Javier Lillo

A first insight into mercury distribution and speciation in soils from the Almadén mining district, Spain

Abstract Almost no environmental data on mercury distribution and speciation in soils have been published so far for the Almaden mining district (central Spain), despite its huge size and historic importance. The mercury distribution in soils of the district reveals the existence of high and extremely high mercury values (up to ∼9000 ppm Hg). The Hg-thermodesorption curves for soils from a decommissioned metallurgical precinct (Almadenejos) and a phytoremediation site show that mercury occurs in the forms of cinnabar and as mercury bound to organic matter. The TEM-EDX study of the highly contaminated anthrosols from Almadenejos (samples with Hg >5000 ppm) shows the existence of cinnabar particles adsorbed to the surface of chlorite grains. Given the generally pyrite-poor character of the ores, and the presence of carbonates in the host rocks, cinnabar solubilization is limited, which in turn mitigates environmental hazards in the district. The only by-product of cinnabar leaching in the mineral dumps is schuetteite (Hg 3 SO 4 O 2 ). Preliminary results on local plants ( Asparagus acutifolius , Dittrichia graveolens , Marrubium vulgare ) show that mercury gets incorporated to roots, stems and leaves, with values of up to about 300 ppm Hg.

Extensional tectonics in the central Iberian Peninsula during the Variscan to Alpine transition

Abstract The passage from the Variscan cycle to the Early Alpine framework in the central part of the Iberian Peninsula can be explained in terms of a transitional process involving four clearly differentiated tectonic episodes. 1. (1) A first Variscan compressional stage (VI, Middle Devonian to Early Carboniferous) dominated by compressional conditions leading to the building-up of the orogenic edifice. The stress regime was relevant to what might be called “Variscan-type” compression (E-W-oriented). This stage was characterized by major Himalayan-type tectonics with frontal nappes, thrusts, overturned folds, lateral transcurrent ramps, and localized anatectic magmatism. Minor synorogenic extension and plutonism was also recorded during this stage in the Tormes Granitic Dome. 2. (2) A second Variscan stage (V2, Early to Middle Carboniferous) was characterized by increasing extensional conditions leading to widespread plutonism (adamellites, granodiorites). Wanning compressional conditions were restricted to the eastern and southern realms of central Iberia (the eastern part of the Spanish Central System, and the Toledo Mountains). 3. (3) A third stage, here defined as Late Variscan (LV), developed from Middle Carboniferous to Early Permian, as a result of N-S late-orogenic extension. This episode is relevant to detachment tectonics and the gravitational collapse of the Variscan orogenic edifice under combined simple/ pure-shear conditions. Plutonism (granites and leucogranites) was still of major importance. Early Permian andesitic to dacitic volcanism and sedimentary basins developed within the eastern part of the Spanish Central System. 4. (4) A fourth stage, here defined as Early Alpine (EA, Early Permian to Triassic) marks the onset of the Alpine framework. This stage was characterized by what might be called an “Early Alpine-type” regional stress regime i.e. E-W extension and N-S compression, within a simple-shear model, and resulted in the configuration of the Iberian Peninsula into two contrasted realms: a western inherited Variscan block, and an eastern Alpine block subjected to post-orogenic extension. Elements developed during this event include N-S high-angle normal faults, NW-SE and NE-SW conjugate strike-slip faulting, and asymmetric rifting involving listric low-angle detachments.

Application of electrical resistivity tomography to the environmental characterization of abandoned massive sulphide mine ponds (Iberian Pyrite Belt, SW Spain)

Mining activity in the Iberian Pyrite Belt, on the south-west of the Iberian Peninsula, has generated a great amount of mine tailing ponds, which once the extractive activity is finished, are abandoned and become a serious environmental problem. Here we present the results of applying the electrical resistivity tomography (ERT) technique to characterize the abandoned mine ponds in two sites: Monte Romero and Mina Concepcion. ERT has allowed us to determine both the general geometry of the pond’s base and the maximum thickness of the mine tailings. In all cases, the resistivity contrast between the infilling and the bedrock is high enough to clearly define the bottom pond boundary. The low-resistivity values (lower than 5 Ωm) obtained for the infilling are explained by the high concentration of pyrite in the tailings and the occurrence of acid waters. Whereas the Monte Romero mine pond is almost completely saturated with water, in Mina Concepcion it has been possible to identify the presence of inner acid water flows, the outlet of which through the damaged dyke originates a spilling of acid waters to the Odiel River. No low-resistivity water flows through the base of the ponds into the bedrock have been observed, indicating a good isolation of the base of the studied mine ponds.

