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《中国科学D辑(英文版)》 1996-S1
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The petrological evidence for the uplift of ultrahigh-pressure met-amorphic rocks in root zone of the Qinling-Dabie orogenic belt

YOU Zhendong(China University of Geoscienoes. Wuhan 430074, China)HAN Yujing and ZHANG Zeming(Open Laboratory of Crust Mantle Constitution, Interaction and Dynamics, Ministry of Geology and Mineral Resources, Wuhan 430094, China)  
Petrographic evidence indicates that some of the ultrahigh-pressure (UHP) eclogites in Dabie Mountains area may be evolved from epidote amphibolite fades rocks recrystallized under ultrahigh pressure conditions. The evolution of the erogenic belt had eventually resulted in the uplift of the metamorphic terrane soon after the peak metamorphic ultrahigh pressure stage of collision. During the uplift the ultrahigh-pressure metamorphic rocks were superimposed by nearly isothermal decompressive retrograde metamorphism through high-pressure (HP) edogite fades to amphibolite fades. Some of them were followed by epidote amphibolite fades and greenschist fades of metamorphism, while others were followed by epidote blueschist fades and then lowered to greenschist fades. Accompanying the retrogressive metamorphism. the rocks underwent at least 6 stages of deformation ranging from plastic to brittle character. The decompressive P-T path is also shown in the evolution of fluid inclusions: the entrapment pressure is estimated as 2.05 GPa and then isothermally decreased to lower than 1.0 GPa. The salinity of the late fluid is obviously decreased. Its ratios of Br/Cl and I/Cl are higher than those of sea water and bulk earth, suggesting a deep source of the fluid.
【Fund】: Project supported by the Doctorate Special Fund of State Education Commission of China and the National Natural Science Foundation of China.
【CateGory Index】: P578
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