大别山东南部高压-超高压变质岩的氢氧同位素地球化学  

Hydrogen and oxygen isotope geochemistry of high to ultrahigh pressure metamorphic rocks from Southeast Dabie.

作　　者：李一良[1] 郑永飞[1] 傅斌[1] 李龙[1] 

机构地区：[1]中国科学技术大学地球与空间科学系化学地球动力学研究实验室,合肥230026

出　　处：《岩石学报》2001年第1期49-60,共12页Acta Petrologica Sinica

基　　金：科技部国家重点基础研究发展规划项目 ( G19990 75 5 0 3);中国科学院知识创新工程项目 ( KZCX2 -10 7)

摘　　要：本文报道了大别山东南部安徽石马地区柯石英榴辉岩组合和黄镇地区石英榴辉岩组合的全岩及单矿物的氢氧同位素特征。石马榴辉岩的 δ1 8O值在 1.0‰～ 7.4‰之间 ,云母 δD值为 - 76‰～ - 6 1‰ ;黄镇榴辉岩的全岩 δ1 8O值为 - 1.1‰～ - 2 .1‰ ,云母 δD值为 - 89‰～ - 77‰。矿物之间的氢氧同位素分馏既有处于平衡状态者 ,也有处于不平衡状态者 ,反映这些岩石除继承变质前母体的 1 8O亏损特征外 ,还经历了显著的同位素退化交换作用。石马和黄镇榴辉岩的矿物对氧同位素温度均给出两个峰值 :380～ 430℃与绿片岩相变质条件一致 ,6 0 0～ 6 40℃与高角闪岩相变质条件一致 ;给不出峰变质温度 (75 0～80 0℃ )是由于岩石经历了退变质流体的强烈改造作用。大别东南部高压 -超高压榴辉岩的南部边界为石英榴辉岩与花岗片麻岩的界线 。The hydrogen and oxygen isotope compositions of single minerals and whole-rock were measured for coesite-hearing eclogite at Shima and quartz-bearing eclogite at Huangzhen in southeastern Dabie. The delta O-18 values of the eclogites vary from 1.0 to 7.4 parts per thousand at Shima but from -2.1 to 1.3 parts per thousand at Huangzhen; the deltaD values of micas from the eclogites are -79 to -61 parts per thousand at Shima and -89 to -77 parts per thousand at Huangzhen. Hydrogen and oxygen isotope fractionations between the minerals are in both equilibrium and disequilibrium, indicating that the eclogites have not only inherited the O-18-depletion feature of their protoliths, but also experienced strong retrograde alteration during exhumation. Oxygen isotope temperatures of the eclogite mineral-pairs are cumulated at two peak values of 600 to 640 degreesC and 380 to 430 degreesC, respectively, corresponding to retrograde reequilibration at greenschist-facie and high amphibolite-facies conditions; the peak eclogite-facies temperatures of 750 to 800 degreesC cannot be retrieved due to the strong retrograde alteration. The high and ultrahigh pressure rocks in southeastern Dabie are geologically separated by the quartz-bearing eclogite and granitic gneiss, but the oxygen isotope analyses indicate an in situ relationship between the two rocks.

关 键 词：超高压 变质岩 氢同位素 氧同位素 原位接触 石英榴辉岩 流体-岩石相互作用 

分 类 号：P588.3[天文地球—岩石学] P587.2[天文地球—地质学]