Mining In Finland Research Articles

Automated microearthquake location using envelope stacking and robust global optimization

Most earthquake location methods require phase identification and arrival-time measurements. These methods are generally fast and efficient but not always applicable to microearthquake data with low signal-to-noise ratios because the phase identification might be very difficult. The migration-based source location methods, which do not require an explicit phase identification, are often more suitable for such noisy data. Whereas some existing migration-based methods are computationally intensive, others are limited to a certain type of data or make use of only a particular phase of the signal. We have developed a migration-based source location method especially applicable to data with relatively low signal-to-noise ratios. We projected seismograms onto the ray coordinate system for each potential source-receiver configuration and subsequently computed their envelopes. The envelopes were time shifted according to synthetic P- and S-wavearrival times (computed using an eikonal solver) and stacked for a predefined time window centered on the arrival time of the corresponding phase. This was done for each component and phase individually, and the squared sum of the stacks was defined as the objective function. We applied a robust global optimization routine called differential evolution to maximize the objective function and thereby locate the seismic event. Our source location method provides a complete algorithm with only a few control parameters, making it suitable for automatic processing. We applied this method to single and multicomponent data using P and/or S phases. We conducted controlled tests using synthetic seismograms contaminated with a minimum of 30% white noise. The synthetic data were computed for a complex and heterogeneous model of the Pyhäsalmi ore mine in Finland. We also successfully applied the method to real seismic data recorded with the in-mine seismic network of the Pyhäsalmi mine.

Seasonal variations of ochreous precipitates in mine effluents in Finland

Ochreous precipitate and water samples were collected from the surroundings of seven closed sulphide mines in Finland. In the Hammaslahti Zn–Cu–Au mine, Otravaara pyrite mine and Paroistenjärvi Cu–W–As mine, the collection was repeated in different seasons to study mineralogical and geochemical variations of precipitates. The sampling was done in 1999–2002 from the ditches and drainage ponds of the tailings and waste rock piles that are susceptible to seasonal changes. Mineralogy of the precipitates was evaluated by X-ray diffraction (XRD) and infrared spectroscopy (IR), and precipitate geochemistry was examined by selective extractions. Schwertmannite (Fe 8O 8(OH) 6SO 4) was the most typical Fe hydroxide mineral found. Goethite was almost as common as schwertmannite, was often poorly ordered, and contained up to 10 wt.% of SO 4. Goethite and schwertmannite were commonly found as mixtures, and they occurred in similar pH and SO 4 concentrations. Ferrihydrite (nominally Fe 5HO 8 · 4H 2O) was typically found in areas not influenced by acid mine drainage, and also in acid mine waters with high organic matter or As content. Jarosite (KFe 3(SO 4) 2(OH) 6) was found only in one site. In addition, some gypsum (CaSO 4 · 2H 2O) and aluminous sulphate precipitates (presumably basaluminite, Al 4(SO 4)(OH) 10 · 5H 2O) were identified. Selective extractions showed that acid extracts Fe tot/S tot-ratios of schwertmannite and goethite samples were similar, but the ratio of oxalate-extractable to total Fe, Fe ox/Fe tot, of goethite samples were lower than those of the schwertmannite samples. Only Al, Si and As were bound to precipitates in substantial amounts, up to several wt.%. In schwertmannites and goethites, Al, Cu, Co, Mn and Zn were mostly structural, substituting for Fe in an Fe oxyhydroxide structure or bound to surface adsorption sites in pores limited by diffusion. In ferrihydrites, heavy metals were also partly bound in adsorbed form dissolving in acid ammonium acetate. Ferrihydrites and goethites were more enriched in Co, Mn and Zn than schwertmannites, but schwertmannites and ferrihydrites were more enriched in As than goethites. Mineralogical and geochemical evidence showed that in the spring, after the snowmelt, the acid mine drainage precipitates were predominantly schwertmannite, and were partly transformed during warm summer months to goethite. The phase transformation of precipitates was followed by a decrease in pH values and increase in SO 4 concentrations of waters. Adsorbed As retarded the phase transformation.

Neutrino oscillations at CERN-Pyhäsalmi baseline

A neutrino factory at CERN could send a neutrino beam to the underground laboratory in the Pyhasalmi mine in Finland. The 2288 km long baseline gives good physics reach, with a possibility to study mass hierarchy. We consider also other neutrino beams. The distance from JPARC, 7090 km, is interestingly close to magic baseline.

Underground multimuon experiment in the Pyhäsalmi mine

An experiment to observe simultaneous, multiple muon events originating from extensive air showers is under preparation. The experiment will be situated in shallow depths in the Pyhasalmi mine in Finland, where the existing free caverns will be used. The aim is to cover an area of about 200 - 300 m(2). The detection of the multimuon events is motivated by partly unknown composition of the primary cosmic rays in the energy region of 10(15) - 10(16) eV, i.e. the 'knee' region. A prototype detector is under construction and is expected to be running at the spring 2005.

