Structural position of ore-bearing areas in Finland

Mikkola, Aimo K.; Niini, H.

doi:10.17741/bgsf/40.003

Cited by 20 publications

(12 citation statements)

References 6 publications

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“…3) which separates it from areas of higher uplift northeast of the trough. This gravity trough, attributed to deep faults by several authors (Paarma and Marmo 1961, Mikkola and Niini 1968, Talvitie 1971, zigzags in line with four of the main trends (I-IV) described. The zigzags coincide with long faults belonging to these trends.…”

Section: Distribution Of Land Upliftsupporting

confidence: 75%

“…3); it is indicated partly by main and partly by subordinate maxima of the rosettes. Numerous Ni-Cu sulfide deposits, associated with basic and ultrabasic plutonic rocks, are aligned with this zone, which is characterized by wide drag folds upon steep axes, and by traces of repeated brecciation (Mikkola and Niini 1968, Talvitie 1971, Gaäl 1972. The zone is seismically active (Fig.…”

Section: Shear Zonesmentioning

confidence: 99%

“…Results obtained in certain areas of Finland support this view (Tuominen 1957(Tuominen , 1962(Tuominen , 1966Tuominen andSöderholm 1966, Talvitie 1971). The fracture trends were studied from the latest fracture map of Finland (Mikkola and Niini 1968). As before, the areas north of the 67th parallel were omitted.…”

Section: Fracture Line Trendsmentioning

confidence: 99%

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Tectonic patterns in the central Baltic Shield

Tuominen¹,

Aarnisalo²,

Söderholm³

1973

Bull Geol Soc Finland

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A network of several sets of subparallel lineaments, extending over the Baltic Shield into the surrounding areas of Paleozoic and later rocks, has been identified in Nimbus satellite imagery. The observed lengths of several lineaments exceed 1 000 km. Each set is distributed all over the Shield. Ground data collected in Finland indicate the following. The strikes of foliation of the Precambrian schists and gneisses are concentrated into eight dominant trends, each parallel to a given set of the lineaments. The strike frequency maxima of the Bouguer gravity isolines and the dominant trends of the basement scarps and trenches fall in these same directions. Schist belts, tanging in age up to 2 800 m.y., as well as the boundaries of the major structural and lithologic units, are aligned with or parallel to the lineaments, which also separate blocks differing in altitude and in rate of recent land-uplift. The data suggest that the lineaments represent a permanent abyssal shear-net system, which has contributed to the evolution of the Shield since Early Precambrian times. The system possibly extends over the surrounding ocean floor.

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Section: Distribution Of Land Upliftsupporting

confidence: 75%

Section: Shear Zonesmentioning

confidence: 99%

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Tectonic patterns in the central Baltic Shield

Tuominen¹,

Aarnisalo²,

Söderholm³

1973

Bull Geol Soc Finland

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“…According to Wahl (1963), the zone, which was later suggested to be potential for Ni-Cu ores, is characterized by hypersthenebearing plutonites, the emplacement of which was controlled by two fracture lines trending NW-SE. The concept of the ore potentiality of the »Ladoga-Bothnian Sea zone» was originally proposed by Paarma and Marmo (1961); it was later corroborated by Mikkola and Niini (1968), Mikkola (1971) and Kahma (1973). Gaål (1972) suggested that the intrusives that act as host rocks for the nickel ores are associated with transcurrent faults, domes and brachyantiforms.…”

Section: Geology Of the Environmentmentioning

confidence: 98%

“…Gaål (1972) suggested that the intrusives that act as host rocks for the nickel ores are associated with transcurrent faults, domes and brachyantiforms. Fault-tectonic analyses on the Ladoga-Bothnian Sea zone have been undertaken by Härme (1961) and Salli (1970), and lineament interpretations by Talvitie (1971), and Mikkola and Vuorela (1977). Parkkinen (1975) maintains that the intrusives were emplaced during large-scale regional movements.…”

Section: Geology Of the Environmentmentioning

confidence: 99%

The Laukunkangas nickel-copper occurrence in southeastern Finland

Grundström¹

1980

Bull Geol Soc Finland

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The Laukunkangas Ni-Cu deposit in a Svecokarelidic synorogenic plutonite is located at the southeastern end of the Kotalahti nickel belt. The mineralization is associated with the norites, olivine gabbros and peridotites of an olivine tholeiitic suite. It contains about 4.5 million tons of ore in situ averaging 0.33 %> Ni and 0.10 %> Cu. The intrusive is a rather small pipelike body with an elliptical surface plan. It extends to a depth of at least 300 m; its largest horizontal dimension is about 1 km and its width in the middle of the intrusive is some 200 m. The variations in the Ni and Fe contents in silicates, the MgO content in rock types and the Ni content in the sulphide phase clearly indicate the internal layering in the intrusive. Emplacement probably took place in two or three stages. The boundaries between the layers show contamination that is reflected in the distribution of MgO and trace elements. »The model crystallization temperatures» suggest that the intrusion was emplaced in three separate phases. The mineralization occurs near the contact zone at the eastern end of the intrusive. The few nickel-rich portions encountered inside the intrusive are small and discontinous lenses or slabs. The mineralization is characterized by the following parameters: Ni/Co = 17.31, Ni/Cu = 3.15, Cu/Co = 5.49, and the Ni content in sulphide phase 4.81 %>.

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