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1.
Integration of hydrogeological and geological data into a conceptual model is critical for site investigation programs, since this model is the basis for hydrogeological modeling and for engineering. In the Hungarian Radioactive Waste Disposal Investigation Program, several methods have been used to characterize the potential host rock (granite) at the Bátaapáti site for a repository for low and intermediate level radioactive waste. Hydrogeological data acquisition revealed some characteristic aspects of the site. One of the most important is the presence of extensive rock deformation zones (faults) with low hydraulic conductivity, which strongly reduce the direct hydraulic communication between adjacent blocks of rock (compartmentalization). This characteristic of the rock mass results in a mosaic-like distribution of rock compartments, each with an almost constant hydraulic head. Within the compartments, hydraulic tests have shown that transmissivity is strongly scale dependent: the larger the scale, the higher the measured transmissivity. The extensive highly transmissive zones cause very low hydraulic gradients within each block, thus the transport processes are strongly influenced by the low or average transmissivity zones and the rock matrix. 相似文献
2.
Dawnika L. Blatter Ian S. E. Carmichael 《Contributions to Mineralogy and Petrology》1998,132(2):121-138
Approximately 150 km west of Mexico City in the central part of the Mexican Volcanic Belt (MVB) near Zitácuaro, Mexico, young
volcanism has produced shield volcanoes, large volume silicic deposits, and fault-related basalt and andesite lava flows and
cinder cones. This paper concerns a small cluster of Pleistocene andesite cones and flows which can be separated into two
distinct groups: high-magnesium andesites (>6% MgO, 57–59% SiO2), conveniently called basaltic andesites, with phenocrysts of orthopyroxene and augite, or augite and olivine; and andesites
(60–62% SiO2, <4.6% MgO), which have phenocrysts of orthopyroxene and augite, and ghosts of relict hornblende. Remarkably, plagioclase
phenocrysts are absent, and evenly distributed but sparse (0.5–3.5%) quartz xenocrysts are present in all the lavas. In order
to establish the conditions under which early crystallizing plagioclase is suppressed in these lavas, water saturated experiments
up to 3 kbars were performed on one of the basaltic andesites. The conditions required to reproduce the phenocryst assemblages
(either olivine + augite or opx + augite) are temperatures in excess of 1000 °C, with water saturated liquids (>3 wt%) at
pressures of about 1 kbar. Compared to basaltic andesites of western Mexico, the Zitácuaro basaltic andesites have ∼2 wt%
lower Al2O3 concentrations, which causes plagioclase to precipitate at significantly lower temperatures, and it therefore follows the
crystallization sequence: olivine, augite, and orthopyroxene. Based on ubiquitous quartz xenocrysts, with glassy rhyolitic
inclusions, a reasonable conclusion is that substantial mixing of a quartz-bearing rhyolitic magma with a parental basaltic
andesite has occurred at low pressure (shallow depth), and this would account for the low Al2O3 concentrations in the Zitácuaro basaltic andesites. Whatever the mechanism of incorporation, the quartz xenocrysts are evidence
of contamination of basaltic magma with more siliceous material, thus making it difficult to use these magmas as indicators
of mantle melting processes.
Received: 29 July 1997 / Accepted: 29 January 1998 相似文献
3.
We evaluate the performance and statistical accuracy of the fast Fourier transform method for unconditional and conditional simulation. The method is applied under difficult but realistic circumstances of a large field (1001 by 1001 points) with abundant conditioning criteria and a band limited, anisotropic, fractal-based statistical characterization (the von Kármán model). The simple Fourier unconditional simulation is conducted by Fourier transform of the amplitude spectrum model, sampled on a discrete grid, multiplied by a random phase spectrum. Although computationally efficient, this method failed to adequately match the intended statistical model at small scales because of sinc-function convolution. Attempts to alleviate this problem through the covariance method (computing the amplitude spectrum by taking the square root of the discrete Fourier transform of the covariance function) created artifacts and spurious high wavenumber content. A modified Fourier method, consisting of pre-aliasing the wavenumber spectrum, satisfactorily remedies sinc smoothing. Conditional simulations using Fourier-based methods require several processing stages, including a smooth interpolation of the differential between conditioning data and an unconditional simulation. Although kriging is the ideal method for this step, it can take prohibitively long where the number of conditions is large. Here we develop a fast, approximate kriging methodology, consisting of coarse kriging followed by faster methods of interpolation. Though less accurate than full kriging, this fast kriging does not produce visually evident artifacts or adversely affect the a posteriori statistics of the Fourier conditional simulation. 相似文献
4.