Source Parameters and Scaling Relations for Mining-Related Seismicity within the Pyhasalmi Ore Mine, Finland

To investigate source-scaling relations for small earthquakes (M{sub w} -1.8 to 1.2) we have determined source parameters for numerous events ({approx}1500) from the 1400-m-deep Pyhasalmi ore mine in Finland. In addition to a spectral integration approach, we have fitted Brune, Boatwright, and Haskell spectral-shape models to the observed spectra and investigated attenuation influences. Of three different constant Q models (200, 350, and 800), a Q of 350 in combination with the Brune spectral model satisfied the data best. We have also investigated the frequency dependence of Q using the spectral decay method and found that Q increases with frequency. For selected events from two distinct clusters, we compared source parameters derived from constant Q models with source parameters using the multiple empirical Green's function (MEGF) approach. By using constant Q models, the apparent stress seems to increase with magnitude, whereas results based on the MEGF approach indicate constant apparent stress with magnitude. In comparison with results from other studies that cover a larger-magnitude scale, we find apparent stresses that are about 1 to 2 orders of magnitude smaller than most of those. A modified M{sub 0} {approx} fc{sup -(3 + {epsilon})} scaling relation allows for increasing apparent stress with magnitudemore » and can hence combine this study's results with apparent stresses found for large earthquakes. However, within the limited-magnitude range of our data, apparent stresses seem constant.« less

Platinum-Group Element Distribution in Some Ore Deposits: Results of EPMA and Micro-PIXE Analyses

The distribution of platinum-group elements (PGE) in the Main Sulfide Zone of the Great Dyke of Zimbabwe, in the arsenide ores of Vammala and Kylmakoski mines in Finland, and in the chromite-Ni arsenide ores from the Ronda and Beni Bousera massifs (Spain and Morocco) has been studied by means of different optical and microanalytical techniques. The results show a bimodal distribution of PGE in the ores from the Great Dyke and the Vammala and Kylmakoski mines where Pd, Pt and, to lesser extent, Rh occur both as discrete platinum-group minerals and in solid solution in sulfides, arsenides and sulfarsenides. In the ores from Ronda and Beni Bousera, platinum-group elements occur only in solid solution in arsenides and sulfarsenides.

Some Legal Aspects of Mining in Finland

Some Legal Aspects of Mining in Finland

Flotation in acid mine drainage control: Beneficiation of concentrate

This paper is focused on recovering residual sulfide minerals by flotation from the tailing of the Pyhäsalmi Cu-Zn mine in Finland. The tailing contains 4–8% sulfide sulfur and according to the static test it is strongly acid producing, having a low ratio of neutralization potential to acid production potential (NP/AP < 1). The NP/AP ratio could be markedly improved (> 1) by flotation treatment of the tailing. Fine pyrite caused sulfide losses in the flotation while incomplete liberation had only a minor effect on the acid production potential. The cleaner concentrate obtained during the flotation of the tailing contained 33% sulfur, 1% zinc, 0.7% copper, 2.8 g/t gold, and 40 g/t silver. Potential process options are available today for partial beneficiation of the concentrate but further development work is needed for recovering all the valuable elements and eliminating the waste pile. © 1997 Canadian Institute of Mining and Metallurgy.

Airborne Mineral Fibers and Quartz Dust in Precambrian Metamorphic Limestone and Dolomite Mines in Finland

Abstract The airborne concentrations of mineral fiber and quartz dust to which miners are exposed are reported here for four limestone and five dolomite mines. The air samples were collected at fixed monitoring points located in the main work areas. The material comprises 46 samples analyzed by phase contrast microscope (PCM), 90 samples analyzed by scanning electron microscope (SEM), and 50 samples of dust analyzed for quartz content. Fibers (length >5 μm, diameter < 3 μm, and aspect ratio ≥ 3:1) were counted and silicate minerals were identified with an energy-dispersive spectrometer. On the basis of morphology the fibers were classified as perfect fibers, fibrous cleavage fragments, or cleavage fragments. In various work stages the mean fiber concentrations were 0.05 to 0.71 fibers/cc as measured with PCM and 0.06 to 0.34 fibers/cc as measured with SEM. The mean concentrations of the respirable quartz dust (<5 μm) were 0.07 to 0.96 mg/m3. The predominant fibrous silicates were tremolite and wollastonit...

Incidence of cancer among anthophyllite asbestos miners in Finland.

