Metamorphic facies series of the crystalline basement of Chile     

Félix González-Bonorino  Luis Aguirre 《International Journal of Earth Sciences》1970,59(3):979-994

The main rock types and mineral assemblages of the metamorphic rocks of the territory of Chile are described, and the metamorphic facies are identified. The crystalline basement of Chile consists of predominantly low-grade, semipelitic metamorphic and granitic rocks, exposed mostly along the coastal area of Central and Southern Chile, and in isolated areas of Northern Chile. Radiometric ages of both metamorphic and igneous rocks indicate Late Paleozoic. Three metamorphic series were recognized in Central Chile and used for a tentative classification of the metamorphic rocks from the remaining areas. The series correspond to intermediate-high pressure, intermediate-low pressure, and low pressure conditions of metamorphism, respectively. The formation of these series, their relation toMiyashiro's circumpacific paired belts, and the role of the basement during the Andean orogeny, are briefly discussed.

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Zusammenfassung Die Haupttypen der metamorphen Gesteine Chiles und deren Mineralzusammensetzung werden beschrieben und deren metamorphe Fazies charakterisiert. Das chilenische kristalline Grundgebirge besteht in der Hauptsache aus Graniten und semipelitischen Gesteinen, die unter den Bedingungen der niedriggradigen Metamorphose umgewandelt wurden. Die Gesteine sind in der Regel in der Küstenzone Süd- und Zentral-Chiles aufgeschlossen; in Nord-Chile treten sie isoliert auf. Radiometrische Altersbestimmungen ergaben sowohl für die Tiefenwie für die metamorphen Gesteine ein spätpaläozoisches Alter. In Zentral-Chile wurden drei metamorphe Serien erkannt und für eine erste Klassifizierung der metamorphen Gesteine dieses Gebietes herangezogen. Die Serien entstanden in der Hauptsache durch Metamorphoseprozesse, die unter mittleren bis hohen, mittleren bis tiefen und tiefen Drücken abliefen. Die Bildung dieser Serien, ihre Beziehung zuMiyashiro's zirkumpazifischen Gürtelpaaren und die Rolle des Grundgebirges während der Anden-Orogenese werden kurz diskutiert.

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Resumen Se describen los principales tipos de rocas y asociaciones minerales del basamento cristalino del territorio chileno. Este basamento consiste predominantemente de rocas metamórficas semipelíticas de bajo grado y de rocas graníticas, expuestas de preferencia a lo largo de la región costera de Chile Central y Austral y en áreas aisladas de Chile Septentrional. La edad radiométrica de las rocas metamórficas y graníticas indica Neopaleozoico. En Chile Central se encontraron tres series metamórficas, las que fueron empleadas para la clasificación provisoria de las rocas de otras partes del país. Estas series corresponden a condiciones de metamorfismo a presiones intermedia-alta, intermedia-baja, y baja, respectivamente. Se discuten brevemente la formación de las series, su relación a los arcos circumpacíficos apareados deMiyashiro, y el papel del basamento durante la orogénesis andina.

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, , . , semipelitischen Gesteinen, . , . . . , . , Miyashiro.

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Sedimentary provenance of the Late Paleozoic metamorphic basement,south-central Chile: Implications for the evolution of the western margin of Gondwana     

Rurik Romero  Fernando Barra  Mathieu Leisen  Eduardo Salazar  José María González-Jiménez  Martin Reich 《International Geology Review》2020,62(5):598-613

ABSTRACT

U-Pb detrital zircon age patterns are presented for nine samples of metapelites from the metamorphic basement of south-central Chile between 37° and 40°S, along with detrital zircon ages for a sample from the Piedra Santa metamorphic complex and a crystallization age of the Chachil plutonic complex, farther east in Argentina. Two distinct zircon age patterns are identified. One is a pattern with a dominant population of zircons at ca. 470 Ma (Ordovician), a widespread presence of Mesoproterozoic ages (1200 ? 1000 Ma), and a Carboniferous maximum deposition age indicated by the youngest zircon population. The second pattern is drastically different, with a main population of Permian zircons, a 290–250 Ma maximum deposition age, and a minor contribution of Pennsylvanian age zircons. Our results, coupled with previously reported metamorphic ages, show that the patterns reflect the presence of different tectonic blocks separated by the Mocha-Villarrica Fault Zone at 39°S. Metapelites north of this structure have the Ordovician-dominated pattern characteristic of the Western Series of the Paleozoic basement, and those south of the fault show the Permian-dominated pattern observed in the younger high-pressure metapelites from the Bahía Mansa metamorphic complex. The Piedra Santa metamorphic complex also shows the Ordovician-dominated pattern and was intruded by the Chachil plutonic complex dated here at ca. 303 Ma. Therefore, the Piedra Santa complex is interpreted as coeval with the Chilean metamorphic basement. The present dislocation of blocks with different ages is attributed to continental-scale dextral strike-slip tectonics along the Huincul Fault Zone, Argentina, which extends to the west as the Mocha-Villarrica Fault Zone in Chile.  相似文献   

