Major benefits and constraints related to mineral extraction within the EU have been identified on the examples of selected critical raw materials’ deposits. Analyzed case studies include the ...following ore deposits: Myszków Mo-W-Cu (Poland), Juomasuo Au-Co (Finland), S. Pedro das Águias W-Sn (Portugal), Penouta Nb-Ta-Sn (Spain), Norra Kärr REEs (Sweden) and Trælen graphite (Norway). They represent different stages of development, from the early/grassroot exploration stage, through advanced exploration and active mining, up to reopening of abandoned mines, and refer to different problems and constraints related to the possibility of exploitation commencement. The multi-criteria analysis of the cases has included geological and economic factors as well as environmental, land use, social acceptance and infrastructure factors. These factors, in terms of cost and benefit analysis, have been considered at three levels: local, country and EU levels. The analyzed cases indicated the major obstacles that occur in different stages of deposit development and need to be overcome in order to enable a new deposit exploitation commencement. These are environmental (Juomasuo and Myszków), spatial (Juomasuo) as well as social constraints (Norra Kärr, Juomasuo). In the analyzed cases, the most important constraints related to future deposit extraction occur primarily at a local level, while some important benefits are identified mainly at the country and the EU levels. These major benefits are related to securing long-term supplies for the national industries and strategically important EU industry sectors.
A petrographic investigation of ore samples from the Assarel porphyry copper deposit in the Srednogorie metallogenic zone (Bulgaria) constrains the setting and character of precious metals (Au, Ag, ...PGE) and related minerals within the deposit. This work supports renewed interest in understanding the deportment of precious metals and provides mineralogical knowledge during the testing and validation of novel drill core 3D X-ray computed tomography–X-ray fluorescence (XCT-XRF) scanning technology being developed as part of the X-MINE project. Scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) results indicate precious metals occur in their native state (Au, Ag), as sulfides (Ag), sulfosalts (Au), tellurides (Ag, Pd), and selenides (Ag), and typically form micron-sized inclusions in pyrite and chalcopyrite or are disseminated in the groundmass of the rock. Preservation of early Fe oxide–chalcopyrite ± bornite assemblage as relics in the more dominant pyrite-chalcopyrite mineralization assemblage supports mineral disequilibrium relationships and multi-stage mineralization events. Several rare minerals (e.g., merenskyite, acanthite, sorosite, tetra-auricupride, auricupride, greenokite, bismuthinite, nagyagite, native Ni) are reported for the first time at Assarel and highlight the mineralogical diversity of the ore. The occurrence of precious metals and related minerals at Assarel attest to a complex hydrothermal system that underwent progressive physicochemical changes during the evolution of the mineralizing system (e.g., redox conditions, fluid chemistry).
Local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern Fennoscandia. These paleoearthquakes, with fault lengths of up to 160 ...kilometers and average displacements of up to 15 meters, were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation. The Fennoscandian faults were probably formed by single events that ruptured through most of the crust. The largest event, moment magnitude M$_W$ ≈ 8.2, was larger than other known stable continent earthquakes outside failed rifts or extended crust.
Seismotectonics of the Cyprian Arc Wdowinski, Shimon; Ben-Avraham, Zvi; Arvidsson, Ronald ...
Geophysical journal international,
01/2006, Volume:
164, Issue:
1
Journal Article
Peer reviewed
Open access
The Cyprian Arc forms the plate boundary between the Anatolian plate in the north and the Nubian and Sinai plates in the south. We examine the tectonic setting and seismic activity along the arc in ...light of new geodetic studies indicating relative NE–SW plate motions across the arc. The first-order tectonic variations are determined by the arc's geometry. The eastern arc, oriented subparallel to relative motion, is dominated by transcurrent tectonism. The western arc is oriented almost normal to relative plate motion and is subjected to convergent processes. Variations in the level and depth of seismic activity along the western arc suggest that the northwestern section of the arc represents a subduction boundary, whereas the southeastern section represents a collision boundary. The two tectonic domains of the western arc are separated by a NE–SW trending tear fault, which produces large earthquakes, such as the MW = 6.8, 1996 Paphos earthquake. We compare the geometrically similar Cyprian and Hellenic Arcs and find significant differences in the rate, direction and type of convergence across the two arcs. The Hellenic Arc is subjected mainly to subduction, whereas the shorter Cyprian Arc is subjected to subduction, collision and transcurrent tectonic processes.
