The Xiongdian eclogite occurring in the Sujiahe tectonic melange zone at Luoshan County, Henan Province, in the western Dabie Mountains, is typical high-pressure (HP)-ultrahigh-pressure (UHP) and medium-temperature ec...The Xiongdian eclogite occurring in the Sujiahe tectonic melange zone at Luoshan County, Henan Province, in the western Dabie Mountains, is typical high-pressure (HP)-ultrahigh-pressure (UHP) and medium-temperature eclogite. The occurrence, internal texture and surface characteristics of zircons in eclogite were studied rather systematically petrographically combined with the cathodoluminescence (CL) and scanning electron microscope (SEM) methods. Zircons are mainly hosted in garnet and other metamorphic minerals with sharp boundaries, have a multifaceted morphology and are homogeneous or exhibit a metamorphic growth texture in the interior, thus indicating that they are the product of metamorphism. SHRIMP analyses give zircon 206Pb/238U ages of 335 to 424 Ma and show a certain degree of radiogenic Pb loss; therefore it may be inferred that the age of 424? Ma represents the minimum age of a HP-UHP metamorphic age. From the above analyses coupled with previous Sm-Nd, 40Ar-39Ar, U-Pb and 207Pb/206Pb age data, it is suggested that the peak metamorphic age of the Xiongdian eclogite should be between 424 and 480 Ma. This study further validate the view of the existence of a Caledonian HP-UHP metamorphic event in the western Dabie Mountains.展开更多
This note reports the SHRIMP U-Pb data of zircons from the Caledonian Xiongdian eclogite, western Dabie Mountains. Zircons from the rock occur mainly in garnet and other metamorphic minerals with sharp boundaries and ...This note reports the SHRIMP U-Pb data of zircons from the Caledonian Xiongdian eclogite, western Dabie Mountains. Zircons from the rock occur mainly in garnet and other metamorphic minerals with sharp boundaries and exhibit textures growing under metamorphic conditions. Analyses of 7 grains give 206Pb/238U ages ranging from 335 to 424 Ma, showing a certain degree of radiogenic lead loss. This suggests a minimum age of (424±)Ma for the metamorphic zircons, as well as the high-pressure metamorphic event. The outer peripheral zone of a zircon gives 206Pb/238U age of about 300 Ma. Combined with Sm-Nd, 40Ar-39Ar, U-Pb and 207Pb/206Pb ages, the peak metamorphism of the Xiongdian eclogite is documented between 424-480 Ma.展开更多
文摘The Xiongdian eclogite occurring in the Sujiahe tectonic melange zone at Luoshan County, Henan Province, in the western Dabie Mountains, is typical high-pressure (HP)-ultrahigh-pressure (UHP) and medium-temperature eclogite. The occurrence, internal texture and surface characteristics of zircons in eclogite were studied rather systematically petrographically combined with the cathodoluminescence (CL) and scanning electron microscope (SEM) methods. Zircons are mainly hosted in garnet and other metamorphic minerals with sharp boundaries, have a multifaceted morphology and are homogeneous or exhibit a metamorphic growth texture in the interior, thus indicating that they are the product of metamorphism. SHRIMP analyses give zircon 206Pb/238U ages of 335 to 424 Ma and show a certain degree of radiogenic Pb loss; therefore it may be inferred that the age of 424? Ma represents the minimum age of a HP-UHP metamorphic age. From the above analyses coupled with previous Sm-Nd, 40Ar-39Ar, U-Pb and 207Pb/206Pb age data, it is suggested that the peak metamorphic age of the Xiongdian eclogite should be between 424 and 480 Ma. This study further validate the view of the existence of a Caledonian HP-UHP metamorphic event in the western Dabie Mountains.
基金This work was sponsored by the Ministry of Geology and Mineral Resources of China(Grant No. 9501102-2), the Open Laboratory of Isotope Geology of the Ministry of Land and Resources of Chinaand China Post-Doctor Foundation.
文摘This note reports the SHRIMP U-Pb data of zircons from the Caledonian Xiongdian eclogite, western Dabie Mountains. Zircons from the rock occur mainly in garnet and other metamorphic minerals with sharp boundaries and exhibit textures growing under metamorphic conditions. Analyses of 7 grains give 206Pb/238U ages ranging from 335 to 424 Ma, showing a certain degree of radiogenic lead loss. This suggests a minimum age of (424±)Ma for the metamorphic zircons, as well as the high-pressure metamorphic event. The outer peripheral zone of a zircon gives 206Pb/238U age of about 300 Ma. Combined with Sm-Nd, 40Ar-39Ar, U-Pb and 207Pb/206Pb ages, the peak metamorphism of the Xiongdian eclogite is documented between 424-480 Ma.
