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Mélanges occur as discontinuous, mappable, units along an extensive N–S-trending, steeply dipping zone of distributed shear in metamorphic complexes along the coast of central Chile. Large mélange zones, from north to south, near Chañaral, Los Vilos, Pichilemu, and Chiloé Island, contain variations in lithologic and structural detail, but are consistent in exhibiting cross-cutting fabric features indicating a progressive transition from earlier ductile to more brittle deformation. In the Infiernillo mélange near Pichilemu, Permian to Early Triassic, sub-horizontal schistosity planes of the Western Series schist are disrupted, incorporated into, and uplifted along high-angle, N–S- to NNE–SSW-trending brittle–ductile shears. Mylonitic and cataclastic zones within the mélange matrix indicate active lateral shear during cumulative exhumation from depths exceeding 12 km in some areas. Exotic lithologies, such as Carboniferous mafic amphibolite and blueschist, formed during earlier Gondwanide subduction, match well with similar rocks in the Bahia Mansa to Los Pabilos region 750 km to the south, suggesting possible dextral offset. The development of the Middle to Late Triassic, N–S=trending, near-vertical shear zones formed weaknesses in the crust facilitating later fault localization, gravitational collapse, and subduction erosion along the continental margin. The length and linearity of this zone of lateral movement, coincident with a general hiatus of regional arc magmatism during the Middle to Late Triassic, is consistent with large-scale dextral transpression, or possible transform movement, during highly oblique NNE–SSW convergence along the pre-Andean (Gondwana) margin. The resultant margin parallel N–S-trending shear planes may be exploited by seismically active faults along the present coastal area of Chile. The palaeo-tectonic setting during the transitional period between earlier Gondwanide (Devonian to Permian) and later Andean (Late Jurassic to present) subduction may have had some similarity to the presently active San Andreas transform system of California. 相似文献
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Carlos Marquardt Alain Lavenu Luc Ortlieb Estanislao Godoy Diana Comte 《Tectonophysics》2004,394(3-4):193-219
Neotectonic observations allow a new interpretation of the recent tectonic behaviour of the outer fore arc in the Caldera area, northern Chile (27°S). Two periods of deformation are distinguished, based on large-scale Neogene to Quaternary features of the westernmost part of the Coastal Cordillera: Late Miocene to Early Pliocene deformations, characterized by a weak NE–SW to E–W extension is followed by uppermost Pliocene NW–SE to E–W compression. The Middle Pleistocene to Recent time is characterized by vertical uplift and NW–SE extension. These deformations provide clear indications of the occurrence of moderate to large earthquakes. Microseismic observations, however, indicate a lack of shallow crustal seismicity in coastal zone. We propose that both long-term brittle deformation and uplift are linked to the subduction seismic cycle. 相似文献
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Anna Jurado Alberto V. Borges Estanislao Pujades Pierre Briers Olha Nikolenko Alain Dassargues Serge Brouyère 《Hydrogeology Journal》2018,26(8):2739-2751
This study investigates the occurrence of greenhouse gases (GHGs) and the role of groundwater as an indirect pathway of GHG emissions into surface waters in a gaining stretch of the Triffoy River agricultural catchment (Belgium). To this end, nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) concentrations, the stable isotopes of nitrate, and major ions were monitored in river and groundwater over 8 months. Results indicated that groundwater was strongly oversaturated in N2O and CO2 with respect to atmospheric equilibrium (50.1 vs. 0.55 μg L?1 for N2O and 14,569 vs. 400 ppm for CO2), but only marginally for CH4 (0.45 vs. 0.056 μg L?1), suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification seemed to be the main process for the accumulation of N2O in groundwater. Oxic conditions prevailing in the aquifer were not prone for the accumulation of CH4. In fact, the emissions of CH4 from the river were one to two orders of magnitude higher than the inputs from groundwater, meaning that CH4 emissions from the river were due to CH4 in-situ production in riverbed or riparian zone sediments. For CO2 and N2O, average emissions from groundwater were 1.5?×?105 kg CO2 ha?1 year?1 and 207 kg N2O ha?1 year?1, respectively. Groundwater is probably an important source of N2O and CO2 in gaining streams but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems. 相似文献
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Francisco Herve Francisco Munizaga Estanislao Godoy Luis Aguirre 《Earth and Planetary Science Letters》1974,23(2):261-264
Two crossite concentrates and one blueschist whole rock were analyzed by the K/Ar method. These samples belong to the high/intermediate pressure Western Series of the Chilean metamorphic basement and, in this area, are intruded by a small monzonite body.Ages obtained were 211 m.y. and 329 m.y. for the mineral concentrates and 211 m.y. for the whole rock. Discussion based on crystal size as a factor for retention of40Ar during localized re-heating of the metamorphic rocks due to the monzonitic intrusion leads to the acceptance of 329 m.y. as the minimum age of crossite crystallization. This age agrees with the whole rock Rb/Sr limiting reference isochrons (273–342 m.y.) previously obtained for the metamorphic basement of Central Chile which did not include samples of the present area.This age provides the first evidence of a Paleozoic blueschist assemblage in the eastern Pacific border and would suggest the existence of a Late Paleozoic subduction zone along the western margin of South America. 相似文献
