scholarly journals Mid-Mesoproterozoic granitoid rocks in the North Bay area, Grenville Province, Ontario; Radiogenic age and isotopic studies: Report 14

2001 ◽  
Author(s):  
A Davidson ◽  
O van Breemen
Keyword(s):  
Grenville Province ◽  
Bay Area ◽  
The North ◽  
Isotopic Studies ◽  
Granitoid Rocks

An application of Nd isotope mapping in structural geology: delineating an allochthonous Grenvillian terrane at North Bay, Ontario

2003 ◽  
Vol 140 (5) ◽  
pp. 539-548 ◽  
Author(s):  
A. P. DICKIN ◽  
R. H. MCNUTT
Keyword(s):  
Structural Geology ◽  
Amphibolite Facies ◽  
High Grade ◽  
Grenville Province ◽  
Nd Isotope ◽  
Bay Area ◽  
The North ◽  
Depleted Mantle ◽  
Different Types ◽  
Isotope Analyses

Fifty new Nd isotope analyses are presented from the North Bay area of the Grenville Province in Ontario. These data are used to map the extent of an allochthonous Grenvillian terrane which is an outlier of the Allochthonous Polycyclic Belt of the Grenville Province. Amphibolite facies orthogneisses from the allochthonous terrane have depleted mantle Nd model ages (TDM) below 1.8 Ga, whereas the gneisses of the structurally underlying parautochthon almost invariably have model ages above 1.8 Ga. The distribution of model ages is consistent with the distribution of distinct types of metabasic rock, used by other researchers as the criterion for recognizing rocks of the allochthonous and parautochthonous belts of the Grenville Province. The agreement between these different types of evidence demonstrates that Nd isotope mapping is a reliable and powerful tool for mapping terrane boundaries in high-grade metamorphic belts.

Paleoproterozoic crustal history of the southwestern Grenville Province: evidence from Nd isotopic mapping

1995 ◽  
Vol 32 (4) ◽  
pp. 472-485 ◽  
Author(s):  
C. Holmden ◽  
A. P. Dickin
Keyword(s):  
Crustal Material ◽  
Grenville Province ◽  
Detrital Zircon Geochronology ◽  
Bay Area ◽  
The North ◽  
History Of ◽  
Depositional Age ◽  
Central Gneiss Belt ◽  
Superior Craton ◽  
Common Association

Nd isotopic mapping in the North Bay area of the Central Gneiss Belt, southwestern Grenville Province, has revealed the precise trend of a TDM model age line developed between the uplifted southern margin of the Archean Superior craton (TDM = 2.7 Ga) and a Paleoproterozoic allochthon (TDM = 1.9 Ga). Separating these two crustal blocks is a narrow zone of gneisses with intermediate TDM ages. These transitional gneisses are interpreted to reflect a remnant fault or ductile shear zone, of uncertain age, along which crustal material from both blocks mechanically mixed during their juxtaposition. Accordingly, the nature of the TDM line in the North Bay area is interpreted to be tectonic. In the Temiscaming area, widespread exposures of mature metasedimentary gneisses are shown by their TDM ages to be dominantly of Paleoproterozoic provenance. These results are consistent with the existing detrital zircon geochronology, inferring a maximum depositional age of ~1.7 Ga. The anorogenic chemistry of the North Bay orthogneiss and mixed calc-alkaline–alkaline chemistry of the Temiscaming gneisses suggest a connection between Paleoproterozoic anorogenic magmatism and synsedimentary quartzite deposition, which is a common association in 1.9–1.6 Ga accretionary orogens of southern Laurentia. The relatively close correspondence between widespread 1.9 Ga TDM ages and U–Pb crystallization ages as old as 1.74 Ga implies that rocks of the Central Gneiss Belt were originally the juvenile products of Paleoproterozoic orogenesis.

scholarly journals Investigations of detrital zircon, rutile and titanite from present-day Labrador drainage basins: fingerprinting the Grenvillean front

