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ThesisUniversity of Iceland>Verkfræði- og náttúruvísindasvið>B.S. verkefni>

Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/8571

Titles
  • is

    Bergfræði Hrímöldu: Uppruni og myndun plagíóklasbasalts

  • Petrology of Hrimalda: Origin and formation of plagioclase ultraphyric basalt

Published
June 2011
Abstracts
  • is

    Berg Hrímöldu er plagíóklas-stórdílótt blandberg af tvennum uppruna: sundrað, frumstætt ólivín-gabbró ásamt grunnmassa úr blöndu af ólivín-þóleiíti og uppbræddum Cr-
    díopsíð. Framandsteindirnar úr djúpberginu eru plagíóklas (An90) með krómspínilinnlyk-
    sum, ólivín (Fo87) og króm-díopsíð. Grunnmassinn er alkristallað fínkorna berg úr ágíti, plagíóklas (An80-An35), og einsleitum ólivín (Fo80) ásamt dreif af þróaðri ólivín (Fo80-Fo30).
    Uppruni framandsteindanna í Hrímöldu er rakinn til gabbrós í botni skorpunnar, sem
    hefur sundrast við innskot af ólivín-þóleiíti. Sundrun gabbrósins leiddi af hvarfabráðn-
    un pyroxens við hitaáverka frá innskostskvikunni. Burðarkvikan er því blanda af ólivín-
    þóleiíti og bráðarhluta pyroxens. Ólivín (Fo80) sem myndaðist við hvarfabráðnun pyroxens
    myndar hóp af einsleitum ólivínkristöllum í burðarkvikunni.

  • Hrimalda is composed of plagioclase ultraphyric hybrid rock of dual origin: disintegrated primitive gabbro and groundmass composed of olivine tholeiite and incongruently melted Cr-diopside. The plutonic xenocrysts are plagioclase (An90) with chromite inclusions, olivine (Fo87) and Cr-diopside. The groundmass is holocrystalline fine-grained rock composed of augite, plagioclase (An80-An35), homogeneous olivine (Fo80) and a population of more evolved olivine (Fo80-Fo30). Origin of the Hrimalda phenocrysts are shown to be xenocrysts derived from gabbro at the base of the crust that suffered disintegration upon intrusion of olivine tholeiite. The disintegration of the gabbro was the result of incongruent melting of pyroxene following a thermal impact from the intruding magma.
    The host rock is, therefore, a mixture of olivine tholeiite and the melt fraction of the pyroxene. Olivine (Fo80) that formed during the incongruent melting of pyroxene is found as a population of homogeneous olivine in the host rock.

Issued Date
18/05/2011


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