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TitleCrustal Evolution of the Northeast Laurentian Margin and the Peri-Gondwanan Microcontinent Ganderia Prior to and During Closure of the Iapetus Ocean: Detrital Zircon U-Pb and Hf Isotope Evidence from Newfoundland
 
AuthorWillner, A P; Gerdes, A; Massonne, H J; van Staal, C R; Zagorevski, AORCID logo
SourceGeoscience Canada vol. 41, no. 3, 2014 p. 345-364, https://doi.org/10.12789/geocanj.2014.41.046 Open Access logo Open Access
Image
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20140246
PublisherGeological Association of Canada
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
NTS1; 2; 11O; 11P; 12A; 12B; 12G; 12H; 12I; 12P
Lat/Long WENS -59.0000 -53.0000 52.0000 46.5000
Subjectstectonics; structural geology; geochronology; general geology; detrital minerals; zircon; orogenic regions; uranium lead dates; crustal models; crustal studies; crustal evolution; accretion; Ganderia; Avalonia; Laurentia; Iapetus Ocean
Illustrationslocation maps; Concordia diagrams; histograms; plots; stratigraphic columns
ProgramTargeted Geoscience Initiative (TGI-4), TGI-4 Program Coordination
Released2014 08 29
AbstractDetrital zircon populations in sedimentary rocks from the Laurentian margin and the accreted microcontinent Ganderia on both sides of the main Iapetus suture (Red Indian Line) in central Newfoundland have been studied by combined U-Pb and Lu-Hf isotope analyses. Variation in eHf(t) values with age of zircon populations of distal provenance (>900 Ma) reflect the crustal evolution within the source continents: in zircon derived from Laurentia, episodes of juvenile magma production in the source could be detected at 1.00 - 1.65 and 2.55 - 3.00 Ga, and mixing of juvenile and recycled crust in continental magmatic arcs occurred at 0.95 - 1.40, 1.45 - 1.60, 1.65 - 2.05 and 2.55 - 2.75 Ga. These ages are consistent with the crustal history of northeastern Laurentia. Similarly, zircon of distal provenance from Ganderia reveals times of juvenile magma production in the source at 0.70 - 0.90, 1.40 - 1.75, 1.85 - 2.40 and 2.7 - 3.5 Ga, and episodes of mixing juvenile and recycled crust at 0.95 - 1.35, 1.45 - 1.60, 1.70 - 2.15 and 2.6 - 2.8 Ga. These data reflect the crustal evolution in the present northern part of Amazonia, its likely source craton.
The evolution of magmatic arcs at the margins of both continents can be studied in a similar way using detrital zircon having a proximal provenance (<900 Ma). In contrast to the Laurentian margin, Ganderia is characterized by development of Neoproterozoic - Cambrian continental arcs (ca. 500 - 670 Ma) that were built on the margin of Gondwana. eHf(t) values indicate recycling of Neo- and Mesoproterozoic crust. During and following accretion of the various elements of Ganderia to Laurentia, the syn-tectonic Late Ordovician to Silurian sedimentary rocks deposited on the upper plate (composite Laurentia) continued showing only detritus derived from Laurentia. These sedimentary rocks contain detrital zircon from Iapetan juvenile, continental and successor arcs that were active between ca. 440 and 550 Ma, and from continuing magmatic activity until 423 Ma. Arrival of the first Laurentian detritus at the outermost part of Ganderia indicates that the Iapetus ocean was closed at ca. 452 Ma. The magmatic arcs along the former Laurentian margin in Newfoundland evolved differently. In the northwestern part, eHf(t) values point to recycling of Mesoproterozoic and Paleoproterozoic crust. In the southwest, eHf(t) values indicate addition of juvenile crust, recycling of Mesoproterozoic crust and mixing with juvenile magma. The long-term evolution of magmatic arcs at the margins of both continents can be studied using detrital zircon in a similar way. In contrast to the Laurentian margin, Ganderia is characterized by development of Neoproterozoic-Cambrian continental arcs (ca. 500-670 Ma) that were built on the margin of Gondwana. eHf(t) -values indicate recycling of Neo- and Mesoproterozoic crust.
During and following accretion of the various elements of Ganderia to Laurentia between 455 to 425 Ma, the syn-tectonic Late Ordovician to Silurian sediments deposited on the upper plate (composite Laurentia) continued showing only detritus derived from Laurentia. These sediments contain detrital zircon from Iapetan juvenile, continental and successor arcs that were active between ca 440 and 550 Ma, and from continuing magmatic activity until 423 Ma. Arrival of the first Laurentian detritus at the outermost part of Ganderia indicates that the Iapetus ocean was closed at ca. 452 Ma. A very different evolution was detected in the magmatic arcs along the former Laurentian margin in Newfoundland. In the northwestern part eHf(t) values point to recycling of Mesoproterozoic crust and also of Palaeoproterozoic crust. In the southwest eHf(t) values indicate addition of juvenile crust, recycling of Mesoproterozoic crust and mixing with juvenile magma.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The aim was to test and improve on regional frameworks developed during TGI program in Newfoundland. Researchers utilized the latest technological developments to identify the origin of crustal blocks using minerals in sediments and defined age and isotopic fingerprints for different crustal blocks. They confirmed that crustal blocks linked to ancient North America were juxtaposed with crustal blocks derived from South America. These results support previous TGI models and help explain distribution of mineral deposits in Newfoundland. These results are applicable for identification of crustal blocks across the eastern North America and the British Isles.
GEOSCAN ID295317

 
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