1969 ◽  
pp. 77-80
Author(s):  
Tonny B. Thomsen ◽  
Christian Knudsen ◽  
Alana M. Hinchey
Keyword(s):  
Newfoundland And Labrador ◽  
Sedimentary Basins ◽  
Geological Survey ◽  
Drainage Basins ◽  
Grenville Province ◽  
Collaborative Project ◽  
North West ◽  
North East ◽  
The North ◽  
Three Samples

A multidisciplinary provenance study was conducted on stream sediment samples from major rivers in the eastern part of Labrador, Canada (Fig. 1). Th e purpose was to fi ngerprint the sources that deliver material to the stream sediments and to the reservoir sand units deposited off shore in the sedimentary basins in the Labrador Sea. We used a multimineral U-Pb geochronological approach employing rutile and titanite in addition to zircon to obtain unbiased age data. Th e purpose of this was to characterise the diff erent igneous and metamorphic episodes that occurred in Labrador, which is an area with highly variable geology characterised by the Palaeoproterozoic south-eastern Churchill province in the north-west, the Archaean Nain plutonic suite in the north-east, the Palaeoproterozoic Makkovik province in the east and the Mesoproterozoic Grenville Province to the south. Th e fi eld work was carried out in 2012 and 2013 and the study is a collaborative project between the Geological Survey of Denmark and Greenland and the Geological Survey of Newfoundland and Labrador. In this paper we focus on three samples from the southern part of the study area where two parts of the Grenville orogeny are found (Fig. 1).

scholarly journals Equilibrium-Line Altitudes and Paleoenvironment in the Merchants Bay Area, Baffin Island, N.W.T., Canada

1985 ◽  
Vol 31 (109) ◽  
pp. 205-213 ◽  
Author(s):  
Fred F. Hawkins
Keyword(s):  
Area Ratio ◽  
Equilibrium Line ◽  
Storm Tracks ◽  
Lateral Moraine ◽  
Baffin Island ◽  
Statistical Comparison ◽  
Bay Area ◽  
The North ◽  
Simple Geometry ◽  
Accumulation Area Ratio

AbstractThe fiordlands south of Merchants Bay contain an extensive, well-preserved moraine record of a late Foxe advance of local valley glaciers. This has allowed accurate reconstruction of former glacier margins and computation of former equilibrium-line altitudes (ELAs) by a variety of methods. Statistical comparison of three methods (maximum lateral-moraine elevation, median elevation, and accumulation area ratio (AAR)) shows that different techniques can give different results for the same glaciers. Lateral moraines gave estimates that were too low, probably due to post-glacial erosion or to non-deposition. Median elevations and the AAR method produced statistically similar results but only for glaciers of simple geometry. The median-elevation method fails to take into account variations in valley morphology and glaciological parameters, and so is not reliable in all situations. The AAR method is supported by empirical evidence and is the best of the three methods for estimating former ELAs.Analysis of trend surfaces of present and late Foxe ELAs shows changes in elevation and orientation through time due to changing environmental factors. Present ELAs are strongly influenced by local factors, southerly storm tracks, and warm maritime conditions. Paleo-ELAs do not show this influence, suggesting that Davis Strait may have been ice-covered during the late Foxe stade and that storm tracks were from the north.

Exhumation of a collisional orogen: A perspective from the North American Grenville Province

2004 ◽  
pp. 391-410 ◽  
Author(s):  
Margaret M. Streepey ◽  
Carolina Lithgow-Bertelloni ◽  
Ben A. van der Pluijm ◽  
Eric J. Essene ◽  
Jerry F. Magloughlin
Keyword(s):  
North American ◽  
Grenville Province ◽  
Collisional Orogen ◽  
The North

From “Jap Crow” to “Jim and Jane Crow”: Black and Blue (and Yellow) in Chicago and the Bay Area

2012 ◽  
Author(s):  
Matthew M. Briones
Keyword(s):  
West Coast ◽  
Critical Mass ◽  
Language Immersion ◽  
Japanese Americans ◽  
South Side ◽  
Bay Area ◽  
The North ◽  
School Based ◽  
The Military ◽  
Intelligence Service

This chapter examines how the resettlement of West Coast Japanese Americans in the Midwest and Northeast after internment irrevocably transformed the population of Japanese Chicagoans. As both Allan Austin and Gary Okihiro have demonstrated, many young Nisei managed to leave the camps earlier than expected by filing education waivers. They matriculated predominantly at midwestern and East Coast schools, and some of their campmates were recruited for Japanese-language immersion at the Military Intelligence Service Language School, based at Camp Savage, Minnesota. Yet residual delinquency among Nisei bachelors and the lack of children's playgrounds still made the North Side area less than appealing to Nisei families; hence, another critical mass of Japanese Americans congregated on the South Side.

