Metallogenic and tectonic characteristics of the paleozoic ophiolitic belt of the southern Chile coastal Cordillera

The comparison of the tectonic, geochemical, and metallogenic information of the Crystalline Paleozoic Basement of the South Coast Range of Chile, with those classical ophiolites complexes like Cyprus, Oman, the Apennines, Magellean, etc., allows to find many similarities between them: ultramafic rocks, mainly wherlites, harzburgites and dunites with strong serpentinization, and rodingites; tholeiitic basalts with pillow structures; volcano-clastic sediments (»green schists«) of tholeiitic composition and meta-pelites (»grey schists«).From a metallogenitic point of view, the frame is completed by podiform chromites: occurrences associated to the serpentinizing banded iron formations, stratiform manganese oxides (mainly pyrolusite) associated to meta-cherts and quartzites, and polymetallic massive sulphide horizons interbedded with green schists.It is proposed that this sequence, based on its tectonic, petrographical, geochemical and metallogenetical characteristics, corresponds to an ophiolite back arc complex associated to an island arc developed during the Paleozoic.

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Zusammenfassung Das kristalline Grundgebirge der Küstenkordillere Südchiles zeigt in tektonischer, geochemischer und metallogenetischer Hinsicht viele Ähnlichkeiten mit den bekannten, klassischen Ophiolithkomplexen, wie z.B. Cypern, Oman, Apenninen und Magallanes. Bemerkenswert sind Rodingite und stark serpentinisierte ultrabasische Gesteine, u.a. Wehrlite, Harzburgite sowie Dunite. Au\erdem treten Basalte mit Pillow-Strukturen, vulkanoklastische Sedimente tholeiitischer Zusammensetzung (Grünschiefer) und Metapelite (Grauschiefer) auf. Von metallogenetischer Bedeutung ist die Anwesenheit von podiformen Chromit in Serpentiniten, von gebÄnderten Eisenerzen (BIF-Typ), stratiformen Mn-Oxid-Lagen in Metacherts und Quarziten sowie polymetallischen, massiven Sulfidschichten in Grünschiefern.Das metamorphe Grundgebirge wird aufgrund seiner tektonischen, petrographischen, geochemischen und metallogenetischen Gegebenheiten als Ophiolithkomplex des »back arc«-Typs angesehen, der im Zusammenhang mit einem palÄozoischen Inselbogen gebildet wurde.

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Resumen Al comparar las características tectónicas, geoquímicas y metalogenéticas del Basamento Cristalino Paleozoico de la Cordillera de la Costa del sur de Chile, con complejos ofiolíticos clásicos como Chipre, Omán, Los Apeninos, Magallanes, etc., se encuentran muchas similaridades entre ellos: rocas ultramáficas, principalmente wehrlitas, harzburgitas y dunitas, con fuerte serpentinización, y rodingitas; basaltos con estructura de almohadilla; sedimentos volcano-clásticos (»esquistos verdes«) de composición tholeiitica y metapelitas (»esquistos grises«).Desde el punto de vista metalogénico, el cuadro se completa con la ocurrencia de cromita podiforme asociada a serpentinitas; formaciones de hierro bandeado (BIF); óxidos de manganeso estratiformes asociados a meta-cherts y cuarcitas, y sulfuros masivos polimetálicos intercalados con esquistos verdes.Se propone que esta secuencia, basado en sus características tectónicas, petrográficas, geoquímicas y metalogénicas, corresponde a un complejo ofiolítico tipo »back arc« asociado a un arco de islas desarrollado durante el Paleozoico.

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Tsunami awareness: a comparative assessment between Japan and the USA

Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure.     

Studies of multiple stellar systems – III. Modulation of orbital elements in the triple-lined system HD 109648

The triple-lined spectroscopic triple system HD 109648 has one of the shortest periods known for the outer orbit in a late-type triple, 120.5 d, and the ratio between the periods of the outer and the inner orbits is small, 22:1. With such extreme values, this system should show orbital element variations over a time-scale of about a decade. We have monitored the radial velocities of HD 109648 with the CfA Digital Speedometers for 8 yr, and have found evidence for modulation of some orbital elements. While we see no definite evidence for modulation of the inner binary eccentricity, we clearly observe variations in the inner and the outer longitudes of periastron, and in the radial velocity amplitudes of the three components. The observational results, combined with numerical simulations, allow us to put constraints on the orientation of the orbits.     

Building participatory landscape-based conservation alternatives: A case study of Michoacán, Mexico

Michoacán, as one of the most species-rich provinces of Mexico and with high levels of endemism, was used for testing the potential of a conservation approach based on biodiversity as determined by scientists and local stakeholder's preferences. The resulting zones covered over 17% of the area of Michoacán in 18 zones. As a result of this study the first “large” tropical dry forest biosphere reserve in Mexico is currently being established. In conclusion, landscape-based conservation zoning based on local stakeholders' perspectives as well as on critical biodiversity indicators, proved to be effective for achieving science-based and politically acceptable nature conservation schemes.     

