Mineralogy,geochemistry and petrogenesis of the V-Ti-bearing and chromiferous magnetite deposits hosted by Neoarchaean Channagiri Mafic-Ultramafic Complex,Western Dharwar Craton,India: Implications for emplacement in differentiated pulses     

Tadasore C. Devaraju  Kallada R. Jayaraj  Thavaraghatta L. Sudhakara  Tuomo T. Alapieti  Beate Spiering  Risto J. Kaukonen 《Central European Journal of Geosciences》2014,6(4):518-548

The Channagiri Mafic-Ultramafic Complex occupies lowermost section of the Neoarchaean Shimoga supracrustal group in the Western Dharwar Craton. It is a segmented body occupying the interdomal troughs of granitoids. The magnetite deposits occur in the northeastern portion; typically occupying the interface zone between gabbro and anorthositic. Mineralogically, the deposits are simple with abundant magnetite and ilmenite. Hogbomite is a consistent minor mineral. Magnetites are typically vanadiferous (0.7–1.25% V₂O₅). Ilmenite consistently analyses more MgO and MnO than coexisting magnetite. Chlorite, almost the only silicate present; lies in the range of ripidolite, corundophilite and sheridanite. The chromiferous suit occupying eastern side of Hanumalapur block (HPB) contains Fe-Cr-oxide analysing 37.8–11.9% Cr₂O₃ and 40.5–80% FeO ^t . In these too, chlorite, typically chromiferous (0.6–1.2% Cr₂O₃), is the most dominant silicate mineral. Geochemistry of V-Ti-magnetite is dominated by Fe, Ti and V with Al, Si, Mg and Mn contributing most of the remaining. Cr, Ni, Zn, Co, Cu, Ga and Sc dominate trace element geochemistry. The Cr-magnetite is high in Cr₂O₃ and PGE. Two separate cycles of mafic magmatism are distinguished in the CMUC. The first phase of first cycle, viz., melagabbro-gabbro, emplaced in the southeastern portion, is devoid of magnetite deposits. The second phase, an evolved ferrogabbroic magma emplaced in differentiated pulses, occupying northeastern portion of the complex, consists of melagabbro→gabbro-anorthosite→V-Ti magnetite→ferrogabbro sequence. Increase in oxygen fugacity facilitated deposition of V-Ti magnetite from ferrogabbroic magma pulse emplaced in late stages. The second cycle of chromiferous PGE mineralized suite comprises fine-grained ultramafite→alternation of pyroxinite-picrite→Crmagnetite sequence formed from fractionation of ferropicritic magma. HPB also includes >65m thick sill-like dioritic phase at the base of the ferriferous suit and a sinuous band of coarse-grained ultramafite enclosed within the chromiferous suit; both unrelated to the two mafic magmatic cycles.  相似文献   

Book review     

Risto Kalliola 《GeoJournal》2006,65(3):239-240

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Continental impact on marine boundary layer coarse particles over the Atlantic Ocean between Europe and Antarctica     

Jarkko V. Niemi  Heikki Tervahattu  Aki Virkkula  Risto Hillamo  Kimmo Teinil  Ismo K. Koponen  Markku Kulmala 《Atmospheric Research》2005,75(4):109

