46,730 research outputs found
Origin, ore forming fluid evolution and timing of the Logrosán Sn-(W) ore deposits (Central Iberian Zone, Spain)
The Logrosán Sn–(W) ore deposits in the metallogenic Sn–W province of the European Variscan Belt consist of endo- and exogranitic greisen-type and quartz–cassiterite veins associated with a S-type granite. Mineral characterization, fluid inclusion study, isotope geochemistry and Ar–Ar geochronology have been combined in order to reconstruct the conditions for Sn–(W) mineralization. The endo- and exogranitic mineralization must have been developed in a relatively long-lived system (~ 308–303 Ma), during or soon after the emplacement of the Logrosán related-granite (at ca. 308 Ma). The mineralizing fluids are characterized by complex aqueous and volatile (H2O–N2–CO2–CH4–NaCl) fluid inclusions. Microthermometry and Raman analyses indicate that fluid composition evolved from N2–CH4 to N2-rich, followed by CO2-rich fluids, with varying amounts of H2O. The presence of N2 and CH4 suggests the interaction with fluids derived from the nearby metasedimentary host rocks. A model of host-rock interaction, assimilation, and mixing of metamorphic and magmatic fluids, resulting in change of the redox conditions, is proposed for tin deposition. Later sulfide minerals were precipitated as a result of pressure and temperature release
Recommended from our members
Removal of lead from aqueous solutions by a poly(acrylic acid)/bentonite nanocomposite
Geological setting and genesis of stratabound barite deposits at Múzquiz, Coahuila in northeastern Mexico
Peer ReviewedPreprin
Synthesis, characterization and thermochemistry of synthetic Pb–As, Pb–Cu and Pb–Zn jarosites
The enthalpy of formation from the elements of well characterized Pb-As, Pb-Cu, and Pb-Zn synthetic jarosites, corresponding to chemical formulas (H3O)0.68±0.03Pb0.32±0.002Fe2.86±0.14(SO4)1.69±0.08(AsO4)0.31±0.02(OH)5.59±0.28(H2O)0.41±0.02, (H3O)0.67±0.03Pb0.33±0.02Fe2.71±0.14Cu0.25±0.01(SO4)2±0.00(OH)5.96±0.30(H2O)0.04±0.002 and (H3O)0.57±0.03Pb0.43±0.02Fe2.70±0.14Zn0.21±0.01(SO4)2±0.00(OH)5.95±0.30(H2O)0.05±0.002, was measured by high temperature oxide melt solution calorimetry and gave ΔH°f = -3691.2 ± 8.6 kJ/mol, ΔH°f = -3653.6 ± 8.2 kJ/mol, and ΔH°f = -3669.4 ± 8.4 kJ/mol, respectively. Using estimated entropies, the standard Gibbs free energy of formation from elements at 298 K ΔG°f of the three compounds were calculated to be -3164.8 ± 9.1 kJ/mol, -3131.4 ± 8.7 kJ/mol, and -3153.6 ± 8.9 kJ/mol, respectively. Based on these free energies, their logKsp values are -13.94 ± 1.89, -4.38 ± 1.81 and -3.75 ± 1.80, respectively. For this compounds, a log10{Pb2+} - pH diagram is presented. The diagram shows that the formation of Pb-As jarosite may decrease aqueous arsenic and lead concentrations to meet drinking water standards. The new thermodynamic data confirm that transformation of Pb-As jarosite to plumbojarosite is thermodynamically possible
NA61/SHINE facility at the CERN SPS: beams and detector system
NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multi-purpose
experimental facility to study hadron production in hadron-proton,
hadron-nucleus and nucleus-nucleus collisions at the CERN Super Proton
Synchrotron. It recorded the first physics data with hadron beams in 2009 and
with ion beams (secondary 7Be beams) in 2011.
