Constraining provenance for the uraniferous Paleoproterozoic Francevillian Group sediments (Gabon) with detrital zircon geochronology and geochemistry
Constraining provenance for the uraniferous Paleoproterozoic Francevillian Group sediments (Gabon) with detrital zircon geochronology and geochemistry
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用碎屑锆石年代学和地球化学约束古元古代弗朗西维利群沉积物（加蓬）的物源
DOI：
10.1016/j.precamres.2020.105724
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发表时间：
2020
影响因子：
3.8
通讯作者：
Bekker
中科院分区：
文献类型：
--
作者：
Ossa Ossa;Hofmann;Ballouard;Vorster;Schoenberg;Friedrich;Mayaga- Mikolo;Bekker
古元古代砂岩。2.1加蓬东南部的Ga Francevillian群拥有已知最古老的氧化还原控制的高品位铀（U）矿床。含铀碎屑矿物（例如，Francevillian群沉积物中的独居石（独居石）是由包围Francevillian盆地的刚果克拉通西北部的东加布阶地块的太古代基底岩石的侵蚀作用产生的。它们被视为U的主要来源，但这些来源的性质仍然缺乏约束。本文利用碎屑锆石U-Pb年龄和Hf同位素数据，结合文献中太古代基底火成岩地球化学资料，对弗朗斯维尔盆地的物源性质、时代和来源以及高品位铀矿床的最终铀源进行了研究。3.1到2.6 Ga之间，优势种群在约. 2.90和2.80 Ga，表明主要贡献来自ca. 2.88到2.81Ga的高钾花岗岩类，约1000 Ga的贡献有限。3.1 2.75 ~ 2.7Ga花岗岩类。大多数碎屑锆石颗粒共享类似的亏损地幔Hf模式年龄之间的约。3.08和3.30 Ga，表明古太古代到中太古代地壳的重大再循环。我们建议CA。2.9~ 2.8Ga高K、U和Th花岗岩类反映了地幔和地壳两种母体的混合熔体，是Francevillian盆地铀的主要碎屑来源，并最终形成铀矿床。我们建议CA。2.9至2.8 Ga碎屑锆石，Hf TDM年龄在约. 3.1和3.3 Ga可能因此允许在横跨刚果克拉通的沉积盆地中进行铀矿床的矢量化。
The Paleoproterozoic sandstones of the ca. 2.1 Ga Francevillian Group, southeast Gabon, host the oldest known redox-controlled high-grade uranium (U) deposits. Uranium-bearing detrital minerals (e.g., monazite) in the Francevillian Group sediments were derived by erosion of Archean basement rocks from the East Gabonian block of the northwestern Congo craton surrounding the Francevillian Basin. They are viewed as primary sources for U, but the nature of these sources remains poorly constrained. Here, U-Pb ages and Hf isotope data for detrital zircon grains are combined with literature geochemical data for igneous rocks from the Archean basement, to characterize the nature, age, and origin of the provenance for the Francevillian Basin and the ultimate source of U for the high-grade uranium deposits.Detrital zircon ages range from ca. 3.1 to 2.6 Ga with a dominant population between ca. 2.90 and 2.80 Ga, suggesting a major contribution from ca. 2.88 to 2.81 Ga high-K granitoids with a limited contribution from ca. 3.1 to 2.84 Ga TTGs and 2.75 to 2.7 Ga granitoids of the East Gabonian block. Most detrital zircon grains share similar depleted-mantle Hf model ages between ca. 3.08 and 3.30 Ga, indicating significant recycling of a Paleoarchean to Mesoarchean crust. We suggest that ca. 2.9 to 2.8 Ga high K, U, and Th granitoids, which reflect hybrid melts of both mantle and crustal parentage were the major detrital sources of U to the Francevillian Basin and, ultimately, for the U deposits. We propose that ca. 2.9 to 2.8 Ga detrital zircons with Hf TDMages between ca. 3.1 and 3.3 Ga may thus allow for vectoring U deposits in sedimentary basins across the Congo craton.
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