scholarly journals GRANULITE MEMBER OF THE ERVING FORMATION, WEST-CENTRAL MASSACHUSETTS: DETRITAL ZIRCONS SUGGEST A LOCHKOVIAN MAXIMUM DEPOSITIONAL AGE

2019 ◽  
Author(s):  
Peter J. Thompson ◽  
◽  
Peter Robinson ◽  
Justin V. Strauss
Keyword(s):  
Detrital Zircons ◽  
West Central ◽  
Depositional Age

Geological evolution of the Manitouwadge greenstone belt and Wawa-Quetico subprovince boundary, Superior Province, Ontario, constrained by U-Pb zircon dates of supracrustal and plutonic rocks

1999 ◽  
Vol 36 (6) ◽  
pp. 945-966 ◽  
Author(s):  
Eva Zaleski ◽  
Otto van Breemen ◽  
Virginia L Peterson
Keyword(s):  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Boundary Region ◽  
Detrital Zircons ◽  
Ductile Deformation ◽  
Superior Province ◽  
Geological Evolution ◽  
Hydrothermal Alteration Zones ◽  
Depositional Age ◽  
East West

Fifty million years of Archean evolution is recorded in the Manitouwadge greenstone belt and the Wawa-Quetico boundary region, from ca. 2720 Ma volcanism and subvolcanic plutonism associated with massive sulphide deposits and hydrothermal alteration zones, to 2689-2687 Ma and 2680-2677 Ma synkinematic plutonism. In the greenstone belt, greywackes were deposited after 2693 Ma, post-dating local volcanism by at least 25 Ma, and requiring that the volcanic-sedimentary contact is an unconformity or a fault. In migmatitic greywackes in the Quetico subprovince, detrital zircons limit the depositional age to <2690 Ma, permitting correlation of greywackes across the Wawa-Quetico subprovince boundary. Upward-facing inclined F2 folds that deform the volcanic-sedimentary contact are bracketed by the 2687 ± 2 Ma Loken Lake pluton, which shows strong D2 fabrics, and by 2680+4-3 Ma foliated granite which cuts D2 fabrics. Dextral transpression producing regional F3 folds and the overall east-west trends of the Wawa-Quetico boundary region post-dated the 2680 ± 2 Ma Nama Creek pluton. Field relationships and isotopic ages support correlation of greywackes across the subprovince boundary, and demonstrate that most or all of the ductile deformation post-dated sedimentation. Ductile structures, especially those associated with dextral transpression, are not directly related to juxtaposition of the Wawa and Quetico subprovinces, as these were already contiguous, either through sedimentation on a volcanic substrate or as a result of earlier cryptic structures. Our results imply that the belt-like configuration of the subprovinces, emphasized in accretionary models of the Superior Province, is a relatively late feature that overprints older, tectonically significant structures.

U–Pb age constraints on arenaceous and volcanic rocks of the Wakeham Group, eastern Grenville Province

2005 ◽  
Vol 42 (10) ◽  
pp. 1677-1697 ◽  
Author(s):  
O van Breemen ◽  
L Corriveau
Keyword(s):  
Volcanic Rocks ◽  
Detrital Zircons ◽  
Morphological Evidence ◽  
Ionization Mass ◽  
Grenville Province ◽  
Metavolcanic Rocks ◽  
Southeastern Margin ◽  
Depositional Age ◽  
Age Constraints ◽  
Group Yield

Combined sensitive high-resolution ion microprobe (SHRIMP) and thermal ionization mass spectrometry (TIMS) U–Pb zircon data from a tightly constrained stratigraphic context of the Wakeham Group provide a precise depositional age for sedimentation within this extensive basin of the Grenville Province. Metavolcanic rocks at the eastern exposure of the Wakeham Group yield ages of 1511 ± 13, 1506 ± 11, 1502 ± 9, and 1491 ± 7 Ma. A crosscutting 1493 ± 10 Ma porphyry vein marks the end of volcanism. The older two volcanic rocks rest stratigraphically above metasediments, with a 1517 ± 20 Ma maximum age of sedimentation derived from the youngest detrital zircons of an arenite. Five 1.61–1.55 Ga inherited zircons in the volcanics, reinforced by coeval inheritance in nearby plutons, indicate a Labradorian basement source to the supracrustals. The predominant arenite detrital zircons dates are in the 1.95–1.75 Ga range, however, and feature both trace element and morphological evidence for metamorphism in the source terrane. Together with zircons as old as 2.95 Ga, the detrital age spectrum is consistent with a circum-Superior provenance. The ages obtained imply that Wakeham Group volcanism and sedimentation were, at least in part, coeval with the onset of 1.52–1.46 Ga Pinwarian plutonism along the southeastern margin of Laurentia. U–Pb zircon analyses record a late Grenvillian metamorphic event around 1019 Ma. U–Pb monazite analyses from one sample yield 1010–1000 Ma ages, and the end of Grenvillian metamorphism is marked by 990 Ma U–Pb titanite ages.

