关键词: 锆石U-Pb定年, 锆石微量元素, 锆石成因, 闪长玢岩, 大石湖沟铜矿床, 辽东地区

Abstract:

The Dashihugou porphyry copper deposit in eastern Liaoning Province is located in the Liao-Ji orogenic belt at the northeastern margin of the North China craton, and its mineralization is spatially closely related to the diorite porphyrite veins intruded into Dashihugou granites. This paper reports for the first time the formation age of diorite porphyrite and its zircon genesis, discusses its metallogenic potential, and provides a theory for regional prospecting. Zircon U-Pb isotopes and trace elements of diorite porphyrite were determined by LA-ICP-MS. Zircon U-Pb dating results show that the emplacement time of diorite porphyrite is 225.6-218.7 Ma, which belongs to the Late Triassic. The study indicates that the magmatic activity of this period is closely related to the first stage of copper mineralization at the same time. Zircons have a typical magmatic origin, and trace elements have characteristic of high REE abundance values with ΣREE content of （216.3-1 305.9）×10-6. Meanwhile, zircons have positive Ce anomaly and weak negative Eu anomaly. The formation temperature of zircons is 568-913 ℃ using Ti thermometer and the oxygen fugidity ranged from ΔFMQ-0.05 to ΔFMQ+4.05, which indicates that the granite has metallogenic potential of porphyry-type copper deposit. Combined with the regional geological tectonic history and zircon trace element characteristics, the magmatic activity of this period may be related to the partial melting of the lower crust caused by the upwelling of the asthenospheric mantle related to plate segment detachment during the continental deep subduction process.

Key words: zircon U-Pb geochronology, zircon trace element, zircon genesis, diorite-porphyrite, Dashihugou copper deposit, eastern Liaoning Province