El Chichón Volcano (Chiapas Volcanic Belt, Mexico)Transitional Calc-Alkaline to Adakitic-Like Magmatism:Petrologic and Tectonic Implications

The rocks of the 1982 eruption of El Chichón volcano (Chiapas, Mexico) display a series of geochemical and mineralogical features that make them a special case within the NW-trending Chiapas volcanic belt. The rocks are transitional between normal arc and adakitic-like trends. They are anhydrite-rich, and were derived from a water-rich, highly oxidized sulfur-rich magma, thus very much resembling adakitic magmas (e.g., the 1991 Pinatubo eruption). We propose that these rocks were generated within a complex plate tectonic scenario involving a torn Cocos plate (Tehuantepec fracture zone) and the ascent of hot asthenospheric mantle. The latter is supported by an outstanding negative S-wave anomaly widely extending beneath the zone, from 70 to 200 km in depth. The adakitic-like trend would be derived from the direct melting of subducting Cocos plate, whereas the transitional rocks would have resulted from the mixing of two poles, one reflecting a mantle source, and the other, the already mentioned adakitic melts. The basaltic source would also account for the high sulfur content and δ34S values of the El Chichón system (about +5.8), as result of a contribution of SO2 in fluids released from an underlying mafic magma.

Strong metal anomalies in stream sediments from semiarid watersheds in northern chile: when geological and structural analyses contribute to understanding environmental disturbances.

We present data from a reconnaissance geochemical environmental survey (stream sediments) in the Limarí watershed (northern Chile), and include information from the neighboring Elqui Basin for a combined analysis. Given that the region has a long historical record of mining activities, important environmental disturbances were expected. However, one of the rivers in the Limarí watershed that was chosen to serve as a baseline, as no mining activities had ever taken place along the valley, showed one of the largest geochemical anomalies. The sampled stream sediments of the Hurtado River are highly enriched in Cu (50-1,880 μg g-1), Zn (65-6,580 μg g-1), and Cd (130-31,350 ng g-1). The river system is sourced in the high-altitude domain of the Andes, and drains important Miocene hydrothermal alteration zones. The Coipita zone (El Indio gold belt) appears to be the most likely candidate to have originated the metal anomaly. The study of Landsat images suggests that the belt of alteration zones is located within a large (400+ km long, ~150 km wide) NW-SE dextral fault zone. This highly fractured domain may have conditioned the rapid unroofing of epithermal ore deposits in Miocene time, contributed to important circulation of meteoric waters, and eventually, to subsequent strong oxidation, leaching, and dispersion of metals, thus contributing to major metal dispersion in the Elqui and Limarí fluvial systems.

Pre-industrial Metal Anomalies in Ice Cores: A Simplified Reassessment of Windborne Soil Dust Contribution and Volcanic Activity during the Last Glaciation

A major issue regarding pre-industrial accumulation of heavy metals such as Cu, Pb, Zn, or Hg in ice cores relates to the source(s) of the metals. We investigate the two possibilities that have been generally advocated for the origin of metal anomalies: (1) increased amounts of windborne dust during particularly cold periods; and (2) volcanic activity. We analyze the time span 35,000-14,000 yrs BP, which is characterized by extreme temperature deviations (ΔT: -2.1° to -9.8°C). Our findings show no definitive relationships between climate, dust, and metal contents, at least during the colder episodes. Thus, although dust deposition undoubtedly adds metals to the ice, it not clear whether climate can fully account for a direct relationship between these variables. In order to study the volcanic hypothesis, we analyze the case under a double perspective: (1) large explosive episodes related to acid magmatism; and (2) quieter mafic volcanic activity. Although the first one can introduce huge volumes of metal-rich aerosols to the stratosphere during single, catastrophic events, the latter is more continuous, accumulative, and far richer in sulfur. However, inasmuch as metals build volatile species with sulfur and halides, the chloride-rich character of the acid volcanism could easily compensate for its deficiency in sulfur. Thus, we suggest that the volcanic activity, via quiescent degassing and eruptive episodes, may account for an important part of the heavy metal contents present in the ice cores.