How reliable are maximum depositional age estimates based on detrital zircon? An example from Early Palaeozoic successions of the Trondheim Nappe Complex, Scandinavian Caledonides

2021 ◽  
Author(s):  
Deta Gasser ◽  
Tor Grenne ◽  
Bjørgunn Dalslåen ◽  
Trond Slagstad ◽  
David Roberts ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Tectonic Setting ◽  
Maximum Error ◽  
Detrital Zircons ◽  
Greenschist Facies ◽  
Scandinavian Caledonides ◽  
Nappe Complex ◽  
Active Tectonic ◽  
Depositional Age ◽  
Age Estimates

&lt;p&gt;U-Pb age spectra of detrital zircons are widely used to estimate maximum depositional ages (MDA) for sedimentary successions of various age. Different methods have been proposed for calculating an MDA. The most common are based on calculated ages of either the youngest single grain (YSG), the youngest grain cluster composed of three or more grains that overlap at 2&amp;#963; (YGC 2&amp;#963;), or the youngest graphical peak (YPP). Many of these methods produce MDAs consistent with biostratigraphic age or the radiometric age of volcanic horizons within the same unit; however, several studies have shown that MDA estimates based on detrital zircon can be younger than the true depositional age, particularly in active tectonic settings, indicating that the methods should be applied with care for successions where independent depositional age control is lacking.&lt;/p&gt;&lt;p&gt;In this contribution we present a compilation of 27 detrital zircon samples from Ordovician to Silurian strata from a part of the Trondheim Nappe Complex of the central Scandinavian Caledonides. The samples belong to six stratigraphically distinct units with independent age control from fossils, dated volcanic horizons or bracketing units of known age. These successions represent various marginal basins filled during the closing stages of the Iapetus Ocean in an overall active tectonic setting with detritus from both continental landmasses and Cambro-Ordovician island arcs. Shortly after deposition, the successions were folded and metamorphosed at up to greenschist facies during Taconian accretionary events and/or the Scandian continent-continent collision.&lt;/p&gt;&lt;p&gt;We calculated MDAs by the three methods YSG, YGC 2&amp;#963; and YPP for all samples based on &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt; 238&lt;/sup&gt;U ages, applying a rigorous discordance filter of 5% (most studies use 10%), in order to use the most reliable analyses possible. Our analysis shows that the YSG MDA is up to 36 m.y. younger than the known depositional age for 17 of the 27 samples, with up to six individual grains giving too young age estimates in some samples. Hence, YSG MDA obviously does not provide a reliable MDA estimate. Of the YGC 2&amp;#963; (weighted mean age) estimates, six are still significantly younger than known depositional age; and an additional seven are younger but overlap with the known depositional age when considering the maximum error on the YGC 2&amp;#963; estimate. The only method which provides an MDA estimate within the age of known deposition or older for all samples is the YPP method.&lt;/p&gt;&lt;p&gt;Our results indicate that statistically robust estimates of MDA from detrital zircon data in such an active orogenic setting are provided only by the YPP method; both the YSG and the YGC 2&amp;#963; methods provided unreliably young estimates even with a discordance filter of 5% (using a filter of only 10% makes the problem considerably worse). The spuriously young ages of up to six near-concordant grains in some samples is probably due to concealed lead loss, possibly caused by (fluid-assisted?) recrystallisation of zircon domains during regional greenschist-facies metamorphism shortly after deposition.&lt;/p&gt;

Latest Jurassic–earliest Cretaceous age for a fossil flora from the Latady Basin, Antarctic Peninsula

2006 ◽  
Vol 18 (2) ◽  
pp. 261-264 ◽  
Author(s):  
Morag A. Hunter ◽  
David J. Cantrill ◽  
Michael J. Flowerdew
Keyword(s):  
Antarctic Peninsula ◽  
Plant Material ◽  
Weddell Sea ◽  
Detrital Zircons ◽  
Fossil Flora ◽  
Fossil Plant ◽  
The North ◽  
Depositional Age ◽  
The Antarctic ◽  
Basin Margin

Dating Jurassic terrestrial floras in the Antarctic Peninsula has proved problematic and controversial. Here U–Pb series dating on detrital zircons from a conglomerate interbedded with fossil plant material provide a maximal depositional age of 144 ± 3 Ma for a presumed Jurassic flora. This is the first confirmed latest Jurassic-earliest Cretaceous flora from the Latady Basin, and represents some of the youngest sedimentation in this basin. The presence of terrestrial sedimentation at Cantrill Nunataks suggests emergence of the arc closer to the Latady Basin margin in the south compared to Larsen Basin in the north, probably as a result of the failure of the southern Weddell Sea to undergo rifting.

