原地原位定年技术工作思路探讨——中深变质岩区精细变质年代学格架的建立

WORK THOUGHT DISCUSSION ON SITED AND IN-SITU DATING TECHNIQUE:A APPROACH IN RECONSTRUCTION OF FINE FRAMEWORK OF METAMORPHIC GEOCHRONOLOGY FOR MEDIUM- TO HIGH-GRADE TERRANE

前寒武纪变质岩区和(或)造山带核部的中深变质岩岩石的结构域常可分为变斑晶域、基质域和后成合晶域三类。利用原位分析技术直接测定岩石薄片中与这三类结构域关系清楚的锆石和独居石不同成因域的年龄的原地原位定年方法,可以有效地确定变质峰期和变质反应的地质时间,因而是建立精细变质年代学格架的可行途径。

Three textural domains can be generally recognized in thin sections as porphyroblast domain,matrix domain and corona domain in medium to highgrade metamorphic rocks from Precambrian craton and/or interior of orogenic belt.The sited and insitu dating is used to analyse directly ages of different genetic microdomains in zircon and monazite with clear spatial relation to the individual textural domains in the thin section.This technique can determine effectively the timing of peak metamorphism or distinct metamorphic reaction,and hence is feasible for establishing a fine framework of metamorphic geochronology for medium to highgrade terrane.