Deformational history of an Archean fold belt, eastern Point Lake area, Slave Structural Province, N.W.T.

1989 ◽  
Vol 26 (1) ◽  
pp. 106-118 ◽  
Author(s):  
J. E. King ◽  
H. Helmstaedt
Keyword(s):  
Lake Area ◽  
Metasedimentary Rocks ◽  
Thermal Peak ◽  
Strain Pattern ◽  
Slave Province ◽  
Deformational History ◽  
Supracrustal Belt ◽  
Two Generations ◽  
History Of ◽  
Granitoid Intrusions

Archean metasedimentary rocks in the eastern Point Lake area of the Slave Structural Province preserve a sequence of Archean structures consisting of two generations of folds (F1 and F2) with little associated penetrative cleavage and two subsequent generations of cleavage (S3 and S4) with little associated folding. Gneissic layering in the high-grade margin of the belt is composed of transposed bedding and the S3 cleavage. Folding occurred prior to the thermal peak of metamorphism, whereas the develoment of subsequent cleavages spanned the thermal peak. The regional orientation of the folds and cleavages appears to be independent of the emplacement of granitoid intrusions, although their orientation is modified adjacent to syn- to late tectonic plutons. The supracrustal belt is interpreted as being part of a pre- to early metamorphic, west-verging fold (thrust?) belt whose strain pattern has been modified by post-folding, synmetamorphic shortening, and syn- to post-tectonic plutons. This deformation sequence is similar to those described in other supracrustal belts of the Slave Province and supports the concept that the Slave Province has undergone regional, horizontally directed compression before and during intrusion of large amounts of granitoids.

An Archean metamorphic core complex in the southern Slave Province: basement–cover structural relations between the Sleepy Dragon Complex and the Yellowknife Supergroup

1992 ◽  
Vol 29 (10) ◽  
pp. 2133-2145 ◽  
Author(s):  
Donald T. James ◽  
James K. Mortensen
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Lake Area ◽  
Metasedimentary Rocks ◽  
Kinematic Indicators ◽  
The North ◽  
Slave Province ◽  
Gneiss Granite ◽  
History Of ◽  
Metamorphic Core

Archean rocks in the Fenton Lake – Brown Lake area, southern Slave Province, are subdivided into two lithotectonic domains: a supracrustal domain, which consists mainly of the Archean Yellowknife Supergroup, and a gneiss–granite domain. The latter is composed of gneissic and metaigneous rocks of the Sleepy Dragon Complex, determined to be basement to the Yellowknife Supergroup, and granite plutons, including the 2641 ± 3.5 Ma Suse Lake granite and the 2583.5 ± 1 Ma Morose Granite. Volcanic rocks of the Cameron River Belt and greywacke–mudstone turbiditic metasedimentary rocks of the Burwash Formation constitute the supracrustal domain.A late Archean, amphibolite- to greenschist-facies, ductile to local brittle, high-strain zone separates the domains. Kinematic indicators demonstrate that the zone experienced two kinematically opposed episodes of displacement. The older episode involved pre- to synthermal peak thrusting of the supracrustal rocks over the gneiss–granite domain. Thrusting is kinematically and temporally consistent with late Archean, pre- to synthermal peak, regional contractional deformation. Structural and metamorphic relations and kinematic indicators suggest that thrusting and regional contraction were followed shortly by intrusion of the peraluminous Morose Granite and thereafter by a late syn- to post-thermal peak episode of extension, resulting in tectonic unroofing of the gneiss–granite domain.The sequential history of contraction and attendant regional metamorphism, granite intrusion, and, ultimately, extensional collapse, which is documented in the Archean rocks in the area, is a common feature of Phanerozoic collisional orogens. Moreover, the tectonic history of the gneiss–granite domain is broadly similar to the evolution of metamorphic core complexes in the North American Cordillera.

Deposition and imbrication of a 2670-2629 Ma supracrustal sequence in the Indin Lake area, southwestern Slave Province, Canada

1999 ◽  
Vol 36 (7) ◽  
pp. 1149-1168 ◽  
Author(s):  
S J Pehrsson ◽  
M E Villeneuve
Keyword(s):  
Volcanic Rocks ◽  
Lake Area ◽  
Regional Deformation ◽  
Tectonic History ◽  
Slave Province ◽  
Gneiss Complex ◽  
Supracrustal Belt ◽  
History Of ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

