Time and Observables in Unimodular General Relativity

A cosmological time variable is emerged from the hamiltonian formulation of unimodular theory of gravity to measure the evolution of dynamical observables in the theory. A set of constants of motion has been identified for the theory on the null hypersurfaces that its evolution is with respect to the volume clock introduced by the cosmological time variable.Comment: 16 page

La evolución metalogenética de la Zona de Ossa Morena

[EN] The Ossa-Morena Zone contains abundant ore deposits and showings for the most part formed during the Cadomian and the Variscan orogenic cycles, and the intermediate rifting and stable platform stages. Despite major tectonic dismembering during Variscan rejuvenation which masked older geologic features, Cadomian mineralisation is comparable to active arc-related ore deposits, i.e., volcanic-hosted massive sulphides, barite and Zn-Pb SEDEX deposits and some minor porphyry copper-like mineralisation. Post-Cadomian Early Paleozoic ore deposits are scarce. Most are iron oxide stratabound deposits probably related to the Early Cambrian rifting volcanism. Variscan tectonic, metamorphic and magmatic activity led to the formation of very different types of mineralisation, including syn-metamorphic and perigranitic base metal-bearing veins, small volcanic-hosted polymetallic massive sulphide deposits, iron oxide replacements and skarns, magnetite and Cu-Ni magmatic ore bodies and Sn-W veins and replacements. Orogenic Au mineralisation is of imprecise age and could be either Variscan or Cadomian. Relatively low temperature Late Variscan hydrothermal activity is believed to be responsible for the formation of abundant Pb-Zn- and Cu-dominated lodes in different geological settings, Hg replacements and uranium-bearing veins. As a whole, the diverse Variscan metallogenesis of the OMZ is interpreted as a vertical continuum in a continental crust undergoing transpressional strain. During the Variscan cycle, the OMZ first was an active continental margin –and magmatic arc-, that evolved into a collided zone after amalgamation to the South Portuguese Zone terrane. Furthermore, the recently discovered large mafic-ultramafic body set in the middle crust, probably played a key role in Variscan metallogenesis.[ES] La Zona de Ossa Morena se caracteriza por la abundancia de depósitos e indicios minerales pertenecientes a los ciclos orogénicos Cadomiense y Varíscico, así como a las etapas intermedias de rifting y plataforma estable. A pesar del desmembramiento producido por la orogénesis Varíscica, que enmascara los rasgos geológicos más antiguos, la mineralización Cadomiense reúne muchas de las características de las ligadas a arcos magmáticos en bordes de placa, tales como la formación de sulfuros masivos asociados a rocas volcánicas, depósitos sedimentario-exhalativos de barita y Zn-Pb y pequeños pórfidos cupríferos. Los depósitos minerales de edad Paleozoico Inferior son escasos, destacando sólo las mineralizaciones estratoides de óxidos de hierro relacionadas con el vulcanismo del Cámbrico inferior. La actividad tectónica y magmática ligadas a la orogenia Varíscica dieron lugar a una gran variedad de estilos y tipos de mineralización, incluyendo venas de Zn-Pb-Cu sin-metamórficas y peri-plutónicas, pequeños sulfuros masivos asociados a rocas magmáticas, remplazamientos y skarns de óxidos de hierro, mineralizaciones