Search results for "Mineral"

Characterisation of the magmatic signature in gas emissions from Turrialba Volcano, Costa Rica

2014

The equilibrium composition of volcanic gases with their magma is often overprinted by interaction with a shallow hydrothermal system. Identifying the magmatic signature of volcanic gases is critical to relate their composition to properties of the magma (temperature, fO2, gas-melt segregation depth). We report measurements of the chemical composition and flux of the major gas species emitted from Turrialba Volcano during March 2013. Measurements were made of two vents in the summit region, one of which opened in 2010 and the other in 2012. We determined an average SO2 flux of 5.2 ± 1.9 kg s-1 using scanning ultraviolet spectroscopy, and molar proportions of H2O, CO2, SO2, HCl, CO and H2 ga…

Reply on Comment by Longinelli (2013) on a revised phosphate-water fractionation equation.

2013

Longinelli (2013) contests the new phosphate–water oxygenisotopefractionation equationpresentedforfishteethin Puceatetal. (2010), and more specifically the pooling of the data of Puceatet al. (2010) with those of Longinelli and Nuti (1973b),performedto better constrain the regression parameters of the fractionationequation.Firstly, Longinelli (2013) criticizes that only 17 of the 24 datareported in Longinelli and Nuti (1973b) appear in Fig. 3. Doubtwas cast on whether the fish data of Longinelli and Nuti (1973b)were mixed with those of marine molluscs from Longinelli andNuti (1973a). Only oxygen isotope ratios of fish (Longinelli andNuti, 1973b) have been taken into account in Puceat et al. (20…

Volcanic plume and bomb field masses from thermal infrared camera imagery

2013

International audience; Masses erupted during normal explosions at Stromboli volcano (Italy) are notoriously difficult to measure. We present a method that uses thermal infrared video for cooling bomb fields to obtain the total power emitted by all hot particles emitted during an explosion. A given mass of magma (M) will emit a finite amount of thermal power, defined by M cp(Te−T0), cp and Te being magma specific heat capacity and temperature, and T0 being ambient temperature. We use this relation to convert the total power emitted by the bomb field to the mass required to generate that power. To do this we extract power flux curves for the field and integrate this through time to obtain to…

Occurrence of fossil organic matter in modern environments: optical, geochemical and isotopic evidence

2011

International audience; This study relates to the input and fate of fossil organic matter (FOM) in the modern environment, and focuses on two experimental watersheds overlying Jurassic marls: Le Laval and Le Brusquet (1 km(2) in area), located near Digne, Alpes-de-Haute-Provence, France. Considering that FOM delivery is mainly a result of different processes affecting sedimentary rocks [(bio)chemical and mechanical weathering], samples from different pools were collected: bedrocks, weathering profiles, soils and riverine particles. The samples were examined using complementary techniques: optical (palynofacies methods), geochemical (Rock-Eval 6 pyrolysis, C/N ratio), molecular (gas chromato…

Chlorine Partitioning Between a Basaltic Melt and H2O-CO2 Fluids at Mount Etna

2009

Partitioning experiments between a basaltic melt from Mt. Etna and a low-density hydrous fluid or vapor containing H(2)O or H(2)O-CO(2) were performed at 1200-1260 degrees C, at pressures between 1 and 200 MPa, either near the nickel-nickel oxide (NNO) buffer or at two log units above it (NNO + 2), and with different chloride concentrations. Most of the experiments were done at chloride-brine-undersaturated conditions, although at the highest Cl concentrations explored brine saturation might have been reached. The average partition coefficients (D(Cl)(fluid/melt)) over the range of Cl concentrations were derived on a weight basis by plotting the calculated concentrations of Cl in the fluid …

Growth of stylolite teeth patterns depending on normal stress and finite compaction

2007

Abstract Stylolites are spectacular rough dissolution surfaces that are found in many rock types. They are formed during a slow irreversible deformation in sedimentary rocks and therefore participate to the dissipation of tectonic stresses in the Earth's upper crust. Despite many studies, their genesis is still debated, particularly the time scales of their formation and the relationship between this time and their morphology. We developed a new discrete simulation technique to explore the dynamic growth of the stylolite roughness, starting from an initially flat dissolution surface. We demonstrate that the typical steep stylolite teeth geometry can accurately be modelled and reproduce natu…

Modelling of stylolite geometries and stress scaling

2012

International audience; In this contribution we present numerical simulations of stylolite growth to decipher the effects of initial rock heterogeneity and stress on their morphology. We show that stylolite growth in a rock with a uniform grain size produces different patterns than stylolite growth in a rock with a bimodal grain size distribution. Strong pinning of large heterogeneities produce stylolite structures that are dominated by pronounced teeth, whereas a uniform grain size leads to spikes and a roughness that shows variable wavelengths. We compare the simulated stylolites with natural examples and show that the model can reproduce the real structures. In addition we show that stro…

Influence of microporosity distribution on the mechanical behavior of oolithic carbonate rocks.

2015

Abstract The mechanical behavior of oolithic carbonate rocks was investigated for selected rocks with two different microstructural attributes: uniform (UP) and rimmed (RP) distribution of microporosity within ooids. These oolithic carbonate rocks are from the Oolithe Blanche formation, a deep saline aquifer in the Paris Basin, and a possible target for CO2 sequestration and geothermal production. Samples of similar physical properties (porosity, grain diameter, cement content) but different microporosity textures were deformed under triaxial configuration, in water saturated conditions, at 28 MPa of confining pressure, 5 MPa of pore pressure and at a temperature of 55 °C. During the experi…

Trace element behaviour in seawater during Etna's pyroclastic activity in 2001: Concurrent effects of nutrients and formation of alteration minerals

2010

volcanic ash ; trace element leaching ; kinetic experiments ; chlorophyll-alpha; International audience; The eruption of Etna in Sicily on 13 July 2001 marked the most intense activity of the volcano in the last 300 years. The eruption occurred while the oceanographic cruise ANSIC 01 was being conducted to the east of Sicily, presenting a unique opportunity for the investigation of the chemical effects on the marine system during a period of significant (similar to 1 g m(-2)) ash deposition. Comparison of trace element data with measured concentrations from the oceanographic cruise JUVENILE 99, carried out two years before, indicates large enrichments of V. Cr, Mn, Fe, Co, Cu and Pb. We att…

2017

Abstract. Mollusks record valuable information in their hard parts that reflect ambient environmental conditions. For this reason, shells can serve as excellent archives to reconstruct past climate and environmental variability. However, animal physiology and biomineralization, which are often poorly understood, can make the decoding of environmental signals a challenging task. Many of the routinely used shell-based proxies are sensitive to multiple different environmental and physiological variables. Therefore, the identification and interpretation of individual environmental signals (e.g., water temperature) often is particularly difficult. Additional proxies not influenced by multiple en…