Geochemical and radiogenic isotope (Sr-Nd) characteristics of Paleoproterozoic anorthositic and granitoid rocks in the Umiakoviarusek Lake region, Labrador, Canada.

1999 ◽  
Vol 36 (12) ◽  
pp. 1957-1972 ◽  
Author(s):  
Stephen J Piercey ◽  
Derek HC Wilton
Keyword(s):  
Crustal Contamination ◽  
Isotopic Data ◽  
North Central ◽  
Radiogenic Isotope ◽  
The North ◽  
Lake Region ◽  
Intrusive Rocks ◽  
Mantle Component ◽  
Granitoid Rocks ◽  
Source Materials

Recent work in the north-central Labrador has identified Paleoproterozoic anorthositic and granitoid rocks that are spatially associated with, yet temporally distinct from, younger Mesoproterozoic intrusions of the Nain Plutonic Suite. The Umiakoviarusek Lake (UL) region of Labrador contains several of these Paleoproterozoic intrusions and provides an opportunity to study their geochemical and radiogenic isotope (Sr-Nd) characteristics. Geochemically, the anorthositic and granitoid rocks have features consistent with contemporary anorthositic and granitoid rocks from other anorthosite-mangerite-charnockite-granite complexes. The anorthositic rocks contain elevated contents of Al2O3, CaO, Sr, and Eu with low Ba, Rb, K, Zr, total rare earth elements (REE), and light REE. The granitoid rocks, on the other hand, contain lower concentrations of these elements along with elevated SiO2 and K2O. Isotopic data at 2050 Ma for the anorthositic rocks (ISr = 0.7048-0.7082; εNd = -4.1 to -15.9) and granitoid rocks (ISr = 0.7036-0.7094, εNd = -5.1 to -9.7) are consistent with variable crustal and mantle contributions to their genesis. The relatively unradiogenic Sr and slightly evolved Nd isotopic data from the UL granitoid rocks is consistent with a significant juvenile mantle component, possibly derived from an underplating mantle plume; this component may also be present in the anorthositic rocks. The Nd and Sr isotopic data are also consistent with crustal contamination from Archean source materials; however, based on the existing isotopic database for the Nain Province gneisses, it is not possible to delineate a specific gneiss component. Furthermore, it is also quite possible that an Archean source, unlike any described at present, was a crustal source component in the UL intrusive rocks.

Nd isotopic evidence for crustal recycling in the ca. 2.0 Ga subsurface of western Canada

1991 ◽  
Vol 28 (8) ◽  
pp. 1140-1147 ◽  
Author(s):  
R. J. Thériault ◽  
G. M. Ross
Keyword(s):  
Isotopic Data ◽  
Tectonic Zone ◽  
Isotopic Signatures ◽  
Crustal Recycling ◽  
The North ◽  
Tectonic History ◽  
Depleted Mantle ◽  
History Of ◽  
Mantle Component ◽  
Northern Alberta

Sm–Nd isotopic data are presented for 23 drill-core samples from five aeromagnetically and geochronologically (U–Pb zircon) distinct domains of the Precambrian basement of northern Alberta. The domains in question are the Taltson (1.96–1.94 Ga), Buffalo Head (2.32–1.99 Ga), Chinchaga (2.19–2.09 Ga), Ksituan (1.99–1.90 Ga), and Nova (2.81 Ga). These domains are truncated to the north and south by the Great Slave Lake shear zone and the Snowbird tectonic zone, respectively.Initial εNd values are −5.0 to −9.7 for the Taltson, +0.2 to −6.3 for the Buffalo Head, +0.6 to −1.8 for the Chinchaga, −1.8 to −2.1 for the Ksituan and +5.6 for the Nova. Crustal residence model ages fall in the 2.5–2.8 Ga range. The Nd isotopic signatures may be viewed in terms of mixing a minimum of 10% Archean continental crust with a depleted-mantle component. Speculations on the tectonic history of the basement domains in question involve the assembly of Archean crustal nuclei to form the Buffalo Head – Chinchaga composite domain. Arc magmatism resulting from plate subduction to the east and west of the Buffalo Head – Chinchaga composite domain would have generated the Taltson and Ksituan domains. The Nd isotopic data suggest that the basement of northern Alberta consists of crust of late Archean crustal residence age which has been extensively remobilized in the Early Proterozoic.

