Flow stresses from microstructures in mylonitic quartzites of the Moine Thrust zone, Assynt area, Scotland

Recrystallized grain sizes, subgrain sizes and dislocation densities of quartz grains in quartzose mylonitic rocks have been examined using optical and transmission electron microscopy (TEM). The samples come from the Moine Thrust zone in the Assynt district, Scotland. They had been studied previously and described in detail with respect to their structural position in relation to the various thrusts in the region and to their preferred orientation. Stresses were derived from these samples using empirical and theoretical equations relating flow stress to the scale of the microstructures. The stresses determined, 43–244 MPa from recrystallized grain size, 9–13 MPa from etched subgrain size, 50–95 MPa from TEM-scale subgrain size and 75–147 MPa from dislocation density, are not constant in individual samples. Simultaneous formation of the quartz fabrics and of the dynamically recrystallized grains during the period of mylonitization may have occurred under flow stresses ranging from 43 to 244 MPa. A later dynamic recovery event reset subgrain sizes and dislocation densities to a constant-value for each microstructure throughout the area. There is insufficient empirical information available on the flow stress/subgrain size relationship and on the effects of annealing recovery and annealing recrystallization to allow for a more detailed interpretation. Recrystallized grain size is still the most easily measured microstructural feature and the relationship of recrystallized grain size to flow stress has a sounder experimental basis than subgrain size or dislocation density. The effect of chemical environment on the behaviour of all the microstructures is still unknown.     

Geochemical assessment of an arsenic mine adjacent to a water reservoir (León, Spain)

A water reservoir constructed for production of hydraulic energy and drinking water in the Riaño valley (León, northern Spain) receives leachates from polluted soils and spoil heaps from a site where small-scale As mining and smelting operations have been developed in the first half of the twentieth century. Water of the upper catchments of the Esla, Yuso and Orza Rivers is stored in this reservoir. The location of these abandoned mine works within the reservoir drainage basin suggested that the stored water could contain high As concentrations. In order to evaluate possible environmental risks, a preliminary soil and surface water geochemical survey has been carried out downstream of the Santa Águeda Mine. Total As concentrations in soils reach 23,800 mg kg^?1 in soils and increase with depth, at least up to a depth of 80 cm. Total As concentrations in surface waters reach 890 μg l^?1. Despite the fact that there is an important As input to the water reservoir, the water flow from the mine catchment is a negligible contribution when compared with the total volume of water inside the dam (0.07%). This fact considerably decreases the environmental risk associated with the presence of untreated spoil heaps containing As-rich minerals at Santa Águeda mine site.     

Self-Organised Criticality and the Response of Wildland Fires to Climate Change

Here I present a new approach to forecasting the effects of climate change on catastrophic events, based on the ‘self-organised criticality’ concept from statistical physics. In particular, I develop the ‘self-organised critical fuel succession model’ (SOCFUS), which deals with wildland fires. I show that there is good agreement between model and data for the response pattern of the whole fire size statistical distribution to weather fluctuations in a boreal forest region. I tentatively predict the fire regime in this region for an instance of possible climate change scenario. I show that the immediate response is sharper than usually thought, but part of the added burning rate might not persist indefinitely. A large fraction of the extra burning in the transition period is likely to be concentrated in a few ‘climate change fires’, much larger than the largest fires that could currently occur. I also suggest that the major fire events recently observed in some tropical rainforest regions belong to a qualitatively different, even more abrupt type of response, which is also predicted by the model. Electronic supplementary material Electronic supplementary material is available for this article at     

The northern Ossa-Morena Cadomian batholith (Iberian Massif): magmatic arc origin and early evolution

Diorites and related rocks in the Mérida area of northern Ossa-Morena (SW Iberia) are intrusive into Precambrian metavolcanic and metasedimentary sequences. Cumulate products from the H₂O-rich magmas are amphibole-rich gabbros to hornblendites. Major and trace element compositions, including Sr and Nd isotope data, allow the definition of a calc-alkaline series likely formed in relation to an immature arc setting. Crystallization of the intrusives has been established between ca. 570 and 580 Ma by U-Pb dating of constituent zircons. Garnet growth in dioritic rocks reflects a tectono–thermal overprint dated by Sm-Nd internal isochrons at around 555 Ma. Older Sm-Nd and Lu-Hf results between ca. 593 and 637 Ma on the same rocks suggest an earlier stage of regional metamorphism within the arc environment. The northern Ossa-Morena composite batholith and related metamorphic units have been tectonized and dismembered in the course of subsequent low-grade events during final stages of the Cadomian orogeny and the Variscan cycle. The units studied represent a well preserved segment of the arc region that evolved in Neoproterozoic times along the western border of Gondwana to conform the Cadomian–Avalonian basement of the Hercynian realm.This revised version was published in October 2004 with corrections to the names and order of the authors.     

