U-Pb geochronology of volcanic rocks from the Jurassic Talkeetna Formation and detrital zircons from prearc and postarc sequences: Implications for the age of magmatism and inheritance in the Talkeetna arc

Author(s):  
Jeffrey M. Amato ◽  
Matthew E. Rioux ◽  
Peter B. Kelemen ◽  
George E. Gehrels ◽  
Peter D. Clift ◽  
...  
Author(s):  
M. Aftalion ◽  
O. van Breemen ◽  
D. R. Bowes

ABSTRACTThe existence of a basement of granulite beneath the Midland Valley is supported by investigations of inclusions in volcanic rocks and the geophysical studies of the LISPB experiment. To establish age constraints for this basement, a compilation is presented of available Rb–Sr whole-rock, common lead, U–Pb zircon and Sm–Nd radiometrie data for crystalline rocks in Scotland from the earliest recognised crust (c. 2900 Ma) to 380 Ma (“end” of Caledonian orogeny) including xenoliths in volcanic vents and boulders in conglomerates.For rocks within the Midland Valley, isotopic data provide four lines of evidence. (1) An upper intercept U–Pb age of c. 1700 Ma for detrital zircons from a lower Palaeozoic greywacke from Dalmellington corresponds to a late stage of the Laxfordian orogenic episode (early Proterozoic) with possibly some overprinting during the Grenvillian episode (mid Proterozoic). (2) The common lead composition of the Distinkhorn granite suggests the participation of early Proterozoic basement during granite emplacement. (3) For xenoliths from the Carboniferous Partan Craig vent, one gives a Sm–Nd CHUR model age of 1180 ± 55 Ma, a second yielded a Sm–Nd garnet—potassium feldspar age of 356 ± 6 Ma and an upper intercept U–Pb age from zircons from the third is c. 2200 (± 240) Ma; for xenoliths from other vents, an Rb–Sr whole-rock isochron of 1101 ± 63 Ma and an Sm–Nd model age of c. 1100 Ma arerecorded. (4) A linear array corresponding to an apparent age of 770 ± 180 Ma on a Pb–Pb isochron diagram for Tertiary igneous rocks of Arran points to an underlying basement of late Precambrian orthogneiss.The existence of basement made of products of the Grenvillian episode, or predominantly so, similar to the basement N of the Highland Boundary fault, is not inconsistent with the available evidence. However, zircons and other rock components appear to have an ultimate Lewisian provenance. At least in parts, there is also a strong late Proterozoic imprint. Further studies are required for an unequivocal solution.


2005 ◽  
Vol 42 (10) ◽  
pp. 1677-1697 ◽  
Author(s):  
O van Breemen ◽  
L Corriveau

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.


1999 ◽  
Vol 36 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Kevin M Ansdell ◽  
Karen A Connors ◽  
Richard A Stern ◽  
Stephen B Lucas

Lithological and structural mapping in the east Wekusko Lake area of the Flin Flon Belt, Trans-Hudson Orogen, suggested an intimate relationship between magmatism, fluvial sedimentation, and initiation of fold and thrust belt deformation. Conventional U-Pb geochronology of volcanic rocks in fault-bounded assemblages provides a minimum age of 1876 ± 2 Ma for McCafferty Liftover back-arc basalts, and ages of between 1833 and 1836 Ma for the Herb Lake volcanic rocks. A rhyolite which unconformably overlies Western Missi Group fluvial sedimentary rocks has complex zircon systematics. This rock may be as old as about 1856 Ma or as young as 1830 Ma. The sedimentary rocks overlying this rhyolite are locally intercalated with 1834 Ma felsic volcanic rocks, and yield sensitive high resolution ion microprobe (SHRIMP) U-Pb and Pb-evaporation detrital zircon ages ranging from 1834 to 2004 Ma. The Eastern Missi Group is cut by an 1826 ± 4 Ma felsic dyke, and contains 1832-1911 Ma detrital zircons. The dominant source for detritus in the Missi Group was the Flin Flon accretionary collage and associated successor arc rocks. The fluvial sedimentary rocks and the Herb Lake volcanic rocks were essentially coeval, and were then incorporated into a southwest-directed fold and thrust belt which was initiated at about 1840 Ma and active until at least peak regional metamorphism.