The region of interest is characterized by incomplete data sets and little information about the tectonic features. Therefore, two methodologies for estimating seismic hazard were used in order to ...elucidate the robustness of the results: the method of spatially smoothed seismicity introduced by Frankel (1995) and later extended by Lapajne et al. (1997) and a Monte Carlo approach presented by Ebel and Kafka (1999). In the first method, fault-rupture oriented elliptical Gaussian smoothing was performed to estimate future activity rates along the causative structures. Peak ground accelerations were computed for a grid size of 15 km × 415 km assuming the centre of the grids as epicentres, from which the seismic hazard map was produced. The attenuation relationship by Ambraseys et al. (1996) was found suitable for the region under study. PGA values for 10% probability of exceedence in 50 years (return period of 475 years) were computed for each model and a combined seismic hazard map was produced by subjectively assigning weights to each of these models. A worst-case map is also obtained by picking the highest value at each grid point from values of the four hazard maps. The Monte Carlo method is used to estimate seismic hazard, for comparison to the results from our previous approach. Results obtained from both methods are comparable except values in the first set of maps estimate greater hazard in areas of low seismicity. Both maps indicate a higher hazard along the main tectonic features of the east African and Red Sea rift systems. Within Eritrea, the highest PGA exceeded a value 25% of g, located north of Red Sea port of Massawa. In areas around the capital, Asmara, PGA values exceed 10% of g.PUBLICATION ABSTRACT
Focal mechanisms from 18 major Swedish earthquakes, ML(UPP) ≥ 3, reveal that: (1) several of the studied earthquakes have focal mechanisms with significant extensional stresses which fit well to the ...idea of postglacial rebound as an important stress generator, (2) in areas like south-western Sweden, the north-westerly trending compressional axes indicate that ridge push from the North Atlantic Ridge is also a considerable stress contributor; (3) some local tectonic features, like the Skälderviken depression in Kattegat, are momentous for seismotectonic interpretations. In addition to first P polarities, full waveform modelling for frequencies up to 3 Hz and epicentral distances up to 225 km provides rather robust focal-mechanism determinations. Focal depths of seven events, ranging from 11 to 37 km, are well resolved within a few km by waveform modelling.
This paper studies the October 18, 1992, M subscript W 7.1 Atrato earthquake and its foreshocks and aftershocks, which occurred in the Atrato valley in northwestern Colombia. The main shock was ...preceded by several foreshocks, of which the M subscript W = 6.6 October 17 earthquake was the largest. Foreshocks and aftershocks are examined by performing joint-hypocenter relocations using high-quality Pn and Sn wave readings from permanent regional networks. A few hours prior to the main shock, a sudden increase in foreshocks was observed. This possibly could be used as a predictor since foreshocks have been known for other major events in the region. The locations align for 90 km, with a trend of 5 deg plus/minus 4 deg in agreement with the Harvard CMT solution showing the fault plane trending 9 deg to be the plane of rupture. In relation to the epicenter of the main shock, maximum intensities were located to the south, consistent with a rupture that traveled from north to south with a larger energy release in the south as suggested by an empirical Green's function study. The boundary between the Panama and North Andes blocks has been placed close to the Panama-Colombia border as either a sharp boundary or a diffuse zone. The Atrato earthquake, however, shows that the plate boundary between the Panama and North Andes microblocks is a diffuse deformation zone. This zone has a width of at least 2 deg stretching from 78 deg W to 76 deg W. Quantification of earthquake moment release (during the past 30 years) in this zone shows a similar amount of moment release in the western and eastern parts of this zone.
We study the October 18, M^sub W^ = 7.1, 1992 Atrato earthquake, and its foreshocks and aftershocks, which occurred in the Atrato valley, northwestern Colombia. The main shock was preceded by several ...foreshocksof which the M^sub W^ = 6.6, October 17 earthquacke was the largest. Inparticular, we examine foreshocks and aftershocks performing joint-hypocenter relocations using high quality Pn and Sn wave readingsfrom permanent regional networks. We observed a few hours prior to the main shock a sudden increase of foreshocks. Maybe this could be used as a predictor since foreshocks have been known for other major events in the region. Our locations align for 90 km with a trend of 5^sup °^ ±4^sup °^ in agreement with the Harvard CMT solution showing the faultplane trending 9^sup °^ to be the plane of rupture. In relation to theepicenter of the main shock, maximum intensities were located to thesouth, consistent with a rupture that traveled from north to south witha larger energy release in the south as suggested by an empirical Green'sfunction study (Li and Toksöz, 1993; Ammon et al., 1994). The boundarybetween the Panama and North Andes blocks has been placed close to thePanama-Colombia border as either a sharp boundary or a diffuse zone. TheAtrato earthquake, however, shows that the plate boundary between thePanama and North Andes microblocks is a diffuse deformation zone. Thiszone has a width of at least 2^sup °^ stretching from 78^sup °^W to 76^sup °^W. Quantification of earthquake moment release (during the past30 years) in this zone shows a similar amount of moment release in thewestern and eastern parts of this zone.PUBLICATION ABSTRACT
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