Sheridan Michael F. Hubbard Bernard Carrasco-núñez Gerardo Siebe Claus 《Natural Hazards》2004,33(2):209-221
Volcán Citlaltépetl (Pico de Orizaba) with an elevation of 5,675 m is the highest volcano in North America. Its most recent catastrophic events involved the production of pyroclastic flows that erupted approximately 4,000, 8,500, and 13,000 years ago. The distribution of mapped deposits from these eruptions gives an approximate guide to the extent of products from potential future eruptions. Because the topography of this volcano is constantly changing computer simulations were made on the present topography using three computer algorithms: energy cone, FLOW2D, and FLOW3D. The Heim Coefficient (), used as a code parameter for frictional sliding in all our algorithms, is the ratio of the assumed drop in elevation (H) divided by the lateral extent of the mapped deposits (L). The viscosity parameter for the FLOW2D and FLOW3D codes was adjusted so that the paths of the flows mimicked those inferred from the mapped deposits. We modeled two categories of pyroclastic flows modeled for the level I and level II events. Level I pyroclastic flows correspond to small but more frequent block-and-ash flows that remain on the main cone. Level II flows correspond to more widespread flows from catastrophic eruptions with an approximate 4,000-year repose period. We developed hazard maps from simulations based on a National Imagery and Mapping Agency (NIMA) DTED-1 DEM with a 90 m grid and a vertical accuracy of ±30 m. Because realistic visualization is an important aid to understanding the risks related to volcanic hazards we present the DEM as modeled by FLOW3D. The model shows that the pyroclastic flows extend for much greater distances to the east of the volcano summit where the topographic relief is nearly 4,300 m. This study was used to plot hazard zones for pyroclastic flows in the official hazard map that was published recently. 相似文献
5.
《Geoforum》2017
The global extraction of minerals is commonly located in areas populated by indigenous people; and while conflicts between multinational corporations and local activists and indigenous people are widespread today, the understanding of their dynamics are lacking. The Swedish government’s encouragement to an expanding mining industry has caused resistance due to environmental and social implications, particularly its effect on Sámi reindeer husbandry. The resistance to a mine in Gállok is based on the belief that the right to decide about land use historically falls on the Sámi people, and the right to affect land use is detrimental for the survival of Sámi culture and reindeer husbandry. Although the conflict may be perceived as concerning access to natural resources, we argue that the perceived environmental conflict can be viewed as part of a larger struggle over social status and recognition. Data have been collected using qualitative methods such as observations, interviews and documents. The subsequent analysis relies on a meta-theoretical framework of justice as recognition using a typology of relations of power. Our findings suggest that relations of power constitute different categories of social actors. Stakeholders like the Sámi population are subordinated to more dominant stakeholders such as the government, the company and media, who have ‘more’ power or ‘different’ kinds of power ‘over’ others. Through these asymmetric power relations, historical state-Sámi relations are continuously reproduced within prevailing institutions, and also in this mining conflict. Interviewees from business and the municipality testified to the discourses driven by a neoliberal and profit-focused worldview. Challenging the neoliberal discourse, other stakeholders, namely civil society and Sámi, expressed an alternative discourse based on a local, traditional, cultural, environmental and anti-neoliberal worldview. 相似文献
6.
Jeff Standish Dennis Geist Karen Harpp Mark D. Kurz 《Contributions to Mineralogy and Petrology》1998,133(1-2):136-148
Roca Redonda volcano is a mostly submarine shield volcano that rises nearly 3 km from the adjacent seafloor. Over twenty
lava flows and palagonite tuff are exposed in a 60 meter high oblong outcrop above sea level, and several other flows are
exposed in the shallow water surrounding the islet. Thick, slightly alkaline picritic flows form the base of the section.
Thinner picrites interbedded with sparsely porphyritic alkali-olivine basaltic pahoehoe toes characterize the upper section.