1992 ◽  
Vol 29 (12) ◽  
pp. 2583-2594 ◽  
Author(s):  
Kevin M. Ansdell ◽  
T. Kurtis Kyser ◽  
Mel R. Stauffer ◽  
Garth Edwards

The Missi Formation in the Flin Flon Basin forms part of a discontinuous series of molasse-type sediments found throughout the Early Proterozoic Trans-Hudson Orogen in northern Saskatchewan and Manitoba. The Flin Flon Basin contains a sequence of proximal-fan to braided-stream fluvial conglomerates and sandstones, which unconformably overlie subaerially weathered Amisk Group volcanic rocks. Stratigraphic way-up indicators have been preserved, even though these rocks have undergone greenschist-facies metamorphism and polyphase deformation. The sedimentary rocks are crosscut by intrusive rocks, which provide a minimum age of sedimentation of 1840 ± 7 Ma.Detrital zircons from each of the six stratigraphic subdivisions of the Flin Flon Basin were analyzed using the single-zircon Pb-evaporation technique. Euhedral to slightly rounded zircons dominate each sample, and these zircons give ages of between about 1854 and 1950 Ma. The Missi sediments were thus deposited between 1840 and 1854 Ma. Possible sources for the detrital zircons are Amisk Group felsic volcanic rocks and post-Amisk granitoid rocks and orthogneisses in adjacent domains within the Trans-Hudson Orogen. However, the immature character of the sedimentary rocks, the composition of clasts, the euhedral character of many of the zircons, and the range in ages suggest that most were likely derived from Amisk Group and granitoid rocks in the western Flin Flon Domain. Rounded zircons are uncommon but provide evidence for the reworking of older Proterozoic sedimentary rocks, or a distant Archean or Early Proterozoic granitoid terrane.


2016 ◽  
Vol 53 (2) ◽  
pp. 140-155 ◽  
Author(s):  
M.L. Golding ◽  
J.K. Mortensen ◽  
F. Ferri ◽  
J.-P. Zonneveld ◽  
M.J. Orchard

Triassic rocks of the Western Canada Sedimentary Basin (WCSB) have previously been interpreted as being deposited on the passive margin of North America. Recent detrital zircon provenance studies on equivalent Triassic rocks in the Yukon have suggested that these rocks were in part derived from the pericratonic Yukon–Tanana terrane and were deposited in a foreland basin related to the Late Permian Klondike orogeny. Detrital zircons within a number of samples collected from Triassic sediments of the WCSB throughout northeastern British Columbia and western Alberta suggest that the bulk of the sediment was derived from recycled sediments of the miogeocline along western North America, with a smaller but significant proportion coming from the Innuitian orogenic wedge in the Arctic and from local plutonic and volcanic rocks. There is also evidence of sediment being derived from the Yukon–Tanana terrane, supporting the model of terrane accretion occurring prior to the Triassic. The age distribution of detrital zircons from the WCSB in British Columbia is similar to those of the Selwyn and Earn sub-basins in the Yukon and is in agreement with previous observations that sediment deposited along the margin of North America during the Triassic was derived from similar source areas. Together these findings support the model of deposition within a foreland basin, similar to the one inferred in the Yukon. Only a small proportion of zircon derived from the Yukon–Tanana terrane is present within Triassic strata in northeastern British Columbia, which may be due to post-Triassic erosion of the rocks containing these zircons.


