A number of large and high-grade unconformity-related uranium deposits formed in intracratonic Proterozoic basins, including the Athabasca Basin in Canada and the McArthur Basin in Australia. These deposits occur close to the unconformities between the Paleo- to Mesoproterozoic basinal sequences and their Archean to Paleoproterozoic metasedimentary basement, and are spatially associated with reactivated basement faults showing reverse offsets due to contractional deformation. Previous studies have suggested that fluid flow responsible for uranium mineralization in such basins may be related to thermal convection and tectonic deformation; however, the relative roles of these two driving forces, as well as their interrelationships, have not been explored in detail. In this study, two-dimensional numerical modeling of fluid flow in relation to coupled tectonic compression and heat transport was carried out to evaluate the relationships between deformation-driven flow and fluid convection, and their relative importance for uranium mineralization. The results indicate that tectonic compression at a relatively high strain rate (6.66 × 10−11 s−1) may instantaneously destroy pre-existing thermal convection developed in the sedimentary rocks in the basin, due to the rapid development of overpressure in the system. Convection may then reappear over time as deformation progresses and the overpressure wanes. By contrast, tectonic compression at a relatively low strain rate (6.66 × 10−13 s−1) does not affect pre-existing thermal convection, and deformation-driven fluid flow in the basement coexists with thermal convection in the basin. It is proposed that during an overall tectonically active period associated with a far-field tectonic event, compressional reactivation of basement faults creates permeability and causes fluid to flow toward dilatant zones accompanying individual seismic events, whereas during seismically quiet times, fluid flow driven by thermal convection dominates. The formation of the unconformity-related uranium deposits likely involves alternating relatively short-lived, deformation-driven fluid flow and relatively prolonged fluid convection events.

中文翻译：

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热对流和挤压断层再激活在不整合相关铀矿床形成中的相互作用

在克拉通内元古代盆地，包括加拿大的阿萨巴斯卡盆地和澳大利亚的麦克阿瑟盆地，形成了许多与不整合面相关的大型高品位铀矿床。这些矿床靠近古至中元古代盆地层序与其太古代至古元古代变沉积基底之间的不整合面，并且在空间上与重新活动的基底断层相关联，这些断层因收缩变形而显示出反向偏移。先前的研究表明，在此类盆地中导致铀矿化的流体流动可能与热对流和构造变形有关；然而，尚未详细探讨这两种驱动力的相对作用以及它们的相互关系。在这项研究中，进行了与耦合构造压缩和热传输相关的流体流动的二维数值模拟，以评估变形驱动的流动和流体对流之间的关系，以及它们对铀矿化的相对重要性。结果表明，由于系统中超压的快速发展，相对高应变率（6.66 × 10-11 s-1）的构造压缩可能会瞬间破坏盆地沉积岩中预先存在的热对流。随着变形的进行和超压的减弱，对流可能会随着时间的推移重新出现。相比之下，相对低应变率 (6.66 × 10−13 s−1) 的构造压缩不会影响预先存在的热对流，基底内变形驱动的流体流动与盆地内的热对流并存。有人提出，在与远场构造事件相关的整个构造活动时期，基底断层的压缩再激活产生渗透性并导致流体流向伴随个别地震事件的膨胀带，而在地震安静时期，流体流动由热驱动对流占主导地位。与不整合面相关的铀矿床的形成可能涉及相对短暂的、变形驱动的流体流动和相对延长的流体对流事件的交替。基底断层的压缩再激活产生渗透性并导致流体流向伴随个别地震事件的膨胀带，而在地震安静时期，由热对流驱动的流体流动占主导地位。与不整合面相关的铀矿床的形成可能涉及相对短暂的、变形驱动的流体流动和相对延长的流体对流事件的交替。基底断层的压缩再激活产生渗透性并导致流体流向伴随个别地震事件的膨胀带，而在地震安静时期，由热对流驱动的流体流动占主导地位。与不整合面相关的铀矿床的形成可能涉及相对短暂的、变形驱动的流体流动和相对延长的流体对流事件的交替。