Timing of emplacement of the Muskox intrusion: constraints from Coppermine homocline cover strata

1983 ◽  
Vol 20 (5) ◽  
pp. 673-683 ◽  
Author(s):  
Charles Kerans
Keyword(s):  
Group Structure ◽  
Layered Intrusion ◽  
Normal Faulting ◽  
West Side ◽  
Shallow Level ◽  
Lower Proterozoic ◽  
Structural Relationships ◽  
Plutonic Complex ◽  
Coppermine River ◽  
Middle Proterozoic

The Muskox intrusion is a Middle Proterozoic shallow-level mafic–ultramafic layered intrusion in the northwest corner of the Bear Province of the Canadian Shield. The intrusion was emplaced into the Lower Proterozoic Akaitcho Group and Hepburn metamorphic–plutonic complex of the Wopmay orogen and overlying Middle Proterozoic Coppermine homocline strata. To date, radiometric, paleomagnetic, and geochemical evidence has produced only equivocal results concerning the age of the Muskox intrusion relative to overlying Coppermine River Group basalts and Mackenzie diabase dykes. Stratigraphic redefinition of and structural relationships to the cover sequence of the intrusion provide the best available evidence for the age of the Muskox intrusion.Although previously inferred to be a pre-Dismal Lakes Group structure, the Canoe Lake Fault is here shown to cross-cut Dismal Lakes strata with west-side-down displacement equivalent to that documented to the south where it offsets the intrusion. This relationship, supported by detailed mapping that shows that the Muskox intrusion intrudes units 11 and 12 of the Dismal Lakes Group, demonstrates a post-Dismal Lakes age for the intrusion. This conclusion strongly supports the contention that the Muskox intrusion and Coppermine River Group are coeval and comagmatic.Syndepositional uplift and normal faulting within uppermost Dismal Lakes Group strata were most pronounced near the exposed roof of the intrusion, and are interpreted to have been related to emplacement of a small sill-like body that probably was the precursor to the main intrusive event. At least 70 m of sediments was deposited after this initial disturbance, but before extrusion of the Coppermine River Group basalts (which heralded the main emplacement event). This thickness of sedimentary strata implies a period of several hundred thousand years between the two igneous events.These results support earlier contentions that the Mackenzie igneous event, comprising emplacement of Mackenzie dykes, Coppermine River Group basalts, and the Muskox intrusion, was a coherent mafic igneous event that occurred approximately 1200 Ma ago, with the Muskox intrusion as a locus.

Geochemistry and petrogenesis of basaltic rocks from Coppermine River area, Northwest Territories

1983 ◽  
Vol 20 (5) ◽  
pp. 684-698 ◽  
Author(s):  
J. Dostal ◽  
W. R. A. Baragar ◽  
C. Dupuy
Keyword(s):  
Northwest Territories ◽  
Crustal Contamination ◽  
Layered Intrusion ◽  
Chemical Compositions ◽  
Basaltic Rocks ◽  
Exposed Part ◽  
Volcanic Pile ◽  
Coppermine River ◽  
P Type ◽  
Ocean Ridge

Proterozoic basaltic flows (> 2000 m thick) and associated dykes and sills from the Coppermine River area, Northwest Territories have chemical compositions typical of continental tholeiites. The low Mg/Fe ratio and abundances of Ni and Cr indicate that the lavas were extensively fractionated prior to extrusion. The variations of incompatible elements such as K, Rb, REE, Y, Zr, Nb, and Th suggest that the rocks were affected by interaction with continental crust. The samples least affected by contamination have trace-element compositions very similar to those of P-type mid-ocean ridge basalts. It is suggested that continental tholeiites have been generated from the same source as P-type oceanic tholeiites, and geochemical features, such as the enrichment of some lithophile elements in many of these rocks, may be related to crustal contamination. The variations within the volcanic pile of the Coppermine River area are related to those of an exposed part of the Muskox layered intrusion.

Paleomagnetic evidence for the extent of Mackenzie igneous events

1969 ◽  
Vol 6 (4) ◽  
pp. 679-688 ◽  
Author(s):  
W. F. Fahrig ◽  
D. L. Jones
Keyword(s):  
Volcanic Rocks ◽  
Pole Position ◽  
Canadian Shield ◽  
Paleomagnetic Data ◽  
Paleomagnetic Pole ◽  
Great Slave Lake ◽  
The Mean ◽  
Coppermine River ◽  
Age Determinations ◽  
Middle Proterozoic

