The Effect Of Radiation Damage On Fission-track Annealing Behavior

The produced fission tracks in minerals can be annealed by temperature and time.Temperature has been regarded as the only source of annealing and directly induces the track annealing.Based on the fundamental principle,apatite multi-kinetics annealing model has been built and widely applied to reconstruct the thermal history of some sedimentary basins,the exhumation history of orogenic belt and provenance analysis.However some researches indicate radiation damage should be the another source of annealing.Whether radiation damage can influence and enhance the annealing or not has been in dispute.This issue will directly affect on the reliability of fission track dating and have important implications for fission-track thermochronology.Therefore,the effect of radiation damage on fission-track annealing behavior of32 magmatic rocks including 27 granites from various regions,4 granites from Lincang county in Yunnan province and 1 granite from Tianshan was studied systematically by the method of fission track dating in this research.At some degree,the work decreased the interference from certain thermal history in previous researches which studied various samples from same region and errors caused by the non-correspondence between age ? length and U concentrates respectively.The analysis results of the relationship between fission track age,length and U concentration respectively indicated fission track age and length decreased as the U concentration increasing.In addition,the trend was displayed more obviously in each apatite grain from one sample than in various samples.The difference reflected because U concentration of each grain exists evidently different,the average of U concentration can not be corresponded accurately to track density and length measured respectively.The problem can increase the error systemically,which causes the effect of radiation damage on fission-track annealing behavior was not presented apparently.The results from the research experiments illustrate radiation damage can influence and enhance the annealing for further.According to the work and experiment results,we supported radiation damage should be the source inducing fission track annealing.Combined with the previous researches,discussed the possible micro-mechanism of the effect of radiation damage on fission-track annealing behavior,supported the following preliminary conclusion:The interaction between ?-recoils produced from some radioactive elements' ?-decay,such as U?Th and atoms surround fission track mainly by the means of nuclear collision caused the inter structure of fission track damaged and made fission track anneal and even disappear finally.