Granitoide der europäischen Varisziden : ein Einblick in ihre Platznahme- und tektonometamorphe Geschichte

This work analyses several granitic bodies of the Variscan Orogen of Central and Western Europe in order to improve our knowledge about different aspects of their evolution, regarding their ascent and emplacement mechanisms, as well as their deformation history. In the Iberian Massif two granitoid bodies, namely the La Bazana pluton and the Nisa-Alburquerque batholith, were studied in order to decipher their ascent and emplacement history. The La Bazana pluton is a small, sub-circular body in map view that intruded into rocks of the Ossa-Morena Zone in the core of a late upright antiform. Its three-dimensional drop-pipe shape, its internal dome foliation pattern and the structure of the host rock suggest that the magma ascended and emplaced diapirically. The Nisa-Alburquerque batholith is a large body that intruded into rocks of the Central Iberian Zone, the Central Unit, and the Ossa-Morena Zone. Its cartographic shape is elongate and parallel to the NW—SE to WNW—ESE Variscan structures. In the light of the available structural data and the gravimetric models, the intrusion is viewed as a continuous lateral magma flow from the eastern root guided towards the west through the southern limb of a kilometre-scale antiform. As mass-transfer mechanisms, a combination of rigid translation of the country rocks, stoping, and possibly ballooning is proposed. In the Bohemian Massif several small granitoid bodies showing a strong solid-state deformation were studied in order to integrate their tectonometamorphic history in the geotectonic framework of the south-western Bohemian Massif, focusing principally on the deformation phase referred to as D3. Four ductile deformation phases are proposed for the study area. D1 produced high-temperature fabrics under upper amphibolite to granulite facies conditions. Its kinematics is unknown. D2 occurred under amphibolite to upper greenschist facies conditions under N—S to NNW—SSE compression. It is responsible for a subvertical NW—SE striking foliation in migmatites developed under dextral simple shear and for the deformation at the Bayerischer Pfahl shear-zone system at its earlier stages. Many granitoid dykes and stocks were found to be affected by sinistral shear along subvertical planes trending ENE to ESE. Since this deformation, which is called D3 in the present work, is not compatible with a N—S to NNW—SSE compression, it is proposed that these sinistral shear zones in granites do not belong to the Bayerischer Pfahl shear-zone system and constitute themselves a separated one, which is called “D3 shear-zone system”. D3 took place under upper greenschist to lower amphibolite facies conditions (~480-550°C). Both the intrusion and the deformation of the granites affected by D3 occurred at deep to intermediate levels of the crust, whereas the deformation took place under NE—SW compression. Datings on two of the deformed granites yielded 324.4 ± 0.8 Ma and 315.0 ± 1.0 Ma: Thus, the age of D3 is most probably ~315 Ma. The intrusion of most of the sheared granitoids was pre-kinematic with respect to D3. After D3 the N—S to NNW—SSE compression which governed D2 was restored, giving way to the next deformation phase D4, which was linked to further deformation at and next to the principal shears of the Bayerischer Pfahl shear-zone system under greenschist facies conditions. The causes for the change of the stress field leading to a NE—SW compression during D3 might be related to (1) global changes in the dynamics of the tectonic plates in late Variscan times, (2) orogenic collapse leading to the sinking of the Teplá-Barrandian and lateral extrusion of the surrounding Moldanubian rocks, (3) distortion of the regional stress field by local intrusion of large stocks, such as the Saldenburg granite of the Fürstenstein Massif, or (4) distortion of the regional stress field due to the existence of ephemeral releasing bends in the Bayerischer Pfahl shear zone during its early evolution.Die vorliegende Arbeit analysiert verschiedene Aspekte der Entwicklung mehrerer Granitoide des Variszischen Orogens Zentral- und Westeuropas, unter Berücksichtigung sowohl ihrer Aufstiegs- und