A U–Pb geochronological review of the Proterozoic history of the eastern Grenville Province

2002 ◽  
Vol 39 (5) ◽  
pp. 795-829 ◽  
Author(s):  
Charles F Gower ◽  
Thomas E Krogh
Keyword(s):  
Continental Margin ◽  
Leading Edge ◽  
Passive Margin ◽  
Grenville Province ◽  
Mafic Magmatism ◽  
Magmatic Arc ◽  
The North ◽  
Geological Evolution ◽  
Thrust Zone ◽  
Laurentian Margin

The geological evolution of the eastern Grenville Province can be subdivided into three stages. During the first stage, namely pre-Labradorian (> 1710 Ma) and Labradorian (1710–1600 Ma) events, a continental-marginal basin was created and subsequently destroyed during accretion of a magmatic arc formed over a south-dipping subduction zone. Subduction was short-lived and arrested, leading to a passive continental margin. The second stage addresses events between 1600 and 1230 Ma. The passive margin lasted until 1520 Ma, following which a continental-margin arc was constructed during Pinwarian (1520–1460 Ma) orogenesis. Elsonian (1460–1230 Ma) distal-inboard, mafic and anorthositic magmatism, decreasing in age northward, is explained by funnelled flat subduction, possibly associated with an overridden spreading centre. As the leading edge of the lower plate advanced, it was forced beneath the Paleoproterozoic Torngat orogen root between the Archean Superior and North Atlantic cratons, achieving its limit of penetration by 1290 Ma. Static north-northeast-trending rifting then ensued, with mafic magmatism flanked by felsic products to the north and south. Far-field orogenic effects heralded the third stage, lasting from 1230 to 955 Ma. Until 1180 Ma, the eastern Grenville Province was under the distal, mild influence of Elzevirian orogenesis. From 1180 to 1120 Ma, mafic and anorthositic magmatism occurred, attributed to back-arc tectonism inboard of a post-Elzevirian Laurentian margin. Quiescence then prevailed until Grenvillian (1080–980 Ma) continent–continent collision. Grenvillian orogenesis peaked in different places at different times as thrusting released stress, thereby precipitating its shift elsewhere (pressure-point orogenesis). High-grade metamorphism, thrusting and minor magmatism characterized the Exterior Thrust Zone, in contrast to voluminous magmatism in the Interior Magmatic Belt. Following final deformation, early posttectonic anorthositic–alkalic–mafic magmatism (985–975 Ma) and late posttectonic monzonitic–syenite–granite magmatism (975–955 Ma) brought the active geological evolution of this region to a close.

Structural Characteristics and Mechanism of the Horsetail Structure in China Offshore Basins: Case Studies from Liaodong Bay Area, Bohai Bay Basin and Weixinan Area, Beibuwan Basin

2020 ◽  
Author(s):  
Jie Zhang ◽  
Zhiping Wu ◽  
Yanjun Cheng
Keyword(s):  
Structural Characteristics ◽  
Strike Slip ◽  
Pacific Plate ◽  
Strike Slip Fault ◽  
Bohai Bay ◽  
Liaodong Bay ◽  
Clockwise Rotation ◽  
Bay Area ◽  
The North ◽  
The Pacific

