Geological evolution of western H.U. Sverdrupfjella, Dronning Maud land, Antarctica.
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Date
1992
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Abstract
The oldest rocks of western H.U. Sverdrupfjella, the Jutulrora Formation, consist of
interlayered mafic to felsic ortho- and paragneisses thought to represent calc-alkaline volcanic
and clastic sedimentary rocks. These rocks are structurally overlain by the largely paragneissic,
carbonate- dominated Fuglefjellet Formation which may represent a miogeosynclinal shelf facies.
This sequence is structurally overlain by the dominantly para-gneissic Sveabreen Formation
which may comprise a eugeosynclinal facies.
Three granitic bodies, the Roerkulten, Jutulrora and Brekkerista Granites intrude the Jutulrora
Formation. The trace element chemistry of these granites suggest that accessory minerals
played significant roles during their generation and crystallization. Various mafic intrusions, now
discordant amphibolites, and a phase of diorite veining are present.
The Dalmatian Granite was emplaced syntectonically with the 470Ma Pan-African (or Ross)
orogeny during D3. This granite was generated by crustal anatexis at >5kb.
Jurassic age intrusions include alkaline complexes at Straumsvola and Tvora and numerous
dolerite dykes, some of which postdate the alkali intrusions.
Five episodes of deformation are recognised. The first two resulted in folds (F1 and F2) which
are co-planar and coaxial resulting in type 3 interference structures. Low angle thrust faulting
occurred during D2. Fold vergence and associated lineations suggest tectonic transport from the
southeast during D1 and D2,
D3 involved folding and reverse faulting. The orientations of the fault and axial planes of
these structures suggest transport from the west and north-west. D4 involved open dome and
basin folding.
D6 involved normal faulting and jointing, adjacent and parallel to the Jutulstraumen Glacier in
the west. The joints affect the Tvora Alkaline Complex.
Three phases of metamorphism, related to the deformation, are recognised. The dominant
mineral assemblages are typical of medium to high grade metamorphism and define S1 and S2
planar fabrics. Discordant mafic intrusions provide evidence of a long history of metamorphism.
M3 mineral development, commonly represented by biotite, is oriented axial planar to D3 folds.
Comparison of the geology of the area with that of southern Mozambique reveals many
similarities. These support reconstructions based on geophysical data which juxtapose Dronning
Maud Land and southern Africa prior to the break up of Gondwanaland.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1992.
Keywords
Geology--Antarctica., Theses--Geology.