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Urban groundwater has often been over-exploited for industrial uses. Now, this usage tends to be reduced or the resource abandoned due to pollution and/or changes in land use. The use and the subsequent disuse of groundwater has resulted in rising water tables that damage underground structures (e.g., building basements and underground car parks and tunnels), leading to the need for additional pumping in urban areas. In the case of the underground parking lot of Sant Adrià del Besòs (Barcelona, NE Spain), large amounts of urban groundwater are pumped to avoid seepage problems. Can this pumped groundwater be used for other purposes (e.g., drinking water and urban irrigation) instead of wasting this valuable resource? To answer this question, it was necessary to quantify the groundwater recharge and to assess the evolution of groundwater quality. The limiting factor at this study site is the groundwater quality because ammonium and some metals (iron and manganese) are present at high concentrations. Hence, further treatment would be needed to meet drinking water requirements. The pumped groundwater could also be used for supplementing river flow for ecological benefit and/or for mitigating seawater intrusion problems. Currently, only a small amount of this urban groundwater is used for cleaning public areas and watering public gardens. This situation highlighted the urgent need to manage this resource in a responsible and more efficient manner, especially in moments of high water demand such as drought periods. 相似文献
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Estanislao Pujades Thibault Willems Sarah Bodeux Philippe Orban Alain Dassargues 《Hydrogeology Journal》2016,24(6):1531-1546
Underground pumped storage hydroelectricity (UPSH) plants using open-pit or deep mines can be used in flat regions to store the excess of electricity produced during low-demand energy periods. It is essential to consider the interaction between UPSH plants and the surrounding geological media. There has been little work on the assessment of associated groundwater flow impacts. The impacts on groundwater flow are determined numerically using a simplified numerical model which is assumed to be representative of open-pit and deep mines. The main impact consists of oscillation of the piezometric head, and its magnitude depends on the characteristics of the aquifer/geological medium, the mine and the pumping and injection intervals. If an average piezometric head is considered, it drops at early times after the start of the UPSH plant activity and then recovers progressively. The most favorable hydrogeological conditions to minimize impacts are evaluated by comparing several scenarios. The impact magnitude will be lower in geological media with low hydraulic diffusivity; however, the parameter that plays the more important role is the volume of water stored in the mine. Its variation modifies considerably the groundwater flow impacts. Finally, the problem is studied analytically and some solutions are proposed to approximate the impacts, allowing a quick screening of favorable locations for future UPSH plants. 相似文献
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Dr.-Ing. Estanislao Dunin-Borkowski 《International Journal of Earth Sciences》1970,59(3):1141-1180
Zusammenfassung Der Acarí-Pluton, eine der zahlreichen Intrusionen des Küstenbatholithen von Perú, hat sich aus einem tonalitischen Magma gebildet, das in der Oberkreide oder im Frühtertiär eingedrungen ist. Der andine Magmatismus dieses Bereiches begann im mittleren Jura und dauerte noch nach der Bildung des Acarí-Pluton bis mindestens ins mittlere Tertiär fort. Innerhalb des Acarí-Plutons kann man drei Gesteinstypen unterscheiden, die während drei verschiedener Etappen der Magmadifferentiation entstanden sind. Der aus intermediärem Plagioklas, Klinopyroxen und Eisen-Titan-Erz aufgebaute feinkörnige Pyroxendiorit stellt den abgeschreckten Rand dar. Der außer den genannten Mineralien noch Quarz und Titanit führende grobkörnige Pyroxendiorit ist das Hauptkristallisat; der hauptsächlich aus Plagioklas und Quarz bestehende Quarzdiorit bildet Aplit und ist auch in manchen Bereichen der Dachregion angesammelt.Die Verteilung dieser Gesteine ist nicht nur für die Bestimmung der ursprünglichen Form des Acari-Plutons ausschlaggebend, sondern erlaubt auch die Bewegungen s Magmas während der Intrusion zu verfolgen.Die den Acarí-Pluton durchquerenden Stöcke und Gänge haben keine direkte Beziehung zu seiner Differentiation. Der Acari-Pluton wird im NE-Teil von rotem Granit und den mit ihm verbundenen Kupfererzgängen durchquert; im SW-Teil dagegen gibt es zwei Gang- (und Stock-) Generationen: Die ältere besteht aus Pyroxeniten und Eisenerzgängen mit ausgeprägter Bänderung und Tendenz zur Bildung monomineraler Bereiche. Die Stöcke und Gänge der jüngeren Generation sind dagegen aus wasserreichem dioritischem Magma auskristallisiert. Sie zeigen große, durch Differentiation, lokale Bildungsverhältnisse und Autometamorphose verursachte Unterschiede in ihrer Ausbildung.
