Accession Number : ADA242531


Title :   Evolution of Icelandic Central Volcanoes: Evidence from the Austurhorn Plutonic and Vestmannaeyjar Volcanic Complexes


Descriptive Note : Doctoral thesis,


Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA


Personal Author(s) : Furman, Tanya H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a242531.pdf


Report Date : Sep 1989


Pagination or Media Count : 378


Abstract : There are several aspects of Icelandic magmatism which are not predicted from its geographic position along the mid-Atlantic Ridge. Specifically, local occurrences of alkalic lavas and oversaturated silicic magmas are uncommon in a mid-ocean ridge setting. This study uses field, petrologic and geochemical data to understand the petrogenesis of these diverse lava types. Two areas have been investigated: the volcanic Vestmannaeyjar archipelago and the hypabyssal Austurhorn intrusive complex. Vestmannaeyjar is located at the tip of a transgressive ridge segment (the eastern neovolcanic zone); the most recent eruption in this area was Eldfell in 1973. Austurhorn is an evolved central volcano in southeastern Iceland which was active approximately 607 Ma and has been exhumed by glaciation. In both areas, the relative contributions of fractional crystallization and crustal melting to geochemical trends among cogenetic magmas have been assessed, and fractionation processes are found to dominate. Vestmannaeyjar moderate pressure(approx. 8 kbar) fractionation of mantle-derived liquids can produce the observed range of erupted compositions. Radiogenic and stable isotope data support this scenario. At Austurhorn sampled mafic and felsic magmas differentiated at near surface conditions ( approx. 2 kbars). The cumulus mineralogy of associated gabbros supports this model.


Descriptors :   *SETTING(ADJUSTING) , STABILITY , SURFACE PROPERTIES , MELTING , ISOTOPES , EARTH CRUST , PATTERNS , ATLANTIC OCEAN , GEOCHEMISTRY , GEOGRAPHY , INTRUSION , OCEAN RIDGES , LAVA , VOLCANOES , RIDGES , MINERALOGY , SILICIC ACIDS , CUMULUS CLOUDS , FRACTIONATION , MAGMA , PETROLOGY , POSITION(LOCATION)


Subject Categories : Physical and Dynamic Oceanography
      Geology, Geochemistry and Mineralogy


Distribution Statement : APPROVED FOR PUBLIC RELEASE