Sedimentary provenance and maximum depositional age analysis of the Cretaceous? Lapur and Muruanachok sandstones (Turkana Grits), Turkana Basin, Kenya

2018 ◽  
Vol 156 (08) ◽  
pp. 1334-1356 ◽  
Author(s):  
Prince C. Owusu Agyemang ◽  
Eric M. Roberts ◽  
Bob Downie ◽  
Joseph J. W. Sertich
Keyword(s):  
East African Rift ◽  
Detrital Zircons ◽  
Sub Saharan Africa ◽  
Rift System ◽  
East African Rift System ◽  
East African ◽  
Turkana Basin ◽  
Sedimentary Provenance ◽  
African Rift ◽  
Depositional Age

AbstractThe Turkana Basin of northwestern Kenya is well known for its rich Neogene–Quaternary vertebrate fossil record; however, it also represents one of the few locations in sub-Saharan Africa where Cretaceous vertebrate fossils, including dinosaurs and other archosaurs, are preserved. These Cretaceous deposits are colloquially referred to as the ‘Turkana Grits’, and assumed to be Cretaceous in age based on their limited biostratigraphy. The ‘Turkana Grits’ are overlain by Palaeogene volcanic rocks (&lt;35 Ma), which are widely considered to record the earliest evidence of plume-related volcanism in the East African Rift System. In this study, we present the results of an integrated sedimentary provenance investigation of two units within the ‘Turkana Grits’ called the Lapur and Muruanachok sandstones. Analysis of U–Pb ages and Lu–Hf initial ɛHf(t) values from 1106 detrital zircons demonstrate that sediments are primarily derived from Neoarchaean and Neoproterozoic basement sources, except for six Palaeogene grains from the upper Lapur Sandstone, which are of unknown provenance. Considered together, these data point to the Mozambique Belt, which makes up the nearby rift flanks, as the primary provenance source. This is consistent with palaeocurrent data, and suggests localized sediment input by alluvial fans, which fed into NNW-directed fluvial systems. Perhaps the most surprising finding is the identification of the late Paleocene detrital zircons, which not only demonstrate that the depositional age for the top of the formation is Paleocene rather than Cretaceous, but also provides possible evidence for the oldest Palaeogene volcanic activity within the East African Rift System.

scholarly journals Detrital zircons and sediment dispersal in the eastern Midcontinent of North America

Geosphere ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 817-843 ◽  
Author(s):  
William A. Thomas ◽  
George E. Gehrels ◽  
Kurt E. Sundell ◽  
Stephen F. Greb ◽  
Emily S. Finzel ◽  
...  
Keyword(s):  
Age Groups ◽  
Appalachian Basin ◽  
Detrital Zircons ◽  
Illinois Basin ◽  
Sediment Dispersal ◽  
Accreted Terranes ◽  
Appalachian Orogen ◽  
Northern Edge ◽  
Depositional Age ◽  
Age Range

Abstract Results of detrital-zircon analyses (U-Pb ages and initial Hf values, εHft) of Mississippian–Pennsylvanian sandstones in the Michigan, Illinois, and Forest City basins are remarkably similar to data for coeval sandstones in the Appalachian basin, indicating dispersal of sediment from the Appalachian orogen through the Appalachian basin to the eastern Midcontinent during the late Paleozoic. The similarities of results include matches of the two most prominent age groups (1300–950 Ma and 490–350 Ma), as well as matches of the less abundant age groups. Comparisons of the data are from observations of probability density plots and multidimensional scaling of U-Pb age data and of εHft values. Despite the dominance of an Appalachian signature in all samples, some samples contain grains with ages that suggest intermittent additional sources. Four samples (three ranging in depositional age from Morrowan to Atokan–Desmoinesian in the Illinois basin, and one of Desmoinesian age in the Forest City basin), in addition to typical Appalachian age distributions, have prominent age modes between 768 and 525 Ma, corresponding in age to Pan-African/Brasiliano rocks in Gondwanan accreted terranes in the Appalachian orogen, suggesting intermittent dispersal from the Moretown terrane of the northern Appalachians. Sandstones in the Appalachian basin and those in the Midcontinent basins have very few grains with ages that correspond to the Alleghanian orogeny in the Appalachian orogen. Nevertheless, three sandstones each in the Illinois basin and Forest City basin with depositional ages of 312–308 Ma have a few zircon grains in the age range of 321 ± 5 to 307 ± 4 Ma. The nearly identical crystallization and depositional ages suggest reworking at the depositional sites of air-fall volcanic ash from the Alleghanian orogen, rather than fluvial transport from the orogen. The basal Pennsylvanian sandstones lap onto a regional unconformity around the northern rims of the Illinois and Forest City basins, suggesting sources for recycled grains. Along the northern edge of the Illinois basin, Ordovician sandstones beneath the unconformity may have contributed minor concentrations of Superior-age zircons in the basal Pennsylvanian sandstones. Basal Pennsylvanian sandstones in the Forest City basin lap onto Mississippian strata, suggesting possible recycling of zircons from eroded Mississippian sandstones.

