The relationship between fe3+fe3++fe2+ ratios in biotite and an aeromagnetic anomaly

Geoexploration, 19 (1981) 143-154 Elsevier Scientific Publishing Company,

Amsterdam

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Printed

in The Netherlands

143

Abstracts* THE RELATIONSHIP BETWEEN Fe3+/Fe3++FeZ+ RATIOS IN BIOTITE AND AN AEROMAGNETIC ANOMALY SVEN

AARO

and TORE

ERICSSON

University of Uppsala, Institute of Geology, Box 555, S-751 22 Uppsala (Sweden)

Department

of Mineralogy

and Petrology,

Petrophysical measurements and mineral-chemical analyses have been made on rocks connected to an aeromagnetic anomaly in a migmatite area westsouthwest of Stockholm. The magnetic susceptibility measurements showed that the anomaly is caused by metavolcanic rocks, and plutonic rocks associated with them. The plutonics outside this complex were found to be practically nonmagnetic. The ferric-ferrous ratios in biotites were determined by use of the Mossbauer technique. The obtained ferricferrous ratios indicate that the biotite samples taken from the area inside the magnetic anomaly have experienced a higher oxygen fugacity compared to the samples from the area outside. This conclusion is supported by some of the opaque assemblages of the analysed samples. By using the compositional triangle Fe3+-Fe’+-Mg*+, the biotites inside the magnetic anomaly area are characterized by oxygen fugacities somewhat greater than the fugacities given by a Ni-NiO buffer. The biotites taken outside the anomaly area are, on the other hand, characterized by an oxygen fugacity comparable with that of the Ni-NiO buffer. The relation between the magnetic susceptibility of the rocks and relevant reduction and oxidation processes will be discussed during the presentation of the subject.

THE APPLICATION INTERPRETATION L. CHRISTER University

OF LANDSAT

DATA ON GEOLOGICAL

STRUCTURE

ANDERSSON

of Luled,

S-951

87 Lule6

(Sweden)

The series of Landsat satellites by NASA yield high quality data relevant to geological linear structures of the earth surface. The emphasis of this lecture is put on mapping these structures interpreted from Landsat images, and in particular the correlation between structure orientation and geological and geophysical data. However, manual interpretation suffers from subjective impressions of the *Abstracts of the papers presented Applied Geophysics held on 12-14 February 19, 1981 00167142/81/0000-0000/$02.50

at the 13th meeting of the Nordic Association for January 1981, Lulei, Sweden, accepted for publication

0 1981

Elsevier

ScientificPublishing

Company