Increased solubility of quartz following ferrous–ferric iron reactions
A knowledge of the solubility of quartz and silicates in natural waters is important to the understanding of many gelogical processes. Here we provide experimental data to support an earlier hypothesis1, that during the supergene enrichment of banded iron-formations, redox reactions involving iron result in a much more rapid dissolution of quartz than would be predicted from its known solubility in water. The process is relevant not only to iron ore genesis but also to the much wider field of chemical weathering— for example, to the genesis of laterites and soils from quartz-bearing rocks. In addition, the reactions may offer a mechanism by which quartz is pseudomorphed by iron oxides.
The Role of Water in Grain-Scale Deformation Within the Cove Fault Zone, South Central Pennsylvania
Charles M. Onasch, Advisor John R. Farver, Co-Advisor Fluids, and water in particular, play an integral role in deformation within the Earth’s crust over a wide range of physical conditions. At low temperatures ( 300 C), water-related chemical processes, such as diffusive mass transfer, advective mass transfer, and hydrolytic weakening dominate. In the transition between high and low temperature regimes, both mechanical and chemical processes operate and interact in complex ways. The Cove fault zone in south central Pennsylvania contains several mapscale blocks of quartz arenite, which display a wide range of brittle and ductile microstructures. Abundant evidence of fluids is present from mapto latticescales, including quartz precipitated in microveins, fluid inclusion planes, and zones of cataclasis, and the removal of quartz along dissolution surfaces. Three different aqueous fluids were identified based on the cathodoluminescence color of quartz precipitated by that fluid, and the homogenization (Th), last ice melting temperatures (Tm), and salt species from aqueous, two-phase fluid inclusions. Fourier Transform Infrared (FTIR) spectroscopy data indicate that a large amount of water has become incorporated in the lattice of deformed detrital grains, especially those in the proximity of fluid conduits (e.g., microveins). The fluids, based on the oxygen isotopic composition of the quartz precipitated, appear to
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.