magmáticas de hierro y Ni-Cu y venas/remplazamientos de Sn-W perigraníticos. Hay algunas mineralizaciones de oro en relación con zonas de cizalla que puede ser Cadomienses o Varíscicicas. Finalmente, en relación con la actividad hidrotermal tardi- a post-Varíscica tuvo lugar la formación de abundantes filones con Pb-Zn, remplazamientos con Hg y venas de uranio. En conjunto, la diversidad de la metalogénesis Varíscica de la Zona Ossa Morena se interpreta como un continuo vertical de procesos, en un contexto de deformación regional transpresiva. La Zona Ossa Morena durante el ciclo Varíscico comenzó siendo un margen continental activo (con arco magmático), que evolucionó hacia una zona de colisión, una vez amalgamada al mismo la Zona Surportuguesa. Además, el cuerpo de máfico-ultramáfico recientemente descubierto en la corteza media, en toda la Zona Ossa Morena, debió de jugar un importante papel en la metalogénesis Varíscica.[PT] A Zona de Ossa Morena contém abundantes jazigos e ocorrências mineiras, principalmente formados durante os ciclos orogénicos Cadomiano e Varisco e durante os estádios intermédios de “rifting”e de plataforma estável. Apesar do forte desmembramento tectónico, as mineralizações Cadomianas assemelham-se nas suas características às tipicamente geradas por processos mineralizantes em arcos insulares activos, com formação de jazigos de sulfuretos maciços encaixados em rochas vulcânicas, jazigos de barita e jazigos SEDEX e alguma mineralização menor assemelhável à do tipo pórfiro cuprífero. Os jazigos minerais do Paleozóico Inferior são escassos e incluem principalmente alguma mineralizacão estratóide de óxidos de ferro. A actividade tectónica, metamórfica e magmática Varisca levou à formação de tipos de jazigos muito diferentes, incluindo veios de metais básicos sin-metamórficos e perigraníticos, pequenas jazidas de sulfuretos maciços polimetálicos em rochas vulcânicas, corpos de substituição e skarns de óxidos de ferro, jazigos magmáticos de magnetite e de Cu-Ni, e veios e corpos metassomáticos de Sn-W. A mineralização mesotermal de Au é de idade controversa, podendo ser Varisca ou Proterozóica. Finalmente, atribui-se à actividade hidrotermal Varisca tardia, de temperatura relativamente baixa, papel determinante na formação dos abundantes veios predominantemente de Pb-Zn ou Cu em diferentes enquadramentos geológicos, de corpos de substituição de Hg e de veios com urânio. De forma geral, a pouco comum metalogénese Varisca é interpretada como resultado da forte influência exercida pelos efeitos estruturais multi-escala ditados pela tectónica oblíqua, em conjunto com uma actividade magmática relevante.We acknowledge fruitful opinions and assistance from many colleagues of IGME and IGM, and mining companies We are specially grateful to L. Baeza (IGME), A.Canales (PRESUR), C. Conde (IGME), P. Florido (IGME), C. Galindo (UCM), C. Maldonado (RNGM), L. Rodriguez Pevida (RNGM), R.Urbano (IGME) and F.Velasco (UPV) for their help in the interpretation of the ore deposits of this complex area. The study has been partially supported by the CICYT projects PB96-0135, AMB-0918-C02-01 and DGI BTE2003-00290 (F.T., C.C.) and the CICYT-FEDER project 1FD97-1894 (F.T, G.O). A.M., C.I. and V.O. acknowledge the financial support of the Research Unit CREMINER-FCUL. This work is a contribution to the GEODE project of the European Science Foundation.Peer reviewe

