Skagi and Langjoekull volcanic zones in Iceland: 1. Petrology and structure

Journal Article · Thu Aug 10 04:00:00 EDT 1978 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB083iB08p03971· OSTI ID:6697074

Sigurdsson, H; Schilling, J; Meyer, P S

The compositional variation of basalts in a 220-km-long profile through the length of the northward extension of the western volcanic zone of Iceland shows an abrupt discontinuity at 65/sup 0/ 10'N, separating high iron-titanium type light-rare-earth-element (REE) -enriched tholeiitic basalts in the Skagi zone (2.5-0.5 m.y.) to the north from Mg-Al-rich olivine tholeiites with REE patterns unfractionated in relation to chondrites in the Langjoekull zone (o.7 m.y. to Recent) to the south. Geophysical evidence indicates that the chemical discontinuity may coincide with steepening of presently existing geothermal gradients and thickening of the Iceland crust from south to north. The two basalt groups exhibit striking petrographic contrasts. Skagi basalts contin phenocrysts of augite, plagioclase, olivine, and minor Fe-Ti oxides and have liquidus temperatures ranging from 1150/sup 0/ to 1170/sup 0/C. Langjoekull basalts are predominantly olivine- and plagioclase-phyric, with minor chromian spinels and liquidus temperatures near 1230/sup 0/C. Petrologic mixing calculations indicate that major element dispersion within Skagi can be accounted for by 15-17% extraction of plagioclase, augite, and olivine in proportions of 4:3:1. The observed major element range in the Langjoekull magma, ascribed to filtering through a thicker crust. However, variable degrees of melting related to the thermal gradients are also required for genesis of these magmas to account for the REE variations observed (Schilling et al., 1978); combination of both processes is therefore invoked.

• Research Organization: Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881
• OSTI ID: 6697074
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 83:B8; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580202* -- Geophysics-- Volcanology-- (1980-1989)
ALKALINE EARTH METAL COMPOUNDS
BASALT
CHONDRITES
EUROPE
GEOLOGY
GEOTHERMAL GRADIENTS
ICELAND
IGNEOUS ROCKS
IRON COMPOUNDS
IRON SILICATES
MAGMA
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
METEORITES
MINERALS
OLIVINES
OXYGEN COMPOUNDS
PETROLOGY
ROCKS
SILICATES
SILICON COMPOUNDS
STONE METEORITES
TEMPERATURE GRADIENTS
TRANSITION ELEMENT COMPOUNDS
VOLCANISM
VOLCANOES