A cohort of 736 male and 167 female workers of two anthophyllite mines in Finland was followed up through the Finnish Cancer Registry for cancer in 1953-91. Compared with the total cancer incidence of the east Finnish population, the men had a raised risk of total cancer (standardised incidence ratio (SIR) 1.7; 95% confidence interval (95% CI) 1.4-1.9), mainly attributable to an excess in lung cancer (SIR 2.8; 95% CI 2.2-3.6). The risk of lung cancer was somewhat higher among workers classified as heavily exposed (SIR 3.2; 95% CI 2.4-4.1) than among those moderately exposed (SIR 2.3; 95% CI 1.5-3.6) and the risk increased with increasing smoking and with increasing time of work with exposure. There were four cases of mesothelioma v 0.1 expected, all in men who smoked and had had a long and heavy asbestos exposure. Among women, a non-significant excess in total cancer (SIR 1.5; 95% CI 0.9-2.4) was found in the subgroup with heavy exposure to asbestos. Anthophyllite asbestos seems to have high potency in the carcinogenesis of lung cancer and low potency in carcinogenesis of mesothelioma in comparison with the other types of asbestos.

Evidence for bacterially generated hydrocarbon gas in Canadian shield and fennoscandian shield rocks

Hydrocarbon-rich gases found in crystalline rocks on the Canadian and Fennoscandian shields are isotopically and compositionally similar, suggesting that such gases are a characteristic feature of Precambrian Shield rocks. Gases occure in association with saline groundwaters and brines in pressurized “pockets” formed by sealed fracture systems within the host rocks. When released by drilling activities, gas pressures as high as 5000 kPa have been recorded. Typical gas flow rates for individual boreholes range from 0.25 L/min to 4 L/min. The highest concentrations of CH 4 are found in the deepest levels of the boreholes associated with CaNaCl (and NaCaCl) brines. N 2 is the second major component of the gases and with CH 4 accounts for up to 80 to >90 vol%. Higher hydrocarbon (C 2 +) concentrations range from <1 to 10 vol.%, with C1/(C2 = C3) ratios from 10−1000. Isotopically the gases show a wide range of values overall ( σ 13 C = −57.5 to −41.1%; σ D = −245 to −470‰ ) but a relatively tight cluster of values within each sampling locality. The Enonkoski Mine methanes are unique with σ 13C values between −65.4 and −67.3‰ and σD values between −297 and −347‰. The shield gases are not readily reconcilable with conventional theories of methanogenesis. The range of C1/(C2 + C3) ratios for the shield gases is too low to be consistent with an entirely bacterial origin. In addition, σD CH 4 values are in general too depleted in the heavy isotope to be produced by thermogenic methanogenesis or by secondary alteration processes such as bacterial oxidation or migration. However, isotopic and compositional evidence indicates that bacterially derived gas can account for a significant component of the gas at all shield sites. Conventional bacterial gas accounts for 75–94 vol% of the occurrences at Enonkoski Mine in Finland. At each of the other shield sites, bacterial gas can account for up to 30–50 vol% of the total gas accumulation. This study and other recent evidence of active bacterial communities in deep hydrogeological environments emphasize the need for more comprehensive investigation of the role of microorganisms in the deep subsurface.

Experimental studies on skin hazard with cycloocta-1,5-diene and cyclododeca-1,5,9-triene.

A cohort of 736 male and 167 female workers of two anthophyllite mines in Finland was followed up through the Finnish Cancer Registry for cancer in 1953-91. Compared with the total cancer incidence of the east Finnish population, the men had a raised risk of total cancer (standardised incidence ratio (SIR) 1.7; 95% confidence interval (95% CI) 1.4-1.9), mainly attributable to an excess in lung cancer (SIR 2.8; 95% CI 2.2-3.6). The risk of lung cancer was somewhat higher among workers classified as heavily exposed (SIR 3.2; 95% CI 2.4-4.1) than among those moderately exposed (SIR 2.3; 95% CI 1.5-3.6) and the risk increased with increasing smoking and with increasing time of work with exposure. There were four cases of mesothelioma v 0.1 expected, all in men who smoked and had had a long and heavy asbestos exposure. Among women, a non-significant excess in total cancer (SIR 1.5; 95% CI 0.9-2.4) was found in the subgroup with heavy exposure to asbestos. Anthophyllite asbestos seems to have high potency in the carcinogenesis of lung cancer and low potency in carcinogenesis of mesothelioma in comparison with the other types of asbestos.

Harmotome from Korsnäs, Finland

SummaryThis paper describes a harmotome from the Korsnäs mine in Finland, which occurs in the same open cavity as the yellow apophyllite previously reported in this journal. The harmotome is always twinned according to the morvenite and Marburg laws. Chemical composition, optical properties, X-ray powder pattern, and single crystal data are given.