Implications for sedimentary transport processes in southwestern Africa: a combined zircon morphology and age study including extensive geochronology databases

AbstractExtensive morphological and age studies on more than 4600 detrital zircon grains recovered from modern sands of Namibia reveal complex mechanisms of sediment transport. These data are further supplemented by a zircon age database containing more than 100,000 single grain analyses from the entire southern Africa and allow for hypothesising of a large Southern Namibian Sediment Vortex located between the Damara Orogen and the Orange River in southern Namibia. The results of this study also allow assuming a modified model of the Orange River sand highway, whose origin is likely located further south than previously expected. Moreover, studied samples from other parts of Namibia give first insights into sediment movements towards the interior of the continent and highlight the potential impact of very little spatial variations of erosion rates. Finally, this study points out the huge potential of detrital zircon morphology and large geo-databases as an easy-to-use additional tool for provenance analysis.

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Late Paleozoic tectonism of the Bogda region in Chinese North Tianshan: Insights from sedimentary provenance analysis

10.5194/egusphere-egu21-16422 ◽

2021 ◽

Author(s):

Qian Wang ◽

Guochun Zhao ◽

Yigui Han ◽

Jinlong Yao

Keyword(s):

Detrital Zircon ◽

Detrital Zircons ◽

Late Paleozoic ◽

Provenance Analysis ◽

The North ◽

Tectonic Transition ◽

Isotopic Analyses ◽

Zircon Morphology ◽

Detrital Zircon Ages ◽

T Values

The Chinese North Tianshan (CNTS) extends E-W along the southern part of the Central Asian Orogenic Belt and has undergone complicated accretion-collision processes in the Paleozoic. This study attempts to clarify the late Paleozoic tectonism in the region by investigating the provenance of the Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS by U-Pb dating and Lu-Hf isotopic analyses of detrital zircons. Detrital zircon U-Pb ages (N=519) from seven samples range from 261 &#177; 4 Ma to 2827 &#177; 32 Ma, with the most prominent age peak at 313 Ma. There are Precambrian detrital zircon ages (~7%) ranged from 694 to 1024 Ma. The youngest age components in each sample yielded weighted mean ages ranging from 272 &#177; 9 Ma to 288 &#177; 5 Ma, representing the maximum depositional ages. These and literature data indicate that some previously-assumed &#8220;Carboniferous&#8221; strata in the Bogda area were deposited in the Early Permian, including the Qijiaojing, Julideneng, Shaleisaierke, Yangbulake, Shamaershayi, Liushugou, Qijiagou, and Aoertu formations. The low maturity of the sandstones, zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East &#173;Junggar Arc and the Harlik-Dananhu Arc in the CNTS. The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc. Zircon &#603;Hf(t) values have increased since ~408 Ma, probably reflecting a tectonic transition from regional compression to extension. This event might correspond to the opening of the Bogda intra-arc/back arc rift basin, possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean. A decrease of zircon &#603;Hf(t) values at ~300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision, which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous. This research was financially supported by the Youth Program of Shaanxi Natural Science Foundation (2020JQ-589), the NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).

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Neoproterozoic active margin in the northwestern Yangtze Block, South China: new clues from detrital zircon U–Pb geochronology and geochemistry of sedimentary rocks from the Hengdan Group

Geological Magazine ◽

10.1017/s0016756820000898 ◽

2020 ◽

pp. 1-17

Author(s):

Bo Hui ◽

Yunpeng Dong ◽

Feifei Zhang ◽

Shengsi Sun ◽

Shuai He

Keyword(s):

South China ◽

Detrital Zircon ◽

Active Continental Margin ◽

Geodynamic Setting ◽

Provenance Analysis ◽

Yangtze Block ◽

Essential Information ◽

Zircon Age ◽

Age Patterns ◽

Depositional Age

Abstract The Yangtze Block in South China constitutes an important Precambrian landmass in the present East Asian continent. The Neoproterozoic sedimentary successions of the Hengdan Group in the NW Yangtze Block record essential information for deciphering the Neoproterozoic tectonics along the NW margin. However, its depositional age, provenance and tectonic properties remain uncertain. Here, a combined analysis of detrital zircon U–Pb dating and geochemistry is performed on representative samples from the Hengdan Group. Concordant dating results of samples from the bottom and upper parts constrain the maximum depositional age at c. 720 Ma. Detrital zircon age patterns of samples reveal a uniformly pronounced age peak at c. 915–720 Ma, which is consistent with the magmatic pulses in domains at the NW end of the Yangtze Block. In addition, these samples display left-sloping post-Archaean Australian shale (PAAS)-normalized rare-earth element patterns and variable trace element patterns, resembling sediments accumulated in a basin related to an active continental margin geodynamic setting. Provenance analysis reveals that the main sources featured intermediate to felsic components, which experienced rapid erosion and sedimentation. These integrated new investigations, along with previous compilations, indicate that the Hengdan Group might have been deposited in a fore-arc basin controlled by subduction beneath the Bikou Terrane. Thus, such interpretation further supports proposals for subduction-related tectonics along the western margin of the Yangtze Block during the early Neoproterozoic.