North-northwesterly striking Mackenzie diabase dikes of middle-Proterozoic (Helikian) age are profuse in the western part of the Canadian Shield. Published paleomagnetic data on dikes of this trend in Mackenzie District, on the Muskox Intrusion, the Coppermine River volcanic rocks, and the Sudbury dikes suggest that they are all products of closely related igneous events. This paper presents paleomagnetic data that suggest that the intrusion of extensive diabase sheets in the East Arm of Great Slave Lake, and of dikes as far to the northeast as Melville Peninsula and as far to the southeast as Manitoba, were also parts of these events. The mean paleomagnetic pole position for the Mackenzie dikes and for related intrusive and extrusive rocks is [Formula: see text], 171 °W with [Formula: see text]. Radioactive age determinations, some of which are unpublished, indicate an age of about 1200 m.y. for the formation of these rocks. It is suggested that for convenience all of these apparently related intrusive and extrusive igneous episodes be referred to as Mackenzie igneous events.

scholarly journals Multistage magma emplacement and progressive strain accumulation in the shallow-level Krkonoše-Jizera plutonic complex, Bohemian Massif

Tectonics ◽  
2013 ◽  
Vol 32 (5) ◽  
pp. 1493-1512 ◽  
Author(s):  
Jiří Žák ◽  
Kryštof Verner ◽  
Jiří Sláma ◽  
Václav Kachlík ◽  
Marta Chlupáčová
Keyword(s):  
Bohemian Massif ◽  
Strain Accumulation ◽  
Shallow Level ◽  
Plutonic Complex ◽  
Magma Emplacement ◽  
Progressive Strain

173 Ma U–Pb age of felsite sills (Kaslo River intrusives) west of Kootenay Lake, southeastern British Columbia

1992 ◽  
Vol 29 (3) ◽  
pp. 531-534 ◽  
Author(s):  
Moira T. Smith ◽  
George E. Gehrels ◽  
David W. Klepacki
Keyword(s):  
British Columbia ◽  
Second Phase ◽  
The West ◽  
West Side ◽  
Lower Paleozoic ◽  
Upper Proterozoic ◽  
Third Phase ◽  
Phase Deformation ◽  
Kootenay Lake ◽  
Middle Proterozoic

U–Pb geochronological analyses of five zircon fractions from a lineated and foliated monzonite sill on the west side of Kootenay Lake are discordant and yield a lower intercept age of 173 ± 5 Ma, interpreted as the minimum crystallization age. An upper intercept of 1710 ± 180 Ma is interpreted as the average age of inherited components, and is consistent with contamination by Middle Proterozoic detritus in Upper Proterozoic to lower Paleozoic strata. The sills are interpreted as pre- to syn-kinematic with respect to regional second-phase or possibly third-phase deformation, thus further constraining the timing of Mesozoic orogeny in the Kootenay Arc, and may represent an early, foliated phase of the Nelson Batholith.

Epeirogenic transgression near a triple junction: the oldest (latest early–middle Cambrian) marine onlap of cratonic New York and Quebec

2009 ◽  
Vol 146 (4) ◽  
pp. 552-566 ◽  
Author(s):  
ED LANDING ◽  
LISA AMATI ◽  
DAVID A. FRANZI
Keyword(s):  
New York ◽  
Triple Junction ◽  
Early Cambrian ◽  
Normal Faulting ◽  
Cooling History ◽  
Middle Cambrian ◽  
Iapetus Ocean ◽  
Rapid Accumulation ◽  
Late Stages ◽  
Middle Proterozoic

AbstractThe discovery of a fossiliferous interval (Altona Formation, new unit) under the Potsdam Formation requires a new geological synthesis of a large part of the northeast Laurentian craton. Potsdam sandstones can no longer be regarded as the oldest sedimentary unit on the middle Proterozoic Grenville orogen in northern New York and adjacent Quebec and Ontario. The thickest Potsdam sections (to 750 m) in the east Ottawa–Bonnechere aulocogen have been explained by deposition with normal faulting possibly associated with Ediacaran rifting (c. 570 Ma) that led to formation of the Iapetus Ocean. However, sparse trilobite faunas show a terminal early Cambrian–middle middle Cambrian age of the Altona, and indicate much later marine transgression (c. 510 Ma) of the northeast Laurentian craton. Altona deposition was followed by rapid accumulation of lower Potsdam (Ausable Member) sandstone in the middle–late middle Cambrian. The Altona–Ausable succession is probably conformable. The Altona is a lower transgressive systems tract unit deposited on the inner shelf (sandstone, reddish mudstone, and carbonates) followed by aggradation and the deposition of highstand systems tract, current cross-bedded, in part terrestrial(?), feldspathic Ausable sandstone. Unexpectedly late Altona transgression and rapid Ausable deposition may reflect renewed subsidence in the Ottawa–Bonnechere aulocogen with coeval (terminal early Cambrian) faulting that formed the anoxic Franklin Basin on the Vermont platform. Thus, the oldest cover units on the northeast New York–Quebec craton record late stages in a cooling history near an Ediacaran triple junction defined by the Quebec Reentrant and New York Promontory and the Ottawa–Bonnechere aulocogen.

