近日，东华理工大学Shuo Yin研究小组取得一项新突破，研究发现了氧化钛的多态转化有助于砂岩中的经济铀矿化。2024年3月20日出版的《地质学》发表了这项成果。

研究基于松辽盆地西南部Yaojia组地层钛氧化物的原位结构、微量元素含量、钛同位素比值、多晶型类型及相关转化，建立了一个新的模型。具体来说，在该模型中，锐钛矿在自发转化为金红石的过程中产生了大量的纳米孔，产生了一种吸附六价铀的多孔材料。在富铀源岩的促进下，Yaojia组下段多孔氧化钛中吸附的铀高达百万分之几千。为了使表面能最小化，通过合并小孔隙而导致的表面积减少是不可避免的。

当析出的表面积足够小时，六价铀被局部还原剂解吸转化为四价铀，在孔洞较大的富铀金红石表面形成相对大孔的晶质铀矿纳米颗粒。研究新提出的机制不仅有助于更好地理解砂岩中铀的经济成矿作用，而且还表明，在砂岩含铀矿床中，铀以氧化铀而不是硼铁矿的形式存在，为矿内加工提供了所需的纳米矿物学视角。

据了解，砂岩铀(U)矿床为世界范围内的核能提供了重要的铀资源。在氧化还原反应的驱动下，四价含铀矿物通常与还原剂(如黄铁矿和有机物)伴生。然而，大量的观察表明，在砂岩含铀矿床中，四价含铀矿物可以与化学稳定的氧化钛物在空间上共存，这需要一个互补的机制来解释这些发现。

附：英文原文

Title: Polymorphic transformations of titanium oxides contribute to economic uranium mineralization in sandstone

Author: Shuo Yin, Zhaobin Yan, Jiali Fu, Wen Zhang, Hong Liu, Fei Xia, Qingfei Wang

Issue&Volume: 2024-03-20

Abstract: Sandstone-hosted uranium (U) deposits provide a significant U resource for nuclear energy worldwide. Driven by redox reactions, tetravalent uranium-bearing minerals are commonly associated with reductants (e.g., pyrite and organic matter). However, numerous observations have revealed that tetravalent uranium-bearing minerals can spatially coexist with chemically stabilized titanium oxides in sandstone-hosted U deposits, requiring a complementary mechanism to interpret these findings. We present a new model based on in situ texture, trace-element content, and titanium isotopic ratio, as well as polymorph type and related transformation for titanium oxides from the Yaojia Formation of the southwestern Songliao Basin in northeast China. Specifically, in our model, abundant nanopores were generated during the spontaneous transformation of anatase to rutile, producing a porous material for hexavalent U adsorption. Facilitated by a U-rich source rock, adsorbed U in porous titanium oxide from the lower Yaojia Formation was up to several thousand parts per million. In order to minimize surface energy, a subsequent decrease in surface area by merging small pores is inevitable. When the evolved surface area was small enough, hexavalent U would be desorbed and subsequently transformed to tetravalent U by local reductants, forming uraninite nanoparticles on the surface of U-rich rutile with relatively large pores. Our newly proposed mechanism not only contributes to a better understanding of economic U mineralization in sandstone, but also suggests that U occurred as uranium oxide instead of brannerite in sandstone-hosted U deposits, providing a nano-mineralogical perspective required for industrial processing.

DOI: 10.1130/G51982.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51982.1/636723/Polymorphic-transformations-of-titanium-oxidesredirectedFrom=fulltext