Aerosol samples were collected in the Atlantic marine boundary layer between the English Channel and Antarctica during November–December 1999. The composition of coarse (aerodynamic diameter 1–3 μm) individual aerosol particles was studied using the SEM/EDX method. The major particle types observed were fresh sea salt, sea-salt particles reacted partly or totally with sulphuric acid or nitric acid, Mg-sulphate, Ca-sulphate, mixed aluminosilicates and sea salt, aluminosilicates, Ca-rich particles and Fe-rich particles. The relative fractions of sea-salt particles with moderate or strong Cl depletion were high near the coasts of Europe (65–74%) and Northern Africa (44–87%), low far from the coast of Western Africa (10–20%) and very low in remote sea areas between Africa and Antarctica (1%). The Cl depletion was strongest when air masses arrived from the direction of anthropogenic pollution sources. The fractions of Mg-sulphate particles were high (18–25%) in 2 samples near Europe. The Mg-sulphate particles were probably formed as a result of fractional recrystallization of sea-salt particles in which Cl was substituted by sulphate. It remained unclear whether these particles were formed in the atmosphere or during and after sampling. The relative fractions of particles from continental sources were quite low (10–15%) near Europe, very high (25–78%) near the coast of Northwestern Africa and very low in the remote sea areas (0–2%). Most of the continental particles were aluminosilicates and some of them were internally mixed with sea salt. Near the coast of Northwestern Africa, the main source of aluminosilicates was Saharan dust, and near the Gulf of Guinea, emissions from biomass burning were also mixed with aluminosilicates and sea salt.  相似文献   

Corporate geography     

Risto Laulajainen 《GeoJournal》1984,9(2):102-104

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Chemistry and sulfur isotope investigation of industrial wastewater contamination into groundwater aquifers, Piteå County, N. Sweden     

Peter Torssander  Carl-Magnus Mrth  Risto Kumpulainen 《Journal of Geochemical Exploration》2006,88(1-3):64

The possible contamination of a groundwater system with industrial wastewater originating from a paper mill factory has been investigated in Piteå, N. Sweden. Six samples were collected from the wastewater in the waste dump and twelve samples from the adjacent groundwater were analyzed for chemistry and sulfur isotopes. The industrial wastewater is a saline water consisting mainly of Na–HCO₃–SO₄, having a high pH and showing δ³⁴S values between 7‰ and 9‰ affected by bacterial sulfate reduction. The groundwaters are relatively dilute, dominated by Na⁺, Ca²⁺ and HCO₃⁻, but with varying concentrations as exemplified by sulfate with concentrations varying between 3 and 69 mg L^− 1 while the δ³⁴S values range from − 0.5‰ to 14.3‰. The data suggest that the main S sources in the waters are the bedrock sulfides and/or atmospheric deposition, which, sometimes, are overlapped by bacterial sulfate reduction. Contamination from the waste dump does not occur.  相似文献   

Recordings and occurrence of geomagnetically induced currents in the Finnish natural gas pipeline network     

Antti Pulkkinen  Ari Viljanen  Kari Pajunp  Risto Pirjola 《Journal of Applied Geophysics》2001,48(4)

A project implemented to study the effects of space weather on the Finnish natural gas pipeline was started in August 1998. The aims of the project were (1) to derive a model for calculating geomagnetically induced currents (GIC) and pipe-to-soil (P/S) voltages in the Finnish natural gas pipeline, (2) to perform measurements of GIC and P/S voltages in the pipeline and (3) to derive statistical predictions for the occurrences of GIC and P/S voltages at different locations in the pipeline network.GIC and P/S voltage were recorded at a compressor station. The GIC measurement was made with two magnetometers, one right above the pipe, and another at the Nurmijärvi Geophysical Observatory about 30 km southwest. The largest GIC since November 1998 has been 30 A. The P/S voltage recording was stopped in May 1999, but GIC is still measured.GIC statistics were derived based on the recordings of the geomagnetic field at Nurmijärvi. The geoelectric field was calculated by using the plane wave model. This field was input to the general pipeline model resulting in the distribution of currents and P/S voltages at selected points in the pipeline. As could be expected, the largest P/S voltage variations occur at the ends of the pipeline network, while the largest GIC flow in the middle parts.  相似文献   

Determination of Exterior Orientation Using Linear Features from Vector Maps     

Mika  Karjalainen  Juha  Hyyppä  Risto  Kuittinen 《The Photogrammetric Record》2006,21(116):329-341

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Sediment focusing and210Pb dating: a new approach     

