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.

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.

Structural and geochronological constraints on the role of partial melting during the formation of the Shuswap metamorphic core complex at the latitude of the Thor-Odin dome, British Columbia

1999 ◽  
Vol 36 (6) ◽  
pp. 917-943 ◽  
Author(s):  
Olivier Vanderhaeghe ◽  
Christian Teyssier ◽  
Richard Wysoczanski
Keyword(s):  
Partial Melting ◽  
Metamorphic Core Complex ◽  
High Grade ◽  
Core Complex ◽  
Genetic Link ◽  
The Core ◽  
Lower Unit ◽  
Geochronological Constraints ◽  
Metamorphic Core ◽  
Middle Unit

At the latitude of the Thor-Odin dome, the Shuswap metamorphic core complex exposes a ~15 km thick structural section composed of an upper unit that preserved Mesozoic metamorphism, structures, and cooling ages, separated from the underlying high-grade rocks by low-angle detachment zones. Below the detachments, the core of the complex consists of an amphibolite-facies middle unit overlying a migmatitic lower unit exposed in the core of the Thor-Odin dome. Combined structural and super high resolution ion microprobe (SHRIMP) U-Pb geochronology studies indicate that the pervasive shallowly dipping foliation and east-west lineation developed in the presence of melt during Paleocene time. SHRIMP analyses of complexly zoned zircon grains suggest that the migmatites of the lower unit crystallized at ~56 Ma, and a syntectonic leucogranite at ~60 Ma. We suggest that leucogranite migrated upward from the migmatites through an array of dikes and sills that permeated the middle unit and ponded to form laccoliths spatially related to the detachment zones. The similarity in ages of inherited zircon cores in the two migmatite and the leucogranite samples suggests a genetic link consistent with the structural analysis. Following the crystallization of migmatites, the terrane cooled rapidly, as indicated by argon thermochronology. We propose that exhumation of the core of the Canadian Cordillera during the formation of the Shuswap metamorphic core complex occurred from ~60 to 56 Ma at a time when the crust was significantly partially molten. These structural and temporal relationships suggest a genetic link between mechanical weakening of the crust by partial melting, late-orogenic collapse, and exhumation of high-grade rocks in the hinterland of a thermally mature orogenic belt.

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.

scholarly journals Carbon Dioxide Absorption from Anæsthetic Atmospheres

1936 ◽  
Vol 30 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Ralph M. Waters
Keyword(s):  
Carbon Dioxide ◽  
Soda Lime ◽  
Face Mask ◽  
Maximum Efficiency ◽  
High Grade ◽  
Chemical Analyses ◽  
Carbon Dioxide Absorption ◽  
Physical Experiments

A safe and practical technique for the application of carbon dioxide absorption from anæsthetic atmospheres is described. It has been found satisfactory in over 20,000 administrations over a period of fifteen years. High-grade soda lime is utilized as the chemical absorbent. Granules are placed in a canister between face mask, and breathing bag. The canister is carefully checked for efficiency by both chemical analyses and physical experiments. Its size, shape and arrangement is shown to be important for safety and maximum efficiency. Detailed techniques are described for the use of various agents. Advantages of carbon dioxide absorption are set forth. The “Apnœa” suggested by Guedel is described under the term “Controlled Respiration” and attention is called to certain of its advantages.

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