Probabilistic compressive strength of sound dry granite

Summary The different functions of cumulative probability of fracture that can be used in the Probabilistic Strength of Materials in the case of constant uniaxial compression are described. Sound fine-grained granite was used to study volume influence by fracturing rectangular prisms, and then no noticeable influence was observed. Since this is showing that all the fracture stresses are belonging to a single set they were included in a single group that exhibited two functions of specific risk of fracture. The population with the lesser fracture stress has no critical zone while the other population does have it and a critical zone in the order of 10^–6 m³ is the minimum size exhibiting a complete fracture of the specimen when the same collapses. All the statistical functions were found to be acceptable according to theX ² criterion.     

Building a 3D geomodel for water resources management: case study in the Regional Park of the lower courses of Manzanares and Jarama Rivers (Madrid, Spain)

Water resources management of protected sites requires a powerful tool to analyze the process and changes that are occurring in the environment. This paper describes a 3D geomodel design of the Jarama River Detrital Aquifer located in Madrid (Spain). That hydrogeological unit is included in the “Parque Regional de los Cursos Bajos de los Ríos Manzanares y Jarama” (Regional Park of the Lower Courses of Manzanares and Jarama Rivers). The goal of this work is to define a method by which a three-dimensional (3D) model can be created with hydrogeologic geometry real of main aquifer, to accomplish an adequate management of the groundwater resources. All data used in this study were integrated in a geographic database: geological and hydrogeological information, geological map (1:25,000), eleven cross-sections, piezometric maps and a digital elevation model. The constructed 3D model of the Jarama Aquifer shows geometric features and spatial distribution and variations of geologic units. Thus, the 3D model allows the assessment of volumes of each unit, the depth and thickness variations of the main aquifer, and the spatial and temporal variations of water tables. From the 3D model, the most suitable areas (in terms of groundwater protection) for managed recharge and mining works have been identified.     

The Hiendelaencina epithermal silver-base metal district,Central Spain: Tectonic and mineralizing processes

The northeastern sector of the Spanish Central System hosts important Stephanian-Permian silver-base metal epithermal mineralizations defining the so-called Hiendelaencina District. The overall geotectonic evolution of this region indicates a major late Variscan extensional period involving the unroofing of dome-shaped metamorphic core complexes, which ultimately led to the radial brittle disruption of these bodies allowing the ascent of andesitic magmas and high-level hydrothermal activity. The deposits are hosted by high-grade metaphorphic rocks belonging to these complexes. Mineralogical and fluid inclusion studies reveal that the mineralizations were formed during two to four hydrothermal stages. These are the result of complex interactions between fluids of contrasted temperatures and salinities. Data on sulphur isotopes suggest that two sources of sulphur existed: magmatic (andesitic derived, with ³⁴S + 6) and metasediment-derived (with initial ³⁴S probably + 25).     

Freezing-resistant liquid water in porous media, a possible mechanism to account for the fluidized transport of sediments on Mars: an example from East Gorgonum crater

ABSTRACT A mudflow-like deposit resting on the bottom of the East Gorgonum Crater (Mars; 37.4°S, 168.0°W) may provide new insight regarding the debate on the existence of water over the Martian surface. Because water in a mudflow is confined to a porous medium, we analyse this case from the perspective of non-equilibrium systems. Fluids confined to porous media behave in a special way, the system being ruled by kinetic restrictions, which alter the expected thermodynamic equilibrium. These non-equilibrium conditions allow the existence of pure liquid water to temperatures as low as − 40 °C, and even less if the system includes brines. Thus, application of the triple point diagram of water on the Martian surface may constitute a simplistic approach if we are dealing with confined, and yet moving, water in the form of a mudflow. We further suggest that the V-shaped channels excavated alongside the mudflow may have been caused by water rejected by syneresis from the moving sediment. We finally indicate that the series of deeply entrenched channels and debris aprons that occur only in the northern half of the crater might be related to the regional slope, which decreases in altitude to the south.     

Giant versus small porphyry copper deposits of Cenozoic age in northern Chile: adakitic versus normal calc-alkaline magmatism

Cenozoic magmatic activity in northern Chile led to the formation of two contrasting porphyry copper belts: (1) a Paleocene-Early Eocene belt comprising small porphyry copper deposits (e.g., Lomas Bayas) of normal calc-alkaline affinity; and (2) a Late Eocene-Early Oligocene belt hosting huge porphyry copper deposits (e.g., Chuquicamata) of adakitic affinity. Although the first belt comprises both volcanic and plutonic rocks (andesitic-basaltic and rhyolitic lavas and tuffs, and associated sub-volcanic porphyries and felsic stocks), the latter only includes intrusions (mostly granodioritic types, including porphyry copper deposits). We suggest that the Late Eocene-Early Oligocene belt formed when fast and oblique convergence between the South America and Farallon plates led to flat subduction and direct melting of the subducting plate, hence giving rise to plutonic rocks of adakitic affinity. The absence of volcanism, under prevailing compressional conditions, prevented the escape of SO₂ from the adakitic, sulfur-rich, highly oxidized magmas ("closed porphyry system"), which allowed formation of huge mineral deposits. On the contrary, coeval volcanic activity during formation of the Paleocene-Early Eocene calc-alkaline porphyries allowed development of "open systems", hence to outgassing, and therefore, to small mineral deposits.     

