含U副矿物的地质年代学研究综述

A Review of Geochronology of U-bearing Accessory Minerals

简要介绍了目前已经发展起来的各种微区原位测年技术的特点和研究矿物内部结构的技术。微区原位测年技术有离子探针、激光探针同位素测年技术、电子探针、质子探针和X射线荧光探针Th-U-全Pb化学等时线年龄技术。综述了锆石、独居石、磷钇矿、榍石、磷灰石、金红石、斜锆石等含U副矿物在U-Th-Pb年代学研究方面的应用及进展,并介绍了锆石、独居石、磷钇矿、榍石等具有多世代性的矿物的成因判别方法,概括了用于岩浆过程、变质过程和沉积过程年代学研究常用的含U副矿物,及其相应的年代学研究需要注意及可解决的地质问题和适用性。总结了岩石年代学研究的主要进展和提取贮存在副矿物中有价值的年龄和成因信息需要解决的问题。

Over the past dacade, there have been many significant advances in the area of accessory mineral＇s geochronology, notably permitted by the development of imaging and in situ microanalytical dating techniques, which include isotopic dating technique and chemical Th-U-total Pb isochron method. The isotopic microanalytical dating techniques include ion microprobe and laser ablation micro-probe-inductively coupled plasma mass spetrometry. There are three kinds of techniques to perform Th-U-total Pb isochron dating analyses, including electron probe X-ray microanalysis, proton-induced x-ray emission micro-probe and X-ray fluorescence probe. The internal textural complexity can be revealed by means of cathodoluminescence （CL） or back-scattered electron （ BSE ） imaging, HF etching imaging and laser raman spectrometry. Zircon, monazite, xenolite, apatite , titanite, rutile and baddeleyite are usually used to U-Th-Pb dating. A review has been made on their applicabilities to geochronology （ including each mineral＇ s superiority or limitation in U-Th-Pb dating, closure temperature）. Methods of determining genesis of those minerals （ such as zircon, monazite, xenolite, titanite ） which usually show multiple generations in a single crystal have been introduced. In addition , some recent advances of geochronology and their geological applications have also been introduced. The accessible accessory minerals used for dating magma, metamorphism and deposition processes have been summed up. Besides, the corresponding requirements , limitations and resoluble problems have been listed. Finally, Main advances in geochronology have been summarized. Viewpoints have been put forward that main problems should be dealt with to extract valuable chronological and genetic information locked in accessory minerals that are often used in petrographical study, mineral microtexture and or microchemical investigations, mechanisms of element mobility within crystals.