Magnetic and nuclear structure and thermal expansion of orthorhombic and monoclinic polymorphs of CoGeO3 pyroxene     

Günther Josef Redhammer  Anatoliy Senyshyn  Gerold Tippelt  Clemens Pietzonka  Georg Roth  Georg Amthauer 《Physics and Chemistry of Minerals》2010,37(5):311-332

CoGeO₃ was synthesized at 1,273 and 1,448 K using ceramic sintering techniques in the monoclinic and orthorhombic modification, respectively. The two compounds were analysed by magnetic susceptibility measurements and neutron diffraction in order to study magnetic ordering and spin structures at low temperature. The monoclinic form of CoGeO₃ has C2/c symmetry and orders magnetically below 36 K with a small negative paramagnetic Curie temperature θ _P = −4.6 (2) K. The magnetic structure can be described with k = (1, 0, 0) in the magnetic space group C2′/c′ having a ferromagnetic spin arrangement within the chains of M1 sites, but a dominating antiferromagnetic coupling between the chains. At the M1 sites the magnetic spins are aligned within the a–c plane forming an angle of 120° with the +a-axis and they are not parallel to the spins at M2. Here spins are also ferromagnetically coupled within, but antiferromagnetically coupled between the M1/M2 site bands. The orthorhombic phase of CoGeO₃ displays Pbca symmetry and transforms to an antiferromagnetically ordered state [θ _P = −18.6(2) K] below 33 K. The magnetic spin structure can be described with k = (0, 0, 0) in space group Pbca′ and it is similar to the one of the C2/c phase except that it is non-collinear in nature, i.e. there are components of the magnetic moment along all three crystallographic axes. Small magneto-elastic coupling is observed in the orthorhombic phase.  相似文献   

Erratum to: ‘Interhemispheric comparison of deglacial sea-surface temperature patterns in Atlantic eastern boundary currents’: [Earth Planet. Sci. Lett. 194 (2002) 383-393]     

Jung-Hyun Kim  Ralph R. SchneiderPeter J. Müller  Gerold Wefer 《Earth and Planetary Science Letters》2002,203(2):779-780

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Tectonic controls on Cenozoic foreland basin development in the north‐eastern Andes,Colombia     

Mauricio Parra  Andrés Mora  Carlos Jaramillo  Vladimir Torres  Gerold Zeilinger  Manfred R. Strecker 《Basin Research》2010,22(6):874-903

In order to evaluate the relationship between thrust loading and sedimentary facies evolution, we analyse the progradation of fluvial coarse‐grained deposits in the retroarc foreland basin system of the northern Andes of Colombia. We compare the observed sedimentary facies distribution with the calculated one‐dimensional (1D) Eocene to Quaternary sediment‐accumulation rates in the Medina wedge‐top basin and with a three‐dimensional (3D) sedimentary budget based on the interpretation of ～1800 km of industry‐style seismic reflection profiles and borehole data. Age constraints are derived from a new chronostratigraphic framework based on extensive fossil palynological assemblages. The sedimentological data from the Medina Basin reveal rapid accumulation of fluvial and lacustrine sediments at rates of up to ～500 m my^?1 during the Miocene. Provenance data based on gravel petrography and paleocurrents reveal that these Miocene fluvial systems were sourced from Upper Cretaceous and Paleocene sedimentary units exposed to the west in the Eastern Cordillera. Peak sediment‐accumulation rates in the upper Carbonera Formation and the Guayabo Group occur during episodes of coarse‐grained facies progradation in the early and late Miocene proximal foredeep. We interpret this positive correlation between sediment accumulation and gravel deposition as the direct consequence of thrust activity along the Servitá–Lengupá faults. This contrasts with one class of models relating gravel progradation in more distal portions of foreland basin systems to episodes of tectonic quiescence.  相似文献   

Book review     

Gerold W. Diepolder 《Mineralium Deposita》1986,21(3):199-206

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Tribute to Erwin Suess on the occasion of receiving the Gustav-Steinmann-Medal award by the Geologische Vereinigung     

Gerold Wefer 《International Journal of Earth Sciences》2005,94(1):1-2

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