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Geophysics in the prognostic analysis of iron ores in Finland
Geoexploration, Elsevier
Science
Abstracts*
23 (1984185) 415-440 Publishers B;V., Amsterdam
Printed
in The Netherlands
’
GEOPHYSICAL
LEIF
415 -
ATLAS OF THE SILJAN AREA - DEEP GAS PROJECT
ERIKSSON
Geological Survey of Sweden, Box 670, 751 28 Uppsala (Sweden)
The Siljan Ring Structure is thought to be a meteorite impact crater. It has been chosen by the Swedish State Power Board as a suitable area for a deep gas study. A first phase of limited field investigations including drillings to 700 m, have been carried out. For this reason the Geological Survey of Sweden compiled airborne geophysical data and ground gravity data to be presented in a geophysical atlas. The main scale is l:lOO,OOO over the central area of interest, and the scale 1: 250,000 over a well sized region. This makes it possible to place the Siljan Structure in a wider regional geological context, to make certain depth estimations and to help deciding the locations for drillings. Preliminary interpretations are summarized and a proposed model is discussed.
GEOPHYSICS FINLAND
VOITTO
IN THE PROGNOSTIC
ANALYSIS
OF IRON ORES IN
HEISKANEN
Rautaruukki
Oy, PL 217, SF-901 01 Oulu (Finland)
Rautaruukki Oy with some Finnish scientists and the Soviet company V/O Technoexport have compiled a prognostic analysis of iron ore potential in Finland. Geological, geophysical and geochemical information was combined during the work. Three of the eleven compiled maps were geophysical. The geophysical interpretation map is based on gravimetric, magnetic and petrophysical data. It depicts combinations of gravimetric and magnetic fields according to their intensity and character. The blocks and structures thus revealed can be correlated to geological complexes and tectonic structures. The map of local magnetic anomalies depicts anomalies according to their intensities and faults and fractures limiting or breaking these anomalies. It *‘Abstracts of papers submitted at the 15th Meeting of Applied Geophysics, Espoo, Finland, 15-17 January 1985.
0016-7142/85/$03.30
0 1985
Elsevier
Science
Publishers
the
B.V.
Nordic
Association
for
416
has been possible to localize horizons critical to iron ore and to contour different formations. In the aeroelectromagnetic interpretation map, the conductors and anomalies caused by susceptibility are shown. It can be used to locate conductive horizons (for example black schists) and rocks containing magnetite. The geophysical maps were used for compiling geological maps and preparing criteria for iron ore critical complexes.
PREDICTION OF AREAS POTENTIAL FOR Cu-Zn SULPHIDE ORE WITH THE AID OF LOW-ALTITUDE AEROGEOPHYSICAL DATA AND STATISTICAL METHODS
HILKKA
ARKIMAA,
EERO
LINDQVIST
and VILJO
KUOSMANEN
Geological Survey of Finland, SF-021 50 Espoo 15 (Finland)
The study area (60 X 75 km’) is situated in the Lake Ladoga-Botnian Bay ore zone. Low-altitude measurements on magnetic total intensity, electromagnetic real and imaginary components and some radiometric ratios were first transformed into principal components (PC). The PC feature space created was studied using unsupervised classification. It was observed that the anomalies in the sites of the known Cu-Zn ore deposits and showings formed in the PC space a unique cluster which also predicted many analogous sites. Several of these sites - after checking - proved to contain altered volcanics potential for Cu-Zn ores. High-pass filtered magnetic and electromagnetic maps revealed strata and faults controlling the structural positions of the potential sites.
GEOPHYSICAL METHODS IN THE EXPLORATION BEARING QUARTZ VEINS IN NICARAGUA
iKE
FOR GOLD-
HESSELBOM
Swedish ~eologicn~, Box 1424, S-75244
Uppsal~ (Sweden)
In a research project financed by the Swedish SAREC research foundation the use of geophysical methods in the exploration for gold-bearing quartz veins were investigated. The project was carried out in collaboration between the Nicaraguan Ministry of Mines (INMINE) and Swedish Geological Company (SGAB) in two mining districts, El Limon and La Libertad. Both areas contain a number of quartz veins located in Tertiary andesites.