Platznahmemechanismen als auch ihrer Deformationsgeschichte. In der Iberischen Masse sind zwei granitoide Körper mit dem Ziel untersucht worden, ihre Aufstiegs- und Platznahmegeschichte zu entschlüsseln. Diese sind der La Bazana Pluton und der Nisa-Alburquerque Batholith. Der La Bazana Pluton ist ein kleiner, rundlicher Körper, der in den Kern einer späten Antiform in Gesteine der Ossa-Morena Zone intrudierte. Seine dreidimensionale Tropfen- bis Rohrform, seine innere Domstruktur und die Struktur des Nebengesteins deuten darauf hin, dass der Aufstieg und die Platznahme des Magmas einen diapirischen Charakter hatten. Der Nisa-Alburquerque Batholith ist ein großer Körper, der in Gesteine der Zentral-Iberischen Zone, der Badajoz-Córdoba Scherzone und der Ossa-Morena Zone intrudierte. Er ist parallel zu den NW—SE-gerichteten variszischen Strukturen gestreckt. Die vorhandenen strukturellen Daten und die neuen gravimetrischen Untersuchungen erlaubten den Entwurf eines Platznahmemodels. Die Intrusion wird als andauernder, seitlicher Magmafluß von einer östlichen Wurzelzone nach Westen hin angesehen, wobei das Magma an der südlichen Flanke einer Antiform kanalisiert wurde. Die Platznahme des Magmas wurde von der prä-existierenden Struktur des Nebengesteins gefördert und durch eine Kombination aus rigider Translation des Nebengesteins, stoping und ballooning ermöglicht. In der Böhmischen Masse wurden mehrere kleine granitoide Körper analysiert, die im Subsolidus-Bereich deformiert wurden. Das Ziel der Untersuchungen war, ihre tektonometamorphe Geschichte in den geotektonischen Rahmen des Bayerischen Waldes zu integrieren, insbesondere in Hinsicht auf die Deformationsphase, die D3 genannt wurde. Vier duktile Deformationsphasen wurden im Untersuchungsgebiet vorgeschlagen. D1 ergab Hochtemperatur-Strukturen unter Bedingungen der Amphibolit- bis Granulitfazies. Ihre Kinematik ist unbekannt. D2 fand unter Bedingungen der unteren Amphibolit- bis oberen Grünschieferfazies unter N—S- bis NNW—SSE-gerichteter Kompression statt. Sie ist für die subvertikale Foliation der Migmatite in Richtung NW—SE verantwortlich, die unter dextraler Scherung entstand, ebenso wie für die Deformation am Bayerischer-Pfahl-Scherzonen-System in seinen früheren Stadien. Viele granitoide Stöcke und Gänge sind von sinistraler Scherung entlang ENE- bis ESE-streichender Flächen betroffen. Diese Deformation ist inkompatibel mit einer Kompression in Richtung N—S bis NNW—SSE. Daher wird vorgeschlagen, dass sie eine neue Deformationsphase darstellt, die D3 genannt wurde. Die sinistralen, ENE- bis ESE-streichenden Scherzonen bilden das sogenannte „D3 Scherzonen-System“, das als unabhängig vom Bayerischer-Pfahl-Scherzonen-System angesehen wird. D3 erfolgte unter Bedingungen der oberen Grünschiefer- bis unteren Amphibolitfazies (~480-550°C). Sowohl die Intrusion als auch die Deformation von Graniten, die von D3 betroffen sind, geschahen in tiefen bis intermediären Krustenniveaus. D3 erfolgte unter NE—SW-gerichteter Kompression. Datierungen an zwei deformierten Granitoiden ergaben Alter von 324.4 ± 0.8 Ma und 315.0 ± 1.0 Ma. Dies bedeutet, dass das Alter von D3 sehr wahrscheinlich bei 315 Ma liegt. Das Eindringen der meisten zerscherten Granitoide war prä-kinematisch in Bezug auf D3. Nach D3 verlief die Richtung der Hauptkompression wieder in Richtung N—S bis NNW—SSE. Dies setzte die nächste Deformationsphase D4 in Gang. D4 war mit weiterer Deformation an und in der Nähe von den Hauptstörungen des Bayerischer-Pfahl-Scherzonen-Systems unter grünschieferfaziellen Bedingungen verbunden. Die Ursachen der Änderung des Stressfeldes, die zu einer Kompression in Richtung NE—SW führten, können mit folgenden Prozessen in Verbindung stehen: (1) mit globalen Änderungen der Dynamik der tektonischen Platten in spätvariszischer Zeit, (2) mit orogenem Kollaps assoziiert mit der Absenkung des Teplá-Barradiums und der lateralen Extrusion moldanubischer Unterkruste, (3) mit Störungen des regionalen Spannungsfeldes durch lokale Magmaintrusion, wie die des Saldenburger Granits im Fürstensteiner Massiv, oder (4) mit Störungen des regionalen Spannungsfeldes durch die Existenz kurzlebiger Releasing Bends während der Frühgeschichte der Bayerischer-Pfahl-Scherzone