Hazard map of El Chichón volcano,Chiapas, México: Constraints posed by eruptive history and computer simulations

El Chichón volcano consists of a 2-km wide Somma crater compound cone 0.2 Ma old with peripheral domes with a central crater reactivated several times during the Holocene. The most recent eruption at El Chichón occurred from March 28 to April 4, 1982, resulting in the worst volcanic disaster during historical times in Mexico, killing more than 2000 people and destroying nine towns and small communities. The volcanic hazard map of El Chichón is based on detailed field work that documented twelve eruptions during the last 8000 years, and computer simulations. To validate the results, computer simulations were first performed over pre-1982 topography mimicking the extent of the actual deposits produced and afterwards run over post-1982 topography. These eruptions have produced pyroclastic fall, surge, flow and lahar deposits. Pyroclastic flows have different volumes and Heim coefficients varying from 0.2 (pumice flows), to 0.15 (block-and-ash flows) and 0.10 (ash flows). Simulations using FLOW3D and TITAN2D indicate that pumice flows and block-and-ash flows can fill the moat area and follow main ravines up to distances of ca. 3 km from the crater, with no effect on populations around the volcano. On the other hand, more mobile ash flows related to column-collapse events can reach up to 4 km from the vent, but will always follow the same paths and still not affect surrounding populations. The energy-cone model was used to simulate the outflow of pyroclastic surges based on the 1982 event (H/L = 0.1 and 0.2), and shows that surges may reach some towns around the volcano.     

El Niño and La Niña influence on mean river flows of southern South America in the 20th century

The influence of the El Niño Southern Oscillation (ENSO) phenomenon on monthly mean river flows of 12 rivers in the extreme south of South America in the 20th century is analysed. The original dataset of each river is divided into two subsets, i.e. warm ENSO events or El Niño, and cold ENSO events or La Niña. The elements of the subsets are composites of 24 consecutive months, from January of the year when the ENSO event begins to December of the following year. The ENSO signal is analysed by comparing the monthly mean value of each subset to the long-term monthly mean. The results reveal that, in general, monthly mean El Niño (La Niña) river flows are predominantly larger (smaller) than the long-term monthly mean in the rivers studied. The anomalies are more evident during the second half of the year in which the event starts and the first months of the following year.     

Progress towards instrument miniaturisation for mid-IR long-baseline interferometry

We report recent results on passive mid-infrared integrated optics from the project “Advanced Laser-writing for Stellar Interferometry” and shortly describe the perspectives of their hybridisation with active components for the benefit of the spectro-interferometry technique.     

The evolution of superbubbles and the detection of Lyα in star-forming galaxies

The detection of Ly α emission in star-forming galaxies in different shapes and intensities (always smaller than predicted for case B recombination) has puzzled the astronomical community for more than a decade. Here we use two-dimensional calculations to follow the evolution of superbubbles and of the H  ii regions generated by the output of UV photons from massive stars. We show the impact caused by massive star formation in the ISM of different galaxies and we look at the conditions required to detect Ly α emission from a nuclear H  ii region, and the variety of profiles that may be expected as a function of time.     

Analysis of pathfinder SST algorithm for global and regional conditions

As part of the Pathfinder program developed jointly by National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA) a large database ofin situ sea surface temperature (SST) measurements coincident with satellite data is now available to the user community. The Pathfinder Matchup Database (PMDB) is a multi-year, multi-satellite collection of coincident measurements from the Advanced Very High Resolution Radiometer (AVHRR) and broadly distributed buoy data (matchups). This database allows the user community to test and validate new SST algorithms to improve the present accuracy of surface temperature measurements from satellites. In this paper we investigate the performance of a global Pathfinder algorithm to specific regional conditions. It is shown that for zenith angles less than 45°, the best-expected statistical discrepancy between satellite and buoy data is about ∼ 0.5 K. In general, the bias of the residuals (satellite — buoy) is negative in most regions, except in the North Atlantic and adjacent seas, where the residuals are always positive. A seasonal signal in SST residuals is observed in all regions and is strongest in the Indian Ocean. The channel-difference term used as a proxy for atmospheric water vapor correction is observed to be unresponsive for columnar water vapor values greater than 45 mm and high zenith angles. This unresponsiveness of the channels leads to underestimation of sea surface temperature from satellites in these conditions.     

A proposal for boundary delimitation for integrated coastal zone management initiatives

ICZM relies heavily on the definition of major multidisciplinary characteristics/elements of the coastal area of interest. Usually, only terrestrial boundaries are considered, which tend to respond to a specific sectoral problem and can be determined by administrative limits. In this study, we propose a method for establishing a decision-making tool to inform boundary delimitation for ICZM initiatives that is proactive and widely applicable as opposed to reactive and problem specific. This method integrates environmental, economic and societal characteristics of the marine and terrestrial boundaries of the coastal zone, starting at the boundary of the jurisdictional zone of influence (shoreline units), increasing in detail through the definition of their influential areas from jurisdictional, environmental or socio-economic perspectives (functional areas) and, within them, specifying the finest scale at which relevant indicator data may be obtained (analysis units).