Olavi Selonen

The late Svecofennian granite-migmatite zone of southern Finland—a belt of transpressive deformation and granite emplacement

Abstract The late Svecofennian granite-migmatite (LSGM) zone in southwestern Finland is a ∼ 100 km wide and 500 km long belt transecting the southern Svecofennides from WSW to ENE. It was formed in an area of thin pillow lavas, volcaniclastic sediments and limestones. The area is interpreted as having been an early basin of crustal extension which was the locus of an inherited zone of weakness in the Proterozoic crust. Early recumbent folding was followed by crustal thickening and intrusions of ∼ 1.89-1.88 Ga old plutonics. The LSGM-zone is characterized by 1.84-1.83 Ga old rhomboidal sheets of late Svecofennian microcline granite and is bounded by ductile shears. Amongst the two major phases of deformation defined in the LSGM-zone, the earlier one (D1) affected only the supracrustals and the 1.89-1.88 Ga old early plutonics. In contrast, the later phase (D2) also deformed the late Svecofennian migmatites and granites. D1 represents a complex and long-lasting deformation event which included overturning and thrusting of the Svecofennian strata. D2 comprised ENE-WSW directed drag accompanied by NNW-SSE compression. The Svecofennian crust was thickened further and anatectic microcline granites intruded along thrusts. The rhomboidal outline of the late Svecofennian granite sheets indicates a sense of movement in agreement with measured dextral strike-slip in the shears delimiting the LSGM-zone. Imbricated feldspar megacrysts in the granites indicate thrusting towards the west during the stage of granitic magmatism. The gently dipping early Svecofennian gneisses and the late granite sheets were folded into upright F2 folds with gently plunging axes. Locally, the F2 axial surfaces were intruded by late Svecofennian granite mobilisates.

Structural observations on the Uusikaupunki trondhjemite sheet, SW Finland

Abstract The Uusikaupunki trondhjemite is located in SW Finland within high-grade Palaeoproterozoic Svecofennian supracrustal rocks. Three phases of deformation are identified in the supracrustal rocks. The D1 deformation produced a schistosity defined by biotite. The D2 deformation is characterized by recumbent or reclined folds with NW vergences and it is accompanied by thrusting towards the NW. The N–S compression and the E–W shear motion define a transpressional tectonic regime during the D3 deformation. The D3 is associated with F3 folds overturned towards the N. It is suggested that the Uusikaupunki trondhjemite intruded as gently dipping sheets before or during the D2 deformation.

A review of dust emission dispersions in rock aggregate and natural stone quarries

Abstract Fugitive dust constitutes one of the most severe environmental problems in quarries because it escapes capture. This review aims to provide overview of dust concentration caused by quarrying by synthesising the current knowledge. The 25 studies explored here were conducted in open-pit quarries or mines. Three main dust sources surfaced from the studies: drilling, crushing and hauling. Analysis revealed a range of dust concentrations caused by different quarrying operations. Crushing was the most significant dust source, while drilling caused the highest variation. Dust concentration decrease was observed with increasing distance, but the retention was incoherent due to local dust sources.

Assessment of Potential Natural Stone Deposits

Research methods for evaluation of natural stone deposits are evaluated as a part of the project “Efficient use of natural stone in the Leningrad region and South-East Finland”. The most common methods in the beginning of the site investigation process of a new natural stone deposit are detailed mapping of fractures and ground penetrating radar (GPR) measurements carried out on an exposed mapping traverse. Small scale samples are also collected to evaluate the aesthetical appearance of the stone. After these diamond core drilling is carried out to get a three-dimensional view of the stone quality. Mapping, GPR measurements and diamond core drilling have each their strengths in evaluation and they also overlap in detection of some common features. Fracture mapping carried out on the surface and GPR measurements can be combined in conditions where GPR reflections are strong, usually in intersections of sub-horizontal and sub-vertical fractures. GPR and diamond core drilling can be combined to detect major sub-horizontal fractures and in some cases also fracture system of the surface layer if the fractures are open enough and contain water or moisture.

Production of Granitic Press Rollers in Finland

The use of granite as material for press rolls in paper machines started in the late 19th century. In Kuru, Finland granitic press rolls were produced from the 1930s until 2008. The suitability of the Kuru grey granite as material for press rolls was defined by its durability, mineral composition, homogeneity, and grain size as well as by the good extractability of the granite. The production of granitic press rolls in Finland developed into a highly specialized industrial process in many phases including: 1. quarrying of the stone block, 2. sawing of the roll, 3. preparation of the ends of the roll, 4. installation of the axis into the roll, 5. pre-compression of the roll, and finally 6. balancing, grinding, and polishing of the roll.

The Wiborg Granite Batholith—The Main Production Area for Granite in Finland

The 1640 Ma Wiborg rapakivi granite batholith is the most important area for natural stone production in Finland. The main quarried stone varieties, Baltic Brown, Baltic Green, Carmen Red/Karelia Red and Eagle Red, are regularly produced in large scale for the global stone market as unique stone qualities. The unique visual appearance with the rapakivi texture, in combination with high durability and long life cycles, makes these stones attractive. During the recent years, the batholith has been studied in several projects by the Geological Survey of Finland, including regional explorations, detailed site investigations, and development of exploration methods. The general regional exploration activities indicate that the batholith as a whole have a good general natural stone potential for the future, which forms a basis for further development. With the new ENPI project more detailed knowledge on the new potential sites for natural stone will be gained.