurred under high-temperature and low-pressure conditions (HT/LP metamorphism), which reflects the high heat flow in this part of the crust. This event is mainly controlled by advective heat input through magmatic intrusions into all levels of the crust. These extensive Eocene metamorphic and magmatic activities can be associated with the early Alpine Orogeny, which resulted in this area from the convergence between the Arabian and Eurasian plates, and the Cenozoic closure of the Tethys oceanic tract(s).}, language = {en} } @article{KoralayCandanChenetal.2012, author = {Koralay, O. E. and Candan, Osman and Chen, F. and Akal, Cemal B. and Oberh{\"a}nsli, Roland and Satir, M. and Dora, O. O.}, title = {Pan-African magmatism in the Menderes Massif - geochronological data from leucocratic tourmaline orthogneisses in western Turkey}, series = {International journal of earth sciences}, volume = {101}, journal = {International journal of earth sciences}, number = {8}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-012-0775-2}, pages = {2055 -- 2081}, year = {2012}, abstract = {The Menderes Massif, exposed in western Anatolia, is a metamorphic complex cropping out in the Alpine orogenic belt. The metamorphic rock succession of the Massif is made up of a Precambrian basement and overlying Paleozoic-early Tertiary cover series. The Pan-African basement is composed of late Proterozoic metasedimentary rocks consisting of partially migmatized paragneisses and conformably overlying medium- to high-grade mica schists, intruded by orthogneisses and metagabbros. Along the southern flank of the southern submassif, we recognized well-preserved primary contact relationship between biotite and leucocratic tourmaline orthogneisses and country rocks as the orthogneisses represent numerous large plutons, stocks and vein rocks intruded into a basement of garnet mica schists. Based on the radiometric data, the primary deposition age of the precursors of the country rocks, garnet mica schist, can be constrained between 600 and 550 Ma (latest Neoproterozoic). The North Africa-Arabian-Nubian Shield in the Mozambique Belt can be suggested as the possible provenance of these metaclastics. The intrusion ages of the leucocratic tourmaline orthogneisses and biotite orthogneisses were dated at 550-540 Ma (latest Neoproterozoic-earliest Cambrian) by zircon U/Pb and Pb/Pb geochronology. These granitoids represent the products of the widespread Pan-African acidic magmatic activity, which can be attributed to the closure of the Mozambique Ocean during the final collision of East and West Gondwana. Detrital zircon ages at about 550 Ma in the Paleozoic muscovite-quartz schists show that these Pan-African granitoids in the basement form the source rocks of the cover series of the Menderes Massif.}, language = {en} } @article{DuesterhoeftBousquetWichuraetal.2012, author = {D{\"u}sterh{\"o}ft, Erik and Bousquet, Romain and Wichura, Henry and Oberh{\"a}nsli, Roland}, title = {Anorogenic plateau formation The importance of density changes in the lithosphere}, series = {Journal of geophysical research : Solid earth}, volume = {117}, journal = {Journal of geophysical research : Solid earth}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1029/2011JB009007}, pages = {13}, year = {2012}, abstract = {Away from active plate boundaries the relationships between spatiotemporal variations in density and geothermal gradient are important for understanding the evolution of topography in continental interiors. In this context the classic concept of the continental lithosphere as comprising three static layers of different densities (upper crust, lower crust, and upper mantle) is not adequate to assess long-term changes in topography and relief in regions associated with pronounced thermal anomalies in the mantle. We have therefore developed a one-dimensional model, which is based on thermodynamic equilibrium assemblage computations and deliberately excludes the effects of melting processes like intrusion or extrusions. Our model calculates the "metamorphic density" of rocks as a function of pressure, temperature, and chemical composition. It not only provides a useful tool for quantifying the influence of petrologic characteristics on density, but also allows the modeled "metamorphic" density to be adjusted to variable geothermal gradients and applied to different geodynamic environments. We have used this model to simulate a scenario in which the lithosphere-asthenosphere boundary is subjected to continuous heating over a long period of time (130 Ma), and demonstrate how an anorogenic plateau with an elevation of 1400 m can be formed solely as a result of heat transfer within the continental lithosphere. Our results show that, beside dynamic topography (of asthenospheric origin), density changes within the lithosphere have an important impact on the evolution of anorogenic plateaus.