The subaerial section probably records the filling of a palagonite tuff cone with younger lavas. Numerous fumaroles that may
have a magmatic component are present in the shallow (<30 m) submarine zone and indicate that the volcano is probably still
active. Three lava types are exposed: the basal picrites with 19% > MgO > 14%, high-Mg basalts with MgO of about 9%, and low-Mg
basalts with MgO of about 6%. The Sr and Nd isotopic ratios of the three lava types are within analytical uncertainty. Olivine
compositions indicate that the picrites are basaltic liquids that have accumulated olivine whose composition is in equilibrium
with the host basaltic liquid. Apparently, basaltic magmas percolated through dunite and troctolite that had crystallized
from slightly older Roca Redonda basaltic magma. Lavas from Roca Redonda have enriched trace element contents and isotopic
ratios relative to nearby Wolf volcano, but they are quite similar to lavas from Cerro Azul and Ecuador volcanoes. The common
characteristic of these volcanoes is that they lie on the periphery of the archipelago and are in a stage of subaerial growth.
This suggests that Galápagos volcanoes may go through a juvenile alkaline stage before a mature tholeiitic stage, analogous
to the Loihi stage of Hawaiian volcanism. A low 3He/4He ratio in olivine from one of the picrites indicates a small contribution by the Galápagos mantle plume.
Received: 15 December 1997 / Accepted: 6 May 1998 相似文献
7.
8.
Ponce-Pacheco Ana B. Novelo-Casanova David A. Agustin-Ortíz Ivonne N. Garduño-González Ana B. 《Natural Hazards》2021,106(1):855-879
The proximity to the Tacaná volcano, to the subduction zone between the Cocos and North America plates, to the Mexican coast, and to the active geologic Polochic-Motagua fault makes the population of Union Juarez (UJ), Chiapas, Mexico, exposed to many natural hazards including hurricanes, earthquakes, landslides, and volcanic eruptions. We assessed the risk perception of UJ, and our findings indicate that the community has moderate level of risk perception according to the scale of the National Center for Disaster Prevention of Mexico. The UJ’s risk perception is mainly dependent on gender and religion because females unlike males in case of disasters and emergencies: (1) believe that it is necessary to improve their preparedness; (2) trust the local civil protection authorities; (3) would know how to respond; (4) would follow the established protocols; and (5) would not relocate. On the other hand, non-religious people know better the protocols to follow in the event of disasters than the religious population. Besides, the community of UJ reasonably perceives earthquakes and extreme rains as the main hazards that they are exposed to, while volcanic hazards are considered less important although the town is located very close to the Tacaná volcano that has been active during the last 30 years. The local population lacks of proper knowledge and resources to develop adequate disaster mitigation plans. Surprisingly, the work of the local civil protection is considered poor. Our results can be used for local authorities as a tool to strength the disaster prevention actions in UJ.
相似文献9.
M. M. Blumenthal 《International Journal of Earth Sciences》1927,18(1):37-45
Ohne Zusammenfassung 相似文献
10.
11.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(5):461-462
GMINV is a computer program for inversion of potencial field data using damped approximate technique. In this paper we evaluate the results of geomagnetic field measuring in the area of Kolárovo basin magnetic anomaly, south-west Slovakia. In order to achieve more precise evaluation of the location and geometry of the perturbative body we use some preliminary knowledge concerning the geological structure of the locality, magnetic profile measuremenrs, etc. 相似文献
12.
《Quaternary Science Reviews》2005,24(1-2):91-104
This paper describes the initial stages of the development of a tephrochronology for the region of the Michoacán–Guanajuato volcanic field (MGVF) in central Mexico. There are two elements to this: the geochemical characterisation of volcanic glass and the linkage of tephra deposits to eruptions of known age. The MGVF is dominated by cinder cones and shield volcanoes which erupt only once. There are only two stratovolcanoes (multiple eruptions) which are common elsewhere in the Trans-Mexican Volcanic Belt. Tephras were sampled from sub-aerial sites close to cones of known age and from lake sediment cores from the Zirahuén, Pátzcuaro and Zacapu basins in the State of Michoacán. Multiple samples were collected to ensure that each tephra was well represented. The glass was analysed by electron microprobe and found to be calc-alkaline in composition. SiO2 abundances varied from 52% to 75%. Full results are available at http://www.geo.ed.ac.uk/tephra/. The ages of the dated cones ranged from the 20th century AD to ca 17,000 14C years BP. Tephras from eruptions of El Jabali (3840 14C years BP), Jorullo (1759–1774) and Paricutín (1943–1952) have been identified in lake cores. These provide a means of correlating between basins and have the potential to provide a basis for understanding the volcanic history of this area and for dating a wider range of sediment sequences. 相似文献
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14.
