T. Elbra

Structure of nickel nanoparticles in a microcrystalline cellulose matrix studied using anomalous small-angle X-ray scattering

Nickel nanoparticles were synthesized by adding aqueous nickel salt into a microcrystalline cellulose matrix. The NiII ions were reduced with either sodium borohydride, NaBH_4, or potassium hypophosphite, KH_2PO_2, in water or aqueous NH_3 medium. The mass fraction of Ni in the samples was between 3.7 and 8.9%. X-ray absorption spectra at the Ni K-edge showed that Ni was partially oxidized only in a sample reduced with NaBH_4. Wide-angle X-ray scattering results showed that nickel was in nanocrystalline or amorphous form in the samples. Upon heating fcc Ni, hcp Ni, NiO, Ni_3P and other Ni–P phases formed depending on the reduction parameters. Using anomalous small-angle X-ray scattering the nanometre-scale particle size distributions of the Ni particles were determined. A large fraction of particles less than 15 nm in size were observed in the samples reduced in aqueous ammonium compared with the samples reduced in water. Particles reduced in aqueous ammonium had a large ferromagnetic component.

Physical properties of Vilppula drill cores and petrographic analysis of associated breccias in Keurusselkä impact structure, central Finland

The Mesoproterozoic deeply eroded Keurusselkä impact structure in central Finland is situated within the ∼1860–1890 Ma Central Finland Granitoid Complex. An estimate for the original size of the structure is 30 km, yielding a 5 km wide central uplift with insitu shatter cones and shock metamorphic features in quartz. Petrophysical and rock magnetic properties of the three shallow drill cores (V-001, V-002 and V-003) in the vicinity of the central uplift are determined in order to assess the dimensions of the central uplifts magnetic anomalies. The drill core lithologies consist of schists (metagraywackes), metavolcanic rocks, gneisses and breccia. Petrophysical properties of the drill core rocks show average densities (D) of 2644–2752 kg/m3, susceptibilities (κ) of 160–761 × 10−6 SI and natural remanent magnetization (NRM) of 3–306 mA/m and Koenigsberger Q ratios of 0.1–10. Rock magnetic measurements with temperature dependence of susceptibility (κ-T) curves and hysteresis indicated mostly paramagnetic behaviour. However, a fraction of fine-grained ferromagnetic minerals (pyrrhotite and magnetite) was detected from all lithologies. Breccia veins cutting the parautochthonous subcrater floor show lower values of petrophysical properties (D, κ, NRM, Q) and this could be related to the impact event. Amphiboles and micas in the breccia are strongly altered and replaced by secondary chlorite. Chloritization may indicate widespread impact-induced hydrothermal alteration of the target rocks or it may be related to regional tectonic shearing. However, planar deformation features in quartz, found from shatter cones in the central uplift area, are decorated with fluid inclusions indicating that alteration by post-impact processes was present.

Palaeo- and rock-magnetic investigations across Jurassic-Cretaceous boundary at St Bertrand’s Spring, Drôme, France: applications to magnetostratigraphy

Palaeo- and rock-magnetic investigations of the St Bertrand’s Spring (Le Ravin de Font de St Bertrand) locality in France were carried out in order to contribute to, and improve, the stratigraphy of the Jurassic-Cretaceous boundary interval. Magnetic susceptibility shows slightly diamagnetic behaviour in the lowermost part of the profile and an increase (paramagnetic) towards its middle and upper parts. Rock-magnetic measurements throughout the section show magnetite as the main magnetic fraction, together with traces of hematite. Additionally, thermal demagnetization indicates the presence of goethite. Our magnetostratigraphy indicates three normal/reversed polarity sequences; possibly encompassing the magnetozones M19r to the M17n. This suggests that the St Bertrand section straddles the Tithonian/Berriasian boundary and reaches the middle Berriasian sensu lato.

Device for Measuring P- and S-Wave Velocities in Rock Samples under Crystal Conditions

An ultrasonic instrument capable of measuring seismic velocities (Vp and Vs) under crustal temperatures (20–300°C) and pressures (0–300 MPa) is built. The results obtained with the device will be used to understand recent seismic reflection (FIRE) data from the Outokumpu area in Finland. Collectively, the data will be integrated to construct a new geological model of the Outokumpu formation.