Late Archaean geological development recorded in the Timiskaming Group sedimentary rocks, Kirkland Lake area, Abitibi greenstone belt, Canada

1994 ◽  
Vol 68 (1-2) ◽  
pp. 23-42 ◽  
Author(s):  
Marc I Legault ◽  
Keiko Hattori
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rocks ◽  
Lake Area ◽  
Late Archaean ◽  
Abitibi Greenstone Belt

U–Pb ages and tectonic significance of late Archean alkalic magmatism and nonmarine sedimentation: Timiskaming Group, southern Abitibi belt, Ontario

1991 ◽  
Vol 28 (4) ◽  
pp. 489-503 ◽  
Author(s):  
F. Corfu ◽  
S. L. Jackson ◽  
R. H. Sutcliffe
Keyword(s):  
Greenstone Belt ◽  
Early Stage ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Geochemical Data ◽  
Lake Area ◽  
Quartz Porphyry ◽  
Bear Lake ◽  
Lake Formation ◽  
Dominant Period

The paper presents U–Pb ages for zircons of the calc-alkalic to alkalic igneous suite and associated alluvial–fluvial sedimentary rocks of the Timiskaming Group in the late Archean Abitibi greenstone belt, Superior Province. The Timiskaming Group rests unconformably on pre-2700 Ma komatiitic to calc-alkalic volcanic sequences and is the expression of the latest stages of magmatism and tectonism that shaped the greenstone belt. An age of 2685 ± 3 Ma for the Bidgood quartz porphyry, an age of about 2685–2682 Ma for a quartz–feldspar porphyry clast in a conglomerate, and ages ranging from 2686 to 2680 Ma for detrital zircons in sandstones appear to reflect an early stage in the development of the Timiskaming Group. The youngest detrital zircons in each of three sandstones at Timmins, Kirkland Lake, and south of Larder Lake define maximum ages of sedimentation at about 2679 Ma; the latter sandstone is cut by a porphyry dyke dated by titanite at [Formula: see text], identical to the 2677 ± 2 Ma age for a volcanic agglomerate of the Bear Lake Formation north of Larder Lake. Similar ages have previously been reported for syenitic to granitic plutons of the region. The dominant period of Timiskaming sedimentation and magmatism was thus 2680–2677 Ma. Xenocrystic zircons found in a porphyry and a lamprophyre dyke have ages of 2750–2720 Ma, which correspond to the ages of the oldest units in the belt, predating the volumetrically dominant ca. 2700 Ma greenstone sequences. The presence of these xenocrysts and the onlapping of the Timiskaming Group on all earlier lithotectonic units of the southern Abitibi belt support the concept that the 2700 Ma ensimatic sequences were thrust onto older assemblages during a phase of compression that culminated with the generation of tonalite and granodiorite at about 2695–2688 Ma. Published geochemical data for the Timiskaming igneous suite, notably the enrichments in large-ion lithophile elements and light rare-earth elements and the relative depletion of Nb, Ta, and Ti compare with the characteristics of suites at modern convergent settings such as the Eolian and the Banda arcs and are consistent with generation of the melts from deep metasomatized mantle in the final stages of, or after cessation of, subduction. Late- and post-Timiskaming compression caused north-directed thrusting and folding. Turbiditic sedimentary units of the Larder Lake area which locally structurally overly the alluvial–fluvial sequence and were earlier thought to be part of the Timiskaming Group, appear to be older "flyschoid" sequences, possibly correlative with sedimentary rocks deposited in the Porcupine syncline at Timmins between 2700 and 2690 Ma.

Orthoquartzite pebbles in Archean conglomerate, North Spirit Lake, northwestern Ontario

1977 ◽  
Vol 14 (9) ◽  
pp. 1980-1990 ◽  
Author(s):  
J. A. Donaldson ◽  
Richard W. Ojakangas
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Superior Province ◽  
Lake Area ◽  
Definite Evidence ◽  
The North ◽  
Northwestern Ontario ◽  
Form Part ◽  
Quartz Grains

An Archean conglomerate in the North Spirit Lake area of northwestern Ontario contains rare orthoquartzite pebbles. Detailed study of these pebbles shows that mineralogically they are very mature, consisting of as much as 99.8 percent quartz and a heavy mineral suite of zircon, tourmaline, and apatite. Textures are typically bimodal, characterized by rounded sand-sized quartz grains set in a 'matrix-cement' of thoroughly recrystallized finer quartz grains. These orthoquartzite pebbles provide the first definite evidence for local tectonic stability of the Canadian Shield before deposition of the immature sedimentary rocks that form part of an Archean (>2.6 Ga) greenstone belt of the Superior Province.

The Pontiac problem, Quebec–Ontario, in the light of gravity data

1987 ◽  
Vol 24 (9) ◽  
pp. 1916-1919 ◽  
Author(s):  
J. Kalliokoski
Keyword(s):  
Gravity Anomaly ◽  
Greenstone Belt ◽  
Gravity Data ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Iron Formation ◽  
Bouguer Gravity ◽  
The West ◽  
Abitibi Greenstone Belt ◽  
Uplifted Block

A belt of Archean quartzose metasedimentary gneisses with minor mafic volcanic rocks (the Pontiac Group) lies south of the Blake River and older Archean mafic volcanic rocks of the Abitibi Greenstone Belt, and is separated from them by the Larder Lake – Cadillac Break. To the west of the Pontiac Group, on strike, is the Archean Larder Lake Group of turbidite conglomerate, argillite, limestone, and iron formation with abundant mafic flows and intrusions. These strata also lie south of the Larder Lake – Cadillac Break and south of the Blake River and older Archean mafic volcanic rocks. The western contact between the Pontiac and Larder Lake groups is covered by a narrow north–south strip of Proterozoic Cobalt sedimentary rocks. On the basis of gravity work that compares the Bouguer gravity anomaly gradient across the Cadillac Break with that across the west margin of the Pontiac Group, it is proposed that the Larder Lake and Pontiac groups are separated by a north–south fault and that the Pontiac Group represents a lithologically distinct uplifted block. The Pontiac block may be an Archean terrane.