《International Geology Review》2012,54(4):279-303
The Xayacatlán area (eastern Mixteca terrane, southern Mexico) was previously inferred to preserve the Ordovician‐Silurian thrust contact between vestiges of the Iapetus Ocean and the para‐autochthon bordering Oaxaquia. Detailed remapping indicates that the rocks occur in four vertically‐bounded, NS fault blocks. The latter record the following tectonothermal events that post‐date Iapetus and occurred along the margins of the Rheic (1) and Pacific (2 and 3) oceans: (1) dextral transtension accompanying intrusion of an NS, tholeiitic dike swarm at ～442 Ma; (2) penetrative, greenschist‐facies deformation during the Mississippian related to extrusion of high‐pressure rocks; and (3) subgreenschist‐facies dextral transtension on NS faults during the generation of Middle Permian fabrics. 相似文献
15.
Earthquakes occurring during the night or early morning hours cause a heavy loss of life. Also, an earthquake occurring in the late evening hours poses serious handicap for disaster mitigation efforts due to failure of electricity and blocking of roads due to fall of debris. The larger aftershocks may cause further damage depending upon the magnitude of the main earthquakes of magnitude 5.5 and more in the Indian region. Out of 7 great earthquakes (M >7.8) in the Indian region during the last 200 years, five (1819, 1897, 1905, 1941 and 1950) have occurred during the evening or early morning hours. About 67% of all the earthquakes of magnitude >7.0 show similar result. It is found that in general, the percentage of earthquakes occurring during evening/early morning is larger than that during the daytime. However, the difference in time of occurrence is not significant at 95% level of confidence using 2 test. Keeping in view that most of the earthquakes in India of magnitude more than 6 have caused significant damage in the last decade (Uttarkashi, 1991; Latur, 1993; Jabalpur, 1997; Chamoli, 1999) and have occurred in the night/ early morning, disaster management plans need to be designed for awareness and education separately for the night and day times.The limitations of the seismic zoning map with reference to the earthquakes in Koyna (1967) and Latur (1993) have suggested to safeguard the life and property of the Indian population from the effects of future damaging earthquakes which should be failsafe instead of following the code and then introduce further changes in the code. It is suggested that residential houses (including tall structures) should be built for a design earthquake of magnitude 6.0 in all the three seismic zones namely I, II and III demarcated by the Bureau of Indian Standards giving proper weight age to site response. However, for Zones IV and V usual code recommendations may be followed through micro zoning of important, densely populated or most vulnerable areas. 相似文献
16.
本文总结了巴西两个最重要的滑石产地,Parana和Bahia区中滑石矿床的地质特征,并探讨了这些矿床的可能成因。巴西的滑石在世界滑石储量与产量中占有十分重要的地位。巴西Parana和Bahia区的滑石矿主要产于前寒武纪地体中。尽管该区的滑石具有不同的地质产状,与变质火山岩和变质沉积岩共生的滑石最为重要。其他类型的滑石,如与镁铁质-超镁铁质岩共生的、在花岗岩与白云质大理岩接触带的、在花岗岩体中呈包体或顶垂体状的、则相对不重要。在巴西与岩浆活动有关的滑石矿化主要发生在前寒武纪(Bahia区)和白垩纪(Parana区)。滑石的成因模式主要有两类:一为与岩浆热液有关的热液交代成矿模式,另一是起源于盆地热卤水的变质流体交代成矿模式。其中后一种成因模式可用来解释巴西的大多数大型滑石矿床,同时也适用于其他地区,如中国辽宁和乌拉尔南部的滑石成矿。 相似文献
17.
Anton Zubrik David Šaman Soňa Vašíčková Bernd R.T. Simoneit L’udmila Turčániová Michal Lovás Josef Cvačka 《Organic Geochemistry》2009,40(1):126-134
Aliphatic diterpenes were isolated from brown coal from Handlová, Slovakia, using microwave assisted extraction of mechanically activated coal powder. The parameters of the extraction procedure were optimized to get the target compounds in high yield. The total extract was separated using adsorption chromatography. GC–MS revealed tetracyclic and tricyclic diterpanes in the aliphatic fraction; they were identified as 16α(H)-phyllocladane (83%), isopimarane (11%), 18-norisopimarane (4%), abietane (2%) and fichtelite (<0.1%). It was found that more than 2 g of the most abundant diterpane, 16α(H)-phyllocladane could be extracted from 1 kg of Handlová coal. Because of the scarcity of relevant analytical data, 16α(H)-phyllocladane was thoroughly characterized by spectroscopic and chromatographic methods. A complete set of 1H and 13C NMR data is given including their comparison with published values and ab initio calculations. EI mass and IR spectra of 16α(H)-phyllocladane are shown and discussed. Kováts retention indices measured on two common GC stationary phases are also given. 相似文献
18.
