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

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• 作者：Bing Gong (1)
  RenXu Chen (1)
  YongFei Zheng (1)
  
• 关键词：eclogite ; gneiss ; mineral ; structural hydroxyl ; molecular water ; metamorphic fluid
• 刊名：Chinese Science Bulletin
• 出版年：2013
• 出版时间：December 2013
• 年：2013
• 卷：58
• 期：35
• 页码：4384-4389
• 全文大小：
• 作者单位：Bing Gong (1)
  RenXu Chen (1)
  YongFei Zheng (1)
  
  1. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China
  
• ISSN：1861-9541

文摘

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 2500 and 3500 ppm, respectively, under the peak UHP metamorphic conditions.