Meteorological information in GPS-RO reflected signals

Vertical profiles of the atmosphere can be obtained globally with the radio-occultation technique. However, the lowest layers of the atmosphere are less accurately extracted. A good description of these layers is important for the good performance of Numerical Weather Prediction (NWP) systems, and an improvement of the observational data available for the low troposphere would thus be of great interest for data assimilation. We outline here how supplemental meteorological information close to the surface can be extracted whenever reflected signals are available. We separate the reflected signal through a radioholographic filter, and we interpret it with a ray tracing procedure, analyzing the trajectories of the electromagnetic waves over a 3-D field of refractive index. A perturbation approach is then used to perform an inversion, identifying the relevant contribution of the lowest layers of the atmosphere to the properties of the reflected signal, and extracting some supplemental information to the solution of the inversion of the direct propagation signals. It is found that there is a significant amount of useful information in the reflected signal, which is sufficient to extract a stand-alone profile of the low atmosphere, with a precision of approximately 0.1 %. The methodology is applied to one reflection case

GeoquÍmica de los elementos traza y tierras raras en caolines hidrotermales

Mina Equivocada se encuentra ubicada a 32 Km al este de la localidad de Los Menucos en el Dpto. 9 de Julio en la Prov. de Río Negro. Se trata de una explotación de caolín en la que los trabajos actuales se sitúan a unos 250 metros al NW del antiguo rajo. La mena es usada en la industria cerámica. Con el fin de avanzar en el conocimiento de la génesis de este depósito, se analizó el contenido de elementos mayoritarios, minoritarios y traza en muestras de dos perfiles levantados en la nueva cantera de Mina Equivocada y se compararon con los resultados de muestras de la labor antigua, estudiadas por Hayase et al. (1970) y Maiza (1972). Es de destacar que Maiza et al. (1981), en un trabajo detallado sobre la mineralogía del depósito descubrieron una zona muy rica en natroalunita. A partir de la mineralogía, textura y estructura del yacimiento, estos autores sugirieron un origen hipogénico del caolín

Tourmaline records the hydrothermal events related to Zn-Pb mineralization around the Murguía diapir (Basque Cantabrian Basin, N Spain)

The chemical composition of tourmaline has been used as a host environment register as well as a potential exploration tool for mineral deposits. In this study, the textural and chemical composition of tourmalines associated with Zn-Pb mineralizations around the Murguía diapir (Basque Cantabrian Basin, N Spain) are examined to verify if they record the mineralizing events in the area. Petrographically, tourmalines have been differentiated between inherited and authigenic. Colorless authigenic tourmalines are present as halos partially around green and pleochroic detrital grains or as individual crystals. Inherited and authigenic tourmalines are also chemically distinct. Authigenic tourmalines show different X-site occupancies, a Mg/(Mg+Fe) ratio above 0.77, and are aluminum rich and plot to the right of the povondraite-oxidravite join, above the schorl-dravite join. Inherited tourmalines plot within the alkaline (Na+K) group field, and have a Mg/(Mg+Fe) ratio below 0.77. These data suggest that authigenic tourmalines grew under reducing conditions, compatible with the hydrothermal event responsible for the ore deposition and caprock formation during the diapir ascent

Reactivity of dolomitizing fluids and Mg source evaluation of fault-controlled dolomitization at the Benicàssim outcrop analogue (Maestrat Basin, E Spain)

Peer reviewedPostprin

Origen de la alunita y la natroalunita del depósito de caolín de Mina Equivocada (Prov. de Río Negro, Argentina)

The origin of alunite and natroalunite from a kaolin deposit (Equivocada Mine, Rio Negro Province) has been studied. Chemical analysis showed that alunite is K<sub>0.89</sub> and natroalunite Na<sub>0.97</sub>, in agreement with X ray diffraction data. The high contents of minor elements in alunite, especially Ba and Sr are compatible with a hydrothermal origin in contrast to natroalunite whose very low values suggest a secondary origin. Alunite has a δ<sup>34<sup/>S = +15.9‰ and a δ<sup>18</sup>O = +12.9‰, while in natroalunite these values are -5.8‰ and +19.0‰ respectively. δ<sup>34<sup/>S values suggest that alunite formed from a hypogenic process of hydrothermal origin whereas natroalunite is probably related to a supergen origin. The occurrence of alunite in veins crosscutting the other minerals, indicates that it was the last mineral to crystallize

