摘要
SHRIMP zircon U-Pb dating for Chibaisong No.1 gabbro in the Tonghua area, Jilin Prov- ince, is discussed in the paper. The cathodoluminescence (CL) images of the zircons indicate that they can be divided into two major types, i.e. euhedral-subhedral one with striped absorption and round one with obvious oscillatory zoning rims. The dating results of the zircons suggest that Chibai- song gabbro in the Tonghua area was formed at 134±7Ma—the Early Cretaceous. The concordia ages of 2497±13Ma, 787±35Ma, 321±10Ma, 217±11Ma of zircons imply that the Tonghua area might geologically be located in the convergent region of the Yangtze Block (YB) and the North China Block (NCB) in the early Mesozoic and the zircons should be caught during magma intrusion. The existence of the Early Cretaceous basic dyke swarm in the Tonghua area shows that an intensive extensional environment occurred in the Early Cretaceous. It is suggested that the magmatism and lithospheric extension in the Tonghua area should be related to the subduction of the Pacific plate.
SHRIMP zircon U-Pb dating for Chibaisong No.1 gabbro in the Tonghua area,Jilin Province, is discussed in the paper. The cathodoluminescence (CL) images of the zirconsindicate that they can be divided into two major types, i.e. euhedral-subhedral one with stripedabsorption and round one with obvious oscillatory zoning rims. The dating results of the zirconssuggest that Chibaisong gabbro in the Tonghua area was formed at 134±7Ma—the Early Cretaceous. Theconcordia ages of 2497±13Ma, 787±35Ma, 321±10Ma, 217±11Ma of zircons imply that the Tonghuaarea might geologically be located in the convergent region of the Yangtze Block (YB) and the NorthChina Block (NCB) in the early Mesozoic and the zircons should be caught during magma intrusion. Theexistence of the Early Cretaceous basic dyke swarm in the Tonghua area shows that an intensiveextensional environment occurred in the Early Cretaceous. It is suggested that the magmatism andlithospheric extension in the Tonghua area should be related to the subduction of the Pacific plate.
基金
supported by the National Natural Science Foundation of China(Grant Nos.40133020 and 40172030)
the Key Laboratory of Continental Dynamics,Northwestern University.
