摘要
Coesite was discovered as inclusions in zircon separates from pelitic gneissassociated with a large eclogite body in the North Qaidam ultrahigh-pressure (UHP) terrane. Somegraphite inclusions were also found. This finding suggested the occurrence of in-situ UHPmetamorphism and that the terrane was most likely recrystallized at pressures below the diamondstability field. It supported other previous indirect UHP evidence, such as polycrystalline quartzinclusions in eclogitic garnet, quartz lamellae in omphacite and P-T estimates for both eclogite andgarnet peridotite. The U-Pb and Sm-Nd ages of the North Qaidam eclogite indicated that subductionof continental crust occurred in the Early Palaeozoic, which probably recorded a collision betweenthe Sino-Korean and Yangtze plates.
Coesite was discovered as inclusions in zircon separates from pelitic gneissassociated with a large eclogite body in the North Qaidam ultrahigh-pressure (UHP) terrane. Somegraphite inclusions were also found. This finding suggested the occurrence of in-situ UHPmetamorphism and that the terrane was most likely recrystallized at pressures below the diamondstability field. It supported other previous indirect UHP evidence, such as polycrystalline quartzinclusions in eclogitic garnet, quartz lamellae in omphacite and P-T estimates for both eclogite andgarnet peridotite. The U-Pb and Sm-Nd ages of the North Qaidam eclogite indicated that subductionof continental crust occurred in the Early Palaeozoic, which probably recorded a collision betweenthe Sino-Korean and Yangtze plates.
基金
the National Natural Science Foundation of China grant 49732070
the Chinese National Key Project for Fundamental Research on the TibetanPlateau(G1998040805).
