The age of the Gaojiacun mafic-ultramafic intrusive complex in the Yanbian area, Sichuan Province: Geochro-nological constraints by U-Pb dating of single zircon grains and ~(40)Ar/~(39)Ar dating of hornblende

摘要

The Gaojiacun mafic-ultramafic intrusive complex in the Yanbian area, Sichuan Province, is a stratiform intrusive body that has undergone intensive magmatic differentiation. This intrusive body involves two magmatic accumulating cycles. Systematic U-Pb dating of single zircon grains and ~(40)Ar/~(39)Ar dating of hornblende were conducted, and the results showed that the age of hornblende gabbro, which was formed at the main phase of intrusion of the Gaojiacun intrusive complex, is 840 +- 5 Ma, casting doubt on the concept of "Yanbian Ophiolite". It is believed that the formation of the Gaojiacun intrusive complex seems to be related to a super-mantle plume underneath the super-continent Rodinia. The above research results are helpful for us to get a better understanding of the characteristics of Neoproterozoic tectonic evolution of the Yanbian area in Sichuan Province.