Geological development of eastern Humber and western Dunnage zones: Corner Brook–Glover Island region, Newfoundland

1996 ◽  
Vol 33 (2) ◽  
pp. 182-198 ◽  
Author(s):  
Peter A. Cawood ◽  
Jeroen A.M. van Gool ◽  
Greg R. Dunning
Keyword(s):  
Shear Zones ◽  
Isotopic Data ◽  
Island Region ◽  
Zircon Age ◽  
Regional Deformation ◽  
Head Groups ◽  
Facies Metamorphism ◽  
External Domain ◽  
Laurentian Margin ◽  
Internal Domain

The Corner Brook–Glover Island region records the development of the internal domain of the Humber Zone and its relationship to the adjoining external domain and Dunnage Zone. The region preserves both the Laurentian margin basement–cover contact and the siliciclastic–carbonate transition within the cover sequence. Precambrian Grenville basement of the Corner Brook Lake Complex is the oldest lithostratigraphic unit and yielded a U/Pb zircon age of 1510 ± 6 Ma. Three main lithostratigraphic assemblages overlie basement: silicic and mafic igneous rocks of the Lady Slipper Pluton which yielded a U/Pb zircon age of [Formula: see text] Ma; siliciclastic lithologies which include the South Brook and Summerside formations; and carbonate-dominated sequences with clastic incursions which include the Port au Port, St. George, and Table Head groups, and the Breeches Pond, Irishtown, and Pinchgut formations. Dunnage Zone units include plutonic ultramafic to mafic rocks of the Grand Lake Complex, dated by U/Pb zircon from trondhjemite at 490 ± 4 Ma, volcanic and epiclastic rocks of the Glover Island Formation, and the Matthews Brook Serpentinite, the latter restricted to fault slivers within the Humber Zone sequence. The deformed Glover Island Granodiorite intrudes the Dunnage Zone rocks on Glover Island and is dated by U/Pb zircon and titanite at 440 ± 2 Ma. Little deformed Carboniferous sedimentary rocks unconformably overlie both Humber Zone and Dunnage Zone rock units. Timing of regional deformation and peak amphibolite-facies metamorphism in the eastern Humber Zone is constrained by isotopic data to the Early Silurian. In the Dunnage Zone, shear zones and foliation development both pre- and postdate the age of the Glover Island Granodiorite, with the later possibly temporally equivalent to deformation in the Humber Zone. Final juxtaposition of the two zones occurred during Carboniferous movement of the Cabot Fault.

scholarly journals Dating of late Archaean crustal mobilisation north of Qugssuk, Godthåbsfjord, southern West Greenland

1986 ◽  
Vol 128 ◽  
pp. 23-36
Author(s):  
A.A Garde ◽  
O Larsen ◽  
A.P Nutman
Keyword(s):  
Granulite Facies ◽  
Isotopic Data ◽  
Zircon Age ◽  
Granulite Facies Metamorphism ◽  
Late Archaean ◽  
West Greenland ◽  
Facies Metamorphism ◽  
The Common

The Taserssuaq tonalite, which is slightly younger than or coeval with the common grey gneisses north of Godthåbsfjord, has yielded a zircon U-Pb age of 2982 ± 7 Ma, and an apparent Rb-Sr whole-rock age of 2882 ± 36 Ma (MSWD = 1.57, initial 87Sr/86Sr = 0.7017). The minerals were isotopicaIly equilibrated at 2500 Ma, and finally biotite was reset at 1700 Ma. The Qugssuk granite, an adjacent granitic mobilisate, has yielded a Rb-Sr age of 2969 ± 32 Ma (MSWD = 1.09, initial 87Sr/86Sr = 0.7020). The intrusion of the Taserssuaq tonalite is probably dated by its zircon age, which broadly correlates it with the Nilk gneisses. Field relations and microtextures strongly suggest that the Qugssuk granite is younger than the Taserssuaq tonalite and post-dates granulite facies metamorphism in the area, and its formation may be related to the extensive retrogression of the Taserssuaq tonalite. Isotopic data may support this interpretation in spite of the apparent inconsistencies in the age values.