}, language = {en} } @article{AkalCandanKoralayetal.2012, author = {Akal, C{\"u}neyt and Candan, Osman and Koralay, O. Ersin and Oberh{\"a}nsli, Roland and Chen, Fukun and Prelevic, Dejan}, title = {Early Triassic potassic volcanism in the Afyon Zone of the Anatolides/Turkey - implications for the rifting of the Neo-Tethys}, series = {International journal of earth sciences}, volume = {101}, journal = {International journal of earth sciences}, number = {1}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-011-0654-2}, pages = {177 -- 194}, year = {2012}, abstract = {Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethys, is made up of pre-Mesozoic basement and unconformably overlying Triassic-Early Tertiary cover series. The Afyon Zone contains widespread metavolcanic rocks, which are dominated by rhyolite, dacite, and trachyandesite. They form a distinct volcanic succession, which is separated from the underlying Silurian-Lower Carboniferous metacarbonates and meta-siliciclastics by a regional unconformity. Trachyandesitic metavolcanics are made up of massive lava flows, pyroclastics and epiclastics, less frequently, domes and dikes, which were developed on a deeply eroded subaerial landmass. U/Pb and Pb/Pb zircon geochronology yielded Lower Triassic (similar to 250 Ma) ages, which are interpreted as extrusion age of trachyandesitic volcanics. Based on the stratigraphic, geochronological, and geochemical data, we suggest that these Lower Triassic magmatic rocks represent an extensional tectonic setting on the northern active margin of the Gondwana, which led to the development of the northern branch of the Neo-Tethys.}, language = {en} } @article{OberhaensliBousquetCandanetal.2012, author = {Oberh{\"a}nsli, Roland and Bousquet, Romain and Candan, Osman and Okay, Aral I.}, title = {Dating subduction events in East Anatolia, Turkey}, series = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, volume = {21}, journal = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, number = {1}, publisher = {T{\"u}bitak}, address = {Ankara}, issn = {1300-0985}, doi = {10.3906/yer-1006-26}, pages = {1 -- 17}, year = {2012}, abstract = {Metamorphic studies in the cover sequences of the Bitlis complex allow the thermal evolution of the massif to be constrained using metamorphic index minerals. Regionally distributed metamorphic index minerals such as glaucophane, carpholite, relics of carpholite in chloritoid-bearing schists and pseudomorphs after aragonite in marbles record a LT-HP evolution:This demonstrates that the Bitlis complex was subducted and stacked to form a nappe complex during the closure of the Neo-Tethys. During late Cretaceous to Cenozoic evolution the Bitlis complex experienced peak metamorphism of 1.0-1.1 GPa at 350-400 degrees C. During the retrograde evolution temperatures remained below 460 degrees C. Ar-39/Ar-40 dating of white mica in different parageneses from the Bitlis complex reveals a 74-79 Ma (Campanian) date of peak metamorphism and rapid exhumation to an almost isothermal greenschist stage at 67-70 Ma (Maastrichtian). The HP Eocene flysch escaped the greenschist facies stage and were exhumed under very cold conditions. These single stage evolutions contrast with the multistage evolution reported further north from the Amassia-Stepanavan Suture in Armenia. Petrological investigations and isotopic dating show that the collision of Arabia with Eurasia resulted in an assemblage of different blocks derived from the northern as well as from the southern plate and a set of subduction zones producing HP rocks with diverse exhumation histories.}, language = {en} } @article{OberhaensliKoralayCandanetal.2013, author = {Oberh{\"a}nsli, Roland and Koralay, E. and Candan, Osman and Pourteau, Amaury and Bousquet, Romain}, title = {Late cretaceous eclogitic high-pressure relics in the Bitlis Massif}, series = {Geodinamica acta : revue de g{\´e}ologie dynamique et de g{\´e}ographie physique}, volume = {26}, journal = {Geodinamica acta : revue de g{\´e}ologie dynamique et de g{\´e}ographie physique}, number = {3-4}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0985-3111}, doi = {10.1080/09853111.2013.858951}, pages = {175 -- 190}, year = {2013}, abstract = {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 degrees C/1.9-2.4GPa. New U/Pb dates of 84.4 +/-.9 and 82.4 +/-.9Ma 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 degrees C/1.0-2.0GPa, respectively). On the other hand, eclogitic metamorphism of Kesandere metasediments occurred shortly before blueschist-facies metamorphism of the sedimentary cover (79-74Ma Ar-40/Ar-39 white mica). Therefore, the exhumation of Kesandere eclogites started between ca. 82 and 79Ma, while the meta-sedimentary cover was being buried. During this short time span, Kesandere eclogite were likely uplifted from similar to 65 to 35km depth, indicating a syn-subduction exhumation rate of similar to 4.3mm/a. Subsequently, eclogite- and blueschist-facies rocks were likely retrogressed contemporarily during collision-type metamorphism (around 72-69Ma). The Bitlis HP rocks thus sample a subduction zone that separated the Bitlis-Puturge (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 retreat or break off.}, language = {en} }