TY - JOUR A1 - Altenberger, Uwe A1 - Mejia Jimenez, D. M. A1 - Günter, C. A1 - Sierra Rodriguez, G. I. A1 - Scheffler, F. A1 - Oberhänsli, Roland T1 - The Garzn Massif, Colombia-a new ultrahigh-temperature metamorphic complex in the early Neoproterozoic of northern South America JF - Mineralogy and petrology N2 - 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. Y1 - 2012 U6 - https://doi.org/10.1007/s00710-012-0202-1 SN - 0930-0708 VL - 105 IS - 3-4 SP - 171 EP - 185 PB - Springer CY - Wien ER - TY - JOUR A1 - Oberhänsli, Roland A1 - Bousquet, Romain A1 - Goffe, B. T1 - 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 Y1 - 2003 SN - 0036-7699 ER - TY - JOUR A1 - Omrani, Hadi A1 - Moazzen, Mohssen A1 - Oberhänsli, Roland T1 - Geodynamic evolution of the Sabzevar zone, northern central Iranian micro-continent JF - Mineralogy and petrology N2 - The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during Eocene. Mafic and ultramafic units are exposed along the northern part of the CIM in the Sabzevar area. The geology and field relation of Sabzevar ophiolite indicate northward subduction of the Sabzevar basin. The average whole rock chemistry of mafic (gabbros) and ultramafic samples (lherzolite, harzburgite and dunite) is characterized by a range of MgO of 11.16-31.88, CaO 5.22-11.53 and Al2O3 2.77-14.57, respectively. Low LREE/HREE ratio of ultramafic samples is accompanied by enrichment of large ion lithophile elements (LILE) such as Sr, Pb and K. Mafic samples show two distinct groups with low and high LREE/HREE ratios. The spider diagram of mafic samples indicates enrichment in Sr, Pb and K and depletion in REE. Petrological and geochemical evidence and field relations show that the mafic rocks formed in a supra-subduction zone setting. Petrological studies reveal the role of fractional crystallization and assimilation effect by released fluids during subduction related generation of the Sabzevar mafic rocks. We suggest that the studied mafic rocks likely represent the basement of an initial island arc, which was generated in a supra-subduction zone setting within the Neotethys branch of the Sabzevar Ocean at the north of CIM. Copper, gold and chromite mineralizations are studied in relation to island arc setting and supra-subduction environment. Similarities in lithology, ophiolite age and mineralization between Sabzevar ophiolite and Bardaskan-Torbat Heydariyeh ophiolites testify for their separation due to rotation (or faulting) of the Central Iranian Micro-continent. KW - Supra-subduction zone KW - Ophiolite KW - Island arc KW - Mineralization KW - Neotethys KW - Iran Y1 - 2017 U6 - https://doi.org/10.1007/s00710-017-0505-3 SN - 0930-0708 SN - 1438-1168 VL - 112 IS - 1 SP - 65 EP - 83 PB - Springer CY - Wien ER - TY - JOUR A1 - Dorani, Maryam A1 - Arvin, Mohsen A1 - Oberhänsli, Roland A1 - Dargahi, Sara T1 - P-T evolution of metapelites from the Bajgan complex in the Makran accretionary prism, south eastern Iran JF - Chemie der Erde : interdisciplinary journal for chemical problems of the geo-sciences and geo-ecology = Geochemistry N2 - The Bajgan Complex, one of the basement constituents of the arc massif in Iranian Makran forms a rugged, deeply incised terrain. The complex consists of pelitic schists with minor psammitic and basic schists, calc silicate rocks, amphibolites, marbles, metavolcanosediments, mafic and felsic intrusives as well as ultramafic rocks. Metapelitic rocks show an amphibolite facies regional metamorphism and contain garnet, biotite, white mica, quartz, albite ± rutile ± apatite. Thermobarometry of garnet schist yields pressure of more than 9 kbar and temperatures between 560 and 675 °C. The geothermal gradient obtained for the peak of regional metamorphism is 19 °C/km, corresponding to a depth of ca. 31 km. Replacement of garnet by chlorite and epidote suggest greenschist facies metamorphism due to a decrease in temperature and pressure through exhumation and retrograde metamorphism (370–450 °C and 3–6 kbar). The metapelitic rocks followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal decline following tectonic thickening. The formation of medium-pressure metamorphic rocks is related to presence of active subduction of the Neotethys Oceanic lithosphere beneath Eurasia in the Makran. KW - Bajgan Complex KW - Makran KW - Metapelitic rock KW - Garnet schist KW - Thermobarometry KW - Clockwise P-T path Y1 - 2017 U6 - https://doi.org/10.1016/j.chemer.2017.07.004 SN - 0009-2819 SN - 1611-5864 VL - 77 IS - 3 SP - 459 EP - 475 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Oberhänsli, Roland T1 - Deep-time Digital Earth (DDE) the first IUGS big science program JF - Journal of the Geological Society of India Y1 - 2020 U6 - https://doi.org/10.1007/s12594-020-1420-5 SN - 0016-7622 SN - 0974-6889 VL - 95 IS - 3 SP - 223 EP - 226 PB - Springer India CY - New Delhi ER - TY - JOUR A1 - Wawrzenitz, Nicole A1 - Romer, Rolf L. A1 - Oberhänsli, Roland A1 - Dong, Shuwen T1 - 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 N2 - 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 Y1 - 2006 UR - http://www.sciencedirect.com/science/article/pii/S0024493705002306 U6 - https://doi.org/10.1016/j.lithos.2005.12.001 ER - TY - JOUR A1 - Candan, O. A1 - Cetinkaplan, Mete A1 - Oberhänsli, Roland A1 - Rimmele, Gaetan A1 - Akal, Cemal B. T1 - Alpine high-P/low-T metamorphism of the Afyon Zone and implications for the metamorphic evolution of Western Anatolia, Turkey N2 - 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 Y1 - 2005 SN - 0024-4937 ER - TY - JOUR A1 - Rimmele, Gaetan A1 - Parra, T. A1 - Goffe, B. A1 - Oberhänsli, Roland A1 - Jolivet, L. A1 - Candan, O. T1 - Exhumation paths of high-pressure-low-temperature metamorphic rocks from the Lycian Nappes and the Menderes Massif (SW Turkey) : a multi-equilibrium approach N2 - 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 Y1 - 2005 SN - 0022-3530 ER - TY - JOUR A1 - Jolivet, L. A1 - Rimmele, Gaetan A1 - Oberhänsli, Roland A1 - Goffe, B. A1 - Candan, O. T1 - Correlation of syn-orogenic tectonic and metamorphic events in the Cyclades, the Lycian nappes and the Menderes massif : Geodynamic implications N2 - 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 Y1 - 2004 SN - 0037-9409 ER - TY - JOUR A1 - Liu, Xiaochun A1 - Jahn, Bor-Ming A1 - Dong, Shuwen A1 - Li, Huimin A1 - Oberhänsli, Roland T1 - Neoproterozoic granitoid did not record ultrahigh-pressure metamorphism from the Southern Dabieshan of China N2 - 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 Y1 - 2003 SN - 0022-1376 ER - TY - CHAP A1 - Riedel, Michael R. A1 - Ziemann, Martin Andreas A1 - Oberhänsli, Roland T1 - Pattern dynamics applied to the kinetics of mineral phase transformations N2 - Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7316 N1 - [Poster] ER - TY - JOUR A1 - Mesbahi, Fatemeh A1 - Mohajjel, Mohammad A1 - Oberhänsli, Roland A1 - Moazzen, Mohsen T1 - The mafic rocks along the North Tabriz Fault, possible remnants of Neo-Tethys oceanic crust in NW Iran JF - Geopersia N2 - The North Tabriz Fault is seismologically an active fault with current right lateral strike-slip movements. Restricted mafic to intermediate Fate Cretaceous igneous rocks are exposed along the North Tabriz Fault. Whole rock and clinopyroxene phenocrysts geochemistry were studied in order to characterize the petrogenesis of these mafic rocks and their possible relation to an oceanic crust. The results indicate a tholeiitic parental magma that formed in an evolved mid-ocean ridge tectonic setting similar to the Iceland mid-Atlantic ridge basalts. The ocean floor basalt characteristics give evidence of an oceanic crust along the North Tabriz Fault. Therefore, the trend of the North Tabriz Fault more likely marks a suture zone related to the closure of a branch of the Neo-Tethys Ocean in the NW Iran. This fault, in addition to the Caucasus and Zagros suture zones, compensates an important part of the convergence between the Arabian and Eurasian plates resulting from the Red Sea divergence. It is concluded that the North Tabriz Fault appears to be possible