RESUMEN
This study deals with the identification of the factors that affect pyrite oxidation in acid mine drainage conditions. For this scope, weathering experiments have been carried at laboratory scale based on the design of experiments methodology to evaluate the effect of factors such as major ion concentrations, crystal size, and humic acids presence over the amount of elemental sulfur produced due to the involved weathering reactions. In particular, metal and anionic concentrations in solution were quantified by inductively coupled plasma-atomic emission spectroscopy and ion-chromatography techniques, respectively, whereas the amount of elemental sulfur was quantified with a high-performance liquid chromatography with diode-array detection technique after proper extraction procedure. A partial least squares regression was calculated to establish a quantitative relationship between the considered factors and the amount of elemental sulfur. After evaluation of the model, ferric iron, crystal size and the presence of humic acids were identified as the relevant factors for pyrite oxidation under acidic conditions. In addition, the surface of the samples was characterized by Raman imaging spectroscopy and subsequently analyzed by explorative hyperspectral analysis methods to assess the spatial distribution of the elemental sulfur as the main weathering product, resulting in a homogenous distribution.
RESUMEN
Marine accumulations of terrigenous sediment are widely assumed to accurately record climatic- and tectonic-controlled mountain denudation and play an important role in understanding late Cenozoic mountain uplift and global cooling. Underpinning this is the assumption that the majority of sediment eroded from hinterland orogenic belts is transported to and ultimately stored in marine basins with little lag between erosion and deposition. Here we use a detailed and multi-technique sedimentary provenance dataset from the Yellow River to show that substantial amounts of sediment eroded from Northeast Tibet and carried by the river's upper reach are stored in the Chinese Loess Plateau and the western Mu Us desert. This finding revises our understanding of the origin of the Chinese Loess Plateau and provides a potential solution for mismatches between late Cenozoic terrestrial sedimentation and marine geochemistry records, as well as between global CO2 and erosion records.
RESUMEN
Raman spectroscopy represents a new way to obtain detailed comprehensive information on heavy-mineral assemblages. In this work are presented several examples from major Alpine (Po River) and Himalayan (Ganga and Brahmaputra Rivers) fluvio-deltaic sands. Our attention was focused on the chemical properties of garnet, which is a widespread mineral in orogenic sediments, easy to be identified, and relatively stable during both equatorial weathering and intrastratal dissolution. Garnet grains were studied in different samples representative of various depositional environments (fluvial bar, fluvial levee, shoreface, beach berm, eolian dune), in order to investigate specifically the hydraulic behaviour of grains with different density in different hydrodynamic conditions. Raman spectra and semi-quantitative analysis of Raman shifts allowed us to rapidly determine the distribution of garnet types in each sample in order to obtain chemical composition, to calculate the density of each garnet, and finally to infer their respective provenance. This manuscript presents one possible application of the "MIRAGEM" method described by Bersani et al. in this volume. References, data sets and details on the analytical routine are widely explained in the above mentioned work.