适合于稀有金属矿床的同位素定年方法及其应用

Isotopicdating method suitable for rare-metal deposits and its application

同位素地质年代学是根据放射性同位素衰变规律,确定地质体形成和地质事件发生时代的新兴学科,也是研究成矿时代的主要手段。本文结合所在实验室研究团队和前人的工作,介绍几种可以直接确定稀有金属成矿时代的同位素地质年龄测定方法及其在稀有矿床中的应用,以期为相关学科研究提供参考。主要是:①Re-Os法,是目前应用最成熟的直接确定金属矿床成矿时代的方法,定年矿物除了辉钼矿,已扩展到黄铁矿、沥青铀矿等;②U-Pb法,是地质学研究应用最广泛的方法,目前的测定对象已不局限于锆石,一些含铀的矿石矿物如锡石、独居石、磷灰石、铌钽矿物的U-Pb年龄也可以直接测定,有助于直接确定金属矿床的成矿时代;③Ar-Ar法,测定对象广泛,理论上含钾矿物均可作为测定对象;④Rb-Sr法,应用广泛,近年来在成矿时代研究中有了长足进展,可以利用包裹体Rb-Sr等时线来确定成矿时代,也可以用同源的不同矿物组合来进行定年。

Isotope geochronology is a newly developed science which determines the geological body formation and geological event occurrence times according to the radioactive isotope decay law, and is also the main means of studying the metallogenic age. Combined with the work of our and previous study, this paper introduces several isotopic geological dating methods that can directly determine the mineralization age of rare metals and its applications, so as to provide references for related disciplines. The main methods are:①Re-Os method, which is the most mature method to directly determine the metallogenic age of metal deposits at present. Besides molybdenite, the measurement objects have been expanded to pyrite and pitchblende, etc.②U-Pb method, which is the most widely used method in geological research, is now not limited to zircon. U-pb age of some uranium-bearing ore minerals, such as cassiterite, monazite, apatite and niobium-tantalum, can also be directly determined, which is helpful to determine the metallogenic age of metal deposits.③Ar-Ar method, with wide rang of measurement objects, in princeple, all the K-bing mierals and rocks can be used for Ar-Ar isotopic dating;④Rb-Sr method, which is widely used, has made great progress in the study of metallogenic age in recent years. It can be used to determine the metallogenic age using the Rb-Sr isochron of inclusions, or can be dated by using different mineral associations of the same origin.