southeastern continuation of the North Anatolian suture zone. KW - North Tabriz Fault KW - Mafic Rocks KW - Tholeiite KW - Late Cretaceous Y1 - 2017 U6 - https://doi.org/10.22059/geope.2017.232747.648323 SN - 2228-7817 VL - 7 SP - 301 EP - 311 PB - Graduate Faculty of Environment, University of Theran CY - Tehran ER - TY - JOUR A1 - Ali, Saleem H. A1 - Giurco, Damien A1 - Arndt, Nicholas A1 - Nickless, Edmund A1 - Brown, Graham A1 - Demetriades, Alecos A1 - Durrheim, Ray A1 - Enriquez, Maria Amelia A1 - Kinnaird, Judith A1 - Littleboy, Anna A1 - Meinert, Lawrence D. A1 - Oberhänsli, Roland A1 - Salem, Janet A1 - Schodde, Richard A1 - Schneider, Gabi A1 - Vidal, Olivier A1 - Yakovleva, Natalia T1 - Mineral supply for sustainable development requires resource governance JF - Nature : the international weekly journal of science N2 - Successful delivery of the United Nations sustainable development goals and implementation of the Paris Agreement requires technologies that utilize a wide range of minerals in vast quantities. Metal recycling and technological change will contribute to sustaining supply, but mining must continue and grow for the foreseeable future to ensure that such minerals remain available to industry. New links are needed between existing institutional frameworks to oversee responsible sourcing of minerals, trajectories for mineral exploration, environmental practices, and consumer awareness of the effects of consumption. Here we present, through analysis of a comprehensive set of data and demand forecasts, an interdisciplinary perspective on how best to ensure ecologically viable continuity of global mineral supply over the coming decades. Y1 - 2017 U6 - https://doi.org/10.1038/nature21359 SN - 0028-0836 SN - 1476-4687 VL - 543 SP - 367 EP - 372 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Sheikholeslami, Mohammad Reza A1 - Oberhänsli, Roland A1 - Ghassemi, Mohammad R. T1 - Transpression tectonics in the eastern Binalud Mountains, northeast Iran; Insight from finite strain analysis, vorticity and Ar-40/Ar-39 dating JF - Journal of Asian earth sciences N2 - Different tectonic episodes from Late Triassic to recent times in the eastern Binalud Mountains have resulted from convergence and transpression between the Turan and Central Iran plates. Heterogeneous deformation and variable portions of pure and simple shear, demonstrated by finite strain and vorticity analysis in the Mashhad metamorphic rocks, indicate strain partitioning during the first tectonic episode. Modern strain partitioning is characterized by reverse and strike-slip faulting along the Neyshabur fault system and Shandiz fault zone in the southern and northern flanks of the eastern Binalud, respectively. Time-transgressive regional deformation migrated from the hinterland of the belt into the foreland basin, from northeast to the southwest of the mountains. Different generations of deformation resulted in obliteration of the subduction-related accretionary wedge, and growth of an orogenic wedge resulted from collision between the Central Iran and Turan plates. KW - Transpression KW - Binalud Mountains KW - Deformation KW - Orogenic wedge KW - Northeast Iran Y1 - 2019 U6 - https://doi.org/10.1016/j.jseaes.2019.04.014 SN - 1367-9120 SN - 1878-5786 VL - 179 SP - 219 EP - 237 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Scheffler, Franziska A1 - Immenhauser, Adrian A1 - Pourteau, Amaury A1 - Natalicchio, Marcello A1 - Candan, Osman A1 - Oberhänsli, Roland T1 - A lost Tethyan evaporitic basin BT - Evidence from a Cretaceous hemipelagic meta-selenite - red chert association in the Eastern Mediterranean realm JF - Sedimentology : the journal of the International Association of Sedimentologists N2 - Ancient evaporite deposits are geological archives of depositional environments characterized by a long‐term negative precipitation balance and bear evidence for global ocean element mass balance calculations. Here, Cretaceous selenite pseudomorphs from western Anatolia (‘Rosetta Marble’) — characterized by their