2020 ◽  
Vol 57 (1) ◽  
pp. 69-86
Author(s):  
C. Knudsen ◽  
U. Gregersen ◽  
T.F. Kokfelt ◽  
M. Olivarius ◽  
T.B. Thomsen

The AT2-1 well in the Davis Strait between Canada and Greenland penetrated an approximately 1.2 km thick sequence of alkaline volcanic rocks with some intercalated sediments at depths between 3690 to 4850 m. These volcanic rocks can be mapped on 2D seismic data and constitute a cone-shaped 5 km × 10 km wide and >1.2 km high structural high named the Atammik Volcano. This sequence comprises two distinct parts, an upper part of phono-tephrite to basaltic trachy-andesite and a lower part of tephriphonolite and phonolite. Rock textures and structures testify to a volcanic origin, with the uppermost units showing textural evidence of being subaerially extruded. Zircon crystals found in a sample of phonolite from 4453 m were dated by in situ laser ablation ICP–MS technique to yield ages between 98 and 93 Ma, indicating a maximum age of the formation of the phonolitic volcano of 93 Ma (Turonian). Further, detrital zircons from the clastic material have been dated yielding Archean ages. The gamma ray log indicates three internal cycles within the phonolites, each cycle displaying a stratigraphically upwards decrease in potassium content, suggesting the existence of a longer-lived system undergoing repeated magmatic differentiation and eruption events. The upper volcanic sequence is less evolved and less alkaline than the lower, suggesting a change in primary magma compositions towards progressively higher degrees of melting of the underlying mantle. This fits into a scheme of progressively higher degrees of melting with time, which in a regional context probably corresponds to a rifting event.


Author(s):  
Hai Zhou ◽  
Guochun Zhao ◽  
Yigui Han ◽  
Bo Wang ◽  
Xianzhi Pei

As a main part of the North China craton collage system, the tectonic origin of the Bainaimiao arc terrane is still hotly debated, especially its relationship with the North China craton. Thus, we report on a field-based petrological and zircon U-Pb-Hf isotopic study of (meta-)sedimentary and volcanic rocks from the Bainaimiao arc terrane and northern margin of the North China craton in the Damao region. The lower and middle successions of the Bayan Obo Group from the northern North China craton, including the Dulahala, Jianshan, Halahuogete, and Bilute Formations, were deposited ca. 1.81−1.35 Ga and show age peaks at 1.85, 1.90, 2.0, and 2.5 Ga. This age pattern is in accordance with the coeval and extensively outcropped metamorphosed basement rocks of the northern North China craton. The upper succession, including the Bayinbaolage and Hujiertu Formations, deposited ca. 1.19−0.92 Ga, shows age peaks at ca. 1.35, 1.57, and 1.69 Ga, and sediments were derived from coeval rift-related magmatism characterized by a significant increase in positive εHf(t) values in detrital zircons. Thus, the Bayan Obo Group can be subdivided into North China craton basement−derived sediments and Mesoproterozoic to Neoproterozoic rift-derived sediments, and the change of the provenance was probably caused by the ca. 1.35−1.30 Ga rifting event related to the breakup of the Nuna supercontinent. In the Bainaimiao arc terrane, zircon U-Pb geochronological results of (meta-)sedimentary rocks indicate they were formed in the Neoproterozoic and Paleozoic and have mainly late Paleoproterozoic to Neoproterozoic ages (ca. 0.6−0.9, 1.1−1.2, 1.4−1.7, and 1.8−2.0 Ga) with peaks at ca. 0.86, 0.96, 1.15, 1.47, 1.66, 1.75, 1.80−1.87, and 1.94 Ga. The abundant Neoproterozoic ages for the Bainaimiao arc terrane detrital zircons are distinct from the scarcity of these ages in the northern North China craton, southern Siberia (age peaks at ca. 1.87, 1.92, and 2.0 Ga), and Mongolia (age peak at ca. 0.62, 0.83, 0.93, 1.84, and 2.0 Ga), but they are similar to the features of the Tarim craton (age peaks at ca. 0.62, 0.85, 1.15, 1.47, 1.66, 1.75−1.80, 1.85, and 1.94 Ga). Together with the recognition of a possible preexisting Proterozoic basement (ca. 0.7−2.0 Ga) in the Bainaimiao arc terrane, as evidenced by the Hf model ages of continental arc magmatism in the Bainaimiao arc terrane, this late Paleoproterozoic to Neoproterozoic detritus probably resulted from local recycled sedimentation, and the preexisting Bainaimiao arc terrane basement rifted away from a continent with Tarim craton affinity. The rifting probably occurred between ca. 0.6 and 0.52 Ga, because the reworking of the Precambrian rocks in the North China collage system occurred between ca. 520 and 230 Ma.