The Acarí Pluton is one of many intrusions of the Peruvian coastal batholith; it was formed from tonalitic magma in Late Cretaceous or Early Tertiary. The tonalitic magma is part of the intensive Andean magmatism, which began in Middle Jurassic and continued after emplacement of the Acarí Pluton at least until Middle Tertiary. Within the Acarí Pluton, three rock types represent three different stages of magma differentiation. Fine grained pyroxene-bearing diorite containing plagioclase of intermediate composition, clinopyroxene, and opaque iron and titanium minerals was formed by marginal chilling. Coarse grained pyroxene-bearing diorite, which in additions to the minerals mentioned above contains quartz and sphene, is the product of the principal phase of crystallization. Quartz diorite with plagioclase and quartz as major components formed aplitic veins; it is also accumulated in some portions of the roof.Distribution of these rock types is the decisive criterion for reconstructing the original shape of the Acari Pluton; moereover, it allows tracing the movement of the magma in the process of intruding.The stocks and veins crossing the Acari Pluton are not related genetically. In its NE part, the Acarí Pluton is crossed by red granite and associated veins of copper minerals. In the SW part, there are two generations of stocks and veins. The older generation consists of pyroxenites and iron ore veins with pronounced banded texture and a tendency toward forming monomineralic domains. In contrast, stocks and veins of the younger generation crystallized from hydrous dioritic magma; differentiation, local conditions, and autometamorphism led to considerable compositional variation in these rocks.
Résumé Le pluton d'Acarí, une des nombreuses intrusions du batholite côtier pérouvien, s'est formé à partir d'un magma tonalitique qui s'est mis en place au cours du Crétacé supérieur ou du Tertiaire inférieur. Le magmatisme andin, intensif, de la région d'Acarí, commençait au Jurassique moyen et s'est prolongé, après l'intrusion du pluton d'Acarí (s.S.), jusqu'au Tertiaire moyen.Au sein du pluton d'Acarí on peut distinguer trois types de roches qui se sont formées au cours de trois étapes distinctes de la differentiation magmatique. L'un est composé de plagioclase intermédiaire, de clinopyroxène et de minéraux opaques de fer et de titane; il s'agit d'une diorite pyroxénique à grain fin qui constitue le faciès de contact, dû à un refroidissement rapide, du pluton d'Acarí. Le second contient, outre les minéraux cités, du quartz et du sphène; c'est une diorite pyroxénique à gros grain formant l'essentiel de la masse cristalline du pluton d'Acarí. Le troisième type est une diorite quartzitique composée surtout de plagioclase et de quartz. Il apparaît en masse dans certaines zones de la partie superieure du pluton d'Acarí, ainsi que sous forme d'aplites. La distribution des roches permet de déterminer la forme originale du pluton d'Acarí, et aussi de suivre les mouvements du magma au cours de l'intrusion.Le pluton d'Acarí est traversé aussi par des amas et des filons intrusifs qui ne sont pas directement en rapport avec sa différentiation. Le pluton d'Acarí est traversé dans sa partie NE par des amas de granite rouge et les filons cuprifères qui lui sont liés. Dans la partie SW, par contre, il existent deux générations de filons et d'amas: la plus ancienne se compose de pyroxénites et de filons de minérais de fer (principalement de la magnétite) caractérisés par un rubannement très net et par une tendance à former des zones à un seul minéral. Les amas et les filons les plus récents, par contre, se sont cristallisés à partir d'un magma dioritique fortement hydraté. Ils présentent une grande variété de roches due aux conditions locales de cristallisation ainsi qu'à la différentiation et à l'autométamorphose.
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北极河流径流是北冰洋淡水的最大来源，其变化会对北冰洋中的诸多过程有重要影响。本文基于全球高分辨率海洋?海冰耦合模式的模拟结果，研究北冰洋温盐、海冰以及环流对北极河流径流的敏感性。通过对比有气候态北极河流径流输入的控制实验结果和径流完全关闭的敏感性实验结果，研究发现北极径流对北冰洋温度、盐度、海冰以及海洋环流等有显著的影响。关闭北极河流径流后，在河口附近的陆架上温度降低、盐度升高，且导致500 m深度处温度下降以及盐度升高；河口附近的陆架处，海冰密集度与海冰厚度增加。关闭北极河流径流也对北冰洋内的环流有影响:由于缺少来自欧亚大陆的北极径流的输入，穿极漂流与东格陵兰流流速减小且盐度增加；关闭北极径流导致近岸海表面高度降低，沿欧亚陆架的北冰洋边界流减弱，白令海入流增强。通过对比关闭北极径流实验与控制实验的温度和盐度剖面，发现关闭北极径流后大西洋层温度降低，各陆架海盐跃层的梯度减小，盐跃层厚度减小。 相似文献
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