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Fluid Evolution during HP and UHP Metamorphism in Dabie Shan, China: Constraints from Mineral Chemistry, Fluid Inclusions and Stable Isotopes

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Year:
2002
Type of Publication:
Article
Authors:
Xiao, Y.; Hoefs, J.; van Kerkhof, A.; Simon, Klaus; Fiebig, J.; Yong-Fei, Zheng
Journal:
Journal of Petrology
Volume:
43
Number:
8
Pages:
1505-1527
BibTex:
Abstract:
The Dabie Shan ultrahigh-pressure (UHP) metamorphic terrane is located in the eastern part of the east–west-striking Qinling–Dabie orogenic belt in China. A major mylonitized contact zone of 200–300 m width divides Dabie Shan into the South Dabie Terrane (SDT) and the North Dabie Complex (NDC). Combined investigation of major and trace element geochemistry, fluid inclusions, and oxygen and hydrogen isotopes constrains the fluid history during the metamorphic evolution of the two metamorphic belts, which differ in their fluid and metamorphic evolution. Fluid inclusions in rocks from the SDT are mainly aqueous with varying salinities, whereas those from the NDC are dominated by CO2. Low δ18O values in the SDT rocks (−2·8 to 8·6‰) indicate meteoric water–rock interactions before UHP metamorphism, whereas rocks from the NDC show ‘normal’ δ18O values (6·7–9·0‰) with no obvious meteoric water–rock signature. Whole-rock rare earth element (REE) contents correlate with oxygen isotope compositions: samples from the SDT have higher REE contents and lower δ18O values, whereas samples from the NDC have lower REE contents and higher δ18O values. During retrograde metamorphism fluids with different hydrogen isotope compositions interacted with the rocks from the SDT.

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