Neoproterozoic Jiangnan Orogeny in southeast Guizhou, South China: evidence from U–Pb ages for detrital zircons from the Sibao Group and Xiajiang Group

2016 ◽  
Vol 53 (3) ◽  
pp. 219-230 ◽  
Author(s):  
Xiao Ma ◽  
Kunguang Yang ◽  
Xuegang Li ◽  
Chuangu Dai ◽  
Hui Zhang ◽  
...  
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
Inductively Coupled Plasma ◽  
Detrital Zircons ◽  
North India ◽  
Yangtze Block ◽  
Inductively Coupled ◽  
Two Samples ◽  
Southeastern Margin ◽  
Depositional Age

The Jiangnan Orogeny generated regional angular unconformities between the Xiajiang Group and the underlying Sibao Group in the western Jiangnan Orogen along the southeastern margin of the Yangtze Block in southeast Guizhou, South China. Laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) U–Pb zircon dating of two samples of the Motianling granitic pluton yielded U–Pb zircon ages of 826.2 ± 3.4 and 825.5 ± 6.1 Ma, with an average age of 825.6 ± 3.0 Ma, which is considered the minimum depositional age of the Sibao Group. The U–Pb ages of the youngest detrital zircon grains from the Sibao Group and the Xiajiang Group yielded average ages of 834.9 ± 3.8 and 794.6 ± 4.2 Ma, respectively. The depositional age of the Sibao Group can be constrained at 825–835 Ma, and deposition of the Xiajiang Group did not begin before ca. 800 Ma. These results suggest that the Jiangnan Orogeny, which led to the assembly of the Yangtze and Cathaysia blocks, ended at 795–835 Ma on the western segment of the Jiangnan Orogen. The detrital zircon distribution spectrums of the Sibao and Xiajiang groups suggest a provenance from Neoproterozoic basement sedimentary sequences along with a mixture of local Neoproterozoic subduction-related felsic granitoids, distant plutons from the western Yangtze Block and eastern Jiangnan Orogen, and recycled materials from the interior of the Yangtze Block. By comparing the basin evolution histories and magmatic and metamorphic events along the continental margins of the Rodinia supercontinent, it is proposed that the South China Block might have been located at the periphery, adjacent to North India and East Antarctica, rather than in the interior of Rodinia in Neoproterozoic time.

Zircon geochronology of anatectic melts and residues from a highgrade pelitic assemblage at Ihosy, southern Madagascar: evidence for Pan-African granulite metamorphism

1996 ◽  
Vol 133 (3) ◽  
pp. 311-323 ◽  
Author(s):  
A. Kröner ◽  
I. Braun ◽  
P. Jaeckel
Keyword(s):  
Source Region ◽  
Granulite Facies ◽  
Detrital Zircons ◽  
High Grade ◽  
Left Behind ◽  
Granulite Metamorphism ◽  
Mozambique Belt ◽  
High Grade Metamorphism ◽  
Depositional Age ◽  
Heterogeneous Source

AbstractWe report U—Pb and207Pb/206Pb zircon ages for a granulite facies gneiss assemblage exposed in a large quarry at Ihosy, southern Madagascar. The granulites are derived from pelitic to arkosic sediments and attained equilibrium conditions at 650–700°C and 4–5 kbar. HigherP—Tconditions of 750–800°C and 6 kbar in the presence of low water activities have led to dehydration melting processes. The formation of granitic melts, which (partly) moved away from their source region, intruded into upper parts of the metapelitic gneisses as small granitic veins and left behind granulitic garnet-cordierite-quartz bearing rocks. Detrital zircons in a sample of metapelite and a sample of quartzofeldspathic gneiss yielded ages between ˜720 and ˜1855 Ma, suggesting a chronologically heterogeneous source region and a depositional age of less than ˜720 Ma for these rocks. High-grade metamorphism and anatexis are documented by zircon ages between 526 ±34 and 557 ±2 Ma with a mean age of about 550 Ma. The broad lithologies, metamorphic grades and ages recorded in the Ihosy rocks are similar to those in the Wanni Complex of northwestern Sri Lanka and in high-grade assemblages of southernmost India and support the contention that all these terrains were part of the Mozambique belt which formed as a result of collision of East and West Gondwana in latest Precambrian time.

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