Episodic tectono-thermal activity in the southern part of the East Greenland Caledonides

2000 ◽  
pp. 42-49 ◽  
Author(s):  
A. Graham Leslie ◽  
Allen P. Nutman
Keyword(s):  
Thermal Activity ◽  
Isotopic Data ◽  
Zircon Age ◽  
East Greenland ◽  
Original Series ◽  
Age Determinations

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Leslie, A. G., & Nutman, A. P. (2000). Episodic tectono-thermal activity in the southern part of the East Greenland Caledonides. Geology of Greenland Survey Bulletin, 186, 42-49. https://doi.org/10.34194/ggub.v186.5214 _______________ Isotopic data from the Renland augen granites of the Scoresby Sund region (Figs 1, 2) provided some of the first convincing support for relicts of potentially Grenvillian tectono-thermal activity within the East Greenland Caledonides. In Renland, Chadwick (1975) showed the presence of major bodies of augen granite (Fig. 2) interpreted by Steiger et al. (1979), on the basis of Rb–Sr whole rock and U–Pb zircon age determinations, to have been emplaced about 1000 Ma ago.

A seismic-based cross-section of the Grenville Orogen in southern Ontario and western Quebec

2000 ◽  
Vol 37 (2-3) ◽  
pp. 183-192 ◽  
Author(s):  
D J White ◽  
D A Forsyth ◽  
I Asudeh ◽  
S D Carr ◽  
H Wu ◽  
...  
Keyword(s):  
Cross Section ◽  
Seismic Refraction ◽  
Shear Zones ◽  
Tectonic Zone ◽  
Grenville Province ◽  
Crustal Layer ◽  
Seismic Reflection Data ◽  
Velocity Models ◽  
Laurentian Margin ◽  
Structural Boundary

A schematic crustal cross-section is presented for the southwestern Grenville Province based on reprocessed Lithoprobe near-vertical incidence seismic reflection data and compiled seismic refraction - wide-angle velocity models interpreted with geological constraints. The schematic crustal architecture of the southwest Grenville Province from southeast to northwest comprises allochthonous crustal elements (Frontenac-Adirondack Belt and Composite Arc Belt) that were assembled prior to ca. 1160 Ma, and then deformed and transported northwest over reworked rocks of pre-Grenvillian Laurentia and the Laurentian margin primarily between 1120 and 980 Ma. Reworked pre-Grenvillian Laurentia and Laurentian margin rocks are interpreted to extend at least 350 km southeast of the Grenville Front beneath all of the Composite Arc Belt. Three major structural boundary zones (the Grenville Front and adjacent Grenville Front Tectonic Zone, the Central Metasedimentary Belt boundary thrust zone, and the Elzevir-Frontenac boundary zone) have been identified across the region of the cross-section based on their prominent geophysical signatures comprising broad zones of southeast-dipping reflections and shallowing of mid-crustal velocity contours by 12-15 km. The structural boundary zones accommodated southeast over northwest crustal stacking at successively earlier times during orogeny (ca. 1010-980 Ma, 1080-1060 Ma, and 1170-1160 Ma, respectively). These shear zones root within an interpreted gently southeast-dipping regional décollement at a depth of 25-30 km corresponding to the top of a high-velocity lower crustal layer.

scholarly journals The perigranitic W-Au Salau deposit (Pyrenees, France): polyphase genesis of a late Variscan intrusion related deposit

2021 ◽  
Vol 192 ◽  
pp. 22
Author(s):  
Thomas Poitrenaud ◽  
Éric Marcoux ◽  
Romain Augier ◽  
Marc Poujol
Keyword(s):  
3D Modeling ◽  
Main Part ◽  
Isotopic Analysis ◽  
Shear Zones ◽  
Coarse Grained ◽  
Axial Zone ◽  
The Past ◽  
Regional Deformation ◽  
Deposit Type ◽  
Ore Types

