铀矿床定年研究进展评述

往往由于铀矿物(沥青铀矿)颗粒细小、易蚀变成铀的次生矿物及多期铀矿化作用相互叠加等在组成和结构上的固有特点,通常难以用挑选铀矿物(沥青铀矿)样品溶样的传统定年方法精确确定其形成年龄。随着分析技术的不断更新和发展,对铀矿床成矿年代学的研究也不断深入。但受铀矿床中铀矿物U-Pb定年方法本身的制约,以及以往对铀矿物U-Pb定年体系中铀矿物样品要求认识的不足,常常导致获得的年龄无实际地质意义或无法获得理想的等时线年龄。本文针对铀矿化定年方法的发展历程进行了系统梳理和分析,评述了铀矿物定年的五种主要方法:(1)铀矿物U-Th-totalPb化学年龄;(2)铀矿物模式年龄;(3)铀矿物传统等时线年龄;(4)铀矿物矿伴生矿物年龄;(5)原位微区铀矿物U-Pb年龄。在此基础上,深入探讨了铀矿化作用定年研究中存在的问题和对应方案,期望促进未来铀矿床成矿年代学的发展。

Review on dating of uranium mineralization

The accurate and precise ages of uranium mineralization are scarce because those uranium minerals (pitchblendes) usually show heterogeneous and fine grains in component and structure, and may have formed in several stages. The conventional bulk uranium minerals (pitchblendes) U-Pb dating methods previously employed were unable to avoid alteration minerals and precisely discriminate different stages of uranium mineralization to obtain the precise ore-forming ages. With the constant improvement and development of analytical techniques, ore-forming age of uranium mineralization has been extensively studied. However, the insufficient understanding on constraint for uranium mineral U-Pb dating techniques, and uranium mineral requirement for U-Pb dating systems commonly resulted in that either the obtained ages were geological meaningless or the isochron ages were failure to be constructed. This paper presents the development process of analysis methods for ore-forming ages of uranium mineralization in detail. These main dating methods include:(1) uranium mineral U-Th-^totalPb chemical age; (2) uranium mineral U-Pb model age; (3) conventional uranium mineral U-Pb isochron age; (4) uranium mineral associated with other minerals dating; and (5) in-situ uranium mineral U-Pb dating. Additionally, we also review these issues on various dating techniques of uranium mineralization and propose some items for future development of metallogenic geochronology on uranium deposit.