Geology of the Cerro Quema Au-Cu deposit (Azuero Peninsula, Panama)

The Cerro Quema district, located on the Azuero Peninsula, Panama, is part of a large regional hydrothermal system controlled by regional faults striking broadly E-W, developed within the Río Quema Formation. This formation is composed of volcanic, sedimentary and volcano-sedimentary rocks indicating a submarine depositional environment, corresponding to the fore-arc basin of a Cretaceous–Paleogene volcanic arc. The structures observed in the area and their tectono-stratigraphic relationship with the surrounding formations suggest a compressive and/or transpressive tectonic regime, at least during Late Cretaceous–Oligocene times. The igneous rocks of the Río Quema Formation plot within the calc-alkaline field with trace and rare earth element (REE) patterns of volcanic arc affinity. This volcanic arc developed on the Caribbean large igneous province during subduction of the Farallon Plate. Mineralization consists of disseminations of pyrite and enargite as well as a stockwork of pyrite and barite with minor sphalerite, galena and chalcopyrite, hosted by a subaqueous dacitic lava dome of the Río Quema Formation. Gold is present as submicroscopic grains and associated with pyrite as invisible gold. A hydrothermal alteration pattern with a core of advanced argillic alteration (vuggy silica with alunite, dickite, pyrite and enargite) and an outer zone of argillic alteration (kaolinite, smectite and illite) has been observed. Supergene oxidation overprinted the hydrothermal alteration resulting in a thick cap of residual silica and iron oxides. The ore minerals, the alteration pattern and the tectono-volcanic environment of Cerro Quema are consistent with a high sulfidation epithermal system developed in the Azuero peninsula during pre-Oligocene time

Petrography and geochemistry of fault-controlled hydrothermal dolomites in the Riópar area (Prebetic Zone, SE Spain)

The present paper reports the first detailed petrographical and geochemical studies of hydrothermal dolomites related to MVT Zn-(Fe-Pb) deposits in the Riópar area (Mesozoic Prebetic Basin, SE Spain), constraining the nature, origin and evolution of dolomitizing and ore-forming fluids. Mapping and stratigraphic studies revealed two stratabound dolostone geobodies connected by other patchy bodies, which replace carbonate units of Upper Jurassic to Lower Cretaceous ages. These dolostones are associated to the W-E trending San Jorge fault, indicating a main tectonic control for fluid flow. Seven different dolomite types were identified: i) matrix-replacive planar-s (ReD-I); ii) matrix-replacive planar-e (ReD-II); iii) planar-e sucrosic cement (SuD); iv) non-planar grey saddle dolomite cement (SaD-I) pre-dating Zn-(Fe-Pb) sulfides; v) non-planar milky to pinkish saddle dolomite cement (SaD-II) post-dating Zn-(Fe-Pb) ores; vi) ore-replacive planar-e porphyrotopic (PoD); and vii) planar-s cloudy cement (CeD). Meteoric calcite types were also recognized. The different dolomite types are isotopically characterized by: i) depleted δ18O (from +25.1 to +27.6¿ V-SMOW) and δ13C (from -2.3 to +0.9¿ V-PDB) values compared to Upper Jurassic to Lower Cretaceous limestone signature (δ18O: +27.6 to +30.9¿ V-SMOW; δ13C: +0.5 to +3.2¿ V-PDB); and ii) 87Sr/86Sr ratios for the main dolomitization phases (ReD and SuD: 0.70736-0.70773) close to the Jurassic and Cretaceous carbonate values (0.70723-0.70731) whereas more radiogenic values (0.70741-0.70830) for saddle dolomites (SaD) related to the Zn-(Fe-Pb) sulfide mineralization prevailed after fluid interaction with Rb-bearing minerals. Microthermometrical studies on two-phase liquid and vapor fluid inclusion populations in planar and non-planar dolomites and sphalerite show homogenization temperatures between 150 and 250ºC. These data indicate that both planar and non-planar dolomite textures formed at high-temperatures under hydrothermal conditions in deep-burial diagenetic environments. The main dolomitizing phase (ReD-I/ReD-II and SaD-I) shows low to moderate fluid inclusions salinity (5 to 14 wt.% eq. NaCl), whereas the dolomitization related to ore precipitation (sphalerite and SaD-II) spreads to higher salinity values (5 to 25 wt.% eq. NaCl). These data may respond to a mixing between a low salinity fluid (fluid A, less than 5 wt.% eq. NaCl) and a more saline brine (fluid B, more than 25 wt.% eq. NaCl) at different fluid proportions

