Structural control on uranium mineralization in South China: Implications for fluid flow in continental strike-slip faults |
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Authors: | Jianwei Li Meifu Zhou Xianfu Li Zhaoren Fu and Zijin Li |
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Affiliation: | 1. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;Department of Earth Sciences, The University of Queensland, Brisbane, Qld 4072, Australia 2. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China 3. Department of Civil Engineering, Wuhan College of Chemical Technology, Wuhan 430073, China 4. Department of Earth Sciences, The University of Queensland, Brisbane, Qld 4072, Australia |
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Abstract: | South China is the most important uranium producer in the country. Much of the Mesozoic-Cenozoic geology of this area was
dominated by NNE-trending intracontinental strike-slip faulting that resulted from oblique subduction of the paleo-Pacific
plate underneath the eastern China continent. This strike-slip fault system was characterized by transpression in the early-mid
Jurassic and by transtension from the latest Jurassic through Cretaceous to early Tertiary. Most uranium ore deposits in South
China are strictly fault-hosted and associated with mid-late Mesozoic granitic intrusions and volcanic rocks, which formed
under transpression and transtension regimes, respectively. Various data demonstrate that the NNE-trending strike-slip faults
have played critical roles in the formation and distribution of hydrothermal uranium deposits. Extensive geochronological
studies show that a majority of uranium deposits in South China formed during the time period of 140–40 Ma with peak ages
between 87–48 Ma, coinciding well with the time interval of transtension. However, hydrothermal uranium deposits are not uniformly
distributed along individual strike-slip fault. The most important ore-hosting segments are pull-apart stepovers, splay structures,
extensional strike-slip duplexes, releasing bends and fault intersections. This non-uniform distribution of ore occurrences
in individual fault zone reflects localization of hydrothermal fluids within those segments that were highly dilational and
thus extremely permeable. The unique geometric patterns and structural styles of strike-slip faults may have facilitated mixing
of deeply derived and near-surface fluids, as evidenced by stable isotopic data from many uranium deposits in South China.
The identification of fault segments favorable for uranium mineralization in South China is important for understanding the
genesis of hydrothermal ore deposits within continental strike-slip faults, and therefore has great implications for exploration
strategies. |
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Keywords: | strike-slip fault transtension fluid flow uranium deposits South China |
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