Neurofilaments and Paired Helical Filaments

1985 ◽  
Vol 43 ◽  
pp. 740-743
Author(s):  
J. Metuzals
Keyword(s):  
Animal Model ◽  
Posttranslational Modifications ◽  
Posttranslational Modification ◽  
Giant Axon ◽  
Paired Helical Filaments ◽  
Squid Giant Axon ◽  
In Vitro Experiments ◽  
Thin Sections ◽  
Structural Relationships

It has been demonstrated that the neurofibrillary tangles in biopsies of Alzheimer patients, composed of typical paired helical filaments (PHF), consist also of typical neurofilaments (NF) and 15nm wide filaments. Close structural relationships, and even continuity between NF and PHF, have been observed. In this paper, such relationships are investigated from the standpoint that the PHF are formed through posttranslational modifications of NF. To investigate the validity of the posttranslational modification hypothesis of PHF formation, we have identified in thin sections from frontal lobe biopsies of Alzheimer patients all existing conformations of NF and PHF and ordered these conformations in a hypothetical sequence. However, only experiments with animal model preparations will prove or disprove the validity of the interpretations of static structural observations made on patients. For this purpose, the results of in vitro experiments with the squid giant axon preparations are compared with those obtained from human patients. This approach is essential in discovering etiological factors of Alzheimer's disease and its early diagnosis.

Structural relationships in the synthesis of cubic boron nitride thin films by ion-assisted deposition

1994 ◽  
Vol 52 ◽  
pp. 638-639
Author(s):  
D. L. Medlin ◽  
T. A. Friedmann ◽  
P. B. Mirkarimi ◽  
M. J. Mills ◽  
K. F. McCarty
Keyword(s):  
Boron Nitride ◽  
Ion Irradiation ◽  
Cubic Boron Nitride ◽  
Film Stress ◽  
Bonded Phases ◽  
Structural Relationships ◽  
Precursor Material ◽  
Pressure Synthesis ◽  
Microstructure Of The Material

The allotropes of boron nitride include two sp2-bonded phases with hexagonal and rhombohedral structures (hBN and rBN) and two sp3-bonded phases with cubic (zincblende) and hexagonal (wurtzitic) structures (cBN and wBN) (Fig. 1). Although cBN is synthesized in bulk form by conversion of hBN at high temperatures and pressures, low-pressure synthesis of cBN as a thin film is more difficult and succeeds only when the growing film is simultaneously irradiated with a high flux of ions. Only sp2-bonded material, which generally has a disordered, turbostratic microstructure (tBN), will form in the absence of ion-irradiation. The mechanistic role of the irradiation is not well understood, but recent work suggests that ion-induced compressive film stress may induce the transformation to cBN.Typically, BN films are deposited at temperatures less than 1000°C, a regime for which the structure of the sp2-bonded precursor material dictates the phase and microstructure of the material that forms from conventional (bulk) high pressure treatment.

Facet Theory

1998 ◽  
Vol 3 (1) ◽  
pp. 13-36 ◽  
Author(s):  
Ruth Guttman ◽  
Charles W. Greenbaum
Keyword(s):  
Data Analysis ◽  
Animal Behavior ◽  
Infant Development ◽  
Facet Theory ◽  
Structural Relationships ◽  
Future Challenges ◽  
Spatial Configurations ◽  
Multidimensional Methods ◽  
Definition Of ◽  
Scalogram Analysis

This article gives an overview of Facet Theory, a systematic approach to facilitating theory construction, research design, and data analysis for complex studies, that is particularly appropriate to the behavioral and social sciences. Facet Theory is based on (1) a definitional framework for a universe of observations in the area of study; (2) empirical structures of observations within this framework; (3) a search for correspondence between the definitional system and aspects of the empirical structure for the observations. The development of Facet Theory and Facet Design is reviewed from early scale analysis and the Guttman Scale, leading to the concepts of “mapping sentence,” “universe of content,” “common range,” “content facets,” and nonmetric multidimensional methods of data analysis. In Facet Theory, the definition of the behavioral domain provides a rationale for hypothesizing structural relationships among variables employed in a study. Examples are presented from various areas of research (intelligence, infant development, animal behavior, etc.) to illustrate the methods and results of structural analysis with Smallest Space Analysis (SSA), Multidimensional Scalogram Analysis (MSA), and Partial Order Scalogram Analysis (POSA). The “radex” and “cylindrex” of intelligence tests are shown to be outstanding examples of predicted spatial configurations that have demonstrated the ubiquitous emergence of the same empirical structures in different studies. Further examples are given from studies of spatial abilities, infant development, animal behavior, and others. The use of Facet Theory, with careful construction of theory and design, is shown to provide new insights into existing data; it allows for the diagnosis and discrimination of behavioral traits and makes the generalizability and replication of findings possible, which in turn makes possible the discovery of lawfulness. Achievements, issues, and future challenges of Facet Theory are discussed.

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