On long-term evolution of seasonal precipitation in southwestern Europe     

F. Valero  F. J. Doblas  J. F. González 《Annales Geophysicae》1996,14(9):976-985

Annual cycles in long time series of precipitation from sixteen southwest European observatories have been analysed using complex demodulation. The stations have been clustered into two distinct regions and a hybrid one. They are referred to as the southwestern Europe precipitation Atlantic regime (SEPAR) and the southwestern Europe precipitation Mediterranean regime (SEPMER), with the hybrid regime referred to in terms of the mean amplitude ratios between semiannual and annual rainfall components. Some evidence of linking between seasonal cycle harmonic amplitudes and the zonal circulation has been found for SEPAR stations and a more obscured relationship for the SEPMER region. Within the SEPAR region the strength of the relationship is diminished towards the north. A trend analysis of the amplitudes against time since 1920 has also been carried out and the results reveal a divergent pattern in trends between annual and semiannual component amplitudes for the SEPAR region. In fact, both an increasing annual-amplitude trend and a decreasing semiannual-amplitude trend are observed, in each case statistically significant. The fact that the seasonal cycle variability of rainfall in southwestern Europe becomes more sensitive southwards to changes in atmospheric zonal circulation over the North Atlantic might, in our opinion, be related to the swing of the circumpolar vortex.  相似文献   

Sea-floor features related to hydrocarbon seeps in deepwater carbonate-mud mounds of the Gulf of Cádiz: from mud flows to carbonate precipitates     

R. León  L. Somoza  T. Medialdea  F. J. González  V. Díaz-del-Río  M. C. Fernández-Puga  A. Maestro  M. P. Mata 《Geo-Marine Letters》2007,27(2-4):237-247

Underwater images taken from deepwater carbonate-mud mounds located along the continental margin of the Gulf of Cádiz (eastern Central Atlantic) have identified a great variety of hydrocarbon seep-related geomorphic features that exist on the sea floor. An extensive photographic survey was made along the Guadalquivir Diapiric Ridge, after detailed examination of the main mounds identified on previous swath bathymetry coverage, high-resolution seismic imagery, dredge and gravity core data. Recognised fluid-induced geomorphic features include seep precipitates, named here generically as hydrocarbon-derived authigenic carbonates (HDACs), mud-breccia flows and piping/rills, at scales ranging from metres to centimetres. Based on the viscosity, texture, morphology, and the nature of observed features, we have categorized the geomorphic seeps into the following types: mud-breccia flows and liquid seepages, which can be grouped as highly viscous and viscous mud-breccia flows, gassy mud-breccia flows, and small-scale piping/rills; HDACs types, including massive crusts, “honeycombed” carbonate crusts, nodular aggregated crusts, steeply dipping to vertical slabs, and pipe-like formations (chimneys). These widespread geomorphic features observed along the carbonate-mud mounds reveal alternate periods of (1) active mud-flow extrusion (mud-volcano formation), (2) reduced seepage activity, with the formation of extensive carbonate features by chemosynthetic organisms, and (3) formation of hardgrounds and colonisation by non-chemosynthetic organisms such as deepwater corals (e.g. Lophelia pertusa, Madrepora oculata). The formation of large amounts of HDACs is related to the microbially mediated oxidation of hydrocarbon fluids (biogenic and thermogenic) during periods of slower fluid venting. This has led to the hypothesis that these carbonate-mud mounds could be built up by alternating episodes of varying fluid-venting rates, with peaks that may have been triggered by tectonic events (e.g. high-seismicity periods) and slower rates controlled by climate/oceanographic factors (e.g. glacial to interglacial climatic transitions, increasing shallow subsurface hydrate formation, and sealing of sea-floor fluid venting).  相似文献   

Novel DNA markers for rapid, accurate, and cost-effective discrimination of the continental origin of Atlantic salmon (Salmo salar L.)     