NA61/SHINE has greatly profited from the long development of the CERN proton
and ion sources and the accelerator chain as well as the H2 beamline of the
CERN North Area. The latter has recently been modified to also serve as a
fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous
components of the NA61/SHINE set-up were inherited from its predecessors, in
particular, the last one, the NA49 experiment. Important new detectors and
upgrades of the legacy equipment were introduced by the NA61/SHINE
Collaboration.
This paper describes the state of the NA61/SHINE facility - the beams and the
detector system - before the CERN Long Shutdown I, which started in March 2013
Neutron-induced background in the CONUS experiment
CONUS is a novel experiment aiming at detecting elastic neutrino nucleus
scattering in the fully coherent regime using high-purity Germanium (Ge)
detectors and a reactor as antineutrino () source. The detector setup
is installed at the commercial nuclear power plant in Brokdorf, Germany, at a
very small distance to the reactor core in order to guarantee a high flux of
more than 10/(scm). For the experiment, a good
understanding of neutron-induced background events is required, as the neutron
recoil signals can mimic the predicted neutrino interactions. Especially
neutron-induced events correlated with the thermal power generation are
troublesome for CONUS. On-site measurements revealed the presence of a thermal
power correlated, highly thermalized neutron field with a fluence rate of
(74530)cmd. These neutrons that are produced by nuclear
fission inside the reactor core, are reduced by a factor of 10 on
their way to the CONUS shield. With a high-purity Ge detector without shield
the -ray background was examined including highly thermal power
correlated N decay products as well as -lines from neutron
capture. Using the measured neutron spectrum as input, it was shown, with the
help of Monte Carlo simulations, that the thermal power correlated field is
successfully mitigated by the installed CONUS shield. The reactor-induced
background contribution in the region of interest is exceeded by the expected
signal by at least one order of magnitude assuming a realistic ionization
quenching factor of 0.2.Comment: 28 pages, 28 figure
Content in the Context of 4D-Var Data Assimilation. II: Application to Global Ozone Assimilation
Data assimilation obtains improved estimates of the state of a physical system
by combining imperfect model results with sparse and noisy observations of reality.
Not all observations used in data assimilation are equally valuable. The ability to
characterize the usefulness of different data points is important for analyzing the
effectiveness of the assimilation system, for data pruning, and for the design of future
sensor systems.
In the companion paper [Sandu et al.(2011)] we derived an ensemble-based computational
procedure to estimate the information content of various observations in
the context of 4D-Var. Here we apply this methodology to quantify two information
metrics (the signal and degrees of freedom for signal) for satellite observations
used in a global chemical data assimilation problem with the GEOS-Chem chemical
transport model. The assimilation of a subset of data points characterized by the
highest information content, gives analyses that are comparable in quality with the
one obtained using the entire data set
Geochemistry and petrogenesis of volcanic rocks from Daimao Seamount (South China Sea) and their tectonic implications
The South China Sea (SCS) experienced three episodes of seafloor spreading and left three fossil spreading centers presently located at 18°N, 17°N and 15.5°N. Spreading ceased at these three locations during magnetic anomaly 10, 8, and 5c, respectively. Daimao Seamount (16.6. Ma) was formed 10. my after the cessation of the 17°N spreading center. Volcaniclastic rocks and shallow-water carbonate facies near the summit of Daimao Seamount provide key information on the seamount's geologic history. New major and trace element and Sr-Nd-Pb isotopic compositions of basaltic breccia clasts in the volcaniclastics suggest that Daimao and other SCS seamounts have typical ocean island basalt-like composition and possess a 'Dupal' isotopic signature. Our new analyses, combined with available data, indicate that the basaltic foundation of Daimao Seamount was formed through subaqueous explosive volcanic eruptions at 16.6. Ma. The seamount subsided rapidly (>. 0.12. mm/y) at first, allowing the deposition of shallow-water, coral-bearing carbonates around its summit and, then, at a slower rate (<. 0.12. mm/y). We propose that the parental magmas of SCS seamount lavas originated from the Hainan mantle plume. In contrast, lavas from contemporaneous seamounts in other marginal basins in the western Pacific are subduction-related
- …