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Straumsvola complex, Queen Maud Land, Eastern Antarctica, Antarctica

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Latitude & Longitude (WGS84): 72° 6' 60'' South , 0° 19' 60'' West
Latitude & Longitude (decimal): -72.11666,-0.33333
Köppen climate type:EF : Ice cap climate


Straumsvola is a nepheline syenite intrusive complex about 7 km in diameter, which intrudes gneisses of the Jutulrøra Formation (Svedrupfjella Group), located on the eastern edge of the Jutulstraumen Glacier (Ravich & Solov'yev, 1966 and 1969; Hjelle, 1972; Allen et al., 1986; Harris & Grantham, 1993). The Straumsvola nepheline syenite complex consists of a massive outer zone and a layered inner zone, whereas the adjacent nunatak 5 km to the southeast, Tvora, consists of quartz syenite (see http://www.mindat.org/loc-266652.html). The Straumsvola complex is exposed mostly on the nunatak Straumsvola itself, but it can be observed also at the easternmost Storjoen and Joungane nunataks.

The outer zone contains numerous pegmatite dykes (southeast ridge of Straumsvola and summit ridge of Storjoen) consisting of alkali feldspar, biotite, sodium-rich pyroxene and amphibole. Such pegmatite dykes can contain cavities up to several metres in diametre, in which large, well-formed crystals of feldspar, amphibole, aegirine, zircon (up to 2 cm accross), analcime, and natrolite are present. Natrolite prismatic crystals are partially enclosed by icositetrahedra of analcime.
The layered rocks are exclusively exposed on Straumsvola. Near the summit of Straumsvola a more mafic facies unconformably overlies the layered zone.

A large number of Jurassic dykes cut the two plutons and the surrounding country-rocks. These dykes are extremely varied in composition and include nephelinites, pyroxenites, lamprophyres, dolerites, phonolites, and peralkaline microgranites. Jurassic dykes of western Dronning Maud Land dyke swarms are probably related to magmatism associated with the Karoo large igneous province in Africa.

In one unusual dyke of peralkaline granite, which crops out on the north ridge of Straumsvola at about 200 m from the summit and cuts both the nepheline syenite country-rock and several dolerite dykes, REE-rich eudialyte occurs together with the rare mineral dalyite (Harris & Rickard, 1987). In other dykes of peralkaline granite narsarsukite and vlasovite have been found (Harris & Grantham, 1993).

Eudialyte is found in fissures and vugs throughout the upper layered zone syenites and in one case as a major phase (up to 20 modal %) in a pegmatite dyke located 100 m south of Straumsvola summit (Harris & Grantham, 1993).


Mineral List


25 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Ma



ID: 3185487
Phanerozoic ice

Age: Anthropocene ( Ma)

Comments: Antarctic Ice Cap

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License



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References

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Ravich, M.G., Solov'yev, D.S. [Равич М.Г., Соловьев Д.С.] (1966): Geology and petrology of the central part of the mountains of Dronning Maud Land (Eastern Antarctica) [Геология и петрология центральной части гор Земли Королевы Мод (Восточная Антарктида)]. Nedra, Leningrad, 290 pp. (in Russian).
Ravich, M.G., Solov'yev, D.S. (1969): Geology and petrology of the mountains of central Dronning Maud Land (Eastern Antarctica). Israel Program for Scientific Translations, Jerusalem, 348 pp. (Translated from the 1966 Russian publication).
Hjelle A. (1972): Some observations on the geology of H. U. Sverdrupfjella, Dronning Maud Land. Norsk Polarinstitutt, Årbok 1972, 7-22.
Allen, A.R., Grantham, G.H., Groenewald, P.B., Hunter, D.R. (1986): Tectonic and metamorphic evolution of H.U. Sverdrupfjella, western Dronning Maud Land, Antarctica - a preliminary review. Geocongress 1986 (Johannesburg), extended abstr., 707-710.
Harris, C., Rickard, R. S. (1987): Rare-earth-rich eudialyte and dalyite from a peralkaline granite dyke at Straumsvola, Dronning Maud Land, Antarctica. Canadian Mineralogist, 25, 755-762.
Harris, C., Grantham, G.H. (1993): Geology and petrogenesis of the Straumsvola nepheline syenite complex, Dronning Maud Land, Antarctica. Geological Magazine, 130, 4, 513-532.
Curtis, M.L., Riley, T.R., Owens, W.H., Leat, P.T., Duncan, R.A. (2008): The form, distribution and anisotropy of magnetic susceptibility of Jurassic dykes in H.U. Sverdrupfjella, Dronning Maud Land, Antarctica. Implications for dyke swarm emplacement. Journal of Structural Geology, 30, 1429-1447.
Riley, T.R., Curtis, M.L., Leat, P.T., Millar, I.L. (2009): The geochemistry of Middle Jurassic dykes associated with the Straumsvola-Tvora alkaline plutons, Dronning Maud Land, Antarctica and their association with the Karoo large igneous province. Mineralogical Magazine, 73, 2, 205-226.

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