<p>The horsetail structure, also named brush structure, generally refers to a sets of secondary faults converged to the primary fault on the plane. Based on 2-D and 3-D seismic data, the structural characteristics, evolution and mechanism of the horsetail structure of Liaodong Bay area in Bohai Bay Basin and Weixinan area in Beibuwan Basin are analyzed. In the Liaodong Bay area, the primary fault of the horsetail structure is the NNE-striking branch fault of Tan-Lu strike-slip fault zone. The NE-striking secondary extensional faults converged to the primary strike-slip fault. Fault activity analysis shows that both the primary and secondary faults intensively activated during the third Member of the Shahejie Formation (42~38 Ma). In the Weixinan area, the NE-striking Weixinan fault is the primary fault of the horsetail structure, which is an extensional fault. A large amount of EW-striking secondary extensional faults converged to the primary NE-striking Weixinan fault. Fault activity analysis shows that NE-striking primary fault intensively activated during the second Member of the Liushagang Formation (48.6~40.4 Ma), whereas the EW-striking secondary faults intensively activated during the Weizhou Formation (33.9~23 Ma). The different structure and evolution of the horsetail structure in the Liaodong Bay area and Weixinan area are mainly resulted from the regional tectonic settings. About 42 Ma, the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the right-lateral strike-slip movement of NNE-striking Tan-Lu fault and the formation of NE-striking extensional faults along the bend of the strike-slip fault, therefore, the horsetail structure of Liaodong Bay area formed. However, the formation of the horsetail structure of Weixinan area is related to the clockwise rotation of extension stress in the South China Sea (SCS): 1) During Paleocene to M. Eocene (65~37.8 Ma), the retreat of Pacific plate subduction zone resulted in the formation of NW-SE extensional stress field in the north margin of the SCS, NE-striking primary fault of horsetail structure formed; 2) During L. Eocene to E. Oligocene (37.8~28.4 Ma), the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the clockwise rotation of extension direction from NW-SE to N-S in the north margin of the SCS, a large amount of EW-striking secondary faults of horsetail structure formed, and the horsetail structure was totally formed in the Weixinan area until this stage.</p>

The timing of Proterozoic magmatism in the Pinware terrane of southeast Labrador, easternmost Quebec and northwest Newfoundland

2004 ◽  
Vol 41 (2) ◽  
pp. 127-150 ◽  
Author(s):  
L M Heaman ◽  
C F Gower ◽  
S Perreault
Keyword(s):  
Long Range ◽  
Alkali Feldspar ◽  
Geochronological Data ◽  
Grenville Province ◽  
Mafic Magmatism ◽  
Granitoid Rocks ◽  
Red Bay ◽  
High Level ◽  
First Time ◽  
Magmatic Event

The Pinware terrane is located in the easternmost Grenville Province and contains crust of Labradorian (1710–1600 Ma), Pinwarian (1520–1460 Ma), Elsonian (1460–1230 Ma), Grenvillian (1080–985 Ma), and late- to post-Grenvillian (985–955 Ma) age. Newly obtained U–Pb geochronological data enhance understanding of all these evolutionary stages. A Labradorian age of 1632 ± 8 Ma has been obtained for the Brador River granite, thereby establishing the presence of mid- to late- Labradorian rocks in the southernmost part of the region. A maximum age of ~1600 Ma obtained for the Ten Mile Lake granite indicates for the first time that Labradorian crust could continue into the northern Long Range Inlier of western Newfoundland. Pinwarian activity is indicated by ages of ~1526–1504, 1500 ± 14, 1467 ± 44, and 1466 ± 8 Ma from granitoid rocks at Rivière St-Paul, West St. Modeste, Diable Bay, and Pinware, respectively. The first evidence for late Elsonian mafic magmatism in this region is provided by a concordant baddeleyite date of 1248 ± 5 Ma from gabbronorite at Lourdes-de-Blanc-Sablon. This study has also identified an early post-tectonic, high-level, mafic–anorthositic–syenitic magmatic event between 985 and 975 Ma. Recognition of the event relies on previous results and newly obtained ages of 979.5 ± 2.8 Ma from the Red Bay gabbro, 974.5 ± 1.8 Ma from the Vieux Fort anorthosite, and 969 ± 11 Ma from the Lower Pinware River alkali-feldspar syenite. Time, composition, and fabric criteria distinguish these rocks from late-post-tectonic monzonite, syenite and granite emplaced between 966 and 956 Ma.

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