The Cu stockwork and massive sulfide ore of the Feitais volcanic-hosted massive sulfide deposit, Aljustrel, Iberian Pyrite Belt, Portugal: A mineralogical, fluid inclusion, and isotopic investigation

The Variscan Feitais volcanic-hosted massive sulfide deposit in the Aljustrel district of the Iberian Pyrite Belt consists of 55 million metric tons of Zn-Pb-Cu massive sulfide overlying a Cu-rich stockwork. The massive ore is overlain by up to 30 m of feldspar-phyric, rhyolitic volcaniclastic rock and locally by a jasper and/or chert layer up to 15 m thick. The massive sulfide orebody consists dominantly of pyrite, sphalerite, galena, chalcopyrite, tetrahedrite-tennantite, arsenopyrite, and bournonite, together with minor quartz, chlorite, sericite, carbonate, and barite. The orebody is up to 100 m thick and is underlain by a tabular alteration zone of chlorite-dominated, locally silicified, felsic volcanic rock, the upper 30 to 60 m of which contains chalcopyrite-quartz-chlorite-sericite-carbonate-bearing stockwork vein(let)s that prior to deformation were at a shallow angle to the base of the massive orebody. Chloritized footwall rocks extend up to 20 in below the Cu stockwork zone and are underlain by up to 50 m of quartz-sericite-pyrite-altered rhyolitic rock. The stockwork veins also contain pyrite, tetrahedrite-tennantite, sphalerite, and arsenopyrite. Pyrite, both in stockwork and massive ore, locally displays partly recrystallized framboidal, reniform, and cellular textures. Two generations of quartz, Q1 and Q2, and carbonate in the stockwork veins contain primary (in growth zones) and pseudosecondary fluid inclusions, with homogenization temperatures of 270° to 315°C and salinities of 2.2 to 8.1 wt percent NaCl equiv. The δ34S(CDT) values of massive and stockwork ores range from -15.4 to +4.7 (mean, -2.8) and -11.2 to +11.9 (mean, -0.4) per mil, respectively, the lowest values from colloform-textured pyrite. With no evidence of oxidation of sulfide sulfur during mineralization, the most negative values indicate an origin by biogenic reduction of seawater sulfate. The 13C(PDB) values for carbonates, -7.5 to -13.7 and +9.3 to -14.3 per mil in massive and stockwork ore, respectively, indicate an origin mostly by oxidation of methane derived from organic matter in underlying sedimentary rocks and possibly a contribution of magmatic carbon. There are no significant lateral or vertical variations in S isotope values in sulfides or C-O isotope values in carbonates, either in massive or stockwork ore. The δ18O(smow) values for quartz in stockwork and massive sulfide are 11.6 to 13.9 and 16.7 to 17.9 per mil, respectively. Coexisting, and texturally contemporaneous, carbonate and quartz in stockwork veins are not in isotopic equilibrium, indicating that the C-O isotope values may have been reset. The δ18O values of fluid calculated to be in equilibrium with quartz at fluid inclusion homogenization temperatures are 4.2 to 5.2 per mil. Barite from the hanging wall and massive ore yields δ34S values (21.9-27.9‰) equal to or slightly higher than those of coeval seawater; 87Sr/86Sr ratios (0.708438-0.709063) are slightly more radiogenic than those of coeval seawater (0.7080-0.7085), and much more radiogenic than those of coeval volcanic rocks (0.703304-0.706642), probably representing mixtures between seawater Sr and radiogenic Sr in fluids sourced in the crustal pile. Deposition of the massive sulfide on the sea floor is suggested by its stratiform nature, the stronger alteration of footwall relative to hanging-wall rocks, the stockwork system terminating sharply at the base of the massive sulfide, the presence of sedimentary-like textures in the massive sulfide, the absence of replacement fronts, and the presence of framboidal and other sea-floor depositional textures indicative of fluid quenching. The sheetlike form, lack of rubble mounds and chimneys, scarcity of barite, reduced mineral assemblage, and metal zoning distinguish Feitais from Kuroko-type deposits. It shares most of the characteristics of those Iberian Pyrite Belt deposits for which a brine-pool origin has been proposed based on fluid inclusion data, suggesting a similar depositional origin, although the evidence from fluid inclusions in this study is equivocal. The sulfate that underwent biogenic reduction may have been derived from mixing with seawater during early filling of the brine pool; diffusion across the brine-seawater interface; and sulfate reduction in the footwall volcaniclastic rocks. Stable and radiogenic isotope compositions of sulfates, sulfides, and carbonates suggest involvement of modified seawater and crustal fluids convecting due to magmatic heating, but the calculated high fluid pressures in the stockwork may indicate the additional involvement of magmatic fluids. © 2008 Society of Economic Geologists, Inc.Carlos M. C. Inverno, Michael Solomon, Mark D. Barton and John Fode