Water contents and hydrogen isotopes in nominally anhydrous minerals from UHP metamorphic rocks in the Dabie-Sulu orogenic belt  

作　　者：GONG Bing CHEN RenXu ZHENG YongFei 

机构地区：[1]CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China

出　　处：《Chinese Science Bulletin》2013年第35期4384-4389,共6页

基　　金：supported by the Ministry of Science and Technology of China(2009CB825004);the National Natural Science Foundation of China(41273006 and 41221062);the Chinese Academy of Sciences(KZCX2-EW-QN502)

摘　　要：A continuous flow method,by a combination of thermal conversion elemental analyzer(TC/EA)with isotope ratio mass spectrometry(MS),was developed to determine both H isotope composition and H2O concentration of ultrahigh-pressure(UHP)metamorphic rocks in the Dabie-Sulu orogenic belt.By using the developed step-heating technique,we have studied H2O concentration and H isotope composition of the different forms of water(structural OH and molecular H2O)in garnet.The quantitative measurements of H2O concentration and H isotope composition of minerals in UHP metamorphic rocks from several typical outcrops indicate that the gneisses can release more amounts of water than the eclogites during exhumation of the deeply subducted continental crust.Therefore,by decompression dehydration at the contact between eclogite and gneiss,the released water could flow from the gneiss to the eclogite and result in significant hydration of the eclogite adjacent to the gneiss.The measured maximum water contents of minerals in eclogites indicate that garnet and omphacite have the maximum water solubilities of 2500and 3500 ppm,respectively,under the peak UHP metamorphic conditions.A continuous flow method, by a combination of thermal conversion elemental analyzer （TC/EA） with isotope ratio mass spec- trometry （MS）, was developed to determine both H isotope composition and H2O concentration of ultrahigh-pressure （UHP） metamorphic rocks in the Dabie-Sulu orogenic belt. By using the developed step-heating technique, we have studied H2O concen- tration and H isotope composition of the different forms of water （structural OH and molecular H2O） in garnet. The quantitative measurements of HzO concentration and H isotope composition of minerals in UHP metamorphic rocks from several typical out- crops indicate that the gneisses can release more amounts of water than the eclogites during exhumation of the deeply subducted continental crust. Therefore, by decompression dehydration at the contact between eclogite and gneiss, the released water could flow from the gneiss to the eclogite and result in significant hydration of the eclogite adjacent to the gneiss. The measured maxi- mum water contents of minerals in eclogites indicate that garnet and omphacite have the maximum water solubilities of 2500 and 3500 ppm, respectively, under the peak UHP metamorphic conditions.

关 键 词：超高压变质岩 苏鲁造山带 氢同位素 矿物质 无水 水含量 同位素组成 利用开发 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]