Jorge A. Dristas

Palaeozoic accretion of the microcontinent Chilenia, North Patagonian Andes: high-pressure metamorphism and subsequent thermal relaxation

Basement rocks of the Colohuincul Complex (CC) crop out in the eastern foothills of the North Patagonian Andes (latitude 41°S). We studied the chemical composition of mineral phases in a mica-schist and a migmatite of this complex and constructed P–T pseudosections contoured by various chemical parameters of minerals. The P–T metamorphic path of the mica-schist is characterized by a high-pressure, low-temperature event (1.8 GPa and 440°C) indicated by a spessartine-rich core in prograde-zoned garnet and phengite relicts with high Si contents (3.40 pfu). The increase of Xpyrope (from 0.02 to 0.08) towards the garnet rim and the decrease of Si (to 3.16) in phengite reflect decompression accompanied by heating to 580°C (1.1 GPa), followed by cooling to 570°C (0.9 GPa). In contrast, the migmatitic paragneiss underwent partial melting and subsequent P–T conditions of 610°C and 0.5 GPa. Thermal relaxation after crustal thickening deduced from the mica-schist is interpreted to be the result of collision as the microcontinent Chilenia was thrust under the western South American part of Gondwana. Mid-upper crustal P–T conditions of the migmatite reflect its location within the Gondwanan crust. Two populations of monazite Th–U–Pb ages in migmatites and schists of the Colohuincul Complex with weighted average peaks at 391.7 ± 4.0 Ma (2σ) and 350.4 ± 5.8 Ma (2σ) are ascribed to the collisional and a later retrograde event.

Influence of CsCu2Cl3 on the electrical conductivity of CuCl

Abstract The influence of CsCu 2 Cl 3 on the conductive properties of gamma CuCl was studied by means of DTA and conductivity measurements. The results are interpreted as an enhancement effect of the dispersion of fine particles of CsCu 2 Cl 3 on the ionic conductivity of the solid electrolyte CuCl. The presence of an interparticle molten film at temperatures above 500 K is also postulated.

Ionic conductivity in montmorillonite-doped silver iodide

Abstract The ionic conductivity of AgI–montmorillonite composites was studied at a temperature ranging from 35 to 520 °C. Composites with montmorillonite as small as 0.89 w/o exhibited a maximum of about eight times the conductivity of the pure β-AgI at low temperatures. These results, which can be ascribed to the large surface area of the clay, may be qualitatively explained on the basis of a stabilisation of the low-temperature, higher-conducting metastable γ-phase of AgI.

On the influence of Cs(I)-doping on the electrical conductivity of cuprous bromide

A remarkable influence of Cs(I)-doping onto the conduction of the gamma-phase and on the gamma-beta transition in CuBr is found by means of DTA and conductivity measurements. The results are explained on the assumption of an increment of the defect concentration due to a lowering of its formation energy resulting from a lattice distortion in γ-CuBr.

THERMAL BEHAVIOUR OF COPPER(II) COMPLEXES OF HALOASPIRINATES

Complexes of Cu(II) with substituted o-acetoxy benzoic acids (5-haloaspirines, X-asp) with and without pyridine (py), of composition [Cu2(X-asp)4] and [Cu(X-asp)2(py)2 ] have been synthesized and characterized. Electronic and vibrational spectroscopic data of these complexes are reported. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. In all complexes, the haloaspirinate ligands decompose in two or three steps, starting with the break up of the coordinated acetoxy groups. CuO is obtained as the final pyrolysis residue in all cases.