Science
Abstracts*
23 (1984185) 415-440 Publishers B;V., Amsterdam
Printed
in The Netherlands
’
GEOPHYSICAL
LEIF
415 -
ATLAS OF THE SILJAN AREA - DEEP GAS PROJECT
ERIKSSON
Geological Survey of Sweden, Box 670, 751 28 Uppsala (Sweden)
The Siljan Ring Structure is thought to be a meteorite impact crater. It has been chosen by the Swedish State Power Board as a suitable area for a deep gas study. A first phase of limited field investigations including drillings to 700 m, have been carried out. For this reason the Geological Survey of Sweden compiled airborne geophysical data and ground gravity data to be presented in a geophysical atlas. The main scale is l:lOO,OOO over the central area of interest, and the scale 1: 250,000 over a well sized region. This makes it possible to place the Siljan Structure in a wider regional geological context, to make certain depth estimations and to help deciding the locations for drillings. Preliminary interpretations are summarized and a proposed model is discussed.
GEOPHYSICS FINLAND
VOITTO
IN THE PROGNOSTIC
ANALYSIS
OF IRON ORES IN
HEISKANEN
Rautaruukki
Oy, PL 217, SF-901 01 Oulu (Finland)
Rautaruukki Oy with some Finnish scientists and the Soviet company V/O Technoexport have compiled a prognostic analysis of iron ore potential in Finland. Geological, geophysical and geochemical information was combined during the work. Three of the eleven compiled maps were geophysical. The geophysical interpretation map is based on gravimetric, magnetic and petrophysical data. It depicts combinations of gravimetric and magnetic fields according to their intensity and character. The blocks and structures thus revealed can be correlated to geological complexes and tectonic structures. The map of local magnetic anomalies depicts anomalies according to their intensities and faults and fractures limiting or breaking these anomalies. It *‘Abstracts of papers submitted at the 15th Meeting of Applied Geophysics, Espoo, Finland, 15-17 January 1985.
0016-7142/85/$03.30
0 1985
Elsevier
Science
Publishers
the
B.V.
Nordic
Association
for
416
has been possible to localize horizons critical to iron ore and to contour different formations. In the aeroelectromagnetic interpretation map, the conductors and anomalies caused by susceptibility are shown. It can be used to locate conductive horizons (for example black schists) and rocks containing magnetite. The geophysical maps were used for compiling geological maps and preparing criteria for iron ore critical complexes.
PREDICTION OF AREAS POTENTIAL FOR Cu-Zn SULPHIDE ORE WITH THE AID OF LOW-ALTITUDE AEROGEOPHYSICAL DATA AND STATISTICAL METHODS
HILKKA
ARKIMAA,
EERO
LINDQVIST
and VILJO
KUOSMANEN
Geological Survey of Finland, SF-021 50 Espoo 15 (Finland)
The study area (60 X 75 km’) is situated in the Lake Ladoga-Botnian Bay ore zone. Low-altitude measurements on magnetic total intensity, electromagnetic real and imaginary components and some radiometric ratios were first transformed into principal components (PC). The PC feature space created was studied using unsupervised classification. It was observed that the anomalies in the sites of the known Cu-Zn ore deposits and showings formed in the PC space a unique cluster which also predicted many analogous sites. Several of these sites - after checking - proved to contain altered volcanics potential for Cu-Zn ores. High-pass filtered magnetic and electromagnetic maps revealed strata and faults controlling the structural positions of the potential sites.
GEOPHYSICAL METHODS IN THE EXPLORATION BEARING QUARTZ VEINS IN NICARAGUA
iKE
FOR GOLD-
HESSELBOM
Swedish ~eologicn~, Box 1424, S-75244
Uppsal~ (Sweden)
In a research project financed by the Swedish SAREC research foundation the use of geophysical methods in the exploration for gold-bearing quartz veins were investigated. The project was carried out in collaboration between the Nicaraguan Ministry of Mines (INMINE) and Swedish Geological Company (SGAB) in two mining districts, El Limon and La Libertad. Both areas contain a number of quartz veins located in Tertiary andesites.