1995 ◽  
Vol 32 (8) ◽  
pp. 1155-1171 ◽  
Author(s):  
C. J. Greig ◽  
G. E. Gehrels

New U–Pb zircon ages are reported from western Stikinia. Devonian and Pennsylvanian ages of volcanic rocks at Oweegee dome confirm the presence of pre-Permian strata, and with Paleozoic and Triassic detrital zircons from Lower Jurassic sandstone, they help to demonstrate pre-Lower Jurassic deformation and uplift. The absence of pre-Paleozoic inherited zircon from all samples is consistent with Nd–Sr isotopic data which suggest that Stikinia consists mainly of juvenile crust. U–Pb ages for posttectonic intrusions suggest that structures in Skeena Fold Belt in the Kinskuch area formed prior to Eocene time. Five ages for felsic volcanic rocks from stratigraphically well-constrained upper parts of the Hazelton arc are approximately 196–199 Ma and suggest near-contemporaneity for cessation of volcanism in the areas studied. The Sinemurian or late Sinemurian – early Pliensbachian ages are older than previously reported U–Pb and biostratigraphic ages for presumed correlative rocks to the west, and westward-migrating volcanism is implied. Together with Toarcian fossils from overlying sandstone, the new ages suggest that a hiatus of moderate duration preceded regionally extensive sedimentation.


2016 ◽  
Vol 53 (10) ◽  
pp. 979-992 ◽  
Author(s):  
Dominique Giesler ◽  
George Gehrels ◽  
Mark Pecha ◽  
Chelsi White ◽  
Intan Yokelson ◽  
...  

The Taku terrane consists of metamorphosed Carboniferous through Triassic marine clastic strata, volcanic rocks, and limestone that occur along the western margin of the Coast Mountains in southeastern Alaska. These rocks are juxtaposed along mid-Cretaceous thrust faults over Jura-Cretaceous basinal strata of the Gravina belt to the west and beneath Proterozoic through Carboniferous metamorphic rocks of the Yukon–Tanana terrane to the east. This paper presents U–Pb ages and Hf isotope analyses of detrital zircons from the Taku terrane, and compares these values with information from the adjacent Wrangellia, Alexander, and northern and southern portions of the Yukon–Tanana terrane (YTTn and YTTs). These comparisons suggest that (i) Carboniferous strata of the Taku terrane were shed mainly from mid-Paleozoic igneous rocks of YTTs, (ii) Permian strata of the Taku terrane were shed from mid-Paleozoic igneous rocks and intraformational Lower Permian volcanic rocks of YTTs as well as Upper Permian volcanic rocks exposed in YTTn, and (iii) Triassic sandstones were shed from mid-Paleozoic igneous rocks of YTTs, whereas conglomerates were shed mainly from mid-Paleozoic arc rocks in YTTn. Hf isotope analyses of Paleozoic zircons record increasing continental input during Silurian–Devonian and Permian phases of magmatism. Similarities in isotopic characteristics, combined with stratigraphic and geochemical information presented by previous workers, suggest that strata of the Taku terrane accumulated on (and partly as lateral equivalents of) rocks of YTTs, and that the combined assemblages formed outboard or along strike of YTTn.


2020 ◽  
Author(s):  
P.J. Umhoefer ◽  
et al.

Consists of geochronology and thermochronology data, and methods related to those data. Geochronology data are from <sup>40</sup>Ar/<sup>39</sup>Ar dating of volcanic rocks and U-Pb analysis of detrital zircons, while thermochronology data are from apatite and zircon fission-track and apatite helium cooling ages.


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