AbstractDuring the Neogene (uppermost Aquitanian-Lower Burdigalian, Tortonian and Pliocene), three successive marine episodes took place in the present-day Malaga Basin. The first of these affected a wide area of the Belic Internal Zones and was brought to an abrupt conclusion by the westward displacement of these Zones, together with important horizontal movements associated with N70-100 direction strike-slip faults and the superposition of materials from the Campo de Gibraltar. The two other marine episodes were clearly controlled by vertical movements of NW-SE and NK-SW faults, caused by a clear E-W distension which, according to regional data, was associated with some compression in an approximately N-S direction. The area has also been affected, although to a lesser extent, by the uplift of the Betic Cordillera from the Upper Miocene to the present day. 相似文献
19.
用中国的历史文献来研究较早历史时期的火山喷发的气候效应,尤其是喷发持续时间长、过程复杂的冰岛式火山喷发的气候效应,是一项探索性的工作。本文主要探讨了-934 AD冰岛Eldgjá火山喷发在中国的气候效应,发现在Eldgjá火山喷发后,中国的气候变冷突出表现在93-～942 AD,初步估计,939/940 AD冬季洛阳开封一带相对于933-938 AD的降温幅度可达5℃-8℃。在北半球范围,Eldgjá火山喷发后的气候变冷集中在935-937 AD(峰值在935 AD)和939-942 AD(峰值在939-940 AD)两个时期。推测Eldgjá火山在长达3-8年的喷发过程中,可能于934-935 AD和938-939 AD前后各出现一个喷发的高潮。 相似文献
20.
Summary Tourmalinites containing quartz, Li- and Cs-micas, and small amounts of arsenopyrite occur near Cáceres, Spain. The tourmalinites are developed within Ordovician pelites near the eastern margin of the Cabeza de Araya batholith and close to several small bodies of tectonized granite. Field and textural relationships document an epigenetic character for the tourmalinites. The tourmaline is fine to very fine-grained and its composition is intermediate within the schorl-dravite solid-solution series. Hydrothermal veins containing quartz, muscovite, amblygonite-montebrasite, apatite, fluorite, and/or cassiterite appear spatially related to the tourmalinites. The mineralized area is located in a shear zone that was active during D3 Hercynian deformation and the emplacement of granitic bodies. Tourmalinites and veins derived from B- and Li-rich magmatic-hydrothermal fluids are believed to have been associated with the intrusion of a hidden granite dome, the tourmalinites being produced by extensive metasomatism of Ordovician metasedimentary rocks.
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Turmalinite and Sn-Li-Vererzungen im Valdeflores Gebiet (Cáceres, Spanien)
Zusammenfassung Turmalinite, die Quarz, Li- und Cs-Glimmer, sowie geringe Mengen an Arsenkies führen, kommen in der Ne von Cáceres, Spanien, vor. Sie sind an ordovizische Metapelite in der Nähe des Cabeza de Araya Batholiths und kleinere tektonisierte Granitkörper gebunden. Eine epigenetische Genese der Turmalinite ist auf Grund von Feldbeziehungen und texturellen Beobachtungen belegt. Die Zusammensetzung der sehr feinkörnigen Turmaline entspricht intermediären Gliedern der Schörl-Dravit- Reihe. Hydrothermale Gänge mit Quarz, Muskowit, Amblygonit-Montebrasit, Apatit, Fluorit und/oder Zinnstein treten benachbart zu den Turmaliniten auf. Der mineralisierte Bereich ist an eine Scherzone gebunden, die während der hercynischen D3 Deformation und der Platznahme der Granite aktiv war. Turmalinite und Gänge lassen sich genetisch von magmatisch-hydrothermalen Fluiden ableiten, die mit der Intrusion eines nicht aufgeschlossenen Granitdomes zusammenhängen. Die Turmalinite sind das Produkt einer weiträumigen Metasomatose der ordovizischen Metasedimente.
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