A field study combined with a laboratory study and 3D modeling have been performed in order to decipher the genesis of the Salau deposit W-Au mineralization (Pyrenees, France), one of the most important for tungsten in Europe. Results show the existence of two superimposed ore types, emplaced ca. 10 km depth and within decreasing temperature conditions: a calcic silicates skarn with rare scheelite and disseminated sulphides followed by a mineralized breccia with massive sulphides (pyrrhotite and chalcopyrite dominant), coarse-grained scheelite and gold, representing the main part of the ore mined in the past. This breccia is localized in ductile-brittle shear-zones which crosscut the granodiorite. U/Pb dating on zircon, apatite and scheelite, previously realized, confirmed this polyphase evolution. These two types of mineralization, linked to the emplacement of two successive intrusions as confirmed by sulphur isotopic analysis, granodioritic then leucogranitic, can be classified as belonging to the Intrusion-Related Gold Deposit type (IRGD). The emplacement of the high-grade gold and scheelite breccia was initiated by the progressive localization of the regional deformation in the Axial Zone of the Pyrenees during the Permian within E-W dextral-reverse faults.

scholarly journals Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xu Kong ◽  
Xueyuan Qi ◽  
Wentian Mi ◽  
Xiaoxin Dong
Keyword(s):  
Regional Metamorphism ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Isotopic Data ◽  
Metamorphic Condition ◽  
Eu Anomaly ◽  
Facies Metamorphism ◽  
Eclogite Facies ◽  
Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

Chronal Cues to a Target

2018 ◽  
Author(s):  
Leonard Talmy
Keyword(s):  
External Domain ◽  
Temporal Location ◽  
The Moment ◽  
Limiting Case ◽  
Internal Domain

A chronal cue informs a hearer about the temporal location of the target as an aid in determining that target. The trigger is lexicalized to require this cue. The chronal cue consists of the trigger moment — the moment of the trigger’s own occurrence — in the speech-external domain, and of the base moment — the moment at which an event in reference occurs — in the speech-internal domain. The target is an interval — the chronal interval - that contains the trigger or base moment or, in the limiting case, coincides with it. A range hearer set the boundaries of this chronal interval. When speech-external, the chronal interval targeted by the trigger can be of three types. It is supersentential if it is longer than and inclusive of the sentence that the trigger appears in; subsentential if shorter than and included within that sentence; and cosentential if coextensive with that sentence.

scholarly journals Timing of Paleozoic Exhumation and Deformation of the High-Pressure Vestgӧtabreen Complex at the Motalafjella Nunatak, Svalbard

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 125 ◽  
Author(s):  
Christopher J. Barnes ◽  
Katarzyna Walczak ◽  
Emilie Janots ◽  
David Schneider ◽  
Jarosław Majka
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Shear Zones ◽  
White Mica ◽  
Strike Slip ◽  
Structural Studies ◽  
Metamorphic Overprint ◽  
Subaerial Exposure ◽  
Facies Metamorphism

The Vestgӧtabreen Complex exposed in the Southwestern Caledonian Basement Province of Svalbard comprises two Caledonian high-pressure units. In situ white mica 40Ar/39Ar and monazite Th-U-total Pb geochronology has resolved the timing of the tectonic evolution of the complex. Cooling of the Upper Unit during exhumation occurred at 476 ± 2 Ma, shortly after eclogite-facies metamorphism. The two units were juxtaposed at 454 ± 6 Ma. This was followed by subaerial exposure and deposition of Bullbreen Group sediments. A 430–400 Ma late Caledonian phase of thrusting associated with major sinistral shearing throughout Svalbard deformed both the complex and the overlying sediments. This phase of thrusting is prominently recorded in the Lower Unit, and is associated with a pervasive greenschist-facies metamorphic overprint of high-pressure lithologies. A c. 365–344 Ma geochronological record may represent an Ellesmerian tectonothermal overprint. Altogether, the geochronological evolution of the Vestgӧtabreen Complex, with previous petrological and structural studies, suggests that it may be a correlative to the high-pressure Tsäkkok Lens in the Scandinavian Caledonides. It is suggested that the Vestgӧtabreen Complex escaped to the periphery of the orogen along the sinistral strike-slip shear zones prior to, or during the initial stages of continental collision between Baltica and Laurentia.