New U-Pb age data from the southwestern Slave Province demonstrate that units of the Indin Lake supracrustal belt form an imbricated structural stack. The oldest rocks of the belt are undated mafic volcanic flows of the Hewitt Lake group that are crosscut by a 2670 Ma felsic sill, itself coeval with mafic through felsic volcanic rocks of the 2668-2671 Ma Leta Arm group. The youngest rocks of the belt are 2647-2629 Ma turbidites and felsic volcanic rocks of the unconformably overlying Chalco Lake group. Tonalite orthogneiss of the adjacent Cotterill gneiss complex is 2680 Ma, suggesting that it does not represent in situ basement to the supracrustal belt. Intercalation of the older Hewitt Lake and Leta Arm groups with the younger Chalco Lake group is interpreted to result from D1 imbrication and folding between 2629 and 2609 Ma, the age of a crosscutting tonalite intrusion. Subsequent D2 folding and regional low-pressure metamorphism occurred between 2609 Ma and ca. 2590 Ma. D3 normal faulting between the belt and Cotterill gneisses, ca. 2590 Ma, is interpreted to overlap with retrograde amphibolite-facies metamorphism and decompression of the gneiss complex. Comparisons between the tectonic history of the Indin Lake area and the central Slave Province show that turbidite deposition was regionally diachronous and overlapped with regional deformation elsewhere, supporting existing models favouring some form of accretionary orogenesis. The imbricated and intercalated 2670-2629 Ma supracrustal sequence may characterize a distinct crustal block in the southwestern Slave Province.

Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996

1997 ◽  
pp. 60-65
Author(s):  
Adam A. Garde ◽  
Brian Chadwick ◽  
John Grocott ◽  
Cees Swager
Keyword(s):  
Field Work ◽  
Deformation History ◽  
The South ◽  
Present Contribution ◽  
East Part ◽  
Metasedimentary Rocks ◽  
Deformational History ◽  
Base Camp ◽  
History Of ◽  
Geological Map

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Garde, A. A., Chadwick, B., Grocott, J., & Swager, C. (1997). Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 60-65. https://doi.org/10.34194/ggub.v176.5063 _______________ The south-east part of the c. 1800 Ma Ketilidian orogen in South Greenland (Allaart, 1976) is dominated by strongly deformed and variably migmatised metasedimentary rocks known as the ‘Psammite and Pelite Zones’ (Chadwick & Garde, 1996); the sediments were mainly derived from the evolving Julianehåb batholith which dominates the central part of the orogen. The main purpose of the present contribution is to outline the deformational history of the Psammite Zone in the region between Lindenow Fjord and Kangerluluk (Fig. 2), investigated in 1994 and 1996 as part of the SUPRASYD project (Garde & Schønwandt, 1995 and references therein; Chadwick et al., in press). The Lindenow Fjord region has high alpine relief and extensive ice and glacier cover, and the fjords are regularly blocked by sea ice. Early studies of this part of the orogen were by boat reconnaissance (Andrews et al., 1971, 1973); extensive helicopter support in the summers of 1992 and 1994 made access to the inner fjord regions and nunataks possible for the first time.A preliminary geological map covering part of the area between Lindenow Fjord and Kangerluluk was published by Swager et al. (1995). Hamilton et al. (1996) have addressed the timing of sedimentation and deformation in the Psammite Zone by means of precise zircon U-Pb geochronology. However, major problems regarding the correlation of individual deformational events and their relationship with the evolution of the Julianehåb batholith were not resolved until the field work in 1996. The SUPRASYD field party in 1996 (Fig. 1) was based at the telestation of Prins Christian Sund some 50 km south of the working area (Fig. 2). In addition to base camp personnel, helicopter crew and the four authors, the party consisted of five geologists and M.Sc. students studying mafic igneous rocks and their mineralisation in selected areas (Stendal et al., 1997), and a geologist investigating rust zones and areas with known gold anomalies.

Fabrics and Deformation of Archean Metasedimentary Rocks, Ross Lake – Gordon Lake Area, Slave Province, Northwest Territories

1975 ◽  
Vol 12 (5) ◽  
pp. 765-776 ◽  
Author(s):  
W. K. Fyson
Keyword(s):  
Northwest Territories ◽  
Small Scale ◽  
Lake Area ◽  
Metasedimentary Rocks ◽  
Slave Province ◽  
Complex Part ◽  
Scale Structures ◽  
Inclusion Trails ◽  
Lake Gordon ◽  
Small Scale Structures

Metagreywackes, which lie stratigraphically above metavolcanics fringing a granitic complex (part basement), exhibit late Archean multiphase fold structures. F1 folds are large linear depressions and anticlinal culminations trending partly concordant with margins of the granitic complex. Open to isoclinal F2 folds vary and curve in trend. Though usually near upright, some F2 folds are overturned away from the complex and others towards F1 depressions. F3 folds are small-scale structures not present in most outcrops, but throughout a large region they are accompanied by a steep S3 axial-plane schistosity striking NW to N.Original orientations of an S2 schistosity, axial planar to F2 folds, are preserved as inclusion trails in biotite porphyroblasts. Angular deflections from the trails show that regional horizontal flattening across the S3 schistosity formed the F3 folds and tightened curved trends of F2 folds. Estimates of strain from the fabrics indicate no increase near the complex.As for folds in other Archean terrains, F1 and F2 folds could have developed mainly as gravity structures during diapiric uprise of a granitic basement. In contrast, the F3 structures may reflect horizontal movements of early crustal plates.

