Petrology and geochemistry of Iceland basalts: Spatial and temporal variations

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5152273

Meyer, P S

A petrological and geochemical study of basalts from Iceland's neovolcanic zones and Tertiary lava piles was carried out in order to investigate volcanic processes associated with the development of the Iceland platform, an anomalously elevated segment of the Mid-Atlantic Ridge (MAR). The Northeast and Southwest axial rift zones are dominated by olivine tholeiites and tholeiites, whereas the Southeast, Skagi, and Snaefellsnes flank zones are characterized by alkali basalts and mildly alkaline FeTi basalts. Phenocryst assemblages and textures are more diverse in flank zone basalts than in axial rift zone basalts, suggesting mixing of more diverse magma compositions and longer residence times in flank zone magma chambers. Geochemical trends observed in 2 to 14 m.y. old basalts from eastern and western Iceland indicate a complex and varied source region for Iceland magmas, dependent on both mantle plume activity and the maturity of rift zones. Decreasing (La/Sm){sub E.F.} and {sup 87}Sr/{sup 86}Sr ratios over the last 14 m.y. suggest decreasing mantle plume activity. Shorter episodes (2 to 5 m.y.) of declining (La/Sm){sub E.F.} and {sup 87}Sr/{sup 86}Sr are explained by the development of new rift zones caused by repeated shifts in the location of the spreading axis. On the average, Tertiary basalts from eastern and western Iceland are chemically more similar to young (< 0.7 m.y.) basalts from immature flank zones than to young basalts from the axial rift zones, implying that the Tertiary basalts were erupted along immature rift zones. Geochemical cycles, lasting 0.1 to 0.3 m.y., in the Borgarfjordur lava pile suggest progressive melting of mantle diapirs, rising from the garnet stability zone where melting begins.

• Research Organization: Rhode Island Univ., Kingston, RI (USA)
• OSTI ID: 5152273
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
BASALT
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
DEVELOPING COUNTRIES
ELEMENTS
EUROPE
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
ICELAND
IGNEOUS ROCKS
ISLANDS
ISOTOPES
MAGMA
MAGMATISM
METALS
PETROGENESIS
PETROLOGY
PLATE TECTONICS
RARE EARTHS
RIFT ZONES
ROCKS
SEA-FLOOR SPREADING
STRONTIUM ISOTOPES
TECTONICS
TERTIARY PERIOD
VARIATIONS
VOLCANIC REGIONS
VOLCANIC ROCKS
WESTERN EUROPE