Palynological age constraint of Les Vilelles unit, Catalan Coastal Chain, Spain

Les Vilelles unit is a detrital sequence exposed at the southwestern margin of the Catalan Coastal Chain (CCC), NE Spain, below the Carboniferous turbiditic series. Based on the palynological content, the age of this unit was initially assigned to the Middle-Late Devonian (Eifelian to Famennian). Additional radiolarian and conodont findings were considered to be Early–Middle Mississippian (Tournaisian to early Visean). To clarify this age discrepancy a new and more comprehensive palynostratigraphic analysis has been conducted in the upper part of the section representative of Les Vilelles unit. This has provided an assemblage of miospores, acritarchs, prasinophyta phycomata and chitinozoans that can be confidently assigned to a latest Frasnian interval, in contact with the Frasnian–Famennian boundary. Therefore, the present analysis refines the Middle–Late Devonian age formerly assigned, establishes a latest Frasnian age for the top of the unit, and provides new insights to the better understanding of the unconformity and hiatus separating the pre-Carboniferous and Carboniferous CCC series in the Priorat Massif. The study also includes a systematic section with the description of three newly established miospore species: Dibolisporites coniugatum, Dibolisporites prioratum and Rugospora spinosa

Palynological age constraint of Les Vilelles unit, Catalan Coastal Chain, Spain

Les Vilelles unit is a detrital sequence exposed at the southwestern margin of the Catalan Coastal Chain (CCC), NE Spain, below the Carboniferous turbiditic series. Based on the palynological content, the age of this unit was initially assigned to the Middle-Late Devonian (Eifelian to Famennian). Additional radiolarian and conodont findings were considered to be Early–Middle Mississippian (Tournaisian to early Visean). To clarify this age discrepancy a new and more comprehensive palynostratigraphic analysis has been conducted in the upper part of the section representative of Les Vilelles unit. This has provided an assemblage of miospores, acritarchs, prasinophyta phycomata and chitinozoans that can be confidently assigned to a latest Frasnian interval, in contact with the Frasnian–Famennian boundary. Therefore, the present analysis refines the Middle–Late Devonian age formerly assigned, establishes a latest Frasnian age for the top of the unit, and provides new insights to the better understanding of the unconformity and hiatus separating the pre-Carboniferous and Carboniferous CCC series in the Priorat Massif. The study also includes a systematic section with the description of three newly established miospore species: Dibolisporites coniugatum, Dibolisporites prioratum and Rugospora spinosa

Stable isotope geochemistry of the Ulldemolins Pb-Zn-Cu deposit (SW Catalonian Coastal Ranges, Spain)

The Pb-Zn-Cu deposit of Ulldemolins occurs within the Carboniferous sedimentary series of the southernmost Catalonian Coastal Ranges. It consists of sulphide-bearing calc-silicate assemblages, with epidote, Ca-amphiboles and Ca-garnet, which develop selectively along a dolomicrite bed near the contact with a granite porphyry. Two mineralisation styles can be differentiated: a) banded and b) irregular. Fluid inclusions and stable isotope compositions of sulphur in sulphides (sphalerite, galena and chalcopyrite) and carbon and oxygen in carbonates (calcite and dolomite) were studied in order to constrain the genesis and the source of mineralizing fluids. Fluid inclusions in sphalerite and calcite are aqueous, liquid+vapour and have a salinity between 1.2 and 7.2 wt% NaCl eq. and homogenization temperatures in the range of 273º to 368ºC. The δ34S(V-CDT) values in the banded mineralisation are mostly between –1.5 and +2.1‰, and those from the irregular mineralisation are between –1.1 and +20.5‰. These δ34S values of the banded mineralisation are in agreement with a magmatic origin of sulphur. In addition, the δ18O(SMOW) values of hydrothermal calcite, from +6.9 to +12.5‰, are consistent with a magmatic origin of the fluids that formed the banded ore deposit. Later, a new input of fluids interacted with the previously formed mineral assemblages and modified part of the deposit, leading locally to an irregular skarn mineralisation

Scheelite bearing quartz veins from Poblet (Catalonian Coastal Ranges): Characterisation of fluid inclussions and genetic model