Regional and local ice-flow history in the vicinity of the Izok Lake Zn–Cu–Pb–Ag deposit, Nunavut

2013 ◽  
Vol 50 (12) ◽  
pp. 1209-1222 ◽  
Author(s):  
Roger C. Paulen ◽  
M. Beth McClenaghan ◽  
Anna K. Hicken
Keyword(s):  
Lake Area ◽  
Massive Sulphide Deposit ◽  
Sulphide Deposit ◽  
Ice Flow ◽  
North Central ◽  
The North ◽  
Slave Province ◽  
Lake Region ◽  
Volcanogenic Massive Sulphide ◽  
Indicator Mineral

Ice-directional indicators were compiled from detailed field mapping at the Izok Lake volcanogenic massive sulphide deposit, in the Point Lake region of western Nunavut and eastern Northwest Territories. Cross-cutting erosional relationships and depositional landforms indicate that the Izok Lake area was affected by four ice-flow phases. It is this new glacial history interpretation that is used to explain the gahnite indicator mineral dispersal train down-ice of the Izok Lake deposit as being the net effect of all ice-flow phases. Its fan-shaped morphology is a function of the duration and intensity of two dominant glacial trajectories. Field-based mapping of all glacial-flow indicators are essential, and must be properly interpreted, to detect palimpsest dispersal trains. The resultant dispersal fan serves as a model for future exploration in the glaciated terrain of the north-central part of the Slave Province.

Precambrian terrane of north-central Wisconsin: an aeromagnetic perspective

1990 ◽  
Vol 27 (11) ◽  
pp. 1472-1477 ◽  
Author(s):  
Elizabeth R. King
Keyword(s):  
Shear Zones ◽  
Superior Province ◽  
Large Area ◽  
Midcontinent Rift ◽  
North Central ◽  
The North ◽  
Magnetic Signatures ◽  
Granitoid Rocks ◽  
Western Side ◽  
Shaded Relief

A shaded relief magnetic map covering most of the region of exposed Precambrian rocks of north-central Wisconsin shows the structural grain and many lithologic units with clarity and comprehensive detail. The area includes part of the volcanic sequence of the Keweenawan Supergroup south of Lake Superior, the southern margin of the Archean Superior Province, the accreted island-arc terranes of the Penokean Orogen, and the Wolf River batholith. Numerous dikes are evident in the shaded relief, some being more than 200 km in length. Many of the longer dikes are reversely magnetized Keweenawan diabase associated with early extension of the Midcontinent Rift; some apparently were intruded along preexisting faults. A northwest system of dikes and faults indicated by the shaded relief map may be related to later stages of Keweenawan rifting. The Wolf River batholith is characterized by low magnetic relief associated with the predominant granitoids but includes circular plutons of highly magnetic anorthosite and a large area of magnetic rock having a signature different from the mapped anorthosite bodies. A fault bounding the western side of the batholith is paralleled by an apparent system of faults or dikes in the older terrane to the west. The magnetic map covering the Wisconsin magmatic terranes and the Archean Superior Province margin to the north is dominated by east-northeast-trending Penokean rocks. Large units of magnetic mafic rocks and less magnetic granitoid rocks are cut by a system of well-defined northeast shear zones and a more easterly trending, possibly younger set of faults, some of which contain dikes along parts of their lengths. Although the sutures bounding the magmatic terranes generally follow the magnetic trends, they do not have distinctive magnetic signatures.