Gilbey  John; Knox  David; O'Sullivan  Martha; Verspoor  Eric 《ICES Journal of Marine Science》2005,62(8):1606-1616

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Die lateritische Zersetzung des Peridotits bei der Bildung der Nickelerzlagerstätte von Frankenstein in Schlesien     

Professor Dr. Kurt Spangenberg  Martha Müller 《Contributions to Mineralogy and Petrology》1949,1(5-6):560-572

Ohne ZusammenfassungAbgeschlossen im Juni 1947.  相似文献   

Using a remote sensing field experiment to investigate flux-footprint relations and flux sampling distributions for tower and aircraft-based observations     

William P. Kustas  Martha C. Anderson  Andrew N. French  Dean Vickers 《Advances in water resources》2006

During a remote sensing field experiment conducted in the Southern Great Plains in 1997 (SGP97), tower and aircraft-based flux observations were collected over one of the main study sites in central Oklahoma. This is an agricultural region and contains primarily grassland/pasture and winter wheat, which was recently harvested leaving a significant number of fields either as wheat stubble or plowed bare soil. Multi-spectral data obtained by aircraft provided high-resolution (30 m) spatially-distributed vegetation cover and surface temperature information over the study area. The spatial variations in these surface states strongly affect the partitioning of surface fluxes between sensible and latent heat. These data, together with coarser resolution (5 km) satellite data, are used in a remote sensing-based energy balance modeling system that disaggregates flux estimates from 5 km to 30-m resolution. The resulting high-resolution flux maps provide a means for evaluating whether tower and aircraft-based flux measurements sample a full range in flux conditions for this landscape. In addition, this remote sensing-based modeling system can be used to investigate the influence of variability in these key surface states on tower and aircraft measurements through flux-footprint modeling. Under the light wind and unstable conditions that existed during the observations, highest correlation between aircraft and modeled estimated heat and water vapor fluxes were obtained using different flux-footprint estimates. More specifically, the source area for heat was estimated to be much closer to the aircraft flight line than for water vapor.  相似文献   

A Simplified Method for Vulnerability Assessment of Dwelling Buildings and Estimation of Damage Scenarios in Catalonia, Spain   总被引：1，自引：1，他引：1  

A. Roca  X. Goula  T. Susagna  J. Chávez  M. González  E. Reinoso 《Bulletin of Earthquake Engineering》2006,4(2):141-158

A simplified method for vulnerability assessment of dwelling buildings with a statistical approach at a regional scale based on the EMS’98 is proposed. It is presented some applications of this methodology in Catalonia, Spain: (i) tools for generation of damage scenarios for preventive purposes; (ii) simulation of damages of historical earthquakes if they would occur today; and (iii) territory zonation to establish the criteria for activating the different levels of earthquake emergency actions.  相似文献   

Updating seismic hazard at Parkfield     

Álvaro González  Javier B. Gómez  Amalio F. Pacheco 《Journal of Seismology》2006,10(2):131-135

The occurrence of the September 28, 2004 M _w = 6.0 mainshock at Parkfield, California, has significantly increased the mean and aperiodicity of the series of time intervals between mainshocks in this segment of the San Andreas fault. We use five different statistical distributions as renewal models to fit this new series and to estimate the time-dependent probability of the next Parkfield mainshock. Three of these distributions (lognormal, gamma and Weibull) are frequently used in reliability and time-to-failure problems. The other two come from physically-based models of earthquake recurrence (the Brownian Passage Time Model and the Minimalist Model). The differences resulting from these five renewal models are emphasized.  相似文献   

Large-Scale Avalanche Braking Mound and Catching Dam Experiments with Snow: A Study of the Airborne Jet     

Kristin Martha Hákonardóttir  Andrew J. Hogg  Tómas Jóhannesson  Martin Kern  Felix Tiefenbacher 《Surveys in Geophysics》2003,24(5-6):543-554

We report a series of ongoing large-scale experiments to studythe interaction of a snow avalanche with a dam and a row of mounds which are of a comparable height to the flow depth.The experimental results indicate that the behaviour of thesupercritical flow around the obstacles is governed by the large-scale properties of the flowing avalanche rather than micro-scaleproperties of the granular current.The experiments show that, similarly to smaller-scale experimentswith glass particles, the avalanche detaches from the top of the dam or mound and forms a coherentairborne jet, which can be modelled as a two dimensional ballistic projectile with negligible air resistance.We study the two parameters that define the trajectory of thejet, namely the speed at which the jet is launched from the top of the obstacle and the deflection of the jet by the obstacle, and compare the resultswith a theory for the deflection of a jet of an ideal fluid.  相似文献