Search results for "MINERALOGY"
showing 10 items of 1516 documents
Characterisation of the magnetic iron phases in Clovis Class rocks in Gusev crater from the MER Spirit Mössbauer spectrometer
2007
Abstract Mossbauer backscattering spectra of eight Martian rocks, acquired by the MIMOS II spectrometer of Rover Spirit (MER-A) and containing goethite in addition to other iron minerals, have been selected for in-depth numerical analysis. Where feasible, different temperature windows for a given rock were considered. A novel calibration/folding procedure, exclusively based on the fitted positions of the eight prominent absorption lines in the transmission spectra of the reference target and not relying on the error signal of the MIMOS II spectrometer, has been developed. It is demonstrated that this procedure yields reliable and reasonably accurate values for the adjusted Mossbauer paramet…
Mineralverwitterung, tonmineralbildung und rubefizierung in Terrae calcis der slowakei Ein beitrag zum paläoklimatischen aussagewert von kalkstein-Ro…
1984
Mineral weathering, clay mineral formation and rubefication of Terrae calcis in Slovakia — A contribution to paleoclimatic evidence of limestone Rotlehm (terra rossa) in Central Europe Limestone Rotlehm (Terra rossa) is very often interpreted as a product of intensive mineral weathering and clay formation under subtropic (to tropic) climate. Especially the formation of hematite in soils as the main process of rubefication is generally believed to occur only in warm climates with a seasonal alternation of precipitation and drought. Fossil or relict Terrae rossae in Central Europe are therefore very often considered as witnesses of a corresponding paleoclimate. On the other side many authors …
Direct dating of gold by radiogenic helium: Testing the method on gold from Diamantina, Minas Gerais, Brazil
2013
New analytical developments have made radiogenic helium ( 4 He) applicable to archeological gold artifacts for age determinations. Here we report the application of the U/Th– 4 He method to the direct dating of gold from the historically important gold deposit in Diamantina, Minas Gerais, Brazil. The U/Th– 4 He age of 515 ± 55 Ma for the Diamantina gold is corroborated by a new U/Pb age of 524 ± 16 Ma for rutile recovered from auriferous pockets. These ages tie the Diamantina gold mineralization to the Brasiliano orogenic event, in the context of the Gondwana amalgamation. Our results indicate that U/Th– 4 He dating of gold is possible, opening new perspectives for the dating of gold deposi…
Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests
2021
Rock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-De…
Solubility and microstructural development of TiO2-containing 3Al2O3·2SiO2 and 2Al2O3·SiO2 mullites obtained from single-phase gels
2007
Abstract The interdependence of the titanium oxide amount and the anisotropic growth of mullites prepared from single-phase gels were investigated. Gels with stoichiometries 3(Al2−xTixO3)·2(SiO2) and 2(Al2−xTixO3)·(SiO2), with 0 ≤ x ≤ 0.15 were prepared by the semialkoxide method. Gels and specimens heated at temperatures between 1200 and 1600 °C were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission and field emission scanning electron microscopies (TEM and FESEM). Al2TiO5 as minor impurity was detected in both series of mullites for gel precursor compositions x = 0.10 and x = 0.15, obtained at temperatures between 1200 and 1600 °C. Variations of l…
Granulometry, mineralogy and trace elements of marine sediments from the Gulf of Milazzo (NE Sicily): evaluation of anthropogenic impact
2010
Granulometry, mineralogy, and trace element concentrations are determined in marine sediments from thirty-six sampling sites in the littoral environment of the Gulf of Milazzo (NE Sicily). Sediment samples were collected in August 2008, along 18 seaward transects, at water depths of ‐10, ‐20 and ‐30 m, by using a Van Veen grab. Grain-size analysis shows predominance of sand (56%) and silt (35%) fractions with respect to clay (7%) and gravel (2%) fractions. Bulk mineralogical analysis documents the presence of quartz, micas, feldspars, calcite, and chlorite, which reflect erosion processes affecting the Kabilian-Calabrian Units. Concentrations of most trace elements in the deeper sediments w…
Authigenic phase formation and microbial activity control Zr, Hf, and rare earth element distributions in deep-sea brine sediments
2014
Abstract. Sediments collected from hypersaline and anoxic deep-sea basins in the eastern Mediterranean (Thetis, Kryos, Medee, and Tyro) were characterised in terms of their mineralogical composition, the distributions of rare earth elements (REE), Zr, and Hf and their content of microbial DNA. We identified two major mineralogical fractions: one fraction of detritic origin was composed of quartz, gypsum, and low-Mg calcite bioclasts (with 0 < Mg < 0.07%) and another fraction of authigenic origin constituted of halite, dolomite, high-Mg calcite (with a Mg content of up to 22%) and rare bischofite and showed a textural evidence of microbial assemblages. We found that in the Medee and Ty…
Investigations of Surface Forces between Gypsum Microcrystals in Air Using Atomic Force Microscopy
2000
This article introduces a new approach to the study of the interactions between gypsum faces in air. We have mounted a gypsum crystal on the end of a microcantilever to measure local forces (van der Waals, capillary forces, electrostatic) directly between two crystals. A systematic study with respect to the orientation of crystalline faces, relative humidity, and the duration of contact between crystals improves the understanding of the mechanism involved in the hardening of plaster in air. In dry air, a physicochemical process of matter transfer is added to the van der Waals forces to ensure the cohesion. Others force measurements were performed by varying the shape of the contact (interac…
Acqua Fitusa cave: An example of inactive water-table sulphuric acid cave in Central Sicily
2012
Description of the sulphuric acid cave in Sicily (see pdf attached)
Atmospheric turbidity and its spectral extinction
1955
The indices of the wavelength dependency of the haze extinction which were currently determined from measurements of solar radiation and visibility at Mainz, show pronounced seasonal variations. The summer values are in general definitely higher than in winter. There is no connection with the scatter light types of the sky-light or with the meteorological situation.