exceptional morphological preservation — and their ‘marine’ geochemical signatures are described and interpreted in a process‐oriented context. These rocks recorded Late Cretaceous high‐pressure/low‐temperature, subduction‐related metamorphism with peak conditions of 1·0 to 1·2 GPa and 300 to 400°C. Metre‐scale, rock‐forming radiating rods, now present as fibrous calcite marble, clearly point to selenitic gypsum as the precursor mineral. Stratigraphic successions are recorded along a reconstructed proximal to distal transect. The cyclical alternation of selenite beds and radiolarian ribbon‐bedded cherts in the distal portions are interpreted as a two type of seawater system. During arid intervals, shallow marine brines cascaded downward into basinal settings and induced precipitation. During more humid times, upwelling‐induced radiolarian blooms caused the deposition of radiolarite facies. Interestingly, there is no comparable depositional setting known from the Cenozoic world. Meta‐selenite geochemical data (δ13C, δ18O and 87Sr/86Sr) plot within the range of reconstructed middle Cretaceous seawater signatures. Possible sources for the 13C‐enriched (mean 2·2‰) values include methanogenesis, gas hydrates and cold seep fluid exhalation. Spatially resolved component‐specific analysis of a rock slab displays isotopic variances between meta‐selenite crystals (mean δ13C 2·2‰) and host matrix (mean δ13C 1·3‰). The Cretaceous evaporite‐pseudomorphs of Anatolia represent a basin wide event coeval with the Aptian evaporites of the Proto‐Atlantic and the pseudomorphs share many attributes, including lateral distribution of 600 km and stratigraphic thickness of 1·5 to 2·0 km, with the evaporites formed during the younger Messinian salinity crisis. The Rosetta Marble of Anatolia may represent the best‐preserved selenite pseudomorphs worldwide and have a clear potential to act as a template for the study of meta‐selenite in deep time. KW - Blueschist metamorphism KW - depositional environment KW - evaporites KW - Neotethys KW - pseudomorphism KW - sedimentology Y1 - 2019 U6 - https://doi.org/10.1111/sed.12606 SN - 0037-0746 SN - 1365-3091 VL - 66 IS - 7 SP - 2627 EP - 2660 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Saki, Adel A1 - Moazzen, Mohssen A1 - Oberhänsli, Roland T1 - Mineral chemistry and thermobarometry of the staurolite-chloritoid schists from Poshtuk, NW Iran T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - 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 ◦ C and ∼ 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). T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 578 KW - thermobarometry KW - HT/LP metamorphism KW - Poshtuk metapelites KW - northwestern Iran Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413942 SN - 1866-8372 IS - 578 SP - 1077 EP - 1088 ER - TY - JOUR A1 - Reigber, Christoph A1 - Wassermann, Joachim A1 - Scherbaum, Frank A1 - Dresen, Georg A1 - Zang, Arno A1 - Altenberger, Uwe A1 - Rahmstorf, Stefan A1 - Klein, Armin A1 - Oberhänsli, Roland A1 - Herzig, Reinhard T1 - Portal = Vulkane, Erdbeben, Klima: Der Planet Erde birgt viele Geheimnisse BT - Die Potsdamer Universitätszeitung N2 - Aus dem Inhalt: - Vulkane, Erdbeben, Klima: Der Planet Erde birgt viele Geheimnisse - Eine Entdeckungsreise durch die Uni Potsdam auf CD-ROM - Gewitter im Gehirn - Herr der Pflanzen: Wolfgang Pifrement T3 - Portal: Das Potsdamer Universitätsmagazin - 01-02/2002 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439544 SN - 1618-6893 IS - 01-02/2002 ER - TY - JOUR A1 - Saki, Adel A1 - Miri, Mirmohammad A1 - Oberhänsli, Roland T1 - High temperature - low pressure metamorphism during subduction of Neo-Tethys beneath the Iranian plate BT - evidence for mafic migmatite formation in the Alvand complex (western Iran) JF - Mineralogy and petrology N2 - Subduction of Neo-Tethys oceanic lithosphere beneath the Iranian plate during the Mesozoic formed several igneous bodies of ultramafic to intermediate and felsic composition. Intrusion of these magmas into a regional metamorphic