Deformational history of an outlier of metasedimentary rocks, Coast Plutonic Complex, British Columbia, Canada

1986 ◽  
Vol 23 (6) ◽  
pp. 813-826 ◽  
Author(s):  
Bruce J. Douglas
Keyword(s):  
Shear Zones ◽  
Metasedimentary Rocks ◽  
Thrust Faulting ◽  
Deformational History ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
History Of ◽  
Peak Metamorphism ◽  
Differential Uplift ◽  
Penetrative Foliation

The Khutzeymateen assemblage records a portion of the polyphase deformation experienced by rocks within the core of the Coast Plutonic Complex. This series of deformational events probably took place during Late Cretaceous to Early Eocene regional orogenic activity. The Khutzeymateen assemblage is dominated by metamorphosed graywackes and volcaniclastic material. The earliest recognizable deformation involves thrust faulting that juxtaposed rocks of the Khutzeymateen assemblage and Central Gneiss Complex. The next deformational event produced isoclinal folds (F1), a penetrative foliation (S1), and a strong mineral lineation (L1). Both F1 and L1 have a 340°, 15 °orientation. Peak metamorphism (P = 450 ± 50 MPa, T = 650° ± 50 °C) was synchronous with this isoclinal folding event. F1 folding was followed by a brittle chevron folding event (F2) with a 335°, 20° orientation. There is a strong lithologic control on the development of F2 minor folds, which are developed predominantly within regularly layered quartzo-feldspathic lithologies. Open F3 folds (065°, 35°) may have developed by buckling related to differential uplift on the Larch Creek Fault. Post-F3 faults and minor shear zones are developed mostly in the eastern half of the area. The different deformational styles associated with the different deformational events probably reflect variations in the position of this group of rocks with respect to the surface during a single orogenic episode.

Late Archean tectono-magmatic evolution of the central Slave Province, Northwest Territories

1992 ◽  
Vol 29 (10) ◽  
pp. 2156-2170 ◽  
Author(s):  
J. E. King ◽  
W. J. Davis ◽  
C. Relf
Keyword(s):  
Northwest Territories ◽  
Lake Area ◽  
Crustal Melting ◽  
Magmatic Evolution ◽  
Calc Alkaline ◽  
Thermal Peak ◽  
Suprasubduction Zone ◽  
Slave Province ◽  
Peraluminous Granites ◽  
Intense Deformation

An early tectono-stratigraphic and late plutonic assemblage are distinguished in the central part of the Archean Slave Province (Contwoyto Lake area) on the basis of their relationship to deformation and metamorphic episodes, and by geochemical characteristics. The older assemblage, which predates the onset of intense deformation and the thermal peak of metamorphism, comprises 2.68–2.65 Ga calc-alkaline volcanic and plutonic rocks, as well as extensive turbidites. The younger assemblage comprises ca. 2.61–2.58 Ga plutonic units that were emplaced during and after deformation (D,–D3) and the thermal peak of metamorphism. Compositions of the late plutonic units vary systematically with time of intrusion from an early, calc-alkaline, diorite – tonalite suite to late peraluminous granites. The early assemblage is interpreted to represent remnants of an island arc (or arcs) overlain by turbidites and accreted during D1 and D2. The later assemblage is interpreted as a product of late- to post-accretion, suprasubduction-zone magmatism and associated crustal melting.

On Crepidostomum farionis O. F. Müll. (= Stephanophiala laureata Zeder), a Distome Parasite of the Trout and Grayling. I. The Life History

Parasitology ◽  
1927 ◽  
Vol 19 (1) ◽  
pp. 86-99 ◽  
Author(s):  
F. J. Brown
Keyword(s):  
Life History ◽  
Gall Bladder ◽  
Excretory Vesicle ◽  
Intermediate Hosts ◽  
Larval Trematode ◽  
Sphaerium Corneum ◽  
Two Generations ◽  
History Of ◽  
Second Intermediate Host ◽  
Ephemera Danica

1. Crepidostomum farionis inhabits the gall bladder, as well as the intestine and pyloric caeca, of the trout and grayling.2. The life history of Crepidostomum farionis has been worked out and is based on the similarity of organisation of the cercaria, encysted larval trematode and the adult.3. The first intermediate hosts in the life history of this trematode are Pisidium amnicum (Müll.) and Sphaerium corneum (L.) though the latter is unusual.4. The second intermediate host is the larva of the mayfly, Ephemera danica (Müll.).5. There are two generations of rediae, the first gives rise to daughter rediae, which in turn produce cercariae.6. The rediae are characterised by the absence of ambulatory processes and a functional intestine.7. The cercaria (n.sp.) possesses “eye spots,” stylet and gland cells (salivary?), and the excretory vesicle is tube-shaped.8. The excretory system of the redia and the cercaria has been worked out in detail.9. The relation of the parasites to their respective hosts is discussed. On account of the need for further observations definite conclusions are held over for a later paper.

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