Scheelite-bearing quartz veins from Poblet, trending in a NE-SW direction, are hosted by calcic granitoids of Late Hercynian age in the southern part of the Catalonian Coast Range. Fluid inclusions from quartz and scheelite have been characterized using microthermometry, Raman microspectrometry and Scanning Electron Microscopy. Except for type I inclusions (not observed in scheelite), similar inclusions have been observed in both minerals. One recognizes, in order of formation : Type I inclusions containing brine, daughter phases (halite, sylvite and sometimes iron chloride) and incidentally trapped minerals (ankerite, siderite, muscovite, K-felspar and unidentified species). Type II(L) inclusions have a low salinity (1 to 6 % eq. NaCl) and homogenize in the liquid phase in the range of 300-400 °C or under critical conditions near 400 °C. Type II(V) are low density, CO2-poor aqueous inclusions, homogenizing in the gas phase in the range of 350-420 °C. Type II(V') have higher CO2 contents. Type II inclusions appear as samples of an initially hypercritical fluid, trapped at different stages of its evolutions towards two subcritical fluids. Type III inclusions indicate later circulation of a colder, low-salinity solution (Th : 150 to 300 °C ; salinity : 0 to 3.5 % NaCl wt %). Abundant iron contents in type I inclusions suggest some interaction at elevated temperature (400 to 600°C) with a biotite granite (Whitney et al., 1985). P-T conditions compatible with measurements performed on type II inclusions are about 400 °C and 0.8 kbar, in a range similar to that determined for the Djbel Aouam occurrence in Hercynian Morocco (Cheilletz, 1984). Equivalent conditions have been postulated for scheelite precipitation at Poblet

Nucleon Decay Searches with large Liquid Argon TPC Detectors at Shallow Depths: atmospheric neutrinos and cosmogenic backgrounds

Grand Unification of the strong, weak and electromagnetic interactions into a single unified gauge group is an extremely appealing idea which has been vigorously pursued theoretically and experimentally for many years. The detection of proton or bound-neutron decays would represent its most direct experimental evidence. In this context, we studied the physics potentialities of very large underground Liquid Argon Time Projection Chambers (LAr TPC). We carried out a detailed simulation of signal efficiency and background sources, including atmospheric neutrinos and cosmogenic backgrounds. We point out that a liquid Argon TPC, offering good granularity and energy resolution, low particle detection threshold, and excellent background discrimination, should yield very good signal over background ratios in many possible decay modes, allowing to reach partial lifetime sensitivities in the range of 1034−1035 years with exposures up to 1000 kton×year, often in quasi-background-free conditions optimal for discoveries at the few events level, corresponding to atmospheric neutrino background rejections of the order of 105. Multi-prong decay modes like e.g. p→μ−π+K+ or p→e+π+π− and channels involving kaons like e.g. p→K+ν¯, p→e+K0 and p→μ+K0 are particularly suitable, since liquid Argon imaging (...)This work was in part supported by ETH and the Swiss National Foundation. AB, AJM and SN have been supported by CICYT Grants FPA-2002-01835 and FPA-2005-07605-C02-01. SN acknowledges support from the Ramon y Cajal Programme. We thank P. Sala for help with FLUKA while she was an ETH employee

Consenso colombiano de atención, diagnóstico y manejo de la infección por SARS-COV-2/COVID-19 en establecimientos de atención de la salud Recomendaciones basadas en consenso de expertos e informadas en la evidencia

The “Asociación Colombiana de Infectología” (ACIN) and the “Instituto de Evaluación de Nuevas Tecnologías de la Salud” (IETS) created a task force to develop recommendations for Covid 19 health care diagnosis, management and treatment informed, and based, on evidence. Theses reccomendations are addressed to the health personnel on the Colombian context of health services. © 2020 Asociacion Colombiana de Infectologia. All rights reserved

Sulphur isotope composition of silurian shale-hosted PGE-Ag-Au- Zn-Cu mineralisations of the Prades Mountains (Catalonia, Spain)

Several Silurian metamorphosed shale-hosted sulphide occurrences have been studied in the Prades Mountains, southern part of the Coastal Catalonian Ranges. Most of the sulphides are found as stratiform or shale-disseminated occurrences. Pyrrhotite is the most abundant sulphide mineral. Chalcopyrite and arsenopyrite are less common. Gold, Pd-bearing lollingite (partly replaced by arsenopyrite), sperrylite, hessite, clausthalite, altaite, galena, sphalerite, molybdenite, scheelite, and V-Cr oxides and silicates are minor components. Sulphur isotopic analyses were made on three outcrops (Roca de portent, Coma Fosca and Sant Miquel) and in the Silurian black shales of the Sant Bernat series, in order to determine the origin of the sulphur which formed these deposits. The Coma Fosca and Sant Miquel outcrops yield a narrow range of delta(34)S values (-11.3 to -4.6parts per thousand), whereas the Roca de Ponent and Sant Bernat series have a wider range (- 19.9 to 7.6%. in pyrrhotite, and up to + 36parts per thousand. in pyrite from the top of the Sant Bernat series). In the Roca de Portent outcrop the delta(34)S values decrease with increasing stratigraphic height. All the deposits have a mean delta(34)S composition close to -9parts per thousand. Annealing of pyrrhotite took place during the Hercynian metamorphism. Later, during the retrograde metamorphism, pyrite replaced pyrrhotite, and arsenopyrite replaced lollingite. Large-scale compositional inhomogeneities survived metamorphism (from pyroxene to amphibolite facies). A hydrothermal source of S has been postulated for the Coma Fosca and Sant Miquel outcrops. Sulphur in these deposits is from leaching of sulphides from the underlying rocks. In the Roca de Portent outcrop and in the Sant Bernat series, sulphur was derived from a hydrothermal source and from biogenic reduction of seawater sulphate. The contribution of the latter source increased with time. Biogenic reduction of seawater sulphide in a closed or semi-closed system for sulphate is considered responsible of the high delta(34)S values of pyrite from the uppermost part of the Sant Bernal series. Based on textural and isotopic evidence, we propose an exhalative origin for the precious metals, cogenetic with the stratiform sulphides