Timing and kinematics of post-Timiskaming deformation within the Larder Lake - Cadillac deformation zone, southwest Abitibi greenstone belt, Ontario, Canada

1999 ◽  
Vol 36 (4) ◽  
pp. 627-647 ◽  
Author(s):  
Lori Wilkinson ◽  
Alexander R Cruden ◽  
Thomas E Krogh
Keyword(s):  
Greenstone Belt ◽  
Deformation Zone ◽  
Greenschist Facies ◽  
Ductile Deformation ◽  
Magmatic Zircon ◽  
Lake Area ◽  
Abitibi Greenstone Belt ◽  
Terrane Accretion ◽  
East West ◽  
Greenschist Facies Metamorphism

The Larder Lake - Cadillac deformation zone is one of several anastomosing zones of high strain within the Abitibi greenstone belt. In the Kirkland Lake area, Ontario, the Larder Lake - Cadillac deformation zone is characterized by extensive carbonate and chlorite alteration, strong south-dipping foliations, and steep lineations. These features formed during two ductile deformation increments, D2 and D3, that occurred after deposition of Timiskaming assemblage sediments. D2 strain accumulation and greenschist facies metamorphism and alteration were localized within the deformation zone, facilitated by channelling of hydrothermal fluids within a preexisting structure, possibly formed during early D1 terrane accretion. During D2 north-south shortening, east-west-trending sectors of the deformation zone accumulated bulk coaxial strains, while southeast- and northeast-trending sectors experienced, respectively, dextral and sinistral transpressive deformations. Preservation of Timiskaming assemblage sediments in the footwall of the deformation zone indicates a component of south-over-north (reverse) displacement that is not recorded by D2 fabrics. Northwest-southeast D3 compression resulted in the formation of a regional, northeast-striking cleavage formed under regional greenschist facies conditions, and local dextral reactivation of suitably oriented sections of the Larder Lake - Cadillac deformation zone. The Murdoch Creek and Lebel stocks abut the Larder Lake - Cadillac deformation zone. Their internal structure and emplacement are interpreted to be a consequence of D2 north-south shortening. Magmatic zircon and titanite in the Murdoch Creek and Lebel stocks yield U-Pb geochronology ages of 2672 ± 2 and 2673 ± 2 Ma, providing a maximum age for D2 deformation. Hydrothermal titantite associated with S3 foliation in the Murdoch Creek stock gives an U-Pb age of 2665 ± 4 Ma, the maximum age of D3 deformation. Pluton emplacement, deformation, and coincident metamorphism occurred over a span of 1 Ma (from 2670 to 2669 Ma) to over 14 Ma (from 2675 to 2661 Ma), during a regime of north-south, followed by northwest-southeast, regional shortening.

Late Archaean clastic sedimentary rocks (Shamvaian Group) of the Zimbabwe craton: first observations from the Bindura-Shamva greenstone belt

2002 ◽  
Vol 39 (11) ◽  
pp. 1689-1708 ◽  
Author(s):  
A Hofmann ◽  
PH GM Dirks ◽  
H A Jelsma
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rocks ◽  
Sedimentary Facies ◽  
Shear Zones ◽  
Alluvial Fan ◽  
Sediment Supply ◽  
Turbidity Currents ◽  
Late Archaean ◽  
Facies Associations ◽  
Felsic Volcanic

The ~2.65 Ga old Shamvaian Group sedimentary rocks occur as a folded succession in the central part of the Bindura–Shamva greenstone belt of Zimbabwe. The strata comprise distinct, shear zone-bounded tectonostratigraphic units which may be stratigraphically arranged as follows. The lower part of the succession is represented by a transgressive, fining-upward sequence of alluvial fan conglomerate, overlain by fluvial braid-plain pebbly sandstone and marine shoreface sandstone. Detritus was derived from a mid-Archaean granitoid-gneiss terrain situated to the east. Sediment supply and subsidence rate must have been high. Shallow shelf sedimentation was followed by deep-water (sub-wave base) deposition by turbidity currents, giving rise to a thick succession of fine to coarse clastic material. The turbidite deposits were locally overlain by shallow-marine sandstone and fluvial to alluvial fan conglomerate. An upward increase in the abundance of intermediate and felsic volcanic clasts suggests an increase in the proximity of a volcanic terrain, such as a volcanic arc. Deposition was followed by layer-parallel shearing during thrust belt-style tectonism. Major shear zones developed preferentially along the contact between shallow- and deep-marine facies associations. Basin initiation may have been related to extensional tectonics, possibly on rifted continental crust, whereas later stages of basin history were characterized by compression, suggesting a foreland or fore-arc basin setting. Sedimentary facies, stratigraphy, and facies distribution are remarkably similar to some late Archaean sedimentary sequences of the Superior Province in Canada.

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