Isotopic assessment of relative contributions from crust and mantle sources to the magma genesis of Precambrian granitoid rocks

1984 ◽  
Vol 310 (1514) ◽  
pp. 605-625 ◽  
Keyword(s):  
Calc Alkaline ◽  
Isotopic Data ◽  
Late Archaean ◽  
Magma Genesis ◽  
West Greenland ◽  
Sialic Crust ◽  
Mantle Sources ◽  
Granitoid Rocks ◽  
Plutonic Rocks ◽  
Source Materials

Rb-Sr, Sm-Nd and U-Th-Pb isotopic data for Precambrian granitoids (i.e. granites and intermediate calc-alkaline plutonic rocks) from Greenland, Scotland and Zimbabwe are used to assess the relative contributions to magma genesis of various source materials. Ancient continental crustal contributions are identified by negative e N d values in the magmas at time of formation. Initial 87 Sr/ 86 Sr (Sr 1 ,) values identify crustal contributions as derived from deep (low Rb/Sr) or upper (high Rb/Sr) crust. Pb isotopic data, expressed as model ( 238 U / 204 Pb) values, permit the distinction between deep (low U/Pb) and upper (high U/Pb) crustal contributions. However, it is not usually possible to distinguish between mantle (low Rb/Sr) and deep crustal sources using Sr 1 values. In contrast, Nd and Pb isotopic data permit such a distinction to be made. The granitoids isotopically analysed for the present study range from calc-alkaline types with mantle or mixed mantle-crust isotopic characteristics (for example, late Archaean orthogneisses from west Greenland) to true granites probably produced solely by anatexis of ancient sialic crust (for example, Badcall Quay red granite, northwest Scotland; Qorqut granite, west Greenland; Mont d’Or granite, Zimbabwe).

Neoarchean high-potassium granites of the Boothia mainland area, Rae domain, Churchill Province: U–Pb zircon and Sm–Nd whole rock isotopic constraintsThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 247-279 ◽  
Author(s):  
Alana M. Hinchey ◽  
William J. Davis ◽  
James J. Ryan ◽  
Léopold Nadeau
Keyword(s):  
Sedimentary Cover ◽  
Amphibolite Facies ◽  
Sedimentary Sequence ◽  
Special Issue ◽  
Isotopic Data ◽  
High Potassium ◽  
North Central ◽  
The North ◽  
Facies Metamorphism

The Boothia mainland region of the north-central Rae domain is underlain by remnants of a Neoarchean volcano sedimentary sequence dismembered by two regionally extensive Neoarchean high-potassium granitoid suites with rare occurrences of a structurally interleaved, Paleoproterozoic sedimentary cover sequence. The granitoids and their gneissic equivalents are dominated by variably deformed and metamorphosed I-type, metaluminous, polyphase, commonly porphyritic to augen, biotite ± hornblende monzogranite, and subordinate granodiorite, with rare tonalite. New geochronological results, the first for this area, demonstrate that the widespread Neoarchean granitoid plutonism is dominantly 2.61–2.59 Ga, with a less prominent 2.66 Ga plutonic event. The age of zircon recrystallization suggests that ca. 2.60 Ga Archean metamorphism and fabric development (S1) affected the 2.66 Ga plutons prior to or contemporaneously with intrusion of the voluminous ca. 2.6 Ga suite. εNd(t) for the ca. 2.61–2.59 Ga suite range from 1.4 to –1.9, overlapping with the ca. 2.66 Ga suite that range from 1.4 to 1.5. The Nd isotopic data, coupled with the presence of inherited ca. 2.65, 2.70, and 2.85–2.90 Ga zircon, suggests recycling of older, Neoarchean to Mesoarchean crust in the formation of these suites. Metaplutonic rocks preserve Paleoproterozoic deformation (F4 and F5) and amphibolite-facies metamorphism, sporadically recorded in zircon rims that formed at 1.81 Ga. This event strongly reoriented the Neoarchean fabrics in metaplutonic rocks, generally without the development of a new coaxial Paleoproterozoic fabric, and we attribute this strain and metamorphism to the Hudsonian orogeny.

Pulpwood production in the North-Central Region, 1997.

1999 ◽  
Author(s):  
Ronald J. Piva
Keyword(s):  
Central Region ◽  
North Central Region ◽  
North Central ◽  
The North

Pulpwood production in the North-Central Region, 1994.

1996 ◽  
Author(s):  
Ronald J. Piva
Keyword(s):  
Central Region ◽  
North Central Region ◽  
North Central ◽  
The North

Pulpwood production in the North-Central Region, 1989.

1991 ◽  
Author(s):  
Ronald L. Hackett
Keyword(s):  
Central Region ◽  
North Central Region ◽  
North Central ◽  
The North
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