sequence (the Sanandaj-Sirjan Zone) caused partial melting and formation of migmatites with meta-pelitic protoliths. The Alvand complex (west Iran) is a unique area comprising migmatites of both mafic and pelitic protoliths. In this area, the gabbroic rocks contain veins of leucosome at their contact with pyroxenite and olivine gabbro. These leucosomes are geochemically and mineralogically different from leucosomes of the meta-pelitic migmatites and clearly show properties of I-type granites. Microscopic observations and whole rock compositions of the mafic migmatite leucosomes show that migmatization occurred through partial melting of biotite, hornblende and plagioclase. Thermobarometric calculations indicate 800 degrees C and 3.7 kbar for partial melting, although phase diagram modeling demonstrates that the presence of water could decrease the solidus temperature by about 40 degrees C. Our results suggest an asthenospheric magma upwelling as the source of heat for partial melting of the gabbroic rock during subduction of Neo-Tethys oceanic crust under the western edge of the Iranian plate. The present study also reveals relationships between migmatization and formation of S- and I -type granites in the area. KW - partial melting KW - mafic migmatite KW - pelitic migmatite KW - Neo-Tethys KW - subduction KW - Gabbroic rocks Y1 - 2020 U6 - https://doi.org/10.1007/s00710-020-00721-z SN - 0930-0708 SN - 1438-1168 VL - 114 IS - 6 SP - 539 EP - 557 PB - Springer CY - Wien [u.a.] ER - TY - JOUR A1 - Saki, Adel A1 - Moazzen, Mohssen A1 - Oberhänsli, Roland T1 - Mineral chemistry and thermobarometry of the staurolite-chloritoid schists from Poshtuk, NW Iran JF - Geological magazine N2 - 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). KW - thermobarometry KW - HT/LP metamorphism KW - Poshtuk metapelites KW - northwestern Iran Y1 - 2012 U6 - https://doi.org/10.1017/S0016756812000209 SN - 0016-7568 VL - 149 IS - 6 SP - 1077 EP - 1088 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Saki, Adel A1 - Miri, Mirmohammad A1 - Oberhänsli, Roland T1 - Pseudosection modelling of the Precambrian meta-pelites from the Poshtuk area, NW Iran JF - Periodico di mineralogia : an international journal of mineralogy, crystallography, geochemistry, ore deposits, petrology, volcanology and applied topics on environment, archaeometry and cultural heritage / Dipartimento di Scienze della Terra, Università degli Studi di Roma la Sapienza N2 - Precambrian meta-pelites of the Poshtuk area in northwest Iran contain the prograde mineral assemblage staurolite-garnet-chloritoid-muscovite-biotite that was replaced by the assemblage garnet-staurolite-chlorite-muscovite-biotite at peak metamorphic condition. Whole-rock compositions reveal that high Fe, Al and Mn contents of their protolith rendered them prone to form these assemblages. Pseudosections calculated in KFMASH, MnKFMASH, and MnNCKFMASHO systems were used to investigate the P-T evolution of the samples. They clearly show the significant effect of MnO on the stability of the chloritoid-bearing assemblages and the formation of garnet through consumption of chlorite and chloritoid. The pseudosection in a T- aH(2)O diagram shows that the studied assemblage could be stable only at a(H2O)>0.8. X-Mg isopleths for garnet and biotite point to peak P-T conditions of about 3.75 kbar and 575 degrees C. Chloritoid stability is overstepped with such conditions. This can be attributed to thermal perturbation due to plutonism. It is concluded, metamorphism was primarily controlled by advective heat from magmatic intrusions in the Poshtuk area. The Precambrian basement complexes were extensively overprinted by the Pan-African Orogeny as well as younger magmatic and metamorphic activities associated to Alpine Orogeny during convergence of Arabian and Eurasian plate. KW - meta-pelites KW - pseudosection KW - chloritoid stability KW - Precambrain KW - Poshtuk Y1 - 2021 U6 - https://doi.org/10.13133/2239-1002/16632 SN - 0369-8963 VL - 90 IS - 3 SP - 325 EP - 340 PB - Bardi CY - Roma ER -