Geochemical analysis of Tertiary dikes emplaced in the Hrafnfjordur central volcano, northwest Iceland: Implications for dike origin

• Main Author: Whitney, Nina Millicent
• Format: Text
• Language: unknown
• Published: Carleton Digital Commons 2012
• Subjects: Iceland; Dike; Central volcano; Rift zone; Geochemistry
• Online Access: https://digitalcommons.carleton.edu/comps/779

The basaltic dikes emplaced in the 14 MA Hrafnfjordur central volcano, located in northwestern Iceland, were fed by one of two potential sources: the magma chamber of the Hrafnfjordur central volcano or the Snaefellsnes paleo-rift, the main active rift in Iceland during the time that the dikes were emplaced. This paper presents geochemical data on these dikes and offers analysis of these data to illuminate the source of the melts that formed the Hrafnfjordur dikes. Samples and orientation measurements were taken from 25 Tertiary dike outcrops located in the extinct Hrafnfjordur central volcano. All but two of the Hrafnfjordur dikes are oriented roughly parallel to the Snaefellsnes paleo-rift, an orientation that suggests that regional stresses dominated the intrusion environment and that the magma chamber of the central volcano had little effect on local stress fields during the emplacement of the dikes. Geochemical analysis of 20 samples taken from select Hrafnfjordur dikes reveals that these dikes likely originated from multiple sources. Dikes 2, 7, 11, 19 and 21 were sourced from a melt originating from fissures of the Snaefellsnes paleo-rift as their high concentrations of trace element ratio Nb/Y is not found in rocks erupted from the Hrafnfjordur central volcano. Dikes 8A, 10 (two outcrops of the same dike) and 8B potentially originated from the central volcano, based on the variation in incompatible element concentration along strike, although it is possible that they also originated from a fissure of the Snaefellsnes paleo-rift. The geochemical analysis of samples of the other dikes intruded in the Hrafnfjordur central volcano gave indefinite results as to the origin of these dikes.