TY - JOUR A1 - Grüneberger, Anja Maria A1 - Schmidt, Christian A1 - Jahn, Sandro A1 - Rhede, Dieter A1 - Loges, Anselm A1 - Wilke, Max T1 - Interpretation of Raman spectra of the zircon-hafnon solid solution JF - European journal of mineralogy N2 - Zircon (ZrSiO4), hafnon (HfSiO4) and five intermediate compositions were synthesized from a Pb silicate melt. The resulting crystals were 20-300 mu m in size and displayed sector and growth zoning. Raman spectra were acquired at locations in the sample for which preceding electron microprobe (EMP) analyses revealed sufficient compositional homogeneity. The dataset documents shifts of Raman bands with changing composition. In this study, bands that have previously not been reported were found for the intermediate compositions and for pure hafnon, in particular at wavenumbers less than 200 cm(-1). For these external modes, the dataset provides new insight into the compositional dependence of their frequencies. Density-functional theory calculations support the observations and are used for a detailed interpretation of the spectra. The pitfalls of the EMP analysis along the zircon-hafnon join are highlighted. KW - zircon KW - hafnon KW - solid solution KW - Raman spectroscopy KW - synthesis KW - density-functional theory KW - hafnium analysis Y1 - 2016 U6 - https://doi.org/10.1127/ejm/2016/0028-2551 SN - 0935-1221 SN - 1617-4011 VL - 28 SP - 721 EP - 733 PB - Schweizerbart CY - Stuttgart ER - TY - JOUR A1 - Oberhänsli, Roland A1 - Koralay, E. A1 - Candan, Osman A1 - Pourteau, Amaury A1 - Bousquet, Romain T1 - Late cretaceous eclogitic high-pressure relics in the Bitlis Massif JF - Geodinamica acta : revue de géologie dynamique et de géographie physique N2 - 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. KW - eclogites KW - zircon KW - U KW - Pb ages KW - E Anatolia KW - subduction-collision Y1 - 2013 U6 - https://doi.org/10.1080/09853111.2013.858951 SN - 0985-3111 SN - 1778-3593 VL - 26 IS - 3-4 SP - 175 EP - 190 PB - Routledge, Taylor & Francis Group CY - Abingdon ER -