The Assabet barcode: Mesoproterozoic detrital zircons in Neoproterozoic strata from Mauritania, West Africa

IF 1.9 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
D. Bradley, D. Evans, P. O’Sullivan, Cliff D. Taylor, B. Eglington
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引用次数: 3

Abstract

Detrital zircon data are reported from Mesoproterozoic to Ordovician strata from two tectonic domains in Mauritania: 14 samples from the Taoudeni Basin of the West African Craton and 15 samples from the Mauritanide orogen. Taoudeni Basin samples show four sequential, distinctive detrital zircon age distributions, which we refer to as “barcodes”. From old to young these are the Char, Assabet, Téniagouri, and Oujeft barcodes, each named for a constituent stratigraphic unit. Zircon age maxima are as follows, with the dominant ones in italics. The Char barcode, from Mesoproterozoic (ca. 1100 Ma) strata including the Char Group, yielded zircon age maxima at 2941, 2871, 2703, 2447, 2076, and 2041 Ma, all potentially traceable to sources in the West African Craton. The Assabet barcode is from strata, including the eponymous Assabet el Hassiane Group, that were deposited between ca. 883 and ca. 570 Ma; it has age maxima at 2137, 2053, 1769, 1510, 1212, 1021, and 936 Ma and a pronounced minimum during Geon 16 (1699–1600 Ma). The Assabet's Mesoproterozoic to early Neoproterozoic zircons cannot have come from the West African Craton or any of its surrounding orogens. The Téniagouri barcode, which takes its name from the Téniagouri Group, was deposited at ca. 569 Ma; it has dominant maxima at 1983, 1872, 1522, 1215, 1109, 988, and 601 Ma and resembles the Assabet barcode but with the addition of the youngest population. The Oujeft barcode, named for the Oujeft Group, is from strata deposited between 541 or slightly earlier and 444 Ma or younger, has age maxima at 2124, 2053, 1197, 624 and 579 Ma. The Téniagouri and Oujeft barcodes record input from Pan-African orogens. In the Mauritanide orogen, most of the metasedimentary rock units that were sampled yielded detrital zircon age spectra that match one of the Taoudeni Basin barcodes. These results imply new depositional age constraints based on barcode correlation and suggest affinities between Mauritanide strata and the West African Craton. Detrital zircon age distributions that broadly resemble the Assabet barcode occur in the Neoproterozoic of Morocco, Ghana, Greece, Russia, Brazil, and, in the Appalachian orogen of Canada and the United States, Avalonia and Ganderia. The recent Rodinia reconstruction of Evans (2021) restores these far-flung localities to a more compact area, with Avalonia, Ganderia, and other peri-Gondwanan terranes occupying an oblong area between Amazonia, Laurentia, Baltica, and West Africa. Our preferred explanation is that most of these places received detritus via the same continent-scale fluvial system as the West African craton. Among the craton's nearest Rodinia neighbors in the Evans (2021) reconstruction for 900 Ma, Amazonia has known igneous rocks corresponding to all of the major Assabet age populations, and also a lull, though not a complete magmatic gap, during Geon 16. This is consistent with overall north-directed paleocurrents in the Assabet El Hassiane Group and its correlatives on the West African Craton.
Assabet条形码:西非毛里塔尼亚新元古代地层中元古代碎屑锆石
本文报道了毛里塔尼亚两个构造域中元古代至奥陶系地层的碎屑锆石资料:西非克拉通Taoudeni盆地14份,毛里塔尼亚造山带15份。陶德尼盆地样品显示出4个顺序分明的碎屑锆石年龄分布,我们称之为“条形码”。从老到年轻分别是Char, Assabet, tsamniagouri和Oujeft条形码,每个条形码都以一个组成地层单位命名。锆石年龄最大值如下,以斜体为优势值。中元古代(约1100 Ma)地层(包括Char群)的Char条形码测得的锆石年龄最大值分别为2941、2871、2703、2447、2076和2041 Ma,均可能溯源于西非克拉通。Assabet条形码来自地层,包括同名的Assabet el Hassiane组,沉积于约883至约570 Ma之间;其年龄最大值在2137、2053、1769、1510、1212、1021和936 Ma,最小值在1699 ~ 1600 Ma。阿萨比特的中元古代至新元古代早期锆石不可能来自西非克拉通或其周围的任何造山带。tsamiagouri条形码,它的名字来自tsamiagouri组,大约在569 Ma;它在1983年、1872年、1522年、1215年、1109年、988年和601年有优势的最大值,类似于Assabet条形码,但增加了最年轻的人口。以Oujeft群命名的Oujeft条形码来自于541或稍早至444 Ma或更年轻的地层,其年龄最大值为2124、2053、1197、624和579 Ma。tsamniagouri和Oujeft条形码记录了来自泛非造山带的输入。在茅里塔尼造山带,大多数变质沉积岩单元的碎屑锆石年龄谱与陶德尼盆地的一个条形码相匹配。这些结果暗示了基于条形码对比的新的沉积时代约束,并表明毛里塔尼地层与西非克拉通之间存在亲缘关系。与Assabet条形码大致相似的碎屑锆石年龄分布出现在摩洛哥、加纳、希腊、俄罗斯、巴西的新元古代,以及加拿大和美国的阿巴拉契亚造山带Avalonia和Ganderia。最近的Rodinia重建Evans(2021)将这些遥远的地区恢复到一个更紧凑的区域,Avalonia, Ganderia和其他周边冈瓦南地区占据了亚马逊,劳伦西亚,波罗的海和西非之间的长方形区域。我们更喜欢的解释是,这些地方中的大多数都是通过与西非克拉通相同的大陆尺度河流系统接收碎屑的。在埃文斯(2021)900 Ma重建中,在克拉通最近的Rodinia邻居中,亚马逊地区已知的火成岩与所有主要的Assabet时代人口相对应,并且在Geon 16期间也有一个平静期,尽管不是完整的岩浆缺口。这与Assabet El Hassiane群及其在西非克拉通上的同类群的整体北向古流一致。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
American Journal of Science
American Journal of Science 地学-地球科学综合
CiteScore
5.80
自引率
3.40%
发文量
17
审稿时长
>12 weeks
期刊介绍: The American Journal of Science (AJS), founded in 1818 by Benjamin Silliman, is the oldest scientific journal in the United States that has been published continuously. The Journal is devoted to geology and related sciences and publishes articles from around the world presenting results of major research from all earth sciences. Readers are primarily earth scientists in academia and government institutions.
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