A Discussion on natural strain and geological structure - Archaean deformation patterns in southern Africa

1976 ◽  
Vol 283 (1312) ◽  
pp. 313-331 ◽  
Keyword(s):  
Shear Zones ◽  
Geological Structure ◽  
Mobile Belt ◽  
Deformation Pattern ◽  
Strain Measurements ◽  
Regional Deformation ◽  
Greenstone Belts ◽  
Extension Direction ◽  
Orogenic Belts ◽  
Limpopo Belt

Strain measurements have been made to help quantify the intensity of deformation and amount of displacement across Archaean greenstone belts in Rhodesia and Botswana and across the gneisses of the Limpopo mobile belt. The area has been divided into three domains based on the orientation of the finite strain fabric and the orientation of the maximum extension direction in associated shear zones. The domains are considered to have different movement patterns and to be similar to small orogenic belts. Early deformation within the greenstone belts accompanied the intrusion of the diaipric granites, but there was also bulk translation and rotation of greenstone belt and gneiss leading to imbrication of the stratigraphic pile and the formation of large nappes of overturned rock. This was followed by regional phases of deformation which affected all the greenstone belts and the gneisses of the Limpopo belt. Detailed strain measurements show a variation in amount of shortening during this phase, from under 30 % across the Shabani-Bellingwe belt in central Rhodesia, to over 60 % across the Tati and Matsitama belts in northern Botswana. Many local variations in intensity of deformation occur within large ductile shear zones and deviations from plane strain may be partly due to such rotational deformation. The regional deformation pattern suggests that there was movement of the Rhodesian craton approximately 200 km to the southwest relative to the gneisses of the Limpopo belt, producing a dominantly flattening deformation in the southwest of Rhodesia, but dominantly simple shear with a nearly horizontal sinistral movement, in the southeast.

Detrital zircon populations of the eastern Laurentian margin in the Appalachians

Geology ◽  
2020 ◽  
Author(s):  
Yvette D. Kuiper ◽  
Christopher Hepburn
Keyword(s):  
United States ◽  
Detrital Zircon ◽  
Orogenic Belt ◽  
Grenville Province ◽  
Zircon Age ◽  
Zircon Population ◽  
Middle Ordovician ◽  
Archean Crust ◽  
Laurentian Margin

Newly compiled U-Pb detrital zircon data from eight geographic domains along the eastern Laurentian margin from Newfoundland (Canada) to Alabama (United States) show a highly consistent signature along strike, with only minor local variations. The Precambrian signature is characterized by a small ca. 2.7 Ga population and a major ca. 1.9–0.9 Ga population that peaks at ca. 1.2–1.0 Ga. Detrital zircon populations are from Laurentian Archean crust (ca. 2.7 Ga population), Paleoproterozoic orogens (ca. 1.9–1.6 Ga), the Granite-Rhyolite Province (ca. 1.5–1.4 Ga), and the Elzevir terrane and Grenville Province (ca. 1.3–0.9 Ga). The Mesoproterozoic populations vary in size depending on proximity to the ca. 1.5–1.4 Ga Granite-Rhyolite Province, the ca. 1245–1225 Ma Elzevir terrane, and the ca. 1.2–0.9 Ga Grenville Province. A middle Ordovician zircon population varies in size along strike depending on input from the Taconic orogenic belt, but it is strongest in the northern Appalachians. Because of the general along-strike consistency in detrital zircon age populations, the compilation of all 7534 concordant U-Pb detrital zircon data can be used in future U-Pb detrital zircon studies as an indicator for eastern Laurentian margin sources.

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