摘要
对大别造山带双河超高压榴辉岩和片麻岩Sm-Nd和Rb-Sr等时线矿物进行了O同位素地质测温。尽管Sm-Nd等时线给出一致的三叠纪年龄（213～238Ma），同一样品Rb-Sr等时线却给出侏罗纪年龄（171～174Ma）。片麻岩、榴辉岩和榴闪岩矿物对0同位素测温得到600-720℃和420-550℃两组温度，分别对应于约225±5Ma榴辉岩相变质和约175±5Ma角闪岩相退变质条件下停止同位素扩散交换的温度。同一样品三叠纪Sm-Nd等时线年龄的保存、侏罗纪Rb-Sr等时线年龄的出现以及有规律的O同位素温度，表明在角闪岩相退变质过程中，Sr和O在含水矿物（如黑云母和角闪石）中的扩散速率在手标本尺度上比石榴石Nd和多硅白云母Sr的扩散速率快。
As the rates of Nd, Sr and O diffusion in metamorphic minerals are comparable in many cases, the state of O isotope equilibrium between metamorphic minerals can provide a test for the validity of mineral Sm-Nd and Rb-Sr chronometers. In order to illustrate this applicability, the authors carried out O isotope geothermometry for Srn-Nd and Rb-Sr isochron minerals from UHP eclogites and gneisses at Shuanghe in Dabie terrane of eastern Central China. Although the Sm-Nd isochrons give consistent Triassic ages of 213-238 Ma for eclogite-facies metamorphism, the Rb-Sr isochrons give Jurassic ages of 171 - 174 Ma for the same samples. O isotope geothermometry of the gneiss, eclogite and amphibolite minerals yields two sets of temperatures of 600-720℃ and 420-550℃, respectively, corresponding to the cessation of isotopic exchange by diffusion at about 225 ± 5 Ma during eclogite-facies recrystallization and that at about 175 ± 5 Ma during amphibolite-fades retrogression.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2005年第B09期98-101,共4页
Acta Geoscientica Sinica
基金
本文为国家973项目（编号：G1999075503）研究成果.
