用锆石年龄的深度剖面来重新认识源-汇系统

To Decipher the“Source-to-Sink”System Using the Depth Profile of Zircon Ages

近年来锆石U-Pb地质年代学已成为研究构造活跃区源-汇系统的重要工具。然而,由于全球锆石集中形成于超大陆的聚合期间,因此出现了单颗锆石的单个结晶年龄对应于多个结晶年龄相似的不同源区的现象。这成为了利用锆石U-Pb地质年代学研究源-汇系统的主要障碍。本文以北美阿巴拉契亚-沃西托-马拉松造山带及其前陆盆地、喜马拉雅淡色花岗岩为例,从锆石核边结构的形成机理、深度剖面定年方法、核边年龄重建构造活跃区源-汇系统的理论基础及核边年龄研究源-汇系统的局限性等方面进行了系统总结,指出锆石深度剖面定年方法是分析复杂结构锆石的有效方法,在研究构造活跃区源-汇系统方面具有独特优势。

Recently,zircon U-Pb geochronology has been an important tool for studying the source-to-sink(S2 S)systems in tectonically active regions.However,because zircons were mainly formed in periods of the aggregation of global supercontinents,a single U-Pb age for a zircon grain could be corresponded to several similar crystallization ages of zircons with different sources.This has become a major obstacle in the study of the S2 S system using zircon U-Pb geochronology.In this study,based on studies of detrital zircons from the Appalachian-Ouachita-Marathon foreland and zircons from leucogranites in Himalayan Orogen,we have made a systematic summary on fields of the formation mechanism of zircon core-rim structure,the zircon depth profiling chronological method,the theoretical basis for reconstructing the S2 S system in tectonically active areas by using zircon core-rim ages,and the limitation for studying the S2 S system by using zircon core-rim ages.In addition,we have pointed out that the zircon depth profiling chronological method is an effective way for analyzing the zircons with complicated core-rim structure and it has unique advantages for studying the S2 S system in tectonically active regions.