Sulfur and lead isotope systematics: Implications for the genesis of the Riópar Zn-(Fe-Pb) carbonate-hosted deposit (Prebetic Zone, SE Spain)

The Zn-(Fe-Pb) deposits of the Riópar area (Prebetic Zone, SE Spain) are hosted by dolostones that replace Berriasian to Valanginian (Upper Jurassic-Lower Cretaceous) limestones. Mineralization consists of hypogene sphalerite, marcasite and galena, and supergene calamine zones. The hypogene ores are associated with a saddle dolomite gangue. The ore bodies occur as discordant and stratiform lenses, ore-cemented breccias, cm- to mm-wide veins and veinlets, disseminations and stylolite porosity filling within the host dolomites. The main ore controls include stratigraphy and/or lithology, tectonics (faults, fractures and breccias) and availability of metals and sulfur. The morphologies and epigenetic character of the hypogene ore bodies are consistent with the classification of this mineralization as a Mississippi Valley-type (MVT) deposit. The Ga/Ge geothermometer in sphalerite yielded a temperature range of 194-252ºC, which represents the temperature of the source region of the ore solution. This value is comparable to the temperature obtained in the ore deposition site, 159±15ºC from the Δ34S geothermometer in sphalerite galena pairs. This similitude points to a hydrothermal fluid that did not cool down significantly during flow from the fluid reservoir area to the precipitation site. δ34S values of base-metal sulfides (-7.5 to +3.5 ¿) are consistent with thermochemical reduction of Triassic sulfate (seawater and/or derived from dissolution of evaporites) by interaction with organic compounds (e.g., hydrocarbons, methane), which reduced sulfate to sulfide in the deposition site. The lead isotope ratios (206Pb/204Pb = 18.736-18.762; 207Pb/204Pb = 15.629-15.660; 208Pb/204Pb = 38.496-38.595) of galena suggest that Pb, and probably other metals as Zn, is derived from continental crustal rocks. On the other hand, these relations points to an unique metal source probably derived from the Paleozoic basement rocks. The relationship between bedding-parallel stylolites, dolomitization, sulfide precipitation and Alpine tectonic affecting the MVT ore, suggests a relative timing range for the mineralization in the Riópar area of 95 to 20 Ma (Upper Cretaceous-Tertiary). The sulfide mineralization and the associated dolomitization are thus explained by the contribution of two fluids that mixed in different proportions during dolomitization and mineralization: i) a fluid probably derived from Cretaceous seawater saturating Mesozoic sediments (Fluid A), characterized by being dilute and initially low temperature, which should have contained organic rich compounds in the ore deposition site (e.g., hydrocarbons and CH4 dissolved gas); and ii) a high salinity hydrothermal brine (Fluid B) rich in both metals and sulfate, circulated through the Paleozoic basement. During the pre-ore dolomitizing stage the fluid phase was dominated by the diluted fluid (Fluid A > Fluid B), whereas in a later fluid pulse, the proportion of the high salinity fluid increased (Fluid A < Fluid B) which allowed sulfide precipitation. MVT exploration in the Prebetic Zone should focus towards the SW of the Riópar mines, in the vicinity of the Alto Guadalquivir-San Jorge fault