Plate Interactions, Evolving Magmatic Styles, and Inheritance of Structural Paths: Development of the Gold-Rich, Miocene El Indio Epithermal Belt, Northern Chile

Ore deposits constitute singularities in the Earth crust, and form in response to a combination in time and space of a variety of geological processes. We here explore the complex setting that led to formation of an outstanding belt of precious-metal epithermal deposits in northern Chile, including the world class Au-Cu-As El Indio deposit. We discuss the formation of the El Indio belt in terms of Oligocene-Miocene plate tectonic and magmatic evolution of the Nazca-South America margin. The analysis of Landsat images allows recognition of a highly fractured domain involving a major Oligocene NW-SE-trending fault zone, with associated R1-R2-type structures. We suggest that a set of time-coincidental factors that occurred between ~10 and 6 Ma may have led to formation of the Late Miocene El Indio belt. Late Miocene subduction of the Juan Fernández Ridge (JFR) coincided with a substancial shift in magmatic emplacement style, linked to a compositional change from andesitic to dacitic, which resulted in the passage from stratovolcanoes to dome and dike complexes. It is not the composition alone, but the style that may be the crucial element here to understand why mineralization developed. Although stratovolcanoes easily vent volatiles and metals (via violent eruptions and quiescent outgassing), intrusions tend to retain these, and therefore, can generate volatile-, metal-rich hydrothermal solutions. We further propose that subduction of the JFR may have involved increased plate coupling, and the reactivation of older NNE trending R2 type shears (inherited structural corridors), along which the belt would have formed preferentially.

Restrictive definition of asbestos and the assessment of potential health hazards: insights from Northern Chile

When asbestos fibres become airborne, they can be inhaled into the lungs, where they may cause significant health problems. The latter includes progressive pulmonary fibrosis (asbestosis), pleural disease (effusion and pleural plaques) and malignancies such as bronchogenic carcinoma and malignant mesothelioma. The term asbestos applies to a group of hydrated fibrous mineral silicates including those belonging to the serpentine group of phyllosilicates (chrysotile) and amphiboles. However, only the ‘asbestiform varieties’ of amphiboles such as grunerite (amosite), riebeckite (crocidolite), anthophyllite, tremolite and actinolite are regarded as asbestos (s.s.). This implies that ‘non-asbestiform varieties’ of such minerals, that nevertheless generate acicular cleavage fragments, cannot be regarded as asbestos s.s. We argue that a discussion on the term asbestos goes beyond mere semantics, because for environmental regulatory bodies, the definition of a term can make the difference between classifying a mineral as harmful or non-harmful. A case of mesothelioma in the small mining town of La Higuera, northern Chile, may shed some light into this matter, because this form of cancer is almost always caused by exposure to asbestos. The town hosts about 20,000 t of fine-grained tailings left behind after flotation of Cu sulphides during 1950–1979. The ore was extracted from actinolite-rich, copper-iron vein deposits. We show that, if a ‘non-asbestiform variety’ of amphibole (e.g. La Higuera actinolite) is finely ground, it will cleave to asbestos-like acicular crystals and as such has the potential to induce similar health hazards to those posed by asbestos (s.s.).

Multispectral image analysis of glaciers and glacier lakes in the Chugach Mountains, Alaska

The Chugach Mountains contain the largest nonpolar alpine glaciers in the world and include a wide variety of glacier types: some are land terminating; some calve variously into tidewater, lakes, and rivers; some are heavily debris covered; some are surge-type, whereas others are neither debris covered nor surge type. Nearly all are retreating, thinning, or both, though some rare ones are advancing, and some are thickening at high elevations. To assist the further documentation of changes, we establish an inventory of glaciers in the eastern Chugach Mountains. Several case studies of diverse glacier types showcase remotesensing applications and are used to derive new knowledge of their current states and dynamical behavior. Several of these glaciers currently discharge into the Copper River and can be used to understand the processes governing glacier damming of large rivers. The Copper River, along with other major valley outlets from the Copper River Basin, was dammed several times by ice during the Pleistocene, forming a lake 10,000–20,000 km2 in area, called Glacial Lake Ahtna. Insights from the modern Childs, Miles, and Allen Glaciers—each of which fronts the Copper River—show that damming is not easily accomplished; direct encroachment, complete crossing, and successful damming require very low river discharge and probably introduction of abundant rock debris from a landslide onto the glacier. The last century has involved degradation of the Little Ice Age piedmont lobes of many valley glaciers in the Chugach Mountains and especially its Copper River corridor. These glaciers are generally losing over a meter per year of surface elevation. In another chapter highlight, we have found that crenulation and chevron folding of medial moraines does not require surging, as is commonly assumed; rather, the deformation can occur by flow diversion, without any surge activity, into ice-marginal lakes—a process we term a glacial aneurysm.

How short can short-term human-induced climate oscillations be?

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