New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach

We have calculated proper motions and re-evaluated the membership probabilities of 810 stars in the area of two NGC objects, NGC 1817 and NGC 1807. We have obtained absolute proper motions from 25 plates in the reference system of the Tycho-2 Catalogue. The plates have a maximum epoch difference of 81 years; and they were taken with the double astrograph at Zo-Se station of Shanghai Observatory, which has an aperture of 40 cm and a plate scale of 30 arcsec/mm. The average proper motion precision is 1.55 mas/yr. These proper motions are used to determine the membership probabilities of stars in the region, based on there being only one very extended physical cluster: NGC 1817. With that aim, we have applied and compared parametric and non-parametric approaches to cluster/field segregation. We have obtained a list of 169 probable member stars.Comment: 11 pages, 8 figures, A&A in pres

Planetary transit observations at the University Observatory Jena: TrES-2

We report on observations of several transit events of the transiting planet TrES-2 obtained with the Cassegrain-Teleskop-Kamera at the University Observatory Jena. Between March 2007 and November 2008 ten different transits and almost a complete orbital period were observed. Overall, in 40 nights of observation 4291 exposures (in total 71.52 h of observation) of the TrES-2 parent star were taken. With the transit timings for TrES-2 from the 34 events published by the TrES-network, the Transit Light Curve project and the Exoplanet Transit Database plus our own ten transits, we find that the orbital period is P=(2.470614 +/- 0.000001) d, a slight change by ~0.6 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we found a second dip after the transit which could either be due to a blended variable star or occultation of a second star or even an additional object in the system. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons.Comment: 10 pages, 13 figures, 5 tables, acceptes for publication in A

uvby-Hbeta CCD photometry and membership segregation of the open cluster NGC 2548; Gaps in the Main Sequence of open clusters

Deep CCD photometry in the uvby-Hbeta intermediate-band system is presented for the cluster NGC 2548 (M 48). A complete membership analysis based on astrometric and photometric criteria is applied. The photometric analysis of a selected sample of stars yields a reddening value of E(b-y)=0.06\pm0.03, a distance modulus of V_0-M_V=9.3\pm0.5 (725 pc) and a metallicity of [Fe/H]= -0.24\pm0.27. Through isochrone fitting we find an age of log t = 8.6\pm0.1 (400 Myr). Our optical photometry and JHK from 2MASS are combined to derive effective temperatures of cluster member stars. The effective temperature distribution along the main sequence of the cluster shows several gaps. A test to study the significance of these gaps in the main sequence of the HR diagram has been applied. The method is also applied to several other open clusters (Pleiades, Hyades, NGC 1817 and M 67) to construct a sequence of metallicities and ages. The comparison of the results of each cluster gives four gaps with high significance (one of them, centred at 4900 K, has not been previously reported).Comment: 11 pages, 8 figures, A&A in press. Corrected typos on Table