D. J. Rowan  R. J. Cornett  K. King  B. Risto 《Journal of Paleolimnology》1995,13(2):107-118

In this paper we test the utility of the mud deposition boundary depth (mud DBD) theory (Rowanet al. 1992) as a means of maximizing sampling efficiency in paleolimnological investigations, particularly those that apply to²¹⁰Pb dating. The mud DBD is defined by the relationship between near bottom wave velocity and particle threshold velocity, with wave and particle threshold theory simplified to terms of exposure and depth. Mud DBD theory can be used to define the depositional zone in lakes, and within the depositional zone defined by the mud DBD: 1) there is a high probability of obtaining a representative core, 2) variation in mass sediment accumulation rate (MSAR) is not correlated with water depth, and 3) variation in MSAR is considerably reduced from the whole lake average. This suggests that mud DBD theory can account for the effects of sediment focusing, and that the mud DBD defined depositional zone is the zone to which fine-grained sediments are focused. Finally, we have shown that to optimize sampling effort, 5 to 10 cores within the depositional zone are necessary for a reasonably precise estimate of the mean mass sediment accumulation rate. In addition, the use of mud DBD theory prior to sampling can dramatically reduce the cost associated with analyzing large numbers of cores for²¹⁰Pb.This is the fifth of a series of papers to be published by this journal following the 20 ^th anniversary of the first application of²¹⁰Pb dating of take sediments. Dr P. G. Appleby is guest editing this series.  相似文献   

Stratification of selected hydrolytic enzyme activities in the sediment in two lakes in Finland     

Mika A.KHKNEN  Risto HAKULINEN 《国际泥沙研究》2012,27(2):250-258

To investigate the stratification of hydrolytic enzyme activities and importance of subsurface layers in depolymerization of detritus biopolymers,nine hydrolytic enzyme activities involved in the cycling of carbon,phosphorus,nitrogen and sulphur were measured in various sediment layers and their extracts at Kylaniemi in Lake Saimaa in southern Finland and in Lake Ahvenjarvi in northern Finland. The results show that for each lake all nine hydrolytic enzyme activities were higher in all sediment layers than in comparable sediment extracts indicating that the major part of enzymes was bound to the sediment particles in all layers in both lakes.Carbohydratase,P-cellobiosidase,activities did not show any gradient with sediment depth at Kylaniemi in Lake Saimaa indicating that there was rapid turnover of carbohydrates in the entire sediment column.The activities of acetate esterase,butyrate esterase,phosphomonoesterase,aminopeptidase,N-acetyl glucosaminidase,sulphatase andβ-glucosidase in the deepest layers were 19-53%of those in the surface sediment indicating that depolymerization of biopolymers involved in the cycling of carbon,nitrogen,phosphorus and sulphur was substantial in subsurface sediment.  相似文献   

Fissure-fill and tunnel-fill sediments: expressions of permafrost and increased hydrostatic pressure     

Risto A. Kumpulainen 《第四纪科学杂志》1994,9(1):59-72

A spectacular network of fissure fillings and pipes (tunnels) cuts Quaternary gravelly delta deposits northeast of Myvatn, precisely on the spreading axis of the North Icelandic rift zone. The delta was formed in an ice-contact lake during deglaciation towards the end of the last glaciation. Subsequently the lake was drained and permafrost conditions developed in these poorly sorted gravel deposits. Hydrostatic pressure was transmitted from the adjacent glacier to the non-frozen core of the delta beneath the discontinuous permafrost crust and the seasonally frozen active layer. Owing to increased hydrostatic pressure, a network of subhorizontal to vertical fissures was opened along the taliks. In these fissures free ground-water flow and sediment transport were established. Tunnel erosion and probably also seepage erosion were associated with these fissures. Subsequently, the fissures and tunnels were filled by laminated fine sediments interbedded with poorly sorted material resulting in the formation of fissure-fill sediments and tunnel-fill sediments.  相似文献