Assessment of groundwater circulation in La Gomera aquifers (Canary Islands, Spain) from their hydrochemical features

La Gomera (Canary Islands, Spain) does not show water scarcity like other islands of the Archipelago. However, the study of its aquifers is paramount as nearly 60 % of the water supplies are covered with spring water. According to the currently accepted hydrogeological model, La Gomera presents an upper aquifer consisting of perched groundwater bodies. Below this hydrogeological unit, the General Saturated Zone or basal groundwater is placed. The model also establishes the presence of flows through them. Many perched groundwater bodies are located under Garajonay National Park where most of the springs are found. Therefore, if upper and lower aquifers are truly connected and new wells are built, the new extractions could affect Garajonay ecosystems. With the aim of identifying spring groups and related potential areas of water transfer, hydrochemical and statistical analyses (principal component analysis and cluster analysis) have been applied. This study shows the great compositional variability of groundwaters, precluding the identification of spring groups, hydrochemical patterns and, therefore, the transfer areas with no possibility of assessing the potential impact of a water demand increase on the Garajonay National Park ecosystems from the present data. Only the springs belonging to group II of the cluster analysis could indicate a transfer area. The lack of conclusive results could be due to: (1) great compositional variability of volcanic materials; (2) unequal influence of marine aerosols; (3) irregular distribution of rainfall; (4) different grades of soils development; and (5) the occurrence of partially disconnected water bodies giving as a result a complex hydrogeological system.     

Functional outlier detection by a local depth with application to NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> levels

This paper proposes methods to detect outliers in functional data sets and the task of identifying atypical curves is carried out using the recently proposed kernelized functional spatial depth (KFSD). KFSD is a local depth that can be used to order the curves of a sample from the most to the least central, and since outliers are usually among the least central curves, we present a probabilistic result which allows to select a threshold value for KFSD such that curves with depth values lower than the threshold are detected as outliers. Based on this result, we propose three new outlier detection procedures. The results of a simulation study show that our proposals generally outperform a battery of competitors. We apply our procedures to a real data set consisting in daily curves of emission levels of nitrogen oxides (NO\(_{x}\)) since it is of interest to identify abnormal NO\(_{x}\) levels to take necessary environmental political actions.     

Environmental assessment of the arsenic-rich,Rodalquilar gold–(copper–lead–zinc) mining district,SE Spain: data from soils and vegetation

The Rodalquilar mineral deposits (SE Spain) were formed in Miocene time in relation to caldera volcanic episodes and dome emplacement phenomena. Two types of ore deposits are recognized: (1) the El Cinto epithermal, Au–As high sulphidation vein and breccia type; and (2) peripheral low sulphidation epithermal Pb–Zn–Cu–(Au) veins. The first metallurgical plants for gold extraction were set up in the 1920s and used amalgamation. Cyanide leaching began in the 1930s and the operations lasted until the mid 1960s. The latter left a huge pile of ~900,000–1,250,000 m³ of abandoned As-rich tailings adjacent to the town of Rodalquilar. A frustrated initiative to reactivate the El Cinto mines took place in the late 1980s and left a heap leaching pile of ~120,000 m³. Adverse mineralogical and structural conditions favoured metal and metalloid dispersion from the ore bodies into soils and sediments, whereas mining and metallurgical operations considerably aggravated contamination. We present geochemical data for soils, tailings and wild plant species. Compared to world and local baselines, both the tailings and soils of Rodalquilar are highly enriched in As (mean concentrations of 950 and 180 μg g⁻¹, respectively). Regarding plants, only the concentrations of As, Bi and Sb in Asparagus horridus, Launaea arborescens, Salsola genistoides, and Stipa tenacissima are above the local baselines. Bioaccumulation factors in these species are generally lower in the tailings, which may be related to an exclusion strategy for metal tolerance. The statistical analysis of geochemical data from soils and plants allows recognition of two well-differentiated clusters of elements (As–Bi–Sb–Se–Sn–Te and Cd–Cu–Hg–Pb–Zn), which ultimately reflect the strong chemical influence of both El Cinto and peripheral deposits mineral assemblages.     

Reply to the comment by F. Tornos et al.

We welcome the discussion of our paper by Tornos et al. The epithermal character of the Hiendelaencina veins might have been an assumption in the early to mid 1980s, however, this early idea has been reaffirmed after many years of research involving fieldwork and mineralogical, sulphur isotopes, and fluid inclusions studies. The same applies to the alleged extensional frame, a tectonic episode now well documented not only in central Spain (Spanish Central System: Doblas 1987; Doblas et al. 1988; Doblas 1991) but in France (French Central Massif: Ménard and Molnar 1988; Malavieille et al. 1990; Munoz et al. 1992).The deposits are hosted by metamorphic rocks and the nearest volcanic outcrops to Hiendelaencina are those of Atienza (andesites; some 12 km northward). This is the reason why the relationships between the Atienza volcanics and the Hiendelaencina veins were initially regarded as obscure. These Stephanian-Permian volcanic outcrops are only local evidence of the late Variscan magmatism, which in the case of Hiendelaencina remained concealed. It is evident that the geologic environments of Hiendelaencina and Atienza are very different (see Discussion, p. 88 of the paper). As a direct consequence of this, the local structural conditions led to contrasted expressions of the late Variscan magmatism i.e. subaereal at Atienza and hypabyssal at Hiendelaencina.