Debate continues over the reducing mechanisms for the formation of unconformity-related uranium (URU) deposits. This paper evaluates, for the first time, the potential of iron-rich chlorite as a reductant for uranium mineralization using reactive fluid flow modeling method. Our results confirm that Fe²⁺, released from the breakdown of iron-rich chlorite, can reduce aqueous hexavalent uranium to precipitate economically significant URU deposits similar in size and grade to those formed with CH₄ as the reducing agent. The resulting uranium mineralization tends to occur in the basement and below the downwelling parts of overlying basinal fluid circulation cells, where oxidizing basinal fluid percolates across the unconformity and reacts with upward flowing reducing basement brine. Therefore, the basinal fluid circulation pattern controlled by the permeability of the sandstone aquifer is critical in determining the formation and distribution of URU deposits. When the sandstone layer is more permeable, the simulated uranium deposits become larger in size, and vice versa. If the sandstone permeability is <5 × 10⁻¹⁴ m², no obvious uranium deposits can be formed. In contrast, the permeability of fault zones does not have a significant effect on uranium mineralization, although it does affect fluid flow behaviors within the fault zone itself. We also demonstrate that fault zones do not appear to be a prerequisite for the formation of URU deposits when Fe⁺² serves as a reductant, which highlights important exploration implications. Uranium exploration should, in addition to continuing to target graphitic fault zones, also consider areas where faults and/or graphite units do not exist.

中文翻译：

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富铁亚氯石中释放的亚铁 （Fe+2） 作为不整合相关铀矿化的还原剂：来自反应流体流动建模的见解


关于形成不整合相关铀 （URU） 矿床的还原机制的争论仍在继续。本文首次使用反应流体流动建模方法评估了富铁亚氯酸盐作为铀矿化还原剂的潜力。我们的结果证实 ²⁺ ，从富铁亚氯酸盐分解中释放的 Fe 可以还原六价铀水溶液，以沉淀具有经济意义的 URU 沉积物，这些沉积物的大小和等级与用 CH ₄ 作为还原剂形成的沉积物相似。由此产生的铀矿化往往发生在上覆盆地流体循环单元的基底和下涌部分下方，氧化性盆地流体渗透穿过不整合面并与向上流动的还原基底盐水发生反应。因此，由砂岩含水层渗透性控制的盆地流体循环模式对于确定 URU 矿床的形成和分布至关重要。当砂岩层的渗透性更强时，模拟的铀矿床的尺寸会变大，反之亦然。如果砂岩渗透率为 <5 × 10 ⁻¹⁴ m ² ，则不会形成明显的铀矿床。相比之下，断层带的渗透性对铀矿化没有显著影响，尽管它确实会影响断层带本身内的流体流动行为。我们还证明，当 Fe ⁺² 作为还原剂时，断层带似乎不是形成 URU 矿床的先决条件，这突出了重要的勘探意义。铀矿勘探除了继续以石墨断层带为目标外，还应考虑不存在断层和/或石墨单元的区域。