The Gulf of California: Review of ecosystem status and sustainability challenges

The Gulf of California is unique because of its geographical location and conformation. It hosts diverse ecosystems and important fisheries that support industry and provide livelihood to coastal settlements. It is also the site of interests and problems, and an intense interaction among managers, producers, and conservationists. In this report, we scrutinize the abiotic (hydrography, climate, ocean circulation, and chemistry) and biotic (phyto- and zooplankton, fish, invertebrates, marine mammals, birds, and turtles) components of the marine ecosystem, and some particular aspects of climate variability, endemisms, harmful algal blooms, oxygen minimum layer, and pollution. We also review the current conditions and conflicts around the main fisheries (shrimp, small and large pelagic fishes, squid, artisanal and sportfishing), the most important human activity in the Gulf of California. We cover some aspects of management and conservation of fisheries, especially the claimed overexploitation of fish resources and the ecosystems, and review proposals for creating networks of marine protected areas. We conclude by identifying main needs for information and research, particularly the integration of data bases, the implementation of models and paleoreconstructions, establishment of monitoring programs, and the evaluation of fishing impacts and management actions.     

辽东半岛海城-大石桥菱镁矿矿床成因探讨

辽东半岛古元古界辽河群大石桥组三段地层中赋存有全球最大工业储量的菱镁矿矿床.在总结和整理已发表的辽东半岛晶质菱镁矿床地质和地球化学数据的基础上,本次研究进行了Mg和B同位素测试及研究工作,获得以下认识:① 菱镁矿矿体呈北东东走向,产于大石桥组三段,但不同矿床的矿体厚度差异较大(30～300 m),菱镁矿矿体与顶、底板高...     

Major moisture sources for Western and Southern India and their role on synoptic‐scale rainfall events

Although the identification of the moisture sources of a region is of prominent importance to characterize precipitation, the origin and amount of moisture towards the Indian Subcontinent and its relationship with the occurrence of precipitation are still not completely understood. In this article, the origin of the atmospheric water arriving to the Western and Southern India during a period of 5 years (1 January 2000–31 December 2004) is investigated by using a Lagrangian diagnosis method. This methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity of thousands of air particles aimed to the study area following the observed winds. During the summer monsoon, the main supply of moisture is the Somali Jet, which crosses the equator by the West Indian Ocean. The recycling process is the main water vapour source in winter. Two additional moisture sources located over northwestern India and the Bay of Bengal are identified. A 30% increase in the moisture flux from the Indian Ocean has been related to the occurrence of strong precipitation in the area, and at the end of the monsoon, the recycling became a significant contribution to the last part of the wet season of Western and Southern India. Copyright © 2011 John Wiley & Sons, Ltd.     

Flocculation–Sedimentation Combined with Chemical Oxidation Process

Flocculation and sedimentation of particles are essential to many environmental and industrial processes. Solid–liquid separation in olive‐oil mill wastewater treatment by means of Fenton system is the key to work continuously and maintain a constant outlet flow of clarified water at the end of the oxidation process. Natural sedimentation is not capable to eliminate the sludge formed. The efficiency of flocculation operation using different flocculants as QG‐2001, QG‐2002, DQGALFLOC‐130H, and Nalco‐77171 was investigated. The optimum dosage of each flocculant, 150, 2.5, 66, and 6 mg dm^?3, respectively, was determined. The results revealed that the best flocculant was Nalco‐77171, which determined 13.5% v/v final sludge separation and 86.5% v/v final clarified water obtained. Kinetics of sludge removal in the transition zone was adjusted to power law, v/v₀ = Kt^ε, where the exponent, ε, varied in the range 0.141–0.670.     

The metamorphic aureole of the Nisa-Alburquerque batholith (SW Iberia): implications for deep structure and emplacement mode

The Nisa-Alburquerque granitic batholith (southern Variscan Belt, Iberian Peninsula) has been studied by petrological, structural and geophysical approaches, obtaining contrasting models for its deep structure and emplacement sequence. In order to test these models and gain knowledge on the thermal increase induced by the intrusion, we have studied its contact aureole, which was developed in similar country rock lithologies (mica schists alternating with metasandstones and feldespatic schists) all along the northern external contact of the batholith. Our results indicate no change in metamorphic grade and some variations in aureole width, which narrows toward the western sectors of the batholith. Cordierite is the only contact metamorphic mineral developed together with a high temperature biotite probably related to the granite thermal input. By considering these new data, together with zircon saturation temperatures within the granite and previous petrological and geophysical studies, we propose a model in which the feeder zones of the granitic magmas were an eastern main one and a western secondary one. We have also made comparisons of the metamorphic grade in the country rocks and the xenoliths within the granite. Most of the xenoliths have the same metamorphic facies as the country rocks (Crd-zone), though some of them contain slightly different assemblages (And + Crd), which could be explained in different ways: (1) differences in the primary schist compositions, (2) increased time-span of xenoliths in contact with the melt and (3) xenolith incorporation at slightly higher depths during final granite ascent.