长白山天池火山U过剩特征——西太平洋板块深俯冲的又一证据  

FEATURES OF EXCESS OF U IN VOLCANIC ROCKS OF CHANGBAISHAN TIANCHI——THE EVIDENCE FOR SUBDUCTION OF WESTEM PACIFIC PLATE

作　　者：王非[1] 陈文寄[1] 彭子成[2] 

机构地区：[1]中国地震局地质研究所,北京100029 [2]中国科学技术大学地球和空间科学系,合肥230026

出　　处：《地震地质》2000年第B12期87-94,共8页Seismology and Geology

基　　金：中国地震局地质研究所论著 !2 0 0 0B0 0 6 1

摘　　要：应用高精度热电离质谱技术 ,测定了长白山天池锥体 11个火山岩样品的U ,Th同位素组成。结果发现 ,天池火山岩中铀不平衡同位素体系以2 38U放射性过剩为特征 (即2 30 Th/ 2 38U放射性比值小于 1) ,表明了岩浆过程中水的参与作用 ;而样品δ2 34U <10‰ ,说明浅部循环水不是造成上述2 38U过剩的原因。由此推断 ,含水组分在岩浆源区参与了部分熔融过程 ,这可能是太平洋俯冲板块脱水作用的结果。samples of lava and pumice from the cone of Changbaishan Tianchi Volcano, Jiling, China were measured for their uranium and thorium isotopic compositions by using the high precision U-series TIMS method. The results indicate that the U-series disequilirium system is characterized by excess of 238U (namely the radioactivity ratio of 230Th/ 238U less than 1), showing the fluids has worked in the magmatic reservoir. This may suggests that the fluids, which participated in the melting of the source rock, came from the dehydration of the subduced Pacific plate.

关 键 词：俯冲板块 长白山天池火山 西太平洋 火山岩 部分熔融 岩浆源区 同位素组成 ^238U 热电离质谱 样品 

分 类 号：P588.14[天文地球—岩石学] P317[天文地球—地质学]