The extended halo of NGC 2682 (M 67) from Gaia DR2

Context: NGC 2682 is a nearby open cluster, approximately 3.5 Gyr old. Dynamically, most open clusters should dissolve on shorter timescales, of ~ 1 Gyr. Having survived until now, NGC 2682 was likely much more massive in the past, and is bound to have an interesting dynamical history. Aims: We investigate the spatial distribution of NGC 2682 stars to constrain its dynamical evolution, especially focusing on the marginally bound stars in the cluster outskirts. Methods: We use Gaia DR2 data to identify NGC 2682 members up to a distance of ~150 pc (10 degrees). Two methods (Clusterix and UPMASK) are applied to this end. We estimate distances to obtain three-dimensional stellar positions using a Bayesian approach to parallax inversion, with an appropriate prior for star clusters. We calculate the orbit of NGC 2682 using the GRAVPOT16 software. Results: The cluster extends up to 200 arcmin (50 pc) which implies that its size is at least twice as previously believed. This exceeds the cluster Hill sphere based on the Galactic potential at the distance of NGC 2682. Conclusions: The extra-tidal stars in NGC 2682 may originate from external perturbations such as disk shocking or dynamical evaporation from two-body relaxation. The former origin is plausible given the orbit of NGC 2682, which crossed the Galactic disk ~40 Myr ago.Comment: 9 pages, 5 figures, accepted for publication on A&

Photometric study of the OB star clusters NGC 1502 and NGC 2169 and mass estimation of their members at the University Observatory Jena

In this work we present detailed photometric results of the trapezium like galactic nearby OB clusters NGC 1502 and NGC 2169 carried out at the University Observatory Jena. We determined absolute $BVRI$ magnitudes of the mostly resolved components using Landolt standard stars. This multi colour photometry enables us to estimate spectral type and absorption as well as the masses of the components, which were not available for most of the cluster members in the literature so far, using models of stellar evolution. Furthermore, we investigated the optical spectrum of the components ADS 2984A and SZ Cam of the sextuple system in NGC 1502. Our spectra clearly confirm the multiplicity of these components, which is the first investigation of this kind at the University Observatory Jena.Comment: seven pages, eight pictures. Submitted to AN in Feb. 21st, accepted April 30t

Photometric analysis of the eclipsing binary 2MASS 19090585+4911585

We report on observations of the eclipsing binary 2MASS 19090585+4911585 with the 25 cm auxiliary telescope of the University Observatory Jena. We show that a nearby brighter star (2MASS 19090783+4912085) was previously misclassified as the eclipsing binary and find 2MASS 19090585+4911585 to be the true source of variation. We present photometric analysis of VRI light curves. The system is an overcontact binary of W UMa type with an orbital period of (0.288374 +/- 0.000010) d.Comment: 7 pages, 7 figures, 5 tables, accepted for publication in A

Constraining galactic structure parameters from a new extinction model and four star count samples

We propose a new 3-dimensional extinction model based on the COBE/IRAS all sky reddening map. Its application to globular and open cluster data evidences that the COBE/IRAS reddening map has an accuracy of 18%, but overestimates visual absorption by a factor of 1.16. This systematic error does not change with galactic latitude and opacity significantly. The implementation of the new extinction model has optimized our galactic structure and kinematic model to low-galactic latitudes. Four star count samples distributed in different galactic directions have been compared with galactic model simulations. Numerical experiments allow us to constrain the radial distribution of the galactic disk. The disk scale length is found to be 2250 +/- 50 pc and the displacement of the Sun from the galactic plane ZSun = 27.5 +/- 6.0 pc

uvby-Hbeta CCD Photometry of NGC 1817 and NGC 1807

We have investigated the area of two NGC entries, NGC 1817 and NGC 1807, with deep CCD photometry in the uvby-Hbeta intermediate-band system. The photometric analysis of a selected sample of stars of the open cluster NGC 1817 yields a reddening value of E(b-y)= 0.19$\pm$0.05, a distance modulus of V0-MV= 10.9$\pm$0.6, a metallicity of [Fe/H]= -0.34$\pm$0.26 and an age of log t = 9.05$\pm$0.05. Our measurements allow us to confirm that NGC 1807 is not a physical cluster.Comment: 11 pages, 8 figures, A&A in pres