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Coupled U-Pb dating and Hf isotopic analysis of detrital zircon of modern river sand from the Yalu River (Yarlung Tsangpo) drainage system in southern Tibet: Constraints on the transport processes and evolution of Himalayan rivers

Geological Society of America Bulletin ◽

10.1130/b30592.1 ◽

2012 ◽

Vol 124 (9-10) ◽

pp. 1449-1473 ◽

Cited By ~ 45

Author(s):

J. Y. Zhang ◽

A. Yin ◽

W. C. Liu ◽

F. Y. Wu ◽

D. Lin ◽

...

Keyword(s):

Detrital Zircon ◽

Drainage System ◽

Isotopic Analysis ◽

Transport Processes ◽

River Sand ◽

Southern Tibet ◽

Yalu River ◽

Yarlung Tsangpo ◽

Himalayan Rivers

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Inversion of detrital zircon data to constrain spatially varying erosion rates

10.5194/egusphere-egu2020-2176 ◽

2020 ◽

Author(s):

Fien De Doncker ◽

Frédéric Herman ◽

Matthew Fox

Keyword(s):

Least Squares ◽

Detrital Zircon ◽

Erosion Rate ◽

Least Squares Method ◽

A Priori ◽

Age Distribution ◽

Inversion Method ◽

Provenance Analysis ◽

Erosion Rates ◽

Geological Unit

Landscapes evolve through surface processes that are often transient in space and time. To understand the underlying geomorphic processes, one must assess how erosion rates vary spatially. This can be done using provenance analysis. Here, we introduce a formal inversion method to derive erosion patterns using detrital zircon age data as fingerprints. Zircons are omnipresent in Earth&#8217;s crust and contain information about the time since (re)crystallization in their U/Th-Pb ratio. For each geological unit having undergone a specific tectonic or magmatic history, one can find a unique age-frequency signature. Hence, erosion and sedimentation of grains originating from diverse source areas lead to a mix of the varying age-frequency signatures in sediments found at the outlet of a catchment. Considering that the age signal is not altered during erosion-transportation-deposition events, and given that recent technological advances enable precise dating of large amounts of grains, U/Th-Pb zircon ages provide an appropriate fingerprinting tool. Our inversion approach relies on the least-squares method with a priori information and model covariance to deal with non-uniqueness. We show with synthetic and natural examples that we are able to retrieve erosion rate patterns of a catchment when the age distribution for each geological unit is well known. Furthermore, relying on the nested form of catchments and their subcatchments, we demonstrate that adding samples taken at the outlet of subcatchments improves the estimation of erosion rate patterns. We conclude that the least squares inverse model applied on detrital zircon data has great potential for investigating erosion rates.

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Detrital zircon age studies of Haast Schist in western Otago and Marlborough, New Zealand: constraints on their protolith age, terrane ancestry and Au–W mineralisation

Australian Journal of Earth Sciences ◽

10.1080/08120099.2020.1776389 ◽

2020 ◽

pp. 1-16

Author(s):

C. J. Adams ◽

H. J. Campbell ◽

W. L. Griffin

Keyword(s):

New Zealand ◽

Detrital Zircon ◽

Zircon Age ◽

Age Studies

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Preliminary detrital zircon U-Pb Geochronology of the Wasatch Formation, Powder River Basin, Wyoming

The Mountain Geologist ◽

10.31582/rmag.mg.56.3.247 ◽

2019 ◽

Vol 56 (3) ◽

pp. 247-266

Author(s):

Ian Anderson ◽

David H. Malone ◽

John Craddock

Keyword(s):

River Basin ◽

Detrital Zircon ◽

Middle Part ◽

Detrital Zircons ◽

Powder River Basin ◽

Zircon Age ◽

Lower Eocene ◽

The North ◽

Mountain Front ◽

Fluvial Sandstone

The lower Eocene Wasatch Formation is more than 1500 m thick in the Powder River Basin of Wyoming. The Wasatch is a Laramide synorgenic deposit that consists of paludal and lacustrine mudstone, fluvial sandstone, and coal. U-Pb geochronologic data on detrital zircons were gathered for a sandstone unit in the middle part of the succession. The Wasatch was collected along Interstate 90 just west of the Powder River, which is about 50 km east of the Bighorn Mountain front. The sandstone is lenticular in geometry and consists of arkosic arenite and wacke. The detrital zircon age spectrum ranged (n=99) from 1433-2957 Ma in age, and consisted of more than 95% Archean age grains, with an age peak of about 2900 Ma. Three populations of Archean ages are evident: 2886.6±10 Ma (24%), 2906.6±8.4 Ma (56%) and 2934.1±6.6 Ma (20%; all results 2 sigma). These ages are consistent with the age of Archean rocks exposed in the northern part of the range. The sparse Proterozoic grains were likely derived from the recycling of Cambrian and Carboniferous strata. These sands were transported to the Powder River Basin through the alluvial fans adjacent to the Piney Creek thrust. Drainage continued to the north through the basin and eventually into the Ancestral Missouri River and Gulf of Mexico. The provenance of the Wasatch is distinct from coeval Tatman and Willwood strata in the Bighorn and Absaroka basins, which were derived from distal source (>500 km) areas in the Sevier Highlands of Idaho and the Laramide Beartooth and Tobacco Root uplifts. Why the Bighorn Mountains shed abundant Eocene strata only to the east and not to the west remains enigmatic, and merits further study.

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