Geology, fluid inclusion and sulphur isotope characteristics of the El Cobre VHMS deposit, Southern Cuba

The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc. The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies, three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite, chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides from the stratabound mineralisation display ∂34S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur isotope zonation of about 2‰ usually, ∂34S values increase towards the rims. Sulphate sulphur has ∂34S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids

Isotopic evidence for biogenic precipitation as a principal mineralization process in coastal gasohydrothermal vents, Punta Mita, Mexico

Mineral deposition in shallow submarine gasohydrothermal vents may be triggered by microbial activity according to isotopic data obtained for sulphides and carbonates. Submarine gasohydrothermal vents in Punta Mita, at the western coast of Mexico, discharge a mixture of water and gas (mainly nitrogen and methane) at a temperature of 85 °C. Algal mats cover the areas where thermal fluids are being discharged. The main minerals deposited due to the hydrothermal activity are calcite and pyrite. Moreover, barite, carbonate-hydroxylapatite, cinnabar and Tl-sulphide are actively depositing. Calcite is deposited as fine-scale laminated tufa-like aggregates with interlayered pyrite in thin layers. Cinnabar and Tl-sulphide are present within pyrite layers. In Punta Mita vents, almost all δ34S values measured in pyrite range from − 13.3‰ to − 4.9‰, and δ13C values in calcite vary from 0‰ to − 39‰. These results agree with the hypothesis that calcite and pyrite were deposited by mediation of microbial activity, caused by the coupled reactions of vent methane oxidation and marine sulphate reduction, and suggest that biomineralization prevails over abiotic precipitation processes in such coastal gasohydrothermal vents. The 14C ages obtained from carbonates, of approximately 40,000 years, may represent the minimum age for the methane that generates the carbonates in the vents

Genesis of sulfide-rich chromite ores by the interaction between chromitite and pegmatitic olivine-norite dikes in the Potosi Mine (Moa-Baracoa ophiolitic massif, eastern Cuba)

The Potosi Mine is located in the Moa-Baracoa massif in the easternmost part of the Cuban Ophiolitic Belt. Chromite mineralization occurs within the mantle-crust transition zone. Two events of magma intrusion overprint the chromitite bodies: one gave rise to the crystallization of pegmatitic olivine- norite dikes. and the other produced pegmatitic gabbro dikes. Sulfide-poor chromite ores, brecciated chromite ores, and sulfide-rich chromite ores can be distinguished in the different chromitite bodies. Sulfide-poor ores represent more than 80 vol% of the chromitites. This type occurs far from the zones intruded by pegmatitic gabbro dikes and shows petrographic and chemical features similar to other chromitite bodies described in the Moa-Baracoa massif. Brecciated chromite ores occur within pegmatitic gabbro dikes. In this type, chromite crystals occur included within chromian diopside and plagioclase. These silicates often contain droplet-like sulfide aggregates. Sulfide-rich ores are spatially associated to the contacts between sulfide-poor chromite and pegmatitic olivine- norite dikes. These ores mainly consist of recrystallized (coarse) chromite with interstitial pyrrhotite. pentlandite, cubanite. and chalcopyrite. Chromite from sulfiderich ores exhibits TiO<sub>2</sub>, FeO, V<sub>2</sub>O<sub>3</sub>, MnO, and especially, Fe<sub>2</sub>O<sub>3</sub> contents, higher than those of chromite from brecciated ores and much higher than those of chromite from sulfide-poor ores. The sulfide-rich ores are PGE-rich (up to 1,113 ppb of total PGE), and show nearly flat chondrite-normalized PGE patterns, slightly above 0.1 times chondritic values. Mineralogical and chemical data indicate that the chromite ores of the Potosi Mine were modified by the intrusions of olivine-norite and gabbro dikes. The interaction between preexisting sulfide-poor chromite ores and the intruding volatile-rich silicate melts produced strong brecciation, partial dissolution, and recrystallization (coarsening) of chromite. The sulfide assemblage formed by fractionation of the immiscible sulfide melt segregated from the volatile-rich silicate melt that generated the pegmatitic olivine-norite. The segregation of the sulfide melt can be interpreted as the consequence of chemical interaction between intruding melts and the host chromite. The variable extent of this interaction produced chromite ores with variable sulfide ratios. The magmatic nature of the sulfide mineralization is supported by sulfur isotope data, which range from -0.4 to +0.9 parts per thousand. Sulfide melt collected incompatible PGE (Rh, Pt, Pd) to produce the typical flat chondrite-normalized pattern of sulfide-rich chromite ores