The structural evolution of the Rauer Group, East Antarctica: mafic dykes as passive markers in a composite Proterozoic terrain

1994 ◽  
Vol 6 (3) ◽  
pp. 379-394 ◽  
Author(s):  
John P. Sims ◽  
Paul H. G. M. Dirks ◽  
Chris J. Carson ◽  
Chris J. L. Wilson
Keyword(s):  
Structural Evolution ◽  
East Antarctica ◽  
Ductile Deformation ◽  
Shear Direction ◽  
High Grade ◽  
Mafic Dyke ◽  
Mafic Dykes ◽  
Deformational History ◽  
Lower Strain ◽  
Vestfold Hills

Archaean gneisses in the Rauer Group of islands, East Antarctica, record a prolonged history of high-grade deformational episodes, many of which predate that identified in mid-Proterozoic gneisses. Eleven generations of mafic dykes, belonging to discrete chemical suites, have been used as relative time markers to constrain this deformational history. Based on the timing of intrusion with respect to structures, dykes in the Rauer Group have been correlated with largely undeformed and dated dyke suites in the adjacent Vestfold Hills. This has allowed absolute ages to be inferred for the early- to mid-Proterozoic mafic dyke suites in the Rauer Group, and a correlation of the interspersed structural events. Most structures in the Rauer Group, however, developed in response to high-grade progressive deformation at approximately 1000 Ma. During this deformational episode, strains were repeatedly partitioned into sub-vertical, noncoaxial, high-strain zones recording NW-directed sinistral transpression, that separated zones of lower strain dominated by coaxial folding with axes parallel to the shear direction. Three additional mafic dyke suites intruded during this deformation which was followed by three stages of brittle-ductile deformation and a final suite of lamprophyre dykes. Due to the numerous intrusive time markers, the Rauer Group serves as an excellent illustration of how complicated gneiss terrains may be.

scholarly journals Polyphase Deformation of the High-Grade Metamorphic Rocks along the Neusspruit Shear Zone in the Kakamas Domain: Insights into the Processes during the Namaquan Orogeny at the Eastern Margin of the Namaqua Metamorphic Province, South Africa

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 759
Author(s):  
Cyrille Stephane Tsakou Sonwa ◽  
Jan van Bever Donker ◽  
Russell Bailie
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Structural Development ◽  
Shear Direction ◽  
High Grade ◽  
Deformation Event ◽  
Intense Deformation ◽  
Western Regional ◽  
Regional Boundary

The central part of the Namaqua Metamorphic Province was subjected to intense deformation under high-grade metamorphic conditions up to granulite facies, but also shows greenschist facies overprints denoting the metamorphic nature during the 1.2–1.0 Ga Namaquan Orogeny. This study examines the structural development of the central Kakamas Domain of the eastern Namaqua Metamorphic Province, which has not been extensively studied previously. The compressional orogenic phase is associated with D1 and D2 deformation events during which northeast–southwest-directed shortening resulted in southwest-directed thrusting illustrated by an intra-domain thrust and southwest-verging isoclinal folds. The post-tectonic Friersdale Charnockite of the Keimoes Suite is emplaced during the D3 deformation event. Late reactivation of the intra-domain thrust in the Kakamas Domain to form the Neusspruit Shear Zone during the D4 event is of a monoclinic nature and is described as a deeply rooted structure with shear direction towards the east. This structure, together with the more local Neusberg Thrust Fault, forms part of an intensely flattened narrow basin in the eastern Namaqua Metamorphic Province. Strain and vorticity indices suggest a transpressional shearing across the Neusspruit Shear Zone and adjacent regions probably initiated during the reactivation of the intra-domain thrust. The ~1.2 to 1.8 km-wide, northwest–southeast striking dextral-dominated Neusspruit Shear Zone constitutes a western regional boundary for the supracrustal Korannaland Group and is composed of steep, narrow zones of relatively high strain, characterised by ductile deformation and penetrative strain.

Geochemical and paleomagnetic characteristics of Vestfold Hills mafic dykes in Prydz Bay region: implications on the Paleoproterozoic connection between East Antarctica and proto-India

2021 ◽  
pp. SP518-2021-33
Author(s):  
Manoj K. Pandit ◽  
Anthony Pivarunas ◽  
Joseph G. Meert
Keyword(s):  
Granite Gneiss ◽  
East Antarctica ◽  
Prydz Bay ◽  
Crustal Component ◽  
Mafic Dykes ◽  
South Indian ◽  
Block Based ◽  
Vestfold Hills ◽  
Dyke Swarms ◽  
High Degree

AbstractThe Archean age granite gneiss basement along the Prydz Bay coastline in East Antarctica hosts N-S, E-W, NE-SW, and NW-SE trending mafic dyke swarms in the Vestfold Hills region that intruded between 2420 and 1250 Ma. The dyke trends do not show a direct correlation with the dyke geochemistry but can be broadly discriminated into high-Mg and Fe-rich tholeiites. The former type being more siliceous, LILE, HFSE, and LREE enriched, crystallized from a fractionated melt with a notable crustal component or fluid enrichment through the previous subduction process. The Fe-rich tholeiites are less siliceous, have lower abundances of LILE and REE, and were derived from an undifferentiated, primitive melt. The geochemical characteristics of both types underline a shallow level and a high degree of melting in the majority of cases, and a broadly Island Arc Basalt (IAB) affinity. Paleomagnetic analysis of hand samples shows directional groups consistent with geochemical groupings. The Vestfold Hills dykes show a possible linkage with the coeval mafic dykes in Eastern Dharwar and Bastar cratons of the South Indian Block, based on the similarity in the Paleoproterozoic paleolatitudes.

Mg-Al yttrian zirconolite in a partially melted sapphirine granulite, Vestfold Hills, East Antarctica

1994 ◽  
Vol 58 (391) ◽  
pp. 259-269 ◽  
Author(s):  
Simon L. Harley
Keyword(s):  
Partial Melting ◽  
East Antarctica ◽  
High Grade ◽  
Chemical Analyses ◽  
Late Archaean ◽  
Granulite Xenolith ◽  
Early Proterozoic ◽  
Coupled Substitution ◽  
Vestfold Hills ◽  
Image Position

AbstractA new compositional variety of zirconolite characterized by high Mg, Al, Y2O3 and REE, and low Fe is described from a sapphirine granulite xenolith entrained in an intrusive norite body which was emplaced into the late Archaean (2520–2480 Ma) Vestfold Hills high-grade terrain during the early Proterozoic. The zirconolite, and similarly Mg-Al rich perrierite-(Ce), formed as a result of sanidinite facies partial melting of the particularly magnesian and aluminous sapphirine granulite xenolith during its incorporation into the c. 1170°C basic magma at c. 2240 Ma. The high REE compared to Al cations require that a previously unrecognized coupled substitution:occurs in this zirconolite. Full chemical analyses are presented for zirconolite and perrierite from this unique occurrence.

Mafic dykes in the Rauer Islands and Vestfold Hills (East Antarctica): A chemical and Nd isotopic comparison

2019 ◽  
Vol 329 ◽  
pp. 273-293 ◽  
Author(s):  
Evgenii V. Mikhalsky ◽  
Nikolay L. Alexeev ◽  
Igor A. Kamenev ◽  
Mikhail S. Egorov ◽  
Evgenii L. Kunakkuzin
Keyword(s):  
East Antarctica ◽  
Mafic Dykes ◽  
Vestfold Hills

Zircon ages and the distribution of Archaean and Proterozoic rocks in the Rauer Islands

1993 ◽  
Vol 5 (2) ◽  
pp. 193-206 ◽  
Author(s):  
P. D. Kinny ◽  
L. P. Black ◽  
J. W. Sheraton
Keyword(s):  
Granulite Facies ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Grade ◽  
Ion Microprobe ◽  
Rock Interaction ◽  
Mafic Rocks ◽  
Grade Fluid ◽  
Vestfold Hills ◽  
Intrusive Suite

The application of zircon U-Pb geochronology using the SHRIMP ion microprobe to the Precambrian high-grade metamorphic rocks of the Rauer Islands on the Prydz Bay coast of East Antarctica, has resulted in major revisions to the interpreted geological history. Large tracts of granitic orthogneisses, previously considered to be mostly Proterozoic in age, are shown here to be Archaean, with crystallization ages of 3270 Ma and 2800 Ma. These rocks and associated granulite-facies mafic rocks and paragneisses account for up to 50% of exposures in the Rauer Islands. Unlike the 2500 Ma rocks in the nearby Vestfold Hills which were cratonized soon after formation, the Rauer Islands rocks were reworked at about 1000 Ma under granulite to amphibolite facies conditions, and mixed with newly generated felsic crust. Dating of components of this felsic intrusive suite indicates that this Proterozoic reworking was accomplished in about 30–40 million years. Low-grade retrogression at 500 Ma was accompanied by brittle shearing, pegmatite injection, partial resetting of U-Pb geochronometers and growth of new zircons. Minor underformed lamprophyre dykes intruded Hop and nearby islands later in the Phanerozoic. Thus, the geology of the Rauer Islands reflects reworking and juxtaposition of unrelated rocks in a Proterozoic orogenic belt, and illustrates the important influence of relatively low-grade fluid-rock interaction on zircon U-Pb systematics in high-grade terranes.

Penguin occupation in the Vestfold Hills

2008 ◽  
Vol 21 (2) ◽  
pp. 131-134 ◽  
Author(s):  
Tao Huang ◽  
Liguang Sun ◽  
Yuhong Wang ◽  
Renbin Zhu
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Sediment Cores ◽  
East Antarctica ◽  
Before Present ◽  
The Holocene ◽  
History Of ◽  
Vestfold Hills ◽  
Free Area ◽  
Ornithogenic Sediment

AbstractDuring CHINARE-22 (December 2005–March 2006), we investigated six penguin colonies in the Vestfold Hills, East Antarctica, and collected several penguin ornithogenic sediment cores, samples of fresh guano and modern penguin bone and feather. We selected seven penguin bones and feathers and six sediments from the longest sediment core and performed AMS14C dating. The results indicate that penguins occupied the Vestfold Hills as early as 8500 calibrated years before present (cal. yrbp), following local deglaciation and the formation of the ice free area. This is the first report on the Holocene history of penguins in the Vestfold Hills. As in other areas of Antarctica, penguins occupied this area as soon as local ice retreated and the ice free area formed, and they are very sensitive to climatic and environmental changes. This work provides the foundation for understanding the history of penguins occupation in Vestfold Hills, East Antarctica.

Landform evolution in the Marine Plain region, Vestfold Hills, East Antarctica

2006 ◽  
Vol 18 (2) ◽  
pp. 239-259 ◽  
Author(s):  
Patrick G. Quilty
Keyword(s):  
Sedimentary Rocks ◽  
East Antarctica ◽  
Patterned Ground ◽  
Antarctic Ice Sheet ◽  
Landform Evolution ◽  
Ice Load ◽  
Exposed Rock ◽  
Plain Region ◽  
Vestfold Hills ◽  
Land Surfaces

Landforms of Marine Plain in the Vestfold Hills contrast with those of most in the Vestfold Hills. They include consistent land surfaces at 40+ m and 25 m, characteristics controlled by orientation of rock features, and imprints of phases of glaciation, deglaciation and marine and freshwater inundation. The 40+ m surface is widespread in the Vestfold Hills and has been noted previously. The 25 m level was an earlier coastline, is more localized and marked by water rounded boulders; it serves to differentiate clearly between two terrains of different relief and erratic distribution. The Pliocene sedimentary rocks below the 25 m level have been dislocated, probably during an interval of glaciotectonism caused by northward movement of sediments under an ice load due to northern extension of the Sørsdal Glacier or expansion of the East Antarctic Ice Sheet some time after the mid-Pliocene. Soil development is active. These features are accompanied by the normal aspects of a glaciated landscape such as glacial striations, sand wedges, erratics, and patterned